Add jsonlog log_destination for JSON server logs

From d5b3f5fe44e91d35aefdd570758d5b2a9e9c1a36 Mon Sep 17 00:00:00 2001
From: Sehrope Sarkuni <sehrope@jackdb.com>
Date: Wed, 10 Jul 2019 10:02:31 -0400
Subject: [PATCH 1/4] Adds separate dest field to log protocol PipeProtoHeader

Adds a separate dest field to PipeProtoHeader to store the log destination
requested by the sending process. Also changes the is_last field to only
store whether the chunk is the last one for a message rather than also
including whether the destination is csvlog.
---
 src/backend/postmaster/syslogger.c | 15 ++++++---------
 src/backend/utils/error/elog.c     |  4 +++-
 src/include/postmaster/syslogger.h |  4 ++--
 3 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index cad43bdef2..edd8f33204 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -878,7 +878,6 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 {
 	char	   *cursor = logbuffer;
 	int			count = *bytes_in_logbuffer;
-	int			dest = LOG_DESTINATION_STDERR;
 
 	/* While we have enough for a header, process data... */
 	while (count >= (int) (offsetof(PipeProtoHeader, data) + 1))
@@ -891,8 +890,9 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&
-			(p.is_last == 't' || p.is_last == 'f' ||
-			 p.is_last == 'T' || p.is_last == 'F'))
+			(p.is_last == 't' || p.is_last == 'f') &&
+			(p.dest == LOG_DESTINATION_CSVLOG ||
+			 p.dest == LOG_DESTINATION_STDERR))
 		{
 			List	   *buffer_list;
 			ListCell   *cell;
@@ -906,9 +906,6 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 			if (count < chunklen)
 				break;
 
-			dest = (p.is_last == 'T' || p.is_last == 'F') ?
-				LOG_DESTINATION_CSVLOG : LOG_DESTINATION_STDERR;
-
 			/* Locate any existing buffer for this source pid */
 			buffer_list = buffer_lists[p.pid % NBUFFER_LISTS];
 			foreach(cell, buffer_list)
@@ -924,7 +921,7 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 					free_slot = buf;
 			}
 
-			if (p.is_last == 'f' || p.is_last == 'F')
+			if (p.is_last == 'f')
 			{
 				/*
 				 * Save a complete non-final chunk in a per-pid buffer
@@ -970,7 +967,7 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 					appendBinaryStringInfo(str,
 										   cursor + PIPE_HEADER_SIZE,
 										   p.len);
-					write_syslogger_file(str->data, str->len, dest);
+					write_syslogger_file(str->data, str->len, p.dest);
 					/* Mark the buffer unused, and reclaim string storage */
 					existing_slot->pid = 0;
 					pfree(str->data);
@@ -979,7 +976,7 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 				{
 					/* The whole message was one chunk, evidently. */
 					write_syslogger_file(cursor + PIPE_HEADER_SIZE, p.len,
-										 dest);
+										 p.dest);
 				}
 			}
 
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index a3e1c59a82..cd13111708 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -3250,6 +3250,8 @@ write_pipe_chunks(char *data, int len, int dest)
 
 	p.proto.nuls[0] = p.proto.nuls[1] = '\0';
 	p.proto.pid = MyProcPid;
+	p.proto.dest = (int32) dest;
+	p.proto.is_last = 'f';
 
 	/* write all but the last chunk */
 	while (len > PIPE_MAX_PAYLOAD)
@@ -3264,7 +3266,7 @@ write_pipe_chunks(char *data, int len, int dest)
 	}
 
 	/* write the last chunk */
-	p.proto.is_last = (dest == LOG_DESTINATION_CSVLOG ? 'T' : 't');
+	p.proto.is_last = 't';
 	p.proto.len = len;
 	memcpy(p.proto.data, data, len);
 	rc = write(fd, &p, PIPE_HEADER_SIZE + len);
diff --git a/src/include/postmaster/syslogger.h b/src/include/postmaster/syslogger.h
index 1491eecb0f..41d026a474 100644
--- a/src/include/postmaster/syslogger.h
+++ b/src/include/postmaster/syslogger.h
@@ -46,8 +46,8 @@ typedef struct
 	char		nuls[2];		/* always \0\0 */
 	uint16		len;			/* size of this chunk (counts data only) */
 	int32		pid;			/* writer's pid */
-	char		is_last;		/* last chunk of message? 't' or 'f' ('T' or
-								 * 'F' for CSV case) */
+	int32		dest;			/* log destination */
+	char		is_last;        /* last chunk of message? 't' or 'f'*/
 	char		data[FLEXIBLE_ARRAY_MEMBER];	/* data payload starts here */
 } PipeProtoHeader;
 
-- 
2.17.1

From dfb17c0b1804b9e54a287e6a058d02dd1be27ffb Mon Sep 17 00:00:00 2001
From: Sehrope Sarkuni <sehrope@jackdb.com>
Date: Tue, 31 Aug 2021 10:00:54 -0400
Subject: [PATCH 2/4] Add TAP test for csvlog

---
 src/bin/pg_ctl/t/005_csvlog.pl | 118 +++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 src/bin/pg_ctl/t/005_csvlog.pl

diff --git a/src/bin/pg_ctl/t/005_csvlog.pl b/src/bin/pg_ctl/t/005_csvlog.pl
new file mode 100644
index 0000000000..c6ab0ddbcc
--- /dev/null
+++ b/src/bin/pg_ctl/t/005_csvlog.pl
@@ -0,0 +1,118 @@
+use strict;
+use warnings;
+
+use PostgresNode;
+use TestLib;
+use Test::More tests => 4;
+use Time::HiRes qw(usleep);
+
+# Set up node with logging collector
+my $node = PostgresNode->new('primary');
+$node->init();
+$node->append_conf(
+	'postgresql.conf', qq(
+logging_collector = on
+lc_messages = 'C'
+log_destination = 'csvlog'
+));
+
+$node->start();
+
+note "Before sleep";
+usleep(100_000);
+note "Before rotate";
+$node->logrotate();
+note "After rotate";
+usleep(100_000);
+note "After rotate sleep";
+
+# Verify that log output gets to the file
+
+$node->psql('postgres', 'SELECT 1/0');
+
+my $current_logfiles = slurp_file($node->data_dir . '/current_logfiles');
+
+for(my $tmp=0;$tmp < 10;$tmp++) {
+   my $current_logfiles = slurp_file($node->data_dir . '/current_logfiles');
+   note "current_logfiles = $current_logfiles";
+   usleep(100_000);
+}
+
+
+like(
+	$current_logfiles,
+	qr|^csvlog log/postgresql-.*$|,
+	'current_logfiles is sane');
+
+my $lfname = $current_logfiles;
+$lfname =~ s/^csvlog //;
+chomp $lfname;
+
+note "current_logfiles = $current_logfiles";
+note "lfname = $lfname";
+
+# might need to retry if logging collector process is slow...
+my $max_attempts = 180 * 10;
+
+my $first_logfile;
+for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
+{
+    my $foo = $node->data_dir . '/' . $lfname;
+    note "will slurp: $foo";
+    $first_logfile = slurp_file($node->data_dir . '/' . $lfname);
+	last if $first_logfile =~ m/division by zero/;
+	usleep(100_000);
+}
+
+note "first_logfile = $first_logfile";
+# Our log entry should the error message and errant SQL
+like(
+	$first_logfile,
+	qr/division by zero.*"SELECT 1\/0"/,
+	'found expected log file content');
+
+# Sleep 2 seconds and ask for log rotation; this should result in
+# output into a different log file name.
+sleep(2);
+$node->logrotate();
+
+# pg_ctl logrotate doesn't wait for rotation request to be completed.
+# Allow a bit of time for it to happen.
+my $new_current_logfiles;
+for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
+{
+	$new_current_logfiles = slurp_file($node->data_dir . '/current_logfiles');
+	last if $new_current_logfiles ne $current_logfiles;
+	usleep(100_000);
+}
+
+note "now current_logfiles = $new_current_logfiles";
+
+like(
+	$new_current_logfiles,
+	qr|^csvlog log/postgresql-.*$|,
+	'new current_logfiles is sane');
+
+$lfname = $new_current_logfiles;
+$lfname =~ s/^csvlog //;
+chomp $lfname;
+
+# Verify that log output gets to this file, too
+
+$node->psql('postgres', 'fee fi fo fum');
+
+my $second_logfile;
+for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
+{
+	$second_logfile = slurp_file($node->data_dir . '/' . $lfname);
+	last if $second_logfile =~ m/syntax error/;
+	usleep(100_000);
+}
+
+like(
+	$second_logfile,
+	# Our log entry should have our bad string wrapped in quotes after the error
+	qr/syntax error.*,"fee fi fo fum"/,
+	'found expected log file content in new log file');
+
+$node->stop();
-- 
2.17.1

From 1fadc727cc77d020e559b6a16db9db72d5678bf5 Mon Sep 17 00:00:00 2001
From: Sehrope Sarkuni <sehrope@jackdb.com>
Date: Wed, 1 Sep 2021 09:06:15 -0400
Subject: [PATCH 3/4] Split csv handling in elog.c into separate csvlog.c

Split out csvlog to its own file and centralize common elog internals
and helpers into its own file as well.
---
 src/backend/utils/error/Makefile  |   1 +
 src/backend/utils/error/csvlog.c  | 270 ++++++++++++++++++++++++++
 src/backend/utils/error/elog.c    | 313 ++----------------------------
 src/include/utils/elog-internal.h |  78 ++++++++
 4 files changed, 365 insertions(+), 297 deletions(-)
 create mode 100644 src/backend/utils/error/csvlog.c
 create mode 100644 src/include/utils/elog-internal.h

diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index 612da215d0..ef770dd2f2 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -14,6 +14,7 @@ include $(top_builddir)/src/Makefile.global
 
 OBJS = \
 	assert.o \
+	csvlog.o \
 	elog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/csvlog.c b/src/backend/utils/error/csvlog.c
new file mode 100644
index 0000000000..923b7e7d73
--- /dev/null
+++ b/src/backend/utils/error/csvlog.c
@@ -0,0 +1,270 @@
+/*-------------------------------------------------------------------------
+ *
+ * csvlog.c
+ *	  CSV logging
+ *
+ * Copyright (c) 2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/csvlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog-internal.h"
+#include "utils/guc.h"
+#include "utils/ps_status.h"
+
+/*
+ * append a CSV'd version of a string to a StringInfo
+ * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
+ * If it's NULL, append nothing.
+ */
+static inline void
+appendCSVLiteral(StringInfo buf, const char *data)
+{
+	const char *p = data;
+	char		c;
+
+	/* avoid confusing an empty string with NULL */
+	if (p == NULL)
+		return;
+
+	appendStringInfoCharMacro(buf, '"');
+	while ((c = *p++) != '\0')
+	{
+		if (c == '"')
+			appendStringInfoCharMacro(buf, '"');
+		appendStringInfoCharMacro(buf, c);
+	}
+	appendStringInfoCharMacro(buf, '"');
+}
+
+/*
+ * Constructs the error message, depending on the Errordata it gets, in a CSV
+ * format which is described in doc/src/sgml/config.sgml.
+ */
+void
+write_csvlog(ErrorData *edata)
+{
+	StringInfoData buf;
+	bool		print_stmt = false;
+
+	/* static counter for line numbers */
+	static long log_line_number = 0;
+
+	/* has counter been reset in current process? */
+	static int	log_my_pid = 0;
+
+	/*
+	 * This is one of the few places where we'd rather not inherit a static
+	 * variable's value from the postmaster.  But since we will, reset it when
+	 * MyProcPid changes.
+	 */
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		formatted_start_time[0] = '\0';
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/*
+	 * timestamp with milliseconds
+	 *
+	 * Check if the timestamp is already calculated for the syslog message,
+	 * and use it if so.  Otherwise, get the current timestamp.  This is done
+	 * to put same timestamp in both syslog and csvlog messages.
+	 */
+	if (formatted_log_time[0] == '\0')
+		setup_formatted_log_time();
+
+	appendStringInfoString(&buf, formatted_log_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* username */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->user_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* database name */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->database_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* Process id  */
+	if (MyProcPid != 0)
+		appendStringInfo(&buf, "%d", MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendStringInfoChar(&buf, '"');
+		appendStringInfoString(&buf, MyProcPort->remote_host);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+		{
+			appendStringInfoChar(&buf, ':');
+			appendStringInfoString(&buf, MyProcPort->remote_port);
+		}
+		appendStringInfoChar(&buf, '"');
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session id */
+	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Line number */
+	appendStringInfo(&buf, "%ld", log_line_number);
+	appendStringInfoChar(&buf, ',');
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData msgbuf;
+		const char *psdisp;
+		int			displen;
+
+		initStringInfo(&msgbuf);
+
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendCSVLiteral(&buf, msgbuf.data);
+
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session start timestamp */
+	if (formatted_start_time[0] == '\0')
+		setup_formatted_start_time();
+	appendStringInfoString(&buf, formatted_start_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Transaction id */
+	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
+	appendStringInfoChar(&buf, ',');
+
+	/* Error severity */
+	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
+	appendStringInfoChar(&buf, ',');
+
+	/* SQL state code */
+	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
+	appendStringInfoChar(&buf, ',');
+
+	/* errmessage */
+	appendCSVLiteral(&buf, edata->message);
+	appendStringInfoChar(&buf, ',');
+
+	/* errdetail or errdetail_log */
+	if (edata->detail_log)
+		appendCSVLiteral(&buf, edata->detail_log);
+	else
+		appendCSVLiteral(&buf, edata->detail);
+	appendStringInfoChar(&buf, ',');
+
+	/* errhint */
+	appendCSVLiteral(&buf, edata->hint);
+	appendStringInfoChar(&buf, ',');
+
+	/* internal query */
+	appendCSVLiteral(&buf, edata->internalquery);
+	appendStringInfoChar(&buf, ',');
+
+	/* if printed internal query, print internal pos too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendStringInfo(&buf, "%d", edata->internalpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* errcontext */
+	if (!edata->hide_ctx)
+		appendCSVLiteral(&buf, edata->context);
+	appendStringInfoChar(&buf, ',');
+
+	/* user query --- only reported if not disabled by the caller */
+	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
+		debug_query_string != NULL &&
+		!edata->hide_stmt)
+		print_stmt = true;
+	if (print_stmt)
+		appendCSVLiteral(&buf, debug_query_string);
+	appendStringInfoChar(&buf, ',');
+	if (print_stmt && edata->cursorpos > 0)
+		appendStringInfo(&buf, "%d", edata->cursorpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		StringInfoData msgbuf;
+
+		initStringInfo(&msgbuf);
+
+		if (edata->funcname && edata->filename)
+			appendStringInfo(&msgbuf, "%s, %s:%d",
+							 edata->funcname, edata->filename,
+							 edata->lineno);
+		else if (edata->filename)
+			appendStringInfo(&msgbuf, "%s:%d",
+							 edata->filename, edata->lineno);
+		appendCSVLiteral(&buf, msgbuf.data);
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* application name */
+	if (application_name)
+		appendCSVLiteral(&buf, application_name);
+
+	appendStringInfoChar(&buf, ',');
+
+	/* backend type */
+	appendCSVLiteral(&buf, get_backend_type_for_log());
+	appendStringInfoChar(&buf, ',');
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendStringInfo(&buf, "%d", leader->pid);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* query id */
+	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
+
+	appendStringInfoChar(&buf, '\n');
+
+	write_syslogger(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index cd13111708..47d6677827 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -82,7 +82,7 @@
 #include "utils/guc.h"
 #include "utils/memutils.h"
 #include "utils/ps_status.h"
-
+#include "utils/elog-internal.h"
 
 /* In this module, access gettext() via err_gettext() */
 #undef _
@@ -155,9 +155,8 @@ static int	recursion_depth = 0;	/* to detect actual recursion */
 static struct timeval saved_timeval;
 static bool saved_timeval_set = false;
 
-#define FORMATTED_TS_LEN 128
-static char formatted_start_time[FORMATTED_TS_LEN];
-static char formatted_log_time[FORMATTED_TS_LEN];
+char formatted_start_time[FORMATTED_TS_LEN];
+char formatted_log_time[FORMATTED_TS_LEN];
 
 
 /* Macro for checking errordata_stack_depth is reasonable */
@@ -175,52 +174,13 @@ static const char *err_gettext(const char *str) pg_attribute_format_arg(1);
 static pg_noinline void set_backtrace(ErrorData *edata, int num_skip);
 static void set_errdata_field(MemoryContextData *cxt, char **ptr, const char *str);
 static void write_console(const char *line, int len);
-static void setup_formatted_log_time(void);
-static void setup_formatted_start_time(void);
 static const char *process_log_prefix_padding(const char *p, int *padding);
 static void log_line_prefix(StringInfo buf, ErrorData *edata);
-static void write_csvlog(ErrorData *edata);
 static void send_message_to_server_log(ErrorData *edata);
 static void write_pipe_chunks(char *data, int len, int dest);
 static void send_message_to_frontend(ErrorData *edata);
-static const char *error_severity(int elevel);
 static void append_with_tabs(StringInfo buf, const char *str);
 
-
-/*
- * is_log_level_output -- is elevel logically >= log_min_level?
- *
- * We use this for tests that should consider LOG to sort out-of-order,
- * between ERROR and FATAL.  Generally this is the right thing for testing
- * whether a message should go to the postmaster log, whereas a simple >=
- * test is correct for testing whether the message should go to the client.
- */
-static inline bool
-is_log_level_output(int elevel, int log_min_level)
-{
-	if (elevel == LOG || elevel == LOG_SERVER_ONLY)
-	{
-		if (log_min_level == LOG || log_min_level <= ERROR)
-			return true;
-	}
-	else if (elevel == WARNING_CLIENT_ONLY)
-	{
-		/* never sent to log, regardless of log_min_level */
-		return false;
-	}
-	else if (log_min_level == LOG)
-	{
-		/* elevel != LOG */
-		if (elevel >= FATAL)
-			return true;
-	}
-	/* Neither is LOG */
-	else if (elevel >= log_min_level)
-		return true;
-
-	return false;
-}
-
 /*
  * Policy-setting subroutines.  These are fairly simple, but it seems wise
  * to have the code in just one place.
@@ -2291,7 +2251,7 @@ write_console(const char *line, int len)
 /*
  * setup formatted_log_time, for consistent times between CSV and regular logs
  */
-static void
+void
 setup_formatted_log_time(void)
 {
 	pg_time_t	stamp_time;
@@ -2323,7 +2283,7 @@ setup_formatted_log_time(void)
 /*
  * setup formatted_start_time
  */
-static void
+void
 setup_formatted_start_time(void)
 {
 	pg_time_t	stamp_time = (pg_time_t) MyStartTime;
@@ -2729,257 +2689,6 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 	}
 }
 
-/*
- * append a CSV'd version of a string to a StringInfo
- * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
- * If it's NULL, append nothing.
- */
-static inline void
-appendCSVLiteral(StringInfo buf, const char *data)
-{
-	const char *p = data;
-	char		c;
-
-	/* avoid confusing an empty string with NULL */
-	if (p == NULL)
-		return;
-
-	appendStringInfoCharMacro(buf, '"');
-	while ((c = *p++) != '\0')
-	{
-		if (c == '"')
-			appendStringInfoCharMacro(buf, '"');
-		appendStringInfoCharMacro(buf, c);
-	}
-	appendStringInfoCharMacro(buf, '"');
-}
-
-/*
- * Constructs the error message, depending on the Errordata it gets, in a CSV
- * format which is described in doc/src/sgml/config.sgml.
- */
-static void
-write_csvlog(ErrorData *edata)
-{
-	StringInfoData buf;
-	bool		print_stmt = false;
-
-	/* static counter for line numbers */
-	static long log_line_number = 0;
-
-	/* has counter been reset in current process? */
-	static int	log_my_pid = 0;
-
-	/*
-	 * This is one of the few places where we'd rather not inherit a static
-	 * variable's value from the postmaster.  But since we will, reset it when
-	 * MyProcPid changes.
-	 */
-	if (log_my_pid != MyProcPid)
-	{
-		log_line_number = 0;
-		log_my_pid = MyProcPid;
-		formatted_start_time[0] = '\0';
-	}
-	log_line_number++;
-
-	initStringInfo(&buf);
-
-	/*
-	 * timestamp with milliseconds
-	 *
-	 * Check if the timestamp is already calculated for the syslog message,
-	 * and use it if so.  Otherwise, get the current timestamp.  This is done
-	 * to put same timestamp in both syslog and csvlog messages.
-	 */
-	if (formatted_log_time[0] == '\0')
-		setup_formatted_log_time();
-
-	appendStringInfoString(&buf, formatted_log_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* username */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->user_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* database name */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->database_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* Process id  */
-	if (MyProcPid != 0)
-		appendStringInfo(&buf, "%d", MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Remote host and port */
-	if (MyProcPort && MyProcPort->remote_host)
-	{
-		appendStringInfoChar(&buf, '"');
-		appendStringInfoString(&buf, MyProcPort->remote_host);
-		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
-		{
-			appendStringInfoChar(&buf, ':');
-			appendStringInfoString(&buf, MyProcPort->remote_port);
-		}
-		appendStringInfoChar(&buf, '"');
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session id */
-	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Line number */
-	appendStringInfo(&buf, "%ld", log_line_number);
-	appendStringInfoChar(&buf, ',');
-
-	/* PS display */
-	if (MyProcPort)
-	{
-		StringInfoData msgbuf;
-		const char *psdisp;
-		int			displen;
-
-		initStringInfo(&msgbuf);
-
-		psdisp = get_ps_display(&displen);
-		appendBinaryStringInfo(&msgbuf, psdisp, displen);
-		appendCSVLiteral(&buf, msgbuf.data);
-
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session start timestamp */
-	if (formatted_start_time[0] == '\0')
-		setup_formatted_start_time();
-	appendStringInfoString(&buf, formatted_start_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* Virtual transaction id */
-	/* keep VXID format in sync with lockfuncs.c */
-	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
-		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Transaction id */
-	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
-	appendStringInfoChar(&buf, ',');
-
-	/* Error severity */
-	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
-	appendStringInfoChar(&buf, ',');
-
-	/* SQL state code */
-	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
-	appendStringInfoChar(&buf, ',');
-
-	/* errmessage */
-	appendCSVLiteral(&buf, edata->message);
-	appendStringInfoChar(&buf, ',');
-
-	/* errdetail or errdetail_log */
-	if (edata->detail_log)
-		appendCSVLiteral(&buf, edata->detail_log);
-	else
-		appendCSVLiteral(&buf, edata->detail);
-	appendStringInfoChar(&buf, ',');
-
-	/* errhint */
-	appendCSVLiteral(&buf, edata->hint);
-	appendStringInfoChar(&buf, ',');
-
-	/* internal query */
-	appendCSVLiteral(&buf, edata->internalquery);
-	appendStringInfoChar(&buf, ',');
-
-	/* if printed internal query, print internal pos too */
-	if (edata->internalpos > 0 && edata->internalquery != NULL)
-		appendStringInfo(&buf, "%d", edata->internalpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* errcontext */
-	if (!edata->hide_ctx)
-		appendCSVLiteral(&buf, edata->context);
-	appendStringInfoChar(&buf, ',');
-
-	/* user query --- only reported if not disabled by the caller */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
-		print_stmt = true;
-	if (print_stmt)
-		appendCSVLiteral(&buf, debug_query_string);
-	appendStringInfoChar(&buf, ',');
-	if (print_stmt && edata->cursorpos > 0)
-		appendStringInfo(&buf, "%d", edata->cursorpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* file error location */
-	if (Log_error_verbosity >= PGERROR_VERBOSE)
-	{
-		StringInfoData msgbuf;
-
-		initStringInfo(&msgbuf);
-
-		if (edata->funcname && edata->filename)
-			appendStringInfo(&msgbuf, "%s, %s:%d",
-							 edata->funcname, edata->filename,
-							 edata->lineno);
-		else if (edata->filename)
-			appendStringInfo(&msgbuf, "%s:%d",
-							 edata->filename, edata->lineno);
-		appendCSVLiteral(&buf, msgbuf.data);
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* application name */
-	if (application_name)
-		appendCSVLiteral(&buf, application_name);
-
-	appendStringInfoChar(&buf, ',');
-
-	/* backend type */
-	if (MyProcPid == PostmasterPid)
-		appendCSVLiteral(&buf, "postmaster");
-	else if (MyBackendType == B_BG_WORKER)
-		appendCSVLiteral(&buf, MyBgworkerEntry->bgw_type);
-	else
-		appendCSVLiteral(&buf, GetBackendTypeDesc(MyBackendType));
-
-	appendStringInfoChar(&buf, ',');
-
-	/* leader PID */
-	if (MyProc)
-	{
-		PGPROC	   *leader = MyProc->lockGroupLeader;
-
-		/*
-		 * Show the leader only for active parallel workers.  This leaves out
-		 * the leader of a parallel group.
-		 */
-		if (leader && leader->pid != MyProcPid)
-			appendStringInfo(&buf, "%d", leader->pid);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* query id */
-	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
-
-	appendStringInfoChar(&buf, '\n');
-
-	/* If in the syslogger process, try to write messages direct to file */
-	if (MyBackendType == B_LOGGER)
-		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-	else
-		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-
-	pfree(buf.data);
-}
-
 /*
  * Unpack MAKE_SQLSTATE code. Note that this returns a pointer to a
  * static buffer.
@@ -3273,6 +2982,16 @@ write_pipe_chunks(char *data, int len, int dest)
 	(void) rc;
 }
 
+void
+write_syslogger(char *data, int len, int dest)
+{
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(data, len, dest);
+	else
+		write_pipe_chunks(data, len, dest);
+}
+
 
 /*
  * Append a text string to the error report being built for the client.
@@ -3483,7 +3202,7 @@ send_message_to_frontend(ErrorData *edata)
  * The string is not localized here, but we mark the strings for translation
  * so that callers can invoke _() on the result.
  */
-static const char *
+const char *
 error_severity(int elevel)
 {
 	const char *prefix;
diff --git a/src/include/utils/elog-internal.h b/src/include/utils/elog-internal.h
new file mode 100644
index 0000000000..ac08b6f12f
--- /dev/null
+++ b/src/include/utils/elog-internal.h
@@ -0,0 +1,78 @@
+/*-------------------------------------------------------------------------
+ *
+ * elog-internal.h
+ *	  POSTGRES error reporting/logging internal definitions.
+ *
+ *
+ * Portions Copyright (c) 2021, PostgreSQL Global Development Group
+ * src/include/utils/elog-internal.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef ELOG_INTERNAL_H
+#define ELOG_INTERNAL_H
+
+#include "postgres.h"
+
+#include "utils/elog.h"
+#include "miscadmin.h"
+#include "postmaster/postmaster.h"
+#include "postmaster/bgworker.h"
+
+const char * error_severity(int elevel);
+void write_syslogger(char *data, int len, int dest);
+
+void write_csvlog(ErrorData *edata);
+
+/*
+ * is_log_level_output -- is elevel logically >= log_min_level?
+ *
+ * We use this for tests that should consider LOG to sort out-of-order,
+ * between ERROR and FATAL.  Generally this is the right thing for testing
+ * whether a message should go to the postmaster log, whereas a simple >=
+ * test is correct for testing whether the message should go to the client.
+ */
+static inline bool
+is_log_level_output(int elevel, int log_min_level)
+{
+	if (elevel == LOG || elevel == LOG_SERVER_ONLY)
+	{
+		if (log_min_level == LOG || log_min_level <= ERROR)
+			return true;
+	}
+	else if (elevel == WARNING_CLIENT_ONLY)
+	{
+		/* never sent to log, regardless of log_min_level */
+		return false;
+	}
+	else if (log_min_level == LOG)
+	{
+		/* elevel != LOG */
+		if (elevel >= FATAL)
+			return true;
+	}
+	/* Neither is LOG */
+	else if (elevel >= log_min_level)
+		return true;
+
+	return false;
+}
+
+static inline const char *
+get_backend_type_for_log() {
+	if (MyProcPid == PostmasterPid)
+		return "postmaster";
+	else if (MyBackendType == B_BG_WORKER)
+		return MyBgworkerEntry->bgw_type;
+	else
+		return GetBackendTypeDesc(MyBackendType);
+}
+
+#define FORMATTED_TS_LEN 128
+extern char formatted_start_time[FORMATTED_TS_LEN];
+extern char formatted_log_time[FORMATTED_TS_LEN];
+
+void setup_formatted_log_time(void);
+void setup_formatted_start_time(void);
+
+#endif
-- 
2.17.1

From 1805e8dbdfc3ea2f5460610d90ecc972e59d8e88 Mon Sep 17 00:00:00 2001
From: Sehrope Sarkuni <sehrope@jackdb.com>
Date: Wed, 1 Sep 2021 13:49:27 -0400
Subject: [PATCH 4/4] Add jsonlog log_destination for JSON server logs

Adds option to write server log files as JSON. Each log entry is written as its
own line with any internal newlines escaped as \n. Other non-ASCII and special
characters are also escaped using standard JSON escape sequences.

JSON logging is enabled by setting the GUC log_destination to "jsonlog" and
defaults to a log file with a ".json" extension.
---
 doc/src/sgml/config.sgml           |  67 ++++++-
 src/backend/postmaster/syslogger.c | 177 ++++++++++++++--
 src/backend/utils/adt/misc.c       |   5 +-
 src/backend/utils/error/Makefile   |   3 +-
 src/backend/utils/error/elog.c     |  26 ++-
 src/backend/utils/error/jsonlog.c  | 312 +++++++++++++++++++++++++++++
 src/backend/utils/misc/guc.c       |   2 +
 src/bin/pg_ctl/t/006_jsonlog.pl    |  98 +++++++++
 src/include/utils/elog-internal.h  |   1 +
 src/include/utils/elog.h           |   1 +
 10 files changed, 669 insertions(+), 23 deletions(-)
 create mode 100644 src/backend/utils/error/jsonlog.c
 create mode 100644 src/bin/pg_ctl/t/006_jsonlog.pl

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 2c31c35a6b..fe4bcd61ef 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5926,7 +5926,8 @@ SELECT * FROM parent WHERE key = 2400;
        <para>
         <productname>PostgreSQL</productname> supports several methods
          for logging server messages, including
-         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem> and
+         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem>,
+         <systemitem>jsonlog</systemitem>, and
          <systemitem>syslog</systemitem>. On Windows,
          <systemitem>eventlog</systemitem> is also supported. Set this
          parameter to a list of desired log destinations separated by
@@ -5944,6 +5945,14 @@ SELECT * FROM parent WHERE key = 2400;
         <xref linkend="guc-logging-collector"/> must be enabled to generate
         CSV-format log output.
        </para>
+       <para>
+        If <systemitem>jsonlog</systemitem> is included in <varname>log_destination</varname>,
+        log entries are output in <acronym>JSON</acronym> format, which is convenient for
+        loading logs into programs.
+        See <xref linkend="runtime-config-logging-jsonlog"/> for details.
+        <xref linkend="guc-logging-collector"/> must be enabled to generate
+        CSV-format log output.
+       </para>
        <para>
         When either <systemitem>stderr</systemitem> or
         <systemitem>csvlog</systemitem> are included, the file
@@ -5955,13 +5964,14 @@ SELECT * FROM parent WHERE key = 2400;
 <programlisting>
 stderr log/postgresql.log
 csvlog log/postgresql.csv
+jsonlog log/postgresql.json
 </programlisting>
 
         <filename>current_logfiles</filename> is recreated when a new log file
         is created as an effect of rotation, and
         when <varname>log_destination</varname> is reloaded.  It is removed when
-        neither <systemitem>stderr</systemitem>
-        nor <systemitem>csvlog</systemitem> are included
+        none of <systemitem>stderr</systemitem>,
+        <systemitem>csvlog</systemitem>, <systemitem>jsonlog</systemitem> are included
         in <varname>log_destination</varname>, and when the logging collector is
         disabled.
        </para>
@@ -6101,6 +6111,13 @@ local0.*    /var/log/postgresql
         (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
         replaced instead.)
        </para>
+       <para>
+        If JSON-format output is enabled in <varname>log_destination</varname>,
+        <literal>.json</literal> will be appended to the timestamped
+        log file name to create the file name for JSON-format output.
+        (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
+        replaced instead.)
+       </para>
        <para>
         This parameter can only be set in the <filename>postgresql.conf</filename>
         file or on the server command line.
@@ -7433,6 +7450,50 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         </orderedlist>
       </para>
     </sect2>
+     <sect2 id="runtime-config-logging-jsonlog">
+     <title>Using JSON-Format Log Output</title>
+
+       <para>
+        Including <literal>jsonlog</literal> in the <varname>log_destination</varname> list
+        provides a convenient way to import log files into many different programs.
+        This option emits log lines in (<acronym>JSON</acronym>) format.
+        Each log line is serialized as a JSON object with the following fields:
+<programlisting>
+        {
+            "timestamp": time stamp with milliseconds (string),
+            "user": user name (string),
+            "dbname": database name (string),
+            "pid": process ID (number),
+            "remote_host": client host (string)
+            "remote_port": port number (string),
+            "session_id": session ID (string),
+            "line_num": per-session line number (number),
+            "ps": current ps display (string),
+            "session_start": session start time (string),
+            "vxid": virtual transaction ID (string),
+            "txid": regular transaction ID (string),
+            "error_severity": error severity (string),
+            "state_code": SQLSTATE code (string),
+            "detail": error message detail (string),
+            "hint": hint (string),
+            "internal_query": internal query that led to the error (string),
+            "internal_position": cursor index into internal query (number),
+            "context": error context (string),
+            "statement": client supplied query string (string),
+            "cursor_position": cursor index into query string (string),
+            "func_name": error location function name (string),
+            "file_name": error location file name (string),
+            "file_line_num": error location file line number (number),
+            "application_name": client application name (string),
+            "message": error message (string)
+        }
+</programlisting>
+        String fields with null values are excluded from output.
+        Additional fields may be added in the future. User applications that process jsonlog
+        output should ignore unknown fields.
+       </para>
+
+    </sect2>
 
    <sect2>
     <title>Process Title</title>
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index edd8f33204..c8f6ef56fc 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -85,9 +85,11 @@ static bool pipe_eof_seen = false;
 static bool rotation_disabled = false;
 static FILE *syslogFile = NULL;
 static FILE *csvlogFile = NULL;
+static FILE *jsonlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
 static char *last_file_name = NULL;
 static char *last_csv_file_name = NULL;
+static char *last_json_file_name = NULL;
 
 /*
  * Buffers for saving partial messages from different backends.
@@ -274,6 +276,8 @@ SysLoggerMain(int argc, char *argv[])
 	last_file_name = logfile_getname(first_syslogger_file_time, NULL);
 	if (csvlogFile != NULL)
 		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
+	if (jsonlogFile != NULL)
+		last_json_file_name = logfile_getname(first_syslogger_file_time, ".json");
 
 	/* remember active logfile parameters */
 	currentLogDir = pstrdup(Log_directory);
@@ -360,6 +364,14 @@ SysLoggerMain(int argc, char *argv[])
 				(csvlogFile != NULL))
 				rotation_requested = true;
 
+			/*
+			 * Force a rotation if JSONLOG output was just turned on or off and
+			 * we need to open or close jsonlogFile accordingly.
+			 */
+			if (((Log_destination & LOG_DESTINATION_JSONLOG) != 0) !=
+				(jsonlogFile != NULL))
+				rotation_requested = true;
+
 			/*
 			 * If rotation time parameter changed, reset next rotation time,
 			 * but don't immediately force a rotation.
@@ -410,6 +422,12 @@ SysLoggerMain(int argc, char *argv[])
 				rotation_requested = true;
 				size_rotation_for |= LOG_DESTINATION_CSVLOG;
 			}
+			if (jsonlogFile != NULL &&
+				ftell(jsonlogFile) >= Log_RotationSize * 1024L)
+			{
+				rotation_requested = true;
+				size_rotation_for |= LOG_DESTINATION_JSONLOG;
+			}
 		}
 
 		if (rotation_requested)
@@ -419,7 +437,7 @@ SysLoggerMain(int argc, char *argv[])
 			 * was sent by pg_rotate_logfile() or "pg_ctl logrotate".
 			 */
 			if (!time_based_rotation && size_rotation_for == 0)
-				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG;
+				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG | LOG_DESTINATION_JSONLOG;
 			logfile_rotate(time_based_rotation, size_rotation_for);
 		}
 
@@ -625,6 +643,20 @@ SysLogger_Start(void)
 		pfree(filename);
 	}
 
+	/*
+	 * Likewise for the initial JSON log file, if that's enabled.  (Note that
+	 * we open syslogFile even when only JSON output is nominally enabled,
+	 * since some code paths will write to syslogFile anyway.)
+	 */
+	if (Log_destination & LOG_DESTINATION_JSONLOG)
+	{
+		filename = logfile_getname(first_syslogger_file_time, ".json");
+
+		jsonlogFile = logfile_open(filename, "a", false);
+
+		pfree(filename);
+	}
+
 #ifdef EXEC_BACKEND
 	switch ((sysloggerPid = syslogger_forkexec()))
 #else
@@ -722,6 +754,11 @@ SysLogger_Start(void)
 				fclose(csvlogFile);
 				csvlogFile = NULL;
 			}
+			if (jsonlogFile != NULL)
+			{
+				fclose(jsonlogFile);
+				jsonlogFile = NULL;
+			}
 			return (int) sysloggerPid;
 	}
 
@@ -744,6 +781,7 @@ syslogger_forkexec(void)
 	int			ac = 0;
 	char		filenobuf[32];
 	char		csvfilenobuf[32];
+	char		jsonfilenobuf[32];
 
 	av[ac++] = "postgres";
 	av[ac++] = "--forklog";
@@ -771,14 +809,25 @@ syslogger_forkexec(void)
 				 fileno(csvlogFile));
 	else
 		strcpy(csvfilenobuf, "-1");
+	if (jsonlogFile != NULL)
+		snprintf(jsonfilenobuf, sizeof(jsonfilenobuf), "%d",
+				 fileno(jsonlogFile));
+	else
+		strcpy(jsonfilenobuf, "-1");
 #else							/* WIN32 */
 	if (csvlogFile != NULL)
 		snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld",
 				 (long) _get_osfhandle(_fileno(csvlogFile)));
 	else
 		strcpy(csvfilenobuf, "0");
+	if (jsonlogFile != NULL)
+		snprintf(jsonfilenobuf, sizeof(jsonfilenobuf), "%ld",
+				 (long) _get_osfhandle(_fileno(jsonlogFile)));
+	else
+		strcpy(jsonfilenobuf, "0");
 #endif							/* WIN32 */
 	av[ac++] = csvfilenobuf;
+	av[ac++] = jsonfilenobuf;
 
 	av[ac] = NULL;
 	Assert(ac < lengthof(av));
@@ -796,8 +845,8 @@ syslogger_parseArgs(int argc, char *argv[])
 {
 	int			fd;
 
-	Assert(argc == 5);
-	argv += 3;
+	Assert(argc == 6);
+	argv += 4;
 
 	/*
 	 * Re-open the error output files that were opened by SysLogger_Start().
@@ -819,6 +868,12 @@ syslogger_parseArgs(int argc, char *argv[])
 		csvlogFile = fdopen(fd, "a");
 		setvbuf(csvlogFile, NULL, PG_IOLBF, 0);
 	}
+	fd = atoi(*argv++);
+	if (fd != -1)
+	{
+		jsonlogFile = fdopen(fd, "a");
+		setvbuf(jsonlogFile, NULL, PG_IOLBF, 0);
+	}
 #else							/* WIN32 */
 	fd = atoi(*argv++);
 	if (fd != 0)
@@ -840,6 +895,16 @@ syslogger_parseArgs(int argc, char *argv[])
 			setvbuf(csvlogFile, NULL, PG_IOLBF, 0);
 		}
 	}
+	fd = atoi(*argv++);
+	if (fd != 0)
+	{
+		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
+		if (fd > 0)
+		{
+			jsonlogFile = fdopen(fd, "a");
+			setvbuf(jsonlogFile, NULL, PG_IOLBF, 0);
+		}
+	}
 #endif							/* WIN32 */
 }
 #endif							/* EXEC_BACKEND */
@@ -892,6 +957,7 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 			p.pid != 0 &&
 			(p.is_last == 't' || p.is_last == 'f') &&
 			(p.dest == LOG_DESTINATION_CSVLOG ||
+			 p.dest == LOG_DESTINATION_JSONLOG ||
 			 p.dest == LOG_DESTINATION_STDERR))
 		{
 			List	   *buffer_list;
@@ -1079,19 +1145,23 @@ write_syslogger_file(const char *buffer, int count, int destination)
 	FILE	   *logfile;
 
 	/*
-	 * If we're told to write to csvlogFile, but it's not open, dump the data
-	 * to syslogFile (which is always open) instead.  This can happen if CSV
+	 * If we're told to write to a structured log file, but it's not open, dump the data
+	 * to syslogFile (which is always open) instead.  This can happen if structured
 	 * output is enabled after postmaster start and we've been unable to open
-	 * csvlogFile.  There are also race conditions during a parameter change
-	 * whereby backends might send us CSV output before we open csvlogFile or
-	 * after we close it.  Writing CSV-formatted output to the regular log
+	 * logFile.  There are also race conditions during a parameter change
+	 * whereby backends might send us structured output before we open the logFile or
+	 * after we close it.  Writing formatted output to the regular log
 	 * file isn't great, but it beats dropping log output on the floor.
 	 *
-	 * Think not to improve this by trying to open csvlogFile on-the-fly.  Any
+	 * Think not to improve this by trying to open logFile on-the-fly.  Any
 	 * failure in that would lead to recursion.
 	 */
-	logfile = (destination == LOG_DESTINATION_CSVLOG &&
-			   csvlogFile != NULL) ? csvlogFile : syslogFile;
+	if ((destination & LOG_DESTINATION_CSVLOG) && csvlogFile != NULL)
+		logfile = csvlogFile;
+	else if ((destination & LOG_DESTINATION_JSONLOG) && jsonlogFile != NULL)
+		logfile = jsonlogFile;
+	else
+		logfile = syslogFile;
 
 	rc = fwrite(buffer, 1, count, logfile);
 
@@ -1162,7 +1232,8 @@ pipeThread(void *arg)
 		if (Log_RotationSize > 0)
 		{
 			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
-				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
+				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L) ||
+				(jsonlogFile != NULL && ftell(jsonlogFile) >= Log_RotationSize * 1024L))
 				SetLatch(MyLatch);
 		}
 		LeaveCriticalSection(&sysloggerSection);
@@ -1235,6 +1306,7 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 {
 	char	   *filename;
 	char	   *csvfilename = NULL;
+	char	   *jsonfilename = NULL;
 	pg_time_t	fntime;
 	FILE	   *fh;
 
@@ -1252,6 +1324,9 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 	filename = logfile_getname(fntime, NULL);
 	if (Log_destination & LOG_DESTINATION_CSVLOG)
 		csvfilename = logfile_getname(fntime, ".csv");
+	if (Log_destination & LOG_DESTINATION_JSONLOG)
+		jsonfilename = logfile_getname(fntime, ".json");
+
 
 	/*
 	 * Decide whether to overwrite or append.  We can overwrite if (a)
@@ -1289,6 +1364,8 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 				pfree(filename);
 			if (csvfilename)
 				pfree(csvfilename);
+			if (jsonfilename)
+				pfree(jsonfilename);
 			return;
 		}
 
@@ -1303,10 +1380,10 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 	}
 
 	/*
-	 * Same as above, but for csv file.  Note that if LOG_DESTINATION_CSVLOG
-	 * was just turned on, we might have to open csvlogFile here though it was
+	 * Same as above, but for a structured file.  Note that if LOG_DESTINATION_[STRUCTURED]LOG
+	 * was just turned on, we might have to open logFile here though it was
 	 * not open before.  In such a case we'll append not overwrite (since
-	 * last_csv_file_name will be NULL); that is consistent with the normal
+	 * last_*_file_name will be NULL); that is consistent with the normal
 	 * rules since it's not a time-based rotation.
 	 */
 	if ((Log_destination & LOG_DESTINATION_CSVLOG) &&
@@ -1362,11 +1439,66 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 			pfree(last_csv_file_name);
 		last_csv_file_name = NULL;
 	}
+	else if ((Log_destination & LOG_DESTINATION_JSONLOG) &&
+		(jsonlogFile == NULL ||
+		 time_based_rotation || (size_rotation_for & LOG_DESTINATION_JSONLOG)))
+	{
+		if (Log_truncate_on_rotation && time_based_rotation &&
+			last_json_file_name != NULL &&
+			strcmp(jsonfilename, last_json_file_name) != 0)
+			fh = logfile_open(jsonfilename, "w", true);
+		else
+			fh = logfile_open(jsonfilename, "a", true);
+
+		if (!fh)
+		{
+			/*
+			 * ENFILE/EMFILE are not too surprising on a busy system; just
+			 * keep using the old file till we manage to get a new one.
+			 * Otherwise, assume something's wrong with Log_directory and stop
+			 * trying to create files.
+			 */
+			if (errno != ENFILE && errno != EMFILE)
+			{
+				ereport(LOG,
+						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
+				rotation_disabled = true;
+			}
+
+			if (filename)
+				pfree(filename);
+			if (jsonfilename)
+				pfree(jsonfilename);
+			return;
+		}
+
+		if (jsonlogFile != NULL)
+			fclose(jsonlogFile);
+		jsonlogFile = fh;
+
+		/* instead of pfree'ing filename, remember it for next time */
+		if (last_json_file_name != NULL)
+			pfree(last_json_file_name);
+		last_json_file_name = jsonfilename;
+		jsonfilename = NULL;
+	}
+	else if (!(Log_destination & LOG_DESTINATION_JSONLOG) &&
+			 jsonlogFile != NULL)
+	{
+		/* JSONLOG was just turned off, so close the old file */
+		fclose(jsonlogFile);
+		jsonlogFile = NULL;
+		if (last_json_file_name != NULL)
+			pfree(last_json_file_name);
+		last_json_file_name = NULL;
+	}
 
 	if (filename)
 		pfree(filename);
 	if (csvfilename)
 		pfree(csvfilename);
+	if (jsonfilename)
+		pfree(jsonfilename);
 
 	update_metainfo_datafile();
 
@@ -1454,7 +1586,8 @@ update_metainfo_datafile(void)
 	mode_t		oumask;
 
 	if (!(Log_destination & LOG_DESTINATION_STDERR) &&
-		!(Log_destination & LOG_DESTINATION_CSVLOG))
+		!(Log_destination & LOG_DESTINATION_CSVLOG) &&
+		!(Log_destination & LOG_DESTINATION_JSONLOG))
 	{
 		if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
 			ereport(LOG,
@@ -1512,6 +1645,18 @@ update_metainfo_datafile(void)
 			return;
 		}
 	}
+	if (last_json_file_name && (Log_destination & LOG_DESTINATION_JSONLOG))
+	{
+		if (fprintf(fh, "jsonlog %s\n", last_json_file_name) < 0)
+		{
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not write file \"%s\": %m",
+							LOG_METAINFO_DATAFILE_TMP)));
+			fclose(fh);
+			return;
+		}
+	}
 	fclose(fh);
 
 	if (rename(LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE) != 0)
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 88faf4dfd7..4931859627 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -843,11 +843,12 @@ pg_current_logfile(PG_FUNCTION_ARGS)
 	{
 		logfmt = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
-		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0)
+		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0 &&
+				strcmp(logfmt, "jsonlog") != 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("log format \"%s\" is not supported", logfmt),
-					 errhint("The supported log formats are \"stderr\" and \"csvlog\".")));
+					 errhint("The supported log formats are \"stderr\", \"csvlog\", and \"jsonlog\".")));
 	}
 
 	fd = AllocateFile(LOG_METAINFO_DATAFILE, "r");
diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index ef770dd2f2..65ba61fb3c 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -15,6 +15,7 @@ include $(top_builddir)/src/Makefile.global
 OBJS = \
 	assert.o \
 	csvlog.o \
-	elog.o
+	elog.o \
+	jsonlog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 47d6677827..c259616a76 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2922,6 +2922,30 @@ send_message_to_server_log(ErrorData *edata)
 			pfree(buf.data);
 		}
 	}
+	/* Write to JSON log if enabled */
+	else if (Log_destination & LOG_DESTINATION_JSONLOG)
+	{
+		if (redirection_done || MyBackendType == B_LOGGER)
+		{
+			/*
+			 * send JSON data if it's safe to do so (syslogger doesn't need the
+			 * pipe). First get back the space in the message buffer.
+			 */
+			pfree(buf.data);
+			write_jsonlog(edata);
+		}
+		else
+		{
+			/*
+			 * syslogger not up (yet), so just dump the message to stderr,
+			 * unless we already did so above.
+			 */
+			if (!(Log_destination & LOG_DESTINATION_STDERR) &&
+				whereToSendOutput != DestDebug)
+				write_console(buf.data, buf.len);
+			pfree(buf.data);
+		}
+	}
 	else
 	{
 		pfree(buf.data);
@@ -2965,7 +2989,7 @@ write_pipe_chunks(char *data, int len, int dest)
 	/* write all but the last chunk */
 	while (len > PIPE_MAX_PAYLOAD)
 	{
-		p.proto.is_last = (dest == LOG_DESTINATION_CSVLOG ? 'F' : 'f');
+		p.proto.is_last = ((dest == LOG_DESTINATION_CSVLOG || dest == LOG_DESTINATION_JSONLOG) ? 'F' : 'f');
 		p.proto.len = PIPE_MAX_PAYLOAD;
 		memcpy(p.proto.data, data, PIPE_MAX_PAYLOAD);
 		rc = write(fd, &p, PIPE_HEADER_SIZE + PIPE_MAX_PAYLOAD);
diff --git a/src/backend/utils/error/jsonlog.c b/src/backend/utils/error/jsonlog.c
new file mode 100644
index 0000000000..2777124977
--- /dev/null
+++ b/src/backend/utils/error/jsonlog.c
@@ -0,0 +1,312 @@
+/*-------------------------------------------------------------------------
+ *
+ * jsonlog.c
+ *	  JSON logging
+ *
+ * Copyright (c) 2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/jsonlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog-internal.h"
+#include "utils/guc.h"
+#include "utils/json.h"
+#include "utils/ps_status.h"
+
+/*
+ * appendJSONKeyValue
+ * Append to given StringInfo a comma followed by a JSON key and value.
+ * Both the key and value will be escaped as JSON string literals.
+ */
+static void
+appendJSONKeyValue(StringInfo buf, const char *key, const char *value)
+{
+	if (value == NULL)
+		return;
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	escape_json(buf, value);
+}
+
+/*
+ * appendJSONKeyValueFmt
+ * Evaluate the fmt string and then invoke appendJSONKeyValue as the
+ * value of the JSON property. Both the key and value will be escaped by
+ * appendJSONKeyValue.
+ */
+static void
+appendJSONKeyValueFmt(StringInfo buf, const char *key, const char *fmt,...)
+{
+	int			save_errno = errno;
+	size_t		len = 128;		/* initial assumption about buffer size */
+	char	    *value;
+
+	for (;;)
+	{
+		va_list		args;
+		size_t		newlen;
+
+		/*
+		 * Allocate result buffer.  Note that in frontend this maps to malloc
+		 * with exit-on-error.
+		 */
+		value = (char *) palloc(len);
+
+		/* Try to format the data. */
+		errno = save_errno;
+		va_start(args, fmt);
+		newlen = pvsnprintf(value, len, fmt, args);
+		va_end(args);
+
+		if (newlen < len)
+			break; /* success */
+
+		/* Release buffer and loop around to try again with larger len. */
+		pfree(value);
+		len = newlen;
+	}
+	appendJSONKeyValue(buf, key, value);
+	/* Clean up */
+	pfree(value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as a signed integer (a JSON number).
+ */
+static void
+appendJSONKeyValueAsInt(StringInfo buf, const char *key, int value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%d", value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as an unsigned integer (a JSON number).
+ */
+static void
+appendJSONKeyValueAsUInt(StringInfo buf, const char *key, int value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%u", value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as a long (a JSON number).
+ */
+static void
+appendJSONKeyValueAsLong(StringInfo buf, const char *key, long value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%ld", value);
+}
+
+/*
+ * Write logs in json format.
+ */
+void
+write_jsonlog(ErrorData *edata)
+{
+	StringInfoData	buf;
+
+	/* static counter for line numbers */
+	static long	log_line_number = 0;
+
+	/* Has the counter been reset in the current process? */
+	static int	log_my_pid = 0;
+
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		formatted_start_time[0] = '\0';
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* Initialize string */
+	appendStringInfoChar(&buf, '{');
+
+	/*
+	 * timestamp with milliseconds
+	 *
+	 * Check if the timestamp is already calculated for the syslog message,
+	 * and use it if so.  Otherwise, get the current timestamp.  This is done
+	 * to put same timestamp in both syslog and jsonlog messages.
+	 */
+	if (formatted_log_time[0] == '\0')
+		setup_formatted_log_time();
+
+	/* First property does not use appendJSONKeyValue as it does not have comma prefix */
+	escape_json(&buf, "timestamp");
+	appendStringInfoChar(&buf, ':');
+	escape_json(&buf, formatted_log_time);
+
+	/* username */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "user", MyProcPort->user_name);
+
+	/* database name */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "dbname", MyProcPort->database_name);
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendJSONKeyValueAsInt(&buf, "leader_pid", leader->pid);
+	}
+
+	/* Process ID */
+	if (MyProcPid != 0)
+		appendJSONKeyValueAsInt(&buf, "pid", MyProcPid);
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendJSONKeyValue(&buf, "remote_host", MyProcPort->remote_host);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+			appendJSONKeyValue(&buf, "remote_port", MyProcPort->remote_port);
+	}
+
+	/* Session id */
+	appendJSONKeyValueFmt(&buf, "session_id", "%lx.%x", (long) MyStartTime, MyProcPid);
+
+	/* Line number */
+	appendJSONKeyValueAsLong(&buf, "line_num", log_line_number);
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData	msgbuf;
+		const char	   *psdisp;
+		int				displen;
+
+		initStringInfo(&msgbuf);
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendJSONKeyValue(&buf, "ps", msgbuf.data);
+
+		pfree(msgbuf.data);
+	}
+
+	/* session start timestamp */
+	if (formatted_start_time[0] == '\0')
+		setup_formatted_start_time();
+	appendJSONKeyValue(&buf, "session_start", formatted_start_time);
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendJSONKeyValueFmt(&buf, "vxid", "%d/%u", MyProc->backendId, MyProc->lxid);
+
+	/* Transaction id */
+	appendJSONKeyValueFmt(&buf, "txid", "%u", GetTopTransactionIdIfAny());
+
+	/* Error severity */
+	if (edata->elevel)
+		appendJSONKeyValue(&buf, "error_severity", (char *) error_severity(edata->elevel));
+
+	/* query id */
+	appendJSONKeyValueFmt(&buf,  "query_id", "%lld", (long long) pgstat_get_my_query_id());
+
+	/* SQL state code */
+	if (edata->sqlerrcode)
+		appendJSONKeyValue(&buf, "state_code", unpack_sql_state(edata->sqlerrcode));
+
+	/* errdetail or error_detail log */
+	if (edata->detail_log)
+		appendJSONKeyValue(&buf, "detail", edata->detail_log);
+	else if (edata->detail)
+		appendJSONKeyValue(&buf, "detail", edata->detail);
+
+	/* errhint */
+	if (edata->hint)
+		appendJSONKeyValue(&buf, "hint", edata->hint);
+
+	/* Internal query */
+	if (edata->internalquery)
+		appendJSONKeyValue(&buf, "internal_query", edata->internalquery);
+
+	/* If the internal query got printed, print internal pos, too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendJSONKeyValueAsUInt(&buf, "internal_position", edata->internalpos);
+
+	/* errcontext */
+	if (edata->context && !edata->hide_ctx)
+		appendJSONKeyValue(&buf, "context", edata->context);
+
+	/* user query --- only reported if not disabled by the caller */
+	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
+		debug_query_string != NULL &&
+		!edata->hide_stmt)
+	{
+		appendJSONKeyValue(&buf, "statement", debug_query_string);
+		if (edata->cursorpos > 0)
+			appendJSONKeyValueAsInt(&buf, "cursor_position", edata->cursorpos);
+	}
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		if (edata->funcname)
+			appendJSONKeyValue(&buf, "func_name", edata->funcname);
+		if (edata->filename)
+		{
+			appendJSONKeyValue(&buf, "file_name", edata->filename);
+			appendJSONKeyValueAsInt(&buf, "file_line_num", edata->lineno);
+		}
+	}
+
+	/* Application name */
+	if (application_name && application_name[0] != '\0')
+		appendJSONKeyValue(&buf, "application_name", application_name);
+
+	/* backend type */
+	appendJSONKeyValue(&buf, "backend_type", get_backend_type_for_log());
+
+	/* Error message */
+	appendJSONKeyValue(&buf, "message", edata->message);
+
+	/* Finish string */
+	appendStringInfoChar(&buf, '}');
+	appendStringInfoChar(&buf, '\n');
+
+	write_syslogger(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 467b0fd6fe..ea4fa0c5c1 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -11691,6 +11691,8 @@ check_log_destination(char **newval, void **extra, GucSource source)
 			newlogdest |= LOG_DESTINATION_STDERR;
 		else if (pg_strcasecmp(tok, "csvlog") == 0)
 			newlogdest |= LOG_DESTINATION_CSVLOG;
+		else if (pg_strcasecmp(tok, "jsonlog") == 0)
+			newlogdest |= LOG_DESTINATION_JSONLOG;
 #ifdef HAVE_SYSLOG
 		else if (pg_strcasecmp(tok, "syslog") == 0)
 			newlogdest |= LOG_DESTINATION_SYSLOG;
diff --git a/src/bin/pg_ctl/t/006_jsonlog.pl b/src/bin/pg_ctl/t/006_jsonlog.pl
new file mode 100644
index 0000000000..e6b9979fd7
--- /dev/null
+++ b/src/bin/pg_ctl/t/006_jsonlog.pl
@@ -0,0 +1,98 @@
+use strict;
+use warnings;
+
+use PostgresNode;
+use TestLib;
+use Test::More tests => 4;
+use Time::HiRes qw(usleep);
+
+# Set up node with logging collector
+my $node = PostgresNode->new('primary');
+$node->init();
+$node->append_conf(
+	'postgresql.conf', qq(
+logging_collector = on
+lc_messages = 'C'
+log_destination = 'jsonlog'
+));
+
+
+$node->start();
+
+# Verify that log output gets to the file
+
+$node->psql('postgres', 'SELECT 1/0');
+
+my $current_logfiles = slurp_file($node->data_dir . '/current_logfiles');
+
+note "current_logfiles = $current_logfiles";
+
+like(
+	$current_logfiles,
+	qr|^jsonlog log/postgresql-.*json$|,
+	'current_logfiles is sane');
+
+my $lfname = $current_logfiles;
+$lfname =~ s/^jsonlog //;
+chomp $lfname;
+
+# might need to retry if logging collector process is slow...
+my $max_attempts = 100;
+
+my $first_logfile;
+for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
+{
+	$first_logfile = slurp_file($node->data_dir . '/' . $lfname);
+	last if $first_logfile =~ m/division by zero/;
+	usleep(100_000);
+}
+
+like(
+	$first_logfile,
+	qr/"statement":"SELECT 1\/0",.*"message":"division by zero/,
+	'found expected log file content');
+
+# Sleep 2 seconds and ask for log rotation; this should result in
+# output into a different log file name.
+sleep(2);
+$node->logrotate();
+
+# pg_ctl logrotate doesn't wait for rotation request to be completed.
+# Allow a bit of time for it to happen.
+my $new_current_logfiles;
+for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
+{
+	$new_current_logfiles = slurp_file($node->data_dir . '/current_logfiles');
+	last if $new_current_logfiles ne $current_logfiles;
+	usleep(100_000);
+}
+
+note "now current_logfiles = $new_current_logfiles";
+
+like(
+	$new_current_logfiles,
+	qr|^jsonlog log/postgresql-.*json$|,
+	'new current_logfiles is sane');
+
+$lfname = $new_current_logfiles;
+$lfname =~ s/^jsonlog //;
+chomp $lfname;
+
+# Verify that log output gets to this file, too
+
+$node->psql('postgres', 'fee fi fo fum');
+
+my $second_logfile;
+for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
+{
+	$second_logfile = slurp_file($node->data_dir . '/' . $lfname);
+	last if $second_logfile =~ m/syntax error/;
+	usleep(100_000);
+}
+
+like(
+	$second_logfile,
+	qr/"statement":"fee fi fo fum",.*"message":"syntax error/,
+	'found expected log file content in new log file');
+
+$node->stop();
diff --git a/src/include/utils/elog-internal.h b/src/include/utils/elog-internal.h
index ac08b6f12f..13c217a29d 100644
--- a/src/include/utils/elog-internal.h
+++ b/src/include/utils/elog-internal.h
@@ -23,6 +23,7 @@ const char * error_severity(int elevel);
 void write_syslogger(char *data, int len, int dest);
 
 void write_csvlog(ErrorData *edata);
+void write_jsonlog(ErrorData *edata);
 
 /*
  * is_log_level_output -- is elevel logically >= log_min_level?
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index f53607e12e..c0c699f485 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -436,6 +436,7 @@ extern bool syslog_split_messages;
 #define LOG_DESTINATION_SYSLOG	 2
 #define LOG_DESTINATION_EVENTLOG 4
 #define LOG_DESTINATION_CSVLOG	 8
+#define LOG_DESTINATION_JSONLOG	16
 
 /* Other exported functions */
 extern void DebugFileOpen(void);
-- 
2.17.1

diff --git a/src/include/postmaster/syslogger.h b/src/include/postmaster/syslogger.h
index 1491eecb0f..c79dfbeba2 100644
--- a/src/include/postmaster/syslogger.h
+++ b/src/include/postmaster/syslogger.h
@@ -46,8 +46,7 @@ typedef struct
 	char		nuls[2];		/* always \0\0 */
 	uint16		len;			/* size of this chunk (counts data only) */
 	int32		pid;			/* writer's pid */
-	char		is_last;		/* last chunk of message? 't' or 'f' ('T' or
-								 * 'F' for CSV case) */
+	bits8		flags;			/* bitmask of PIPE_PROTO_* */
 	char		data[FLEXIBLE_ARRAY_MEMBER];	/* data payload starts here */
 } PipeProtoHeader;
 
@@ -60,6 +59,11 @@ typedef union
 #define PIPE_HEADER_SIZE  offsetof(PipeProtoHeader, data)
 #define PIPE_MAX_PAYLOAD  ((int) (PIPE_CHUNK_SIZE - PIPE_HEADER_SIZE))
 
+/* flag bits for PipeProtoHeader->flags */
+#define PIPE_PROTO_IS_LAST	0x01	/* last chunk of message? */
+/* log destinations */
+#define PIPE_PROTO_DEST_STDERR	0x10
+#define PIPE_PROTO_DEST_CSVLOG	0x20
 
 /* GUC options */
 extern bool Logging_collector;
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index cad43bdef2..c00b2dc186 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -891,8 +891,7 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&
-			(p.is_last == 't' || p.is_last == 'f' ||
-			 p.is_last == 'T' || p.is_last == 'F'))
+			(p.flags & (PIPE_PROTO_DEST_STDERR | PIPE_PROTO_DEST_CSVLOG)) != 0)
 		{
 			List	   *buffer_list;
 			ListCell   *cell;
@@ -906,8 +905,15 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 			if (count < chunklen)
 				break;
 
-			dest = (p.is_last == 'T' || p.is_last == 'F') ?
-				LOG_DESTINATION_CSVLOG : LOG_DESTINATION_STDERR;
+			if ((p.flags & PIPE_PROTO_DEST_STDERR) != 0)
+				dest = LOG_DESTINATION_STDERR;
+			else if ((p.flags & PIPE_PROTO_DEST_CSVLOG) != 0)
+				dest = LOG_DESTINATION_CSVLOG;
+			else
+			{
+				/* this should never happen as of the header validation */
+				Assert(false);
+			}
 
 			/* Locate any existing buffer for this source pid */
 			buffer_list = buffer_lists[p.pid % NBUFFER_LISTS];
@@ -924,7 +930,7 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 					free_slot = buf;
 			}
 
-			if (p.is_last == 'f' || p.is_last == 'F')
+			if ((p.flags & PIPE_PROTO_IS_LAST) == 0)
 			{
 				/*
 				 * Save a complete non-final chunk in a per-pid buffer
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 816b071afa..2af87ee3bd 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -3250,11 +3250,16 @@ write_pipe_chunks(char *data, int len, int dest)
 
 	p.proto.nuls[0] = p.proto.nuls[1] = '\0';
 	p.proto.pid = MyProcPid;
+	p.proto.flags = 0;
+	if (dest == LOG_DESTINATION_STDERR)
+		p.proto.flags |= PIPE_PROTO_DEST_STDERR;
+	else if (dest == LOG_DESTINATION_CSVLOG)
+		p.proto.flags |= PIPE_PROTO_DEST_CSVLOG;
 
 	/* write all but the last chunk */
 	while (len > PIPE_MAX_PAYLOAD)
 	{
-		p.proto.is_last = (dest == LOG_DESTINATION_CSVLOG ? 'F' : 'f');
+		/* no need to set PIPE_PROTO_IS_LAST yet */
 		p.proto.len = PIPE_MAX_PAYLOAD;
 		memcpy(p.proto.data, data, PIPE_MAX_PAYLOAD);
 		rc = write(fd, &p, PIPE_HEADER_SIZE + PIPE_MAX_PAYLOAD);
@@ -3264,7 +3269,7 @@ write_pipe_chunks(char *data, int len, int dest)
 	}
 
 	/* write the last chunk */
-	p.proto.is_last = (dest == LOG_DESTINATION_CSVLOG ? 'T' : 't');
+	p.proto.flags |= PIPE_PROTO_IS_LAST;
 	p.proto.len = len;
 	memcpy(p.proto.data, data, len);
 	rc = write(fd, &p, PIPE_HEADER_SIZE + len);

diff --git a/src/include/postmaster/syslogger.h b/src/include/postmaster/syslogger.h
index 1491eecb0f..c79dfbeba2 100644
--- a/src/include/postmaster/syslogger.h
+++ b/src/include/postmaster/syslogger.h
@@ -46,8 +46,7 @@ typedef struct
 	char		nuls[2];		/* always \0\0 */
 	uint16		len;			/* size of this chunk (counts data only) */
 	int32		pid;			/* writer's pid */
-	char		is_last;		/* last chunk of message? 't' or 'f' ('T' or
-								 * 'F' for CSV case) */
+	bits8		flags;			/* bitmask of PIPE_PROTO_* */
 	char		data[FLEXIBLE_ARRAY_MEMBER];	/* data payload starts here */
 } PipeProtoHeader;
 
@@ -60,6 +59,11 @@ typedef union
 #define PIPE_HEADER_SIZE  offsetof(PipeProtoHeader, data)
 #define PIPE_MAX_PAYLOAD  ((int) (PIPE_CHUNK_SIZE - PIPE_HEADER_SIZE))
 
+/* flag bits for PipeProtoHeader->flags */
+#define PIPE_PROTO_IS_LAST	0x01	/* last chunk of message? */
+/* log destinations */
+#define PIPE_PROTO_DEST_STDERR	0x10
+#define PIPE_PROTO_DEST_CSVLOG	0x20
 
 /* GUC options */
 extern bool Logging_collector;
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index cad43bdef2..bca3883572 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -38,6 +38,7 @@
 #include "nodes/pg_list.h"
 #include "pgstat.h"
 #include "pgtime.h"
+#include "port/pg_bitutils.h"
 #include "postmaster/fork_process.h"
 #include "postmaster/interrupt.h"
 #include "postmaster/postmaster.h"
@@ -885,14 +886,15 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 	{
 		PipeProtoHeader p;
 		int			chunklen;
+		bits8		dest_flags;
 
 		/* Do we have a valid header? */
 		memcpy(&p, cursor, offsetof(PipeProtoHeader, data));
+		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR | PIPE_PROTO_DEST_CSVLOG);
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&
-			(p.is_last == 't' || p.is_last == 'f' ||
-			 p.is_last == 'T' || p.is_last == 'F'))
+			pg_popcount((char *) &dest_flags, 1) == 1)
 		{
 			List	   *buffer_list;
 			ListCell   *cell;
@@ -906,8 +908,15 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 			if (count < chunklen)
 				break;
 
-			dest = (p.is_last == 'T' || p.is_last == 'F') ?
-				LOG_DESTINATION_CSVLOG : LOG_DESTINATION_STDERR;
+			if ((p.flags & PIPE_PROTO_DEST_STDERR) != 0)
+				dest = LOG_DESTINATION_STDERR;
+			else if ((p.flags & PIPE_PROTO_DEST_CSVLOG) != 0)
+				dest = LOG_DESTINATION_CSVLOG;
+			else
+			{
+				/* this should never happen as of the header validation */
+				Assert(false);
+			}
 
 			/* Locate any existing buffer for this source pid */
 			buffer_list = buffer_lists[p.pid % NBUFFER_LISTS];
@@ -924,7 +933,7 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 					free_slot = buf;
 			}
 
-			if (p.is_last == 'f' || p.is_last == 'F')
+			if ((p.flags & PIPE_PROTO_IS_LAST) == 0)
 			{
 				/*
 				 * Save a complete non-final chunk in a per-pid buffer
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 816b071afa..2af87ee3bd 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -3250,11 +3250,16 @@ write_pipe_chunks(char *data, int len, int dest)
 
 	p.proto.nuls[0] = p.proto.nuls[1] = '\0';
 	p.proto.pid = MyProcPid;
+	p.proto.flags = 0;
+	if (dest == LOG_DESTINATION_STDERR)
+		p.proto.flags |= PIPE_PROTO_DEST_STDERR;
+	else if (dest == LOG_DESTINATION_CSVLOG)
+		p.proto.flags |= PIPE_PROTO_DEST_CSVLOG;
 
 	/* write all but the last chunk */
 	while (len > PIPE_MAX_PAYLOAD)
 	{
-		p.proto.is_last = (dest == LOG_DESTINATION_CSVLOG ? 'F' : 'f');
+		/* no need to set PIPE_PROTO_IS_LAST yet */
 		p.proto.len = PIPE_MAX_PAYLOAD;
 		memcpy(p.proto.data, data, PIPE_MAX_PAYLOAD);
 		rc = write(fd, &p, PIPE_HEADER_SIZE + PIPE_MAX_PAYLOAD);
@@ -3264,7 +3269,7 @@ write_pipe_chunks(char *data, int len, int dest)
 	}
 
 	/* write the last chunk */
-	p.proto.is_last = (dest == LOG_DESTINATION_CSVLOG ? 'T' : 't');
+	p.proto.flags |= PIPE_PROTO_IS_LAST;
 	p.proto.len = len;
 	memcpy(p.proto.data, data, len);
 	rc = write(fd, &p, PIPE_HEADER_SIZE + len);

diff --git a/src/bin/pg_ctl/t/004_logrotate.pl b/src/bin/pg_ctl/t/004_logrotate.pl
index fa14b98c7d..aa0d64a4f7 100644
--- a/src/bin/pg_ctl/t/004_logrotate.pl
+++ b/src/bin/pg_ctl/t/004_logrotate.pl
@@ -6,15 +6,64 @@ use warnings;
 
 use PostgresNode;
 use TestLib;
-use Test::More tests => 5;
+use Test::More tests => 10;
 use Time::HiRes qw(usleep);
 
+# Extract the file name of a $format from the contents of
+# current_logfiles.
+sub fetch_file_name
+{
+	my $logfiles = shift;
+	my $format   = shift;
+	my @lines    = split(/\n/, $logfiles);
+	my $filename = undef;
+	foreach my $line (@lines)
+	{
+		if ($line =~ /$format (.*)$/gm)
+		{
+			$filename = $1;
+		}
+	}
+
+	return $filename;
+}
+
+# Check for a pattern in the logs associated to one format.
+sub check_log_pattern
+{
+	my $format   = shift;
+	my $logfiles = shift;
+	my $pattern  = shift;
+	my $node     = shift;
+	my $lfname   = fetch_file_name($logfiles, $format);
+
+	my $max_attempts = 180 * 10;
+
+	my $logcontents;
+	for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
+	{
+		$logcontents = slurp_file($node->data_dir . '/' . $lfname);
+		last if $logcontents =~ m/$pattern/;
+		usleep(100_000);
+	}
+
+	like($logcontents, qr/$pattern/,
+		"found expected log file content for $format");
+
+	# While we're at it, test pg_current_logfile() function
+	is( $node->safe_psql('postgres', "SELECT pg_current_logfile('$format')"),
+		$lfname,
+		"pg_current_logfile() gives correct answer with $format");
+	return;
+}
+
 # Set up node with logging collector
 my $node = PostgresNode->new('primary');
 $node->init();
 $node->append_conf(
 	'postgresql.conf', qq(
 logging_collector = on
+log_destination = 'stderr, csvlog'
 # these ensure stability of test results:
 log_rotation_age = 0
 lc_messages = 'C'
@@ -44,26 +93,12 @@ note "current_logfiles = $current_logfiles";
 
 like(
 	$current_logfiles,
-	qr|^stderr log/postgresql-.*log$|,
+	qr|^stderr log/postgresql-.*log
+csvlog log/postgresql-.*csv$|,
 	'current_logfiles is sane');
 
-my $lfname = $current_logfiles;
-$lfname =~ s/^stderr //;
-chomp $lfname;
-
-my $first_logfile;
-for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
-{
-	$first_logfile = slurp_file($node->data_dir . '/' . $lfname);
-	last if $first_logfile =~ m/division by zero/;
-	usleep(100_000);
-}
-
-like($first_logfile, qr/division by zero/, 'found expected log file content');
-
-# While we're at it, test pg_current_logfile() function
-is($node->safe_psql('postgres', "SELECT pg_current_logfile('stderr')"),
-	$lfname, 'pg_current_logfile() gives correct answer');
+check_log_pattern('stderr', $current_logfiles, 'division by zero', $node);
+check_log_pattern('csvlog', $current_logfiles, 'division by zero', $node);
 
 # Sleep 2 seconds and ask for log rotation; this should result in
 # output into a different log file name.
@@ -84,28 +119,14 @@ note "now current_logfiles = $new_current_logfiles";
 
 like(
 	$new_current_logfiles,
-	qr|^stderr log/postgresql-.*log$|,
+	qr|^stderr log/postgresql-.*log
+csvlog log/postgresql-.*csv$|,
 	'new current_logfiles is sane');
 
-$lfname = $new_current_logfiles;
-$lfname =~ s/^stderr //;
-chomp $lfname;
-
 # Verify that log output gets to this file, too
-
 $node->psql('postgres', 'fee fi fo fum');
 
-my $second_logfile;
-for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
-{
-	$second_logfile = slurp_file($node->data_dir . '/' . $lfname);
-	last if $second_logfile =~ m/syntax error/;
-	usleep(100_000);
-}
-
-like(
-	$second_logfile,
-	qr/syntax error/,
-	'found expected log file content in new log file');
+check_log_pattern('stderr', $new_current_logfiles, 'syntax error', $node);
+check_log_pattern('csvlog', $new_current_logfiles, 'syntax error', $node);
 
 $node->stop();

From a08e9df54c5960225055a0c999090dad8cf839be Mon Sep 17 00:00:00 2001
From: Sehrope Sarkuni <sehrope@jackdb.com>
Date: Wed, 1 Sep 2021 09:06:15 -0400
Subject: [PATCH v3 1/2] Split csv handling in elog.c into separate csvlog.c

Split out csvlog to its own file and centralize common elog internals
and helpers into its own file as well.
---
 src/include/utils/elog-internal.h |  78 ++++++++
 src/backend/utils/error/Makefile  |   1 +
 src/backend/utils/error/csvlog.c  | 270 ++++++++++++++++++++++++++
 src/backend/utils/error/elog.c    | 313 ++----------------------------
 4 files changed, 365 insertions(+), 297 deletions(-)
 create mode 100644 src/include/utils/elog-internal.h
 create mode 100644 src/backend/utils/error/csvlog.c

diff --git a/src/include/utils/elog-internal.h b/src/include/utils/elog-internal.h
new file mode 100644
index 0000000000..ac08b6f12f
--- /dev/null
+++ b/src/include/utils/elog-internal.h
@@ -0,0 +1,78 @@
+/*-------------------------------------------------------------------------
+ *
+ * elog-internal.h
+ *	  POSTGRES error reporting/logging internal definitions.
+ *
+ *
+ * Portions Copyright (c) 2021, PostgreSQL Global Development Group
+ * src/include/utils/elog-internal.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef ELOG_INTERNAL_H
+#define ELOG_INTERNAL_H
+
+#include "postgres.h"
+
+#include "utils/elog.h"
+#include "miscadmin.h"
+#include "postmaster/postmaster.h"
+#include "postmaster/bgworker.h"
+
+const char * error_severity(int elevel);
+void write_syslogger(char *data, int len, int dest);
+
+void write_csvlog(ErrorData *edata);
+
+/*
+ * is_log_level_output -- is elevel logically >= log_min_level?
+ *
+ * We use this for tests that should consider LOG to sort out-of-order,
+ * between ERROR and FATAL.  Generally this is the right thing for testing
+ * whether a message should go to the postmaster log, whereas a simple >=
+ * test is correct for testing whether the message should go to the client.
+ */
+static inline bool
+is_log_level_output(int elevel, int log_min_level)
+{
+	if (elevel == LOG || elevel == LOG_SERVER_ONLY)
+	{
+		if (log_min_level == LOG || log_min_level <= ERROR)
+			return true;
+	}
+	else if (elevel == WARNING_CLIENT_ONLY)
+	{
+		/* never sent to log, regardless of log_min_level */
+		return false;
+	}
+	else if (log_min_level == LOG)
+	{
+		/* elevel != LOG */
+		if (elevel >= FATAL)
+			return true;
+	}
+	/* Neither is LOG */
+	else if (elevel >= log_min_level)
+		return true;
+
+	return false;
+}
+
+static inline const char *
+get_backend_type_for_log() {
+	if (MyProcPid == PostmasterPid)
+		return "postmaster";
+	else if (MyBackendType == B_BG_WORKER)
+		return MyBgworkerEntry->bgw_type;
+	else
+		return GetBackendTypeDesc(MyBackendType);
+}
+
+#define FORMATTED_TS_LEN 128
+extern char formatted_start_time[FORMATTED_TS_LEN];
+extern char formatted_log_time[FORMATTED_TS_LEN];
+
+void setup_formatted_log_time(void);
+void setup_formatted_start_time(void);
+
+#endif
diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index 612da215d0..ef770dd2f2 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -14,6 +14,7 @@ include $(top_builddir)/src/Makefile.global
 
 OBJS = \
 	assert.o \
+	csvlog.o \
 	elog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/csvlog.c b/src/backend/utils/error/csvlog.c
new file mode 100644
index 0000000000..923b7e7d73
--- /dev/null
+++ b/src/backend/utils/error/csvlog.c
@@ -0,0 +1,270 @@
+/*-------------------------------------------------------------------------
+ *
+ * csvlog.c
+ *	  CSV logging
+ *
+ * Copyright (c) 2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/csvlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog-internal.h"
+#include "utils/guc.h"
+#include "utils/ps_status.h"
+
+/*
+ * append a CSV'd version of a string to a StringInfo
+ * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
+ * If it's NULL, append nothing.
+ */
+static inline void
+appendCSVLiteral(StringInfo buf, const char *data)
+{
+	const char *p = data;
+	char		c;
+
+	/* avoid confusing an empty string with NULL */
+	if (p == NULL)
+		return;
+
+	appendStringInfoCharMacro(buf, '"');
+	while ((c = *p++) != '\0')
+	{
+		if (c == '"')
+			appendStringInfoCharMacro(buf, '"');
+		appendStringInfoCharMacro(buf, c);
+	}
+	appendStringInfoCharMacro(buf, '"');
+}
+
+/*
+ * Constructs the error message, depending on the Errordata it gets, in a CSV
+ * format which is described in doc/src/sgml/config.sgml.
+ */
+void
+write_csvlog(ErrorData *edata)
+{
+	StringInfoData buf;
+	bool		print_stmt = false;
+
+	/* static counter for line numbers */
+	static long log_line_number = 0;
+
+	/* has counter been reset in current process? */
+	static int	log_my_pid = 0;
+
+	/*
+	 * This is one of the few places where we'd rather not inherit a static
+	 * variable's value from the postmaster.  But since we will, reset it when
+	 * MyProcPid changes.
+	 */
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		formatted_start_time[0] = '\0';
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/*
+	 * timestamp with milliseconds
+	 *
+	 * Check if the timestamp is already calculated for the syslog message,
+	 * and use it if so.  Otherwise, get the current timestamp.  This is done
+	 * to put same timestamp in both syslog and csvlog messages.
+	 */
+	if (formatted_log_time[0] == '\0')
+		setup_formatted_log_time();
+
+	appendStringInfoString(&buf, formatted_log_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* username */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->user_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* database name */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->database_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* Process id  */
+	if (MyProcPid != 0)
+		appendStringInfo(&buf, "%d", MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendStringInfoChar(&buf, '"');
+		appendStringInfoString(&buf, MyProcPort->remote_host);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+		{
+			appendStringInfoChar(&buf, ':');
+			appendStringInfoString(&buf, MyProcPort->remote_port);
+		}
+		appendStringInfoChar(&buf, '"');
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session id */
+	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Line number */
+	appendStringInfo(&buf, "%ld", log_line_number);
+	appendStringInfoChar(&buf, ',');
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData msgbuf;
+		const char *psdisp;
+		int			displen;
+
+		initStringInfo(&msgbuf);
+
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendCSVLiteral(&buf, msgbuf.data);
+
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session start timestamp */
+	if (formatted_start_time[0] == '\0')
+		setup_formatted_start_time();
+	appendStringInfoString(&buf, formatted_start_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Transaction id */
+	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
+	appendStringInfoChar(&buf, ',');
+
+	/* Error severity */
+	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
+	appendStringInfoChar(&buf, ',');
+
+	/* SQL state code */
+	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
+	appendStringInfoChar(&buf, ',');
+
+	/* errmessage */
+	appendCSVLiteral(&buf, edata->message);
+	appendStringInfoChar(&buf, ',');
+
+	/* errdetail or errdetail_log */
+	if (edata->detail_log)
+		appendCSVLiteral(&buf, edata->detail_log);
+	else
+		appendCSVLiteral(&buf, edata->detail);
+	appendStringInfoChar(&buf, ',');
+
+	/* errhint */
+	appendCSVLiteral(&buf, edata->hint);
+	appendStringInfoChar(&buf, ',');
+
+	/* internal query */
+	appendCSVLiteral(&buf, edata->internalquery);
+	appendStringInfoChar(&buf, ',');
+
+	/* if printed internal query, print internal pos too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendStringInfo(&buf, "%d", edata->internalpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* errcontext */
+	if (!edata->hide_ctx)
+		appendCSVLiteral(&buf, edata->context);
+	appendStringInfoChar(&buf, ',');
+
+	/* user query --- only reported if not disabled by the caller */
+	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
+		debug_query_string != NULL &&
+		!edata->hide_stmt)
+		print_stmt = true;
+	if (print_stmt)
+		appendCSVLiteral(&buf, debug_query_string);
+	appendStringInfoChar(&buf, ',');
+	if (print_stmt && edata->cursorpos > 0)
+		appendStringInfo(&buf, "%d", edata->cursorpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		StringInfoData msgbuf;
+
+		initStringInfo(&msgbuf);
+
+		if (edata->funcname && edata->filename)
+			appendStringInfo(&msgbuf, "%s, %s:%d",
+							 edata->funcname, edata->filename,
+							 edata->lineno);
+		else if (edata->filename)
+			appendStringInfo(&msgbuf, "%s:%d",
+							 edata->filename, edata->lineno);
+		appendCSVLiteral(&buf, msgbuf.data);
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* application name */
+	if (application_name)
+		appendCSVLiteral(&buf, application_name);
+
+	appendStringInfoChar(&buf, ',');
+
+	/* backend type */
+	appendCSVLiteral(&buf, get_backend_type_for_log());
+	appendStringInfoChar(&buf, ',');
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendStringInfo(&buf, "%d", leader->pid);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* query id */
+	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
+
+	appendStringInfoChar(&buf, '\n');
+
+	write_syslogger(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 2af87ee3bd..68fb167976 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -82,7 +82,7 @@
 #include "utils/guc.h"
 #include "utils/memutils.h"
 #include "utils/ps_status.h"
-
+#include "utils/elog-internal.h"
 
 /* In this module, access gettext() via err_gettext() */
 #undef _
@@ -155,9 +155,8 @@ static int	recursion_depth = 0;	/* to detect actual recursion */
 static struct timeval saved_timeval;
 static bool saved_timeval_set = false;
 
-#define FORMATTED_TS_LEN 128
-static char formatted_start_time[FORMATTED_TS_LEN];
-static char formatted_log_time[FORMATTED_TS_LEN];
+char formatted_start_time[FORMATTED_TS_LEN];
+char formatted_log_time[FORMATTED_TS_LEN];
 
 
 /* Macro for checking errordata_stack_depth is reasonable */
@@ -175,52 +174,13 @@ static const char *err_gettext(const char *str) pg_attribute_format_arg(1);
 static pg_noinline void set_backtrace(ErrorData *edata, int num_skip);
 static void set_errdata_field(MemoryContextData *cxt, char **ptr, const char *str);
 static void write_console(const char *line, int len);
-static void setup_formatted_log_time(void);
-static void setup_formatted_start_time(void);
 static const char *process_log_prefix_padding(const char *p, int *padding);
 static void log_line_prefix(StringInfo buf, ErrorData *edata);
-static void write_csvlog(ErrorData *edata);
 static void send_message_to_server_log(ErrorData *edata);
 static void write_pipe_chunks(char *data, int len, int dest);
 static void send_message_to_frontend(ErrorData *edata);
-static const char *error_severity(int elevel);
 static void append_with_tabs(StringInfo buf, const char *str);
 
-
-/*
- * is_log_level_output -- is elevel logically >= log_min_level?
- *
- * We use this for tests that should consider LOG to sort out-of-order,
- * between ERROR and FATAL.  Generally this is the right thing for testing
- * whether a message should go to the postmaster log, whereas a simple >=
- * test is correct for testing whether the message should go to the client.
- */
-static inline bool
-is_log_level_output(int elevel, int log_min_level)
-{
-	if (elevel == LOG || elevel == LOG_SERVER_ONLY)
-	{
-		if (log_min_level == LOG || log_min_level <= ERROR)
-			return true;
-	}
-	else if (elevel == WARNING_CLIENT_ONLY)
-	{
-		/* never sent to log, regardless of log_min_level */
-		return false;
-	}
-	else if (log_min_level == LOG)
-	{
-		/* elevel != LOG */
-		if (elevel >= FATAL)
-			return true;
-	}
-	/* Neither is LOG */
-	else if (elevel >= log_min_level)
-		return true;
-
-	return false;
-}
-
 /*
  * Policy-setting subroutines.  These are fairly simple, but it seems wise
  * to have the code in just one place.
@@ -2291,7 +2251,7 @@ write_console(const char *line, int len)
 /*
  * setup formatted_log_time, for consistent times between CSV and regular logs
  */
-static void
+void
 setup_formatted_log_time(void)
 {
 	pg_time_t	stamp_time;
@@ -2323,7 +2283,7 @@ setup_formatted_log_time(void)
 /*
  * setup formatted_start_time
  */
-static void
+void
 setup_formatted_start_time(void)
 {
 	pg_time_t	stamp_time = (pg_time_t) MyStartTime;
@@ -2729,257 +2689,6 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 	}
 }
 
-/*
- * append a CSV'd version of a string to a StringInfo
- * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
- * If it's NULL, append nothing.
- */
-static inline void
-appendCSVLiteral(StringInfo buf, const char *data)
-{
-	const char *p = data;
-	char		c;
-
-	/* avoid confusing an empty string with NULL */
-	if (p == NULL)
-		return;
-
-	appendStringInfoCharMacro(buf, '"');
-	while ((c = *p++) != '\0')
-	{
-		if (c == '"')
-			appendStringInfoCharMacro(buf, '"');
-		appendStringInfoCharMacro(buf, c);
-	}
-	appendStringInfoCharMacro(buf, '"');
-}
-
-/*
- * Constructs the error message, depending on the Errordata it gets, in a CSV
- * format which is described in doc/src/sgml/config.sgml.
- */
-static void
-write_csvlog(ErrorData *edata)
-{
-	StringInfoData buf;
-	bool		print_stmt = false;
-
-	/* static counter for line numbers */
-	static long log_line_number = 0;
-
-	/* has counter been reset in current process? */
-	static int	log_my_pid = 0;
-
-	/*
-	 * This is one of the few places where we'd rather not inherit a static
-	 * variable's value from the postmaster.  But since we will, reset it when
-	 * MyProcPid changes.
-	 */
-	if (log_my_pid != MyProcPid)
-	{
-		log_line_number = 0;
-		log_my_pid = MyProcPid;
-		formatted_start_time[0] = '\0';
-	}
-	log_line_number++;
-
-	initStringInfo(&buf);
-
-	/*
-	 * timestamp with milliseconds
-	 *
-	 * Check if the timestamp is already calculated for the syslog message,
-	 * and use it if so.  Otherwise, get the current timestamp.  This is done
-	 * to put same timestamp in both syslog and csvlog messages.
-	 */
-	if (formatted_log_time[0] == '\0')
-		setup_formatted_log_time();
-
-	appendStringInfoString(&buf, formatted_log_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* username */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->user_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* database name */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->database_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* Process id  */
-	if (MyProcPid != 0)
-		appendStringInfo(&buf, "%d", MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Remote host and port */
-	if (MyProcPort && MyProcPort->remote_host)
-	{
-		appendStringInfoChar(&buf, '"');
-		appendStringInfoString(&buf, MyProcPort->remote_host);
-		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
-		{
-			appendStringInfoChar(&buf, ':');
-			appendStringInfoString(&buf, MyProcPort->remote_port);
-		}
-		appendStringInfoChar(&buf, '"');
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session id */
-	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Line number */
-	appendStringInfo(&buf, "%ld", log_line_number);
-	appendStringInfoChar(&buf, ',');
-
-	/* PS display */
-	if (MyProcPort)
-	{
-		StringInfoData msgbuf;
-		const char *psdisp;
-		int			displen;
-
-		initStringInfo(&msgbuf);
-
-		psdisp = get_ps_display(&displen);
-		appendBinaryStringInfo(&msgbuf, psdisp, displen);
-		appendCSVLiteral(&buf, msgbuf.data);
-
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session start timestamp */
-	if (formatted_start_time[0] == '\0')
-		setup_formatted_start_time();
-	appendStringInfoString(&buf, formatted_start_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* Virtual transaction id */
-	/* keep VXID format in sync with lockfuncs.c */
-	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
-		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Transaction id */
-	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
-	appendStringInfoChar(&buf, ',');
-
-	/* Error severity */
-	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
-	appendStringInfoChar(&buf, ',');
-
-	/* SQL state code */
-	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
-	appendStringInfoChar(&buf, ',');
-
-	/* errmessage */
-	appendCSVLiteral(&buf, edata->message);
-	appendStringInfoChar(&buf, ',');
-
-	/* errdetail or errdetail_log */
-	if (edata->detail_log)
-		appendCSVLiteral(&buf, edata->detail_log);
-	else
-		appendCSVLiteral(&buf, edata->detail);
-	appendStringInfoChar(&buf, ',');
-
-	/* errhint */
-	appendCSVLiteral(&buf, edata->hint);
-	appendStringInfoChar(&buf, ',');
-
-	/* internal query */
-	appendCSVLiteral(&buf, edata->internalquery);
-	appendStringInfoChar(&buf, ',');
-
-	/* if printed internal query, print internal pos too */
-	if (edata->internalpos > 0 && edata->internalquery != NULL)
-		appendStringInfo(&buf, "%d", edata->internalpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* errcontext */
-	if (!edata->hide_ctx)
-		appendCSVLiteral(&buf, edata->context);
-	appendStringInfoChar(&buf, ',');
-
-	/* user query --- only reported if not disabled by the caller */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
-		print_stmt = true;
-	if (print_stmt)
-		appendCSVLiteral(&buf, debug_query_string);
-	appendStringInfoChar(&buf, ',');
-	if (print_stmt && edata->cursorpos > 0)
-		appendStringInfo(&buf, "%d", edata->cursorpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* file error location */
-	if (Log_error_verbosity >= PGERROR_VERBOSE)
-	{
-		StringInfoData msgbuf;
-
-		initStringInfo(&msgbuf);
-
-		if (edata->funcname && edata->filename)
-			appendStringInfo(&msgbuf, "%s, %s:%d",
-							 edata->funcname, edata->filename,
-							 edata->lineno);
-		else if (edata->filename)
-			appendStringInfo(&msgbuf, "%s:%d",
-							 edata->filename, edata->lineno);
-		appendCSVLiteral(&buf, msgbuf.data);
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* application name */
-	if (application_name)
-		appendCSVLiteral(&buf, application_name);
-
-	appendStringInfoChar(&buf, ',');
-
-	/* backend type */
-	if (MyProcPid == PostmasterPid)
-		appendCSVLiteral(&buf, "postmaster");
-	else if (MyBackendType == B_BG_WORKER)
-		appendCSVLiteral(&buf, MyBgworkerEntry->bgw_type);
-	else
-		appendCSVLiteral(&buf, GetBackendTypeDesc(MyBackendType));
-
-	appendStringInfoChar(&buf, ',');
-
-	/* leader PID */
-	if (MyProc)
-	{
-		PGPROC	   *leader = MyProc->lockGroupLeader;
-
-		/*
-		 * Show the leader only for active parallel workers.  This leaves out
-		 * the leader of a parallel group.
-		 */
-		if (leader && leader->pid != MyProcPid)
-			appendStringInfo(&buf, "%d", leader->pid);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* query id */
-	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
-
-	appendStringInfoChar(&buf, '\n');
-
-	/* If in the syslogger process, try to write messages direct to file */
-	if (MyBackendType == B_LOGGER)
-		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-	else
-		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-
-	pfree(buf.data);
-}
-
 /*
  * Unpack MAKE_SQLSTATE code. Note that this returns a pointer to a
  * static buffer.
@@ -3276,6 +2985,16 @@ write_pipe_chunks(char *data, int len, int dest)
 	(void) rc;
 }
 
+void
+write_syslogger(char *data, int len, int dest)
+{
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(data, len, dest);
+	else
+		write_pipe_chunks(data, len, dest);
+}
+
 
 /*
  * Append a text string to the error report being built for the client.
@@ -3475,7 +3194,7 @@ send_message_to_frontend(ErrorData *edata)
  * The string is not localized here, but we mark the strings for translation
  * so that callers can invoke _() on the result.
  */
-static const char *
+const char *
 error_severity(int elevel)
 {
 	const char *prefix;
-- 
2.33.0

From 823aab1f809a47f1a525a6ad8ae0366fd07328b6 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Mon, 13 Sep 2021 10:41:55 +0900
Subject: [PATCH v3 2/2] Add jsonlog log_destination for JSON server logs

Adds option to write server log files as JSON. Each log entry is written as its
own line with any internal newlines escaped as \n. Other non-ASCII and special
characters are also escaped using standard JSON escape sequences.

JSON logging is enabled by setting the GUC log_destination to "jsonlog" and
defaults to a log file with a ".json" extension.
---
 src/include/postmaster/syslogger.h |   1 +
 src/include/utils/elog-internal.h  |   1 +
 src/include/utils/elog.h           |   1 +
 src/backend/postmaster/syslogger.c | 182 +++++++++++++++--
 src/backend/utils/adt/misc.c       |   5 +-
 src/backend/utils/error/Makefile   |   3 +-
 src/backend/utils/error/elog.c     |  26 +++
 src/backend/utils/error/jsonlog.c  | 312 +++++++++++++++++++++++++++++
 src/backend/utils/misc/guc.c       |   2 +
 src/bin/pg_ctl/t/004_logrotate.pl  |  12 +-
 doc/src/sgml/config.sgml           |  67 ++++++-
 11 files changed, 585 insertions(+), 27 deletions(-)
 create mode 100644 src/backend/utils/error/jsonlog.c

diff --git a/src/include/postmaster/syslogger.h b/src/include/postmaster/syslogger.h
index c79dfbeba2..18448b76e5 100644
--- a/src/include/postmaster/syslogger.h
+++ b/src/include/postmaster/syslogger.h
@@ -64,6 +64,7 @@ typedef union
 /* log destinations */
 #define PIPE_PROTO_DEST_STDERR	0x10
 #define PIPE_PROTO_DEST_CSVLOG	0x20
+#define PIPE_PROTO_DEST_JSONLOG	0x40
 
 /* GUC options */
 extern bool Logging_collector;
diff --git a/src/include/utils/elog-internal.h b/src/include/utils/elog-internal.h
index ac08b6f12f..13c217a29d 100644
--- a/src/include/utils/elog-internal.h
+++ b/src/include/utils/elog-internal.h
@@ -23,6 +23,7 @@ const char * error_severity(int elevel);
 void write_syslogger(char *data, int len, int dest);
 
 void write_csvlog(ErrorData *edata);
+void write_jsonlog(ErrorData *edata);
 
 /*
  * is_log_level_output -- is elevel logically >= log_min_level?
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index f53607e12e..c0c699f485 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -436,6 +436,7 @@ extern bool syslog_split_messages;
 #define LOG_DESTINATION_SYSLOG	 2
 #define LOG_DESTINATION_EVENTLOG 4
 #define LOG_DESTINATION_CSVLOG	 8
+#define LOG_DESTINATION_JSONLOG	16
 
 /* Other exported functions */
 extern void DebugFileOpen(void);
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index bca3883572..c0ce072900 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -86,9 +86,11 @@ static bool pipe_eof_seen = false;
 static bool rotation_disabled = false;
 static FILE *syslogFile = NULL;
 static FILE *csvlogFile = NULL;
+static FILE *jsonlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
 static char *last_file_name = NULL;
 static char *last_csv_file_name = NULL;
+static char *last_json_file_name = NULL;
 
 /*
  * Buffers for saving partial messages from different backends.
@@ -275,6 +277,8 @@ SysLoggerMain(int argc, char *argv[])
 	last_file_name = logfile_getname(first_syslogger_file_time, NULL);
 	if (csvlogFile != NULL)
 		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
+	if (jsonlogFile != NULL)
+		last_json_file_name = logfile_getname(first_syslogger_file_time, ".json");
 
 	/* remember active logfile parameters */
 	currentLogDir = pstrdup(Log_directory);
@@ -361,6 +365,14 @@ SysLoggerMain(int argc, char *argv[])
 				(csvlogFile != NULL))
 				rotation_requested = true;
 
+			/*
+			 * Force a rotation if JSONLOG output was just turned on or off and
+			 * we need to open or close jsonlogFile accordingly.
+			 */
+			if (((Log_destination & LOG_DESTINATION_JSONLOG) != 0) !=
+				(jsonlogFile != NULL))
+				rotation_requested = true;
+
 			/*
 			 * If rotation time parameter changed, reset next rotation time,
 			 * but don't immediately force a rotation.
@@ -411,6 +423,12 @@ SysLoggerMain(int argc, char *argv[])
 				rotation_requested = true;
 				size_rotation_for |= LOG_DESTINATION_CSVLOG;
 			}
+			if (jsonlogFile != NULL &&
+				ftell(jsonlogFile) >= Log_RotationSize * 1024L)
+			{
+				rotation_requested = true;
+				size_rotation_for |= LOG_DESTINATION_JSONLOG;
+			}
 		}
 
 		if (rotation_requested)
@@ -420,7 +438,7 @@ SysLoggerMain(int argc, char *argv[])
 			 * was sent by pg_rotate_logfile() or "pg_ctl logrotate".
 			 */
 			if (!time_based_rotation && size_rotation_for == 0)
-				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG;
+				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG | LOG_DESTINATION_JSONLOG;
 			logfile_rotate(time_based_rotation, size_rotation_for);
 		}
 
@@ -626,6 +644,20 @@ SysLogger_Start(void)
 		pfree(filename);
 	}
 
+	/*
+	 * Likewise for the initial JSON log file, if that's enabled.  (Note that
+	 * we open syslogFile even when only JSON output is nominally enabled,
+	 * since some code paths will write to syslogFile anyway.)
+	 */
+	if (Log_destination & LOG_DESTINATION_JSONLOG)
+	{
+		filename = logfile_getname(first_syslogger_file_time, ".json");
+
+		jsonlogFile = logfile_open(filename, "a", false);
+
+		pfree(filename);
+	}
+
 #ifdef EXEC_BACKEND
 	switch ((sysloggerPid = syslogger_forkexec()))
 #else
@@ -723,6 +755,11 @@ SysLogger_Start(void)
 				fclose(csvlogFile);
 				csvlogFile = NULL;
 			}
+			if (jsonlogFile != NULL)
+			{
+				fclose(jsonlogFile);
+				jsonlogFile = NULL;
+			}
 			return (int) sysloggerPid;
 	}
 
@@ -745,6 +782,7 @@ syslogger_forkexec(void)
 	int			ac = 0;
 	char		filenobuf[32];
 	char		csvfilenobuf[32];
+	char		jsonfilenobuf[32];
 
 	av[ac++] = "postgres";
 	av[ac++] = "--forklog";
@@ -772,14 +810,25 @@ syslogger_forkexec(void)
 				 fileno(csvlogFile));
 	else
 		strcpy(csvfilenobuf, "-1");
+	if (jsonlogFile != NULL)
+		snprintf(jsonfilenobuf, sizeof(jsonfilenobuf), "%d",
+				 fileno(jsonlogFile));
+	else
+		strcpy(jsonfilenobuf, "-1");
 #else							/* WIN32 */
 	if (csvlogFile != NULL)
 		snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld",
 				 (long) _get_osfhandle(_fileno(csvlogFile)));
 	else
 		strcpy(csvfilenobuf, "0");
+	if (jsonlogFile != NULL)
+		snprintf(jsonfilenobuf, sizeof(jsonfilenobuf), "%ld",
+				 (long) _get_osfhandle(_fileno(jsonlogFile)));
+	else
+		strcpy(jsonfilenobuf, "0");
 #endif							/* WIN32 */
 	av[ac++] = csvfilenobuf;
+	av[ac++] = jsonfilenobuf;
 
 	av[ac] = NULL;
 	Assert(ac < lengthof(av));
@@ -797,8 +846,8 @@ syslogger_parseArgs(int argc, char *argv[])
 {
 	int			fd;
 
-	Assert(argc == 5);
-	argv += 3;
+	Assert(argc == 6);
+	argv += 4;
 
 	/*
 	 * Re-open the error output files that were opened by SysLogger_Start().
@@ -820,6 +869,12 @@ syslogger_parseArgs(int argc, char *argv[])
 		csvlogFile = fdopen(fd, "a");
 		setvbuf(csvlogFile, NULL, PG_IOLBF, 0);
 	}
+	fd = atoi(*argv++);
+	if (fd != -1)
+	{
+		jsonlogFile = fdopen(fd, "a");
+		setvbuf(jsonlogFile, NULL, PG_IOLBF, 0);
+	}
 #else							/* WIN32 */
 	fd = atoi(*argv++);
 	if (fd != 0)
@@ -841,6 +896,16 @@ syslogger_parseArgs(int argc, char *argv[])
 			setvbuf(csvlogFile, NULL, PG_IOLBF, 0);
 		}
 	}
+	fd = atoi(*argv++);
+	if (fd != 0)
+	{
+		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
+		if (fd > 0)
+		{
+			jsonlogFile = fdopen(fd, "a");
+			setvbuf(jsonlogFile, NULL, PG_IOLBF, 0);
+		}
+	}
 #endif							/* WIN32 */
 }
 #endif							/* EXEC_BACKEND */
@@ -890,7 +955,9 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 
 		/* Do we have a valid header? */
 		memcpy(&p, cursor, offsetof(PipeProtoHeader, data));
-		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR | PIPE_PROTO_DEST_CSVLOG);
+		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR |
+								PIPE_PROTO_DEST_CSVLOG |
+								PIPE_PROTO_DEST_JSONLOG);
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&
@@ -912,6 +979,8 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 				dest = LOG_DESTINATION_STDERR;
 			else if ((p.flags & PIPE_PROTO_DEST_CSVLOG) != 0)
 				dest = LOG_DESTINATION_CSVLOG;
+			else if ((p.flags & PIPE_PROTO_DEST_JSONLOG) != 0)
+				dest = LOG_DESTINATION_JSONLOG;
 			else
 			{
 				/* this should never happen as of the header validation */
@@ -1091,19 +1160,23 @@ write_syslogger_file(const char *buffer, int count, int destination)
 	FILE	   *logfile;
 
 	/*
-	 * If we're told to write to csvlogFile, but it's not open, dump the data
-	 * to syslogFile (which is always open) instead.  This can happen if CSV
+	 * If we're told to write to a structured log file, but it's not open, dump the data
+	 * to syslogFile (which is always open) instead.  This can happen if structured
 	 * output is enabled after postmaster start and we've been unable to open
-	 * csvlogFile.  There are also race conditions during a parameter change
-	 * whereby backends might send us CSV output before we open csvlogFile or
-	 * after we close it.  Writing CSV-formatted output to the regular log
+	 * logFile.  There are also race conditions during a parameter change
+	 * whereby backends might send us structured output before we open the logFile or
+	 * after we close it.  Writing formatted output to the regular log
 	 * file isn't great, but it beats dropping log output on the floor.
 	 *
-	 * Think not to improve this by trying to open csvlogFile on-the-fly.  Any
+	 * Think not to improve this by trying to open logFile on-the-fly.  Any
 	 * failure in that would lead to recursion.
 	 */
-	logfile = (destination == LOG_DESTINATION_CSVLOG &&
-			   csvlogFile != NULL) ? csvlogFile : syslogFile;
+	if ((destination & LOG_DESTINATION_CSVLOG) && csvlogFile != NULL)
+		logfile = csvlogFile;
+	else if ((destination & LOG_DESTINATION_JSONLOG) && jsonlogFile != NULL)
+		logfile = jsonlogFile;
+	else
+		logfile = syslogFile;
 
 	rc = fwrite(buffer, 1, count, logfile);
 
@@ -1174,7 +1247,8 @@ pipeThread(void *arg)
 		if (Log_RotationSize > 0)
 		{
 			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
-				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
+				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L) ||
+				(jsonlogFile != NULL && ftell(jsonlogFile) >= Log_RotationSize * 1024L))
 				SetLatch(MyLatch);
 		}
 		LeaveCriticalSection(&sysloggerSection);
@@ -1247,6 +1321,7 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 {
 	char	   *filename;
 	char	   *csvfilename = NULL;
+	char	   *jsonfilename = NULL;
 	pg_time_t	fntime;
 	FILE	   *fh;
 
@@ -1264,6 +1339,9 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 	filename = logfile_getname(fntime, NULL);
 	if (Log_destination & LOG_DESTINATION_CSVLOG)
 		csvfilename = logfile_getname(fntime, ".csv");
+	if (Log_destination & LOG_DESTINATION_JSONLOG)
+		jsonfilename = logfile_getname(fntime, ".json");
+
 
 	/*
 	 * Decide whether to overwrite or append.  We can overwrite if (a)
@@ -1301,6 +1379,8 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 				pfree(filename);
 			if (csvfilename)
 				pfree(csvfilename);
+			if (jsonfilename)
+				pfree(jsonfilename);
 			return;
 		}
 
@@ -1315,10 +1395,10 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 	}
 
 	/*
-	 * Same as above, but for csv file.  Note that if LOG_DESTINATION_CSVLOG
-	 * was just turned on, we might have to open csvlogFile here though it was
+	 * Same as above, but for a structured file.  Note that if LOG_DESTINATION_[STRUCTURED]LOG
+	 * was just turned on, we might have to open logFile here though it was
 	 * not open before.  In such a case we'll append not overwrite (since
-	 * last_csv_file_name will be NULL); that is consistent with the normal
+	 * last_*_file_name will be NULL); that is consistent with the normal
 	 * rules since it's not a time-based rotation.
 	 */
 	if ((Log_destination & LOG_DESTINATION_CSVLOG) &&
@@ -1374,11 +1454,66 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 			pfree(last_csv_file_name);
 		last_csv_file_name = NULL;
 	}
+	else if ((Log_destination & LOG_DESTINATION_JSONLOG) &&
+		(jsonlogFile == NULL ||
+		 time_based_rotation || (size_rotation_for & LOG_DESTINATION_JSONLOG)))
+	{
+		if (Log_truncate_on_rotation && time_based_rotation &&
+			last_json_file_name != NULL &&
+			strcmp(jsonfilename, last_json_file_name) != 0)
+			fh = logfile_open(jsonfilename, "w", true);
+		else
+			fh = logfile_open(jsonfilename, "a", true);
+
+		if (!fh)
+		{
+			/*
+			 * ENFILE/EMFILE are not too surprising on a busy system; just
+			 * keep using the old file till we manage to get a new one.
+			 * Otherwise, assume something's wrong with Log_directory and stop
+			 * trying to create files.
+			 */
+			if (errno != ENFILE && errno != EMFILE)
+			{
+				ereport(LOG,
+						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
+				rotation_disabled = true;
+			}
+
+			if (filename)
+				pfree(filename);
+			if (jsonfilename)
+				pfree(jsonfilename);
+			return;
+		}
+
+		if (jsonlogFile != NULL)
+			fclose(jsonlogFile);
+		jsonlogFile = fh;
+
+		/* instead of pfree'ing filename, remember it for next time */
+		if (last_json_file_name != NULL)
+			pfree(last_json_file_name);
+		last_json_file_name = jsonfilename;
+		jsonfilename = NULL;
+	}
+	else if (!(Log_destination & LOG_DESTINATION_JSONLOG) &&
+			 jsonlogFile != NULL)
+	{
+		/* JSONLOG was just turned off, so close the old file */
+		fclose(jsonlogFile);
+		jsonlogFile = NULL;
+		if (last_json_file_name != NULL)
+			pfree(last_json_file_name);
+		last_json_file_name = NULL;
+	}
 
 	if (filename)
 		pfree(filename);
 	if (csvfilename)
 		pfree(csvfilename);
+	if (jsonfilename)
+		pfree(jsonfilename);
 
 	update_metainfo_datafile();
 
@@ -1466,7 +1601,8 @@ update_metainfo_datafile(void)
 	mode_t		oumask;
 
 	if (!(Log_destination & LOG_DESTINATION_STDERR) &&
-		!(Log_destination & LOG_DESTINATION_CSVLOG))
+		!(Log_destination & LOG_DESTINATION_CSVLOG) &&
+		!(Log_destination & LOG_DESTINATION_JSONLOG))
 	{
 		if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
 			ereport(LOG,
@@ -1524,6 +1660,18 @@ update_metainfo_datafile(void)
 			return;
 		}
 	}
+	if (last_json_file_name && (Log_destination & LOG_DESTINATION_JSONLOG))
+	{
+		if (fprintf(fh, "jsonlog %s\n", last_json_file_name) < 0)
+		{
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not write file \"%s\": %m",
+							LOG_METAINFO_DATAFILE_TMP)));
+			fclose(fh);
+			return;
+		}
+	}
 	fclose(fh);
 
 	if (rename(LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE) != 0)
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 88faf4dfd7..4931859627 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -843,11 +843,12 @@ pg_current_logfile(PG_FUNCTION_ARGS)
 	{
 		logfmt = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
-		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0)
+		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0 &&
+				strcmp(logfmt, "jsonlog") != 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("log format \"%s\" is not supported", logfmt),
-					 errhint("The supported log formats are \"stderr\" and \"csvlog\".")));
+					 errhint("The supported log formats are \"stderr\", \"csvlog\", and \"jsonlog\".")));
 	}
 
 	fd = AllocateFile(LOG_METAINFO_DATAFILE, "r");
diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index ef770dd2f2..65ba61fb3c 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -15,6 +15,7 @@ include $(top_builddir)/src/Makefile.global
 OBJS = \
 	assert.o \
 	csvlog.o \
-	elog.o
+	elog.o \
+	jsonlog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 68fb167976..064fbf7e61 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2922,6 +2922,30 @@ send_message_to_server_log(ErrorData *edata)
 			pfree(buf.data);
 		}
 	}
+	/* Write to JSON log if enabled */
+	else if (Log_destination & LOG_DESTINATION_JSONLOG)
+	{
+		if (redirection_done || MyBackendType == B_LOGGER)
+		{
+			/*
+			 * send JSON data if it's safe to do so (syslogger doesn't need the
+			 * pipe). First get back the space in the message buffer.
+			 */
+			pfree(buf.data);
+			write_jsonlog(edata);
+		}
+		else
+		{
+			/*
+			 * syslogger not up (yet), so just dump the message to stderr,
+			 * unless we already did so above.
+			 */
+			if (!(Log_destination & LOG_DESTINATION_STDERR) &&
+				whereToSendOutput != DestDebug)
+				write_console(buf.data, buf.len);
+			pfree(buf.data);
+		}
+	}
 	else
 	{
 		pfree(buf.data);
@@ -2964,6 +2988,8 @@ write_pipe_chunks(char *data, int len, int dest)
 		p.proto.flags |= PIPE_PROTO_DEST_STDERR;
 	else if (dest == LOG_DESTINATION_CSVLOG)
 		p.proto.flags |= PIPE_PROTO_DEST_CSVLOG;
+	else if (dest == LOG_DESTINATION_JSONLOG)
+		p.proto.flags |= PIPE_PROTO_DEST_JSONLOG;
 
 	/* write all but the last chunk */
 	while (len > PIPE_MAX_PAYLOAD)
diff --git a/src/backend/utils/error/jsonlog.c b/src/backend/utils/error/jsonlog.c
new file mode 100644
index 0000000000..2777124977
--- /dev/null
+++ b/src/backend/utils/error/jsonlog.c
@@ -0,0 +1,312 @@
+/*-------------------------------------------------------------------------
+ *
+ * jsonlog.c
+ *	  JSON logging
+ *
+ * Copyright (c) 2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/jsonlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog-internal.h"
+#include "utils/guc.h"
+#include "utils/json.h"
+#include "utils/ps_status.h"
+
+/*
+ * appendJSONKeyValue
+ * Append to given StringInfo a comma followed by a JSON key and value.
+ * Both the key and value will be escaped as JSON string literals.
+ */
+static void
+appendJSONKeyValue(StringInfo buf, const char *key, const char *value)
+{
+	if (value == NULL)
+		return;
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	escape_json(buf, value);
+}
+
+/*
+ * appendJSONKeyValueFmt
+ * Evaluate the fmt string and then invoke appendJSONKeyValue as the
+ * value of the JSON property. Both the key and value will be escaped by
+ * appendJSONKeyValue.
+ */
+static void
+appendJSONKeyValueFmt(StringInfo buf, const char *key, const char *fmt,...)
+{
+	int			save_errno = errno;
+	size_t		len = 128;		/* initial assumption about buffer size */
+	char	    *value;
+
+	for (;;)
+	{
+		va_list		args;
+		size_t		newlen;
+
+		/*
+		 * Allocate result buffer.  Note that in frontend this maps to malloc
+		 * with exit-on-error.
+		 */
+		value = (char *) palloc(len);
+
+		/* Try to format the data. */
+		errno = save_errno;
+		va_start(args, fmt);
+		newlen = pvsnprintf(value, len, fmt, args);
+		va_end(args);
+
+		if (newlen < len)
+			break; /* success */
+
+		/* Release buffer and loop around to try again with larger len. */
+		pfree(value);
+		len = newlen;
+	}
+	appendJSONKeyValue(buf, key, value);
+	/* Clean up */
+	pfree(value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as a signed integer (a JSON number).
+ */
+static void
+appendJSONKeyValueAsInt(StringInfo buf, const char *key, int value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%d", value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as an unsigned integer (a JSON number).
+ */
+static void
+appendJSONKeyValueAsUInt(StringInfo buf, const char *key, int value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%u", value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as a long (a JSON number).
+ */
+static void
+appendJSONKeyValueAsLong(StringInfo buf, const char *key, long value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%ld", value);
+}
+
+/*
+ * Write logs in json format.
+ */
+void
+write_jsonlog(ErrorData *edata)
+{
+	StringInfoData	buf;
+
+	/* static counter for line numbers */
+	static long	log_line_number = 0;
+
+	/* Has the counter been reset in the current process? */
+	static int	log_my_pid = 0;
+
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		formatted_start_time[0] = '\0';
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* Initialize string */
+	appendStringInfoChar(&buf, '{');
+
+	/*
+	 * timestamp with milliseconds
+	 *
+	 * Check if the timestamp is already calculated for the syslog message,
+	 * and use it if so.  Otherwise, get the current timestamp.  This is done
+	 * to put same timestamp in both syslog and jsonlog messages.
+	 */
+	if (formatted_log_time[0] == '\0')
+		setup_formatted_log_time();
+
+	/* First property does not use appendJSONKeyValue as it does not have comma prefix */
+	escape_json(&buf, "timestamp");
+	appendStringInfoChar(&buf, ':');
+	escape_json(&buf, formatted_log_time);
+
+	/* username */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "user", MyProcPort->user_name);
+
+	/* database name */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "dbname", MyProcPort->database_name);
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendJSONKeyValueAsInt(&buf, "leader_pid", leader->pid);
+	}
+
+	/* Process ID */
+	if (MyProcPid != 0)
+		appendJSONKeyValueAsInt(&buf, "pid", MyProcPid);
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendJSONKeyValue(&buf, "remote_host", MyProcPort->remote_host);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+			appendJSONKeyValue(&buf, "remote_port", MyProcPort->remote_port);
+	}
+
+	/* Session id */
+	appendJSONKeyValueFmt(&buf, "session_id", "%lx.%x", (long) MyStartTime, MyProcPid);
+
+	/* Line number */
+	appendJSONKeyValueAsLong(&buf, "line_num", log_line_number);
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData	msgbuf;
+		const char	   *psdisp;
+		int				displen;
+
+		initStringInfo(&msgbuf);
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendJSONKeyValue(&buf, "ps", msgbuf.data);
+
+		pfree(msgbuf.data);
+	}
+
+	/* session start timestamp */
+	if (formatted_start_time[0] == '\0')
+		setup_formatted_start_time();
+	appendJSONKeyValue(&buf, "session_start", formatted_start_time);
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendJSONKeyValueFmt(&buf, "vxid", "%d/%u", MyProc->backendId, MyProc->lxid);
+
+	/* Transaction id */
+	appendJSONKeyValueFmt(&buf, "txid", "%u", GetTopTransactionIdIfAny());
+
+	/* Error severity */
+	if (edata->elevel)
+		appendJSONKeyValue(&buf, "error_severity", (char *) error_severity(edata->elevel));
+
+	/* query id */
+	appendJSONKeyValueFmt(&buf,  "query_id", "%lld", (long long) pgstat_get_my_query_id());
+
+	/* SQL state code */
+	if (edata->sqlerrcode)
+		appendJSONKeyValue(&buf, "state_code", unpack_sql_state(edata->sqlerrcode));
+
+	/* errdetail or error_detail log */
+	if (edata->detail_log)
+		appendJSONKeyValue(&buf, "detail", edata->detail_log);
+	else if (edata->detail)
+		appendJSONKeyValue(&buf, "detail", edata->detail);
+
+	/* errhint */
+	if (edata->hint)
+		appendJSONKeyValue(&buf, "hint", edata->hint);
+
+	/* Internal query */
+	if (edata->internalquery)
+		appendJSONKeyValue(&buf, "internal_query", edata->internalquery);
+
+	/* If the internal query got printed, print internal pos, too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendJSONKeyValueAsUInt(&buf, "internal_position", edata->internalpos);
+
+	/* errcontext */
+	if (edata->context && !edata->hide_ctx)
+		appendJSONKeyValue(&buf, "context", edata->context);
+
+	/* user query --- only reported if not disabled by the caller */
+	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
+		debug_query_string != NULL &&
+		!edata->hide_stmt)
+	{
+		appendJSONKeyValue(&buf, "statement", debug_query_string);
+		if (edata->cursorpos > 0)
+			appendJSONKeyValueAsInt(&buf, "cursor_position", edata->cursorpos);
+	}
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		if (edata->funcname)
+			appendJSONKeyValue(&buf, "func_name", edata->funcname);
+		if (edata->filename)
+		{
+			appendJSONKeyValue(&buf, "file_name", edata->filename);
+			appendJSONKeyValueAsInt(&buf, "file_line_num", edata->lineno);
+		}
+	}
+
+	/* Application name */
+	if (application_name && application_name[0] != '\0')
+		appendJSONKeyValue(&buf, "application_name", application_name);
+
+	/* backend type */
+	appendJSONKeyValue(&buf, "backend_type", get_backend_type_for_log());
+
+	/* Error message */
+	appendJSONKeyValue(&buf, "message", edata->message);
+
+	/* Finish string */
+	appendStringInfoChar(&buf, '}');
+	appendStringInfoChar(&buf, '\n');
+
+	write_syslogger(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 23236fa4c3..e38a312b53 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -11702,6 +11702,8 @@ check_log_destination(char **newval, void **extra, GucSource source)
 			newlogdest |= LOG_DESTINATION_STDERR;
 		else if (pg_strcasecmp(tok, "csvlog") == 0)
 			newlogdest |= LOG_DESTINATION_CSVLOG;
+		else if (pg_strcasecmp(tok, "jsonlog") == 0)
+			newlogdest |= LOG_DESTINATION_JSONLOG;
 #ifdef HAVE_SYSLOG
 		else if (pg_strcasecmp(tok, "syslog") == 0)
 			newlogdest |= LOG_DESTINATION_SYSLOG;
diff --git a/src/bin/pg_ctl/t/004_logrotate.pl b/src/bin/pg_ctl/t/004_logrotate.pl
index aa0d64a4f7..c6f03f1047 100644
--- a/src/bin/pg_ctl/t/004_logrotate.pl
+++ b/src/bin/pg_ctl/t/004_logrotate.pl
@@ -6,7 +6,7 @@ use warnings;
 
 use PostgresNode;
 use TestLib;
-use Test::More tests => 10;
+use Test::More tests => 15;
 use Time::HiRes qw(usleep);
 
 # Extract the file name of a $format from the contents of
@@ -63,7 +63,7 @@ $node->init();
 $node->append_conf(
 	'postgresql.conf', qq(
 logging_collector = on
-log_destination = 'stderr, csvlog'
+log_destination = 'stderr, csvlog, jsonlog'
 # these ensure stability of test results:
 log_rotation_age = 0
 lc_messages = 'C'
@@ -94,11 +94,13 @@ note "current_logfiles = $current_logfiles";
 like(
 	$current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'current_logfiles is sane');
 
 check_log_pattern('stderr', $current_logfiles, 'division by zero', $node);
 check_log_pattern('csvlog', $current_logfiles, 'division by zero', $node);
+check_log_pattern('jsonlog', $current_logfiles, 'division by zero', $node);
 
 # Sleep 2 seconds and ask for log rotation; this should result in
 # output into a different log file name.
@@ -120,7 +122,8 @@ note "now current_logfiles = $new_current_logfiles";
 like(
 	$new_current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'new current_logfiles is sane');
 
 # Verify that log output gets to this file, too
@@ -128,5 +131,6 @@ $node->psql('postgres', 'fee fi fo fum');
 
 check_log_pattern('stderr', $new_current_logfiles, 'syntax error', $node);
 check_log_pattern('csvlog', $new_current_logfiles, 'syntax error', $node);
+check_log_pattern('jsonlog', $new_current_logfiles, 'syntax error', $node);
 
 $node->stop();
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index ef0e2a7746..c1544cab26 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5926,7 +5926,8 @@ SELECT * FROM parent WHERE key = 2400;
        <para>
         <productname>PostgreSQL</productname> supports several methods
          for logging server messages, including
-         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem> and
+         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem>,
+         <systemitem>jsonlog</systemitem>, and
          <systemitem>syslog</systemitem>. On Windows,
          <systemitem>eventlog</systemitem> is also supported. Set this
          parameter to a list of desired log destinations separated by
@@ -5944,6 +5945,14 @@ SELECT * FROM parent WHERE key = 2400;
         <xref linkend="guc-logging-collector"/> must be enabled to generate
         CSV-format log output.
        </para>
+       <para>
+        If <systemitem>jsonlog</systemitem> is included in <varname>log_destination</varname>,
+        log entries are output in <acronym>JSON</acronym> format, which is convenient for
+        loading logs into programs.
+        See <xref linkend="runtime-config-logging-jsonlog"/> for details.
+        <xref linkend="guc-logging-collector"/> must be enabled to generate
+        CSV-format log output.
+       </para>
        <para>
         When either <systemitem>stderr</systemitem> or
         <systemitem>csvlog</systemitem> are included, the file
@@ -5955,13 +5964,14 @@ SELECT * FROM parent WHERE key = 2400;
 <programlisting>
 stderr log/postgresql.log
 csvlog log/postgresql.csv
+jsonlog log/postgresql.json
 </programlisting>
 
         <filename>current_logfiles</filename> is recreated when a new log file
         is created as an effect of rotation, and
         when <varname>log_destination</varname> is reloaded.  It is removed when
-        neither <systemitem>stderr</systemitem>
-        nor <systemitem>csvlog</systemitem> are included
+        none of <systemitem>stderr</systemitem>,
+        <systemitem>csvlog</systemitem>, <systemitem>jsonlog</systemitem> are included
         in <varname>log_destination</varname>, and when the logging collector is
         disabled.
        </para>
@@ -6101,6 +6111,13 @@ local0.*    /var/log/postgresql
         (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
         replaced instead.)
        </para>
+       <para>
+        If JSON-format output is enabled in <varname>log_destination</varname>,
+        <literal>.json</literal> will be appended to the timestamped
+        log file name to create the file name for JSON-format output.
+        (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
+        replaced instead.)
+       </para>
        <para>
         This parameter can only be set in the <filename>postgresql.conf</filename>
         file or on the server command line.
@@ -7433,6 +7450,50 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         </orderedlist>
       </para>
     </sect2>
+     <sect2 id="runtime-config-logging-jsonlog">
+     <title>Using JSON-Format Log Output</title>
+
+       <para>
+        Including <literal>jsonlog</literal> in the <varname>log_destination</varname> list
+        provides a convenient way to import log files into many different programs.
+        This option emits log lines in (<acronym>JSON</acronym>) format.
+        Each log line is serialized as a JSON object with the following fields:
+<programlisting>
+        {
+            "timestamp": time stamp with milliseconds (string),
+            "user": user name (string),
+            "dbname": database name (string),
+            "pid": process ID (number),
+            "remote_host": client host (string)
+            "remote_port": port number (string),
+            "session_id": session ID (string),
+            "line_num": per-session line number (number),
+            "ps": current ps display (string),
+            "session_start": session start time (string),
+            "vxid": virtual transaction ID (string),
+            "txid": regular transaction ID (string),
+            "error_severity": error severity (string),
+            "state_code": SQLSTATE code (string),
+            "detail": error message detail (string),
+            "hint": hint (string),
+            "internal_query": internal query that led to the error (string),
+            "internal_position": cursor index into internal query (number),
+            "context": error context (string),
+            "statement": client supplied query string (string),
+            "cursor_position": cursor index into query string (string),
+            "func_name": error location function name (string),
+            "file_name": error location file name (string),
+            "file_line_num": error location file line number (number),
+            "application_name": client application name (string),
+            "message": error message (string)
+        }
+</programlisting>
+        String fields with null values are excluded from output.
+        Additional fields may be added in the future. User applications that process jsonlog
+        output should ignore unknown fields.
+       </para>
+
+    </sect2>
 
    <sect2>
     <title>Process Title</title>
-- 
2.33.0

From bd5a4ff0435c721de3e7eb9b9207d9e96d79baf4 Mon Sep 17 00:00:00 2001
From: Sehrope Sarkuni <sehrope@jackdb.com>
Date: Thu, 16 Sep 2021 14:43:31 -0400
Subject: [PATCH 1/3] Add constant for list of log destinations that use files

---
 src/backend/postmaster/syslogger.c | 5 ++---
 src/include/utils/elog.h           | 3 +++
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index bca3883572..bc546af7ff 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -420,7 +420,7 @@ SysLoggerMain(int argc, char *argv[])
 			 * was sent by pg_rotate_logfile() or "pg_ctl logrotate".
 			 */
 			if (!time_based_rotation && size_rotation_for == 0)
-				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG;
+				size_rotation_for = LOG_DESTINATIONS_WITH_FILES;
 			logfile_rotate(time_based_rotation, size_rotation_for);
 		}
 
@@ -1465,8 +1465,7 @@ update_metainfo_datafile(void)
 	FILE	   *fh;
 	mode_t		oumask;
 
-	if (!(Log_destination & LOG_DESTINATION_STDERR) &&
-		!(Log_destination & LOG_DESTINATION_CSVLOG))
+	if (!(Log_destination & LOG_DESTINATIONS_WITH_FILES))
 	{
 		if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
 			ereport(LOG,
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index f53607e12e..bea8b93da6 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -437,6 +437,9 @@ extern bool syslog_split_messages;
 #define LOG_DESTINATION_EVENTLOG 4
 #define LOG_DESTINATION_CSVLOG	 8
 
+/* Log destinations with file handles */
+#define LOG_DESTINATIONS_WITH_FILES (LOG_DESTINATION_CSVLOG | LOG_DESTINATION_STDERR)
+
 /* Other exported functions */
 extern void DebugFileOpen(void);
 extern char *unpack_sql_state(int sql_state);
-- 
2.17.1

From 653ea6865ce81de89bec4fc41f3c0be2933e6b2b Mon Sep 17 00:00:00 2001
From: Sehrope Sarkuni <sehrope@jackdb.com>
Date: Thu, 16 Sep 2021 15:57:00 -0400
Subject: [PATCH 2/3] Split out syslogger EXEC_BACKEND fd serialization and
 opening into helper functions

---
 src/backend/postmaster/syslogger.c | 109 ++++++++++++-----------------
 1 file changed, 44 insertions(+), 65 deletions(-)

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index bc546af7ff..4f0477794e 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -730,9 +730,23 @@ SysLogger_Start(void)
 	return 0;
 }
 
-
 #ifdef EXEC_BACKEND
 
+static long syslogger_get_fileno(FILE *file)
+{
+#ifndef WIN32
+	if (file != NULL)
+		return (long) fileno(file);
+	else
+		return -1;
+#else							/* WIN32 */
+	if (file != NULL)
+		return (long) _get_osfhandle(_fileno(file));
+	else
+		return 0;
+#endif							/* WIN32 */
+}
+
 /*
  * syslogger_forkexec() -
  *
@@ -751,34 +765,9 @@ syslogger_forkexec(void)
 	av[ac++] = NULL;			/* filled in by postmaster_forkexec */
 
 	/* static variables (those not passed by write_backend_variables) */
-#ifndef WIN32
-	if (syslogFile != NULL)
-		snprintf(filenobuf, sizeof(filenobuf), "%d",
-				 fileno(syslogFile));
-	else
-		strcpy(filenobuf, "-1");
-#else							/* WIN32 */
-	if (syslogFile != NULL)
-		snprintf(filenobuf, sizeof(filenobuf), "%ld",
-				 (long) _get_osfhandle(_fileno(syslogFile)));
-	else
-		strcpy(filenobuf, "0");
-#endif							/* WIN32 */
+	snprintf(filenobuf, sizeof(filenobuf), "%ld", syslogger_get_fileno(syslogFile));
 	av[ac++] = filenobuf;
-
-#ifndef WIN32
-	if (csvlogFile != NULL)
-		snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%d",
-				 fileno(csvlogFile));
-	else
-		strcpy(csvfilenobuf, "-1");
-#else							/* WIN32 */
-	if (csvlogFile != NULL)
-		snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld",
-				 (long) _get_osfhandle(_fileno(csvlogFile)));
-	else
-		strcpy(csvfilenobuf, "0");
-#endif							/* WIN32 */
+	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld", syslogger_get_fileno(csvlogFile));
 	av[ac++] = csvfilenobuf;
 
 	av[ac] = NULL;
@@ -787,6 +776,31 @@ syslogger_forkexec(void)
 	return postmaster_forkexec(ac, av);
 }
 
+static FILE* syslogger_fdopen(int fd)
+{
+	FILE *file = NULL;
+
+#ifndef WIN32
+	if (fd != -1)
+	{
+		file = fdopen(fd, "a");
+		setvbuf(file, NULL, PG_IOLBF, 0);
+	}
+#else							/* WIN32 */
+	if (fd != 0)
+	{
+		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
+		if (fd > 0)
+		{
+			file = fdopen(fd, "a");
+			setvbuf(file, NULL, PG_IOLBF, 0);
+		}
+	}
+#endif							/* WIN32 */
+
+	return file;
+}
+
 /*
  * syslogger_parseArgs() -
  *
@@ -795,8 +809,6 @@ syslogger_forkexec(void)
 static void
 syslogger_parseArgs(int argc, char *argv[])
 {
-	int			fd;
-
 	Assert(argc == 5);
 	argv += 3;
 
@@ -807,41 +819,8 @@ syslogger_parseArgs(int argc, char *argv[])
 	 * fails there's not a lot we can do to report the problem anyway.  As
 	 * coded, we'll just crash on a null pointer dereference after failure...
 	 */
-#ifndef WIN32
-	fd = atoi(*argv++);
-	if (fd != -1)
-	{
-		syslogFile = fdopen(fd, "a");
-		setvbuf(syslogFile, NULL, PG_IOLBF, 0);
-	}
-	fd = atoi(*argv++);
-	if (fd != -1)
-	{
-		csvlogFile = fdopen(fd, "a");
-		setvbuf(csvlogFile, NULL, PG_IOLBF, 0);
-	}
-#else							/* WIN32 */
-	fd = atoi(*argv++);
-	if (fd != 0)
-	{
-		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
-		if (fd > 0)
-		{
-			syslogFile = fdopen(fd, "a");
-			setvbuf(syslogFile, NULL, PG_IOLBF, 0);
-		}
-	}
-	fd = atoi(*argv++);
-	if (fd != 0)
-	{
-		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
-		if (fd > 0)
-		{
-			csvlogFile = fdopen(fd, "a");
-			setvbuf(csvlogFile, NULL, PG_IOLBF, 0);
-		}
-	}
-#endif							/* WIN32 */
+	syslogFile = syslogger_fdopen(atoi(*argv++));
+	csvlogFile = syslogger_fdopen(atoi(*argv++));
 }
 #endif							/* EXEC_BACKEND */
 
-- 
2.17.1

From 99eb9e6b69a75fec3356696d10910c4cf89dae57 Mon Sep 17 00:00:00 2001
From: Sehrope Sarkuni <sehrope@jackdb.com>
Date: Thu, 16 Sep 2021 16:14:04 -0400
Subject: [PATCH 3/3] Refactor syslogger to consolidate common tasks for file
 based destinations

---
 src/backend/postmaster/syslogger.c | 415 ++++++++++++++---------------
 1 file changed, 199 insertions(+), 216 deletions(-)

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index 4f0477794e..0f5d3b7862 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -84,11 +84,28 @@ extern bool redirection_done;
 static pg_time_t next_rotation_time;
 static bool pipe_eof_seen = false;
 static bool rotation_disabled = false;
-static FILE *syslogFile = NULL;
-static FILE *csvlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
-static char *last_file_name = NULL;
-static char *last_csv_file_name = NULL;
+
+typedef struct
+{
+	FILE *file;
+	char *last_file_name;
+	const int dest;
+	const char* name;
+	const char* suffix;
+} FileLogDestination;
+
+static FileLogDestination stderr_file_info = {NULL, NULL, LOG_DESTINATION_STDERR, "stderr", NULL};
+static FileLogDestination csvlog_file_info = {NULL, NULL, LOG_DESTINATION_CSVLOG, "csvlog", ".csv"};
+
+static inline void file_log_dest_initial_open(FileLogDestination *info);
+static inline void file_log_dest_initial_set_last_file_name(FileLogDestination *info);
+static inline void file_log_dest_check_rotate_for_open(FileLogDestination *info);
+static inline void file_log_dest_check_rotate_for_size(FileLogDestination *info, int *p_size_rotation_for);
+static inline void file_log_dest_close(FileLogDestination *info);
+static inline bool file_log_dest_should_rotate_for_size(FileLogDestination *info);
+static inline bool file_log_dest_rotate(FileLogDestination *info, pg_time_t fntime, bool time_based_rotation, int size_rotation_for);
+static bool inline file_log_dest_write_metadata(FileLogDestination *info, FILE *metadata_file);
 
 /*
  * Buffers for saving partial messages from different backends.
@@ -272,9 +289,8 @@ SysLoggerMain(int argc, char *argv[])
 	 * time because passing down just the pg_time_t is a lot cheaper than
 	 * passing a whole file path in the EXEC_BACKEND case.
 	 */
-	last_file_name = logfile_getname(first_syslogger_file_time, NULL);
-	if (csvlogFile != NULL)
-		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
+	file_log_dest_initial_set_last_file_name(&stderr_file_info);
+	file_log_dest_initial_set_last_file_name(&csvlog_file_info);
 
 	/* remember active logfile parameters */
 	currentLogDir = pstrdup(Log_directory);
@@ -353,13 +369,7 @@ SysLoggerMain(int argc, char *argv[])
 				rotation_requested = true;
 			}
 
-			/*
-			 * Force a rotation if CSVLOG output was just turned on or off and
-			 * we need to open or close csvlogFile accordingly.
-			 */
-			if (((Log_destination & LOG_DESTINATION_CSVLOG) != 0) !=
-				(csvlogFile != NULL))
-				rotation_requested = true;
+			file_log_dest_check_rotate_for_open(&csvlog_file_info);
 
 			/*
 			 * If rotation time parameter changed, reset next rotation time,
@@ -399,18 +409,8 @@ SysLoggerMain(int argc, char *argv[])
 
 		if (!rotation_requested && Log_RotationSize > 0 && !rotation_disabled)
 		{
-			/* Do a rotation if file is too big */
-			if (ftell(syslogFile) >= Log_RotationSize * 1024L)
-			{
-				rotation_requested = true;
-				size_rotation_for |= LOG_DESTINATION_STDERR;
-			}
-			if (csvlogFile != NULL &&
-				ftell(csvlogFile) >= Log_RotationSize * 1024L)
-			{
-				rotation_requested = true;
-				size_rotation_for |= LOG_DESTINATION_CSVLOG;
-			}
+			file_log_dest_check_rotate_for_size(&stderr_file_info, &size_rotation_for);
+			file_log_dest_check_rotate_for_size(&csvlog_file_info, &size_rotation_for);
 		}
 
 		if (rotation_requested)
@@ -541,7 +541,6 @@ int
 SysLogger_Start(void)
 {
 	pid_t		sysloggerPid;
-	char	   *filename;
 
 	if (!Logging_collector)
 		return 0;
@@ -606,25 +605,10 @@ SysLogger_Start(void)
 	 */
 	first_syslogger_file_time = time(NULL);
 
-	filename = logfile_getname(first_syslogger_file_time, NULL);
-
-	syslogFile = logfile_open(filename, "a", false);
-
-	pfree(filename);
-
-	/*
-	 * Likewise for the initial CSV log file, if that's enabled.  (Note that
-	 * we open syslogFile even when only CSV output is nominally enabled,
-	 * since some code paths will write to syslogFile anyway.)
-	 */
-	if (Log_destination & LOG_DESTINATION_CSVLOG)
-	{
-		filename = logfile_getname(first_syslogger_file_time, ".csv");
-
-		csvlogFile = logfile_open(filename, "a", false);
-
-		pfree(filename);
-	}
+	/* stderr file will always be opened */
+	file_log_dest_initial_open(&stderr_file_info);
+	/* other files are opened if destination is enabled */
+	file_log_dest_initial_open(&csvlog_file_info);
 
 #ifdef EXEC_BACKEND
 	switch ((sysloggerPid = syslogger_forkexec()))
@@ -716,13 +700,8 @@ SysLogger_Start(void)
 			}
 
 			/* postmaster will never write the file(s); close 'em */
-			fclose(syslogFile);
-			syslogFile = NULL;
-			if (csvlogFile != NULL)
-			{
-				fclose(csvlogFile);
-				csvlogFile = NULL;
-			}
+			file_log_dest_close(&stderr_file_info);
+			file_log_dest_close(&csvlog_file_info);
 			return (int) sysloggerPid;
 	}
 
@@ -765,9 +744,9 @@ syslogger_forkexec(void)
 	av[ac++] = NULL;			/* filled in by postmaster_forkexec */
 
 	/* static variables (those not passed by write_backend_variables) */
-	snprintf(filenobuf, sizeof(filenobuf), "%ld", syslogger_get_fileno(syslogFile));
+	snprintf(filenobuf, sizeof(filenobuf), "%ld", syslogger_get_fileno(stderr_file_info->file));
 	av[ac++] = filenobuf;
-	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld", syslogger_get_fileno(csvlogFile));
+	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld", syslogger_get_fileno(csvlog_file_info->file));
 	av[ac++] = csvfilenobuf;
 
 	av[ac] = NULL;
@@ -819,8 +798,8 @@ syslogger_parseArgs(int argc, char *argv[])
 	 * fails there's not a lot we can do to report the problem anyway.  As
 	 * coded, we'll just crash on a null pointer dereference after failure...
 	 */
-	syslogFile = syslogger_fdopen(atoi(*argv++));
-	csvlogFile = syslogger_fdopen(atoi(*argv++));
+	stderr_file_info->file = syslogger_fdopen(atoi(*argv++));
+	csvlog_file_info->file = syslogger_fdopen(atoi(*argv++));
 }
 #endif							/* EXEC_BACKEND */
 
@@ -1050,6 +1029,26 @@ flush_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 	*bytes_in_logbuffer = 0;
 }
 
+static inline FILE* get_syslogger_file(int dest)
+{
+	/*
+	 * If we're told to write to a logfile, but it's not open, dump the data
+	 * to stderr (which is always open) instead.  This can happen if the
+	 * output is enabled after postmaster start and we've been unable to open
+	 * outputs's file.  There are also race conditions during a parameter change
+	 * whereby backends might send us the output before we open the log file or
+	 * after we close it.  Writing formatted output to the regular log
+	 * file isn't great, but it beats dropping log output on the floor.
+	 *
+	 * Think not to improve this by trying to open a logfile on-the-fly.  Any
+	 * failure in that would lead to recursion.
+	 */
+	if (dest == LOG_DESTINATION_CSVLOG && csvlog_file_info.file != NULL) {
+		return csvlog_file_info.file;
+	}
+	return stderr_file_info.file;
+}
+
 
 /* --------------------------------
  *		logfile routines
@@ -1067,24 +1066,8 @@ void
 write_syslogger_file(const char *buffer, int count, int destination)
 {
 	int			rc;
-	FILE	   *logfile;
 
-	/*
-	 * If we're told to write to csvlogFile, but it's not open, dump the data
-	 * to syslogFile (which is always open) instead.  This can happen if CSV
-	 * output is enabled after postmaster start and we've been unable to open
-	 * csvlogFile.  There are also race conditions during a parameter change
-	 * whereby backends might send us CSV output before we open csvlogFile or
-	 * after we close it.  Writing CSV-formatted output to the regular log
-	 * file isn't great, but it beats dropping log output on the floor.
-	 *
-	 * Think not to improve this by trying to open csvlogFile on-the-fly.  Any
-	 * failure in that would lead to recursion.
-	 */
-	logfile = (destination == LOG_DESTINATION_CSVLOG &&
-			   csvlogFile != NULL) ? csvlogFile : syslogFile;
-
-	rc = fwrite(buffer, 1, count, logfile);
+	rc = fwrite(buffer, 1, count, get_syslogger_file(destination));
 
 	/*
 	 * Try to report any failure.  We mustn't use ereport because it would
@@ -1152,8 +1135,8 @@ pipeThread(void *arg)
 		 */
 		if (Log_RotationSize > 0)
 		{
-			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
-				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
+			if (file_log_dest_should_rotate_for_size(&stderr_file_info) ||
+				file_log_dest_should_rotate_for_size(&csvlog_file_info))
 				SetLatch(MyLatch);
 		}
 		LeaveCriticalSection(&sysloggerSection);
@@ -1224,10 +1207,7 @@ logfile_open(const char *filename, const char *mode, bool allow_errors)
 static void
 logfile_rotate(bool time_based_rotation, int size_rotation_for)
 {
-	char	   *filename;
-	char	   *csvfilename = NULL;
 	pg_time_t	fntime;
-	FILE	   *fh;
 
 	rotation_requested = false;
 
@@ -1240,124 +1220,15 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 		fntime = next_rotation_time;
 	else
 		fntime = time(NULL);
-	filename = logfile_getname(fntime, NULL);
-	if (Log_destination & LOG_DESTINATION_CSVLOG)
-		csvfilename = logfile_getname(fntime, ".csv");
-
-	/*
-	 * Decide whether to overwrite or append.  We can overwrite if (a)
-	 * Log_truncate_on_rotation is set, (b) the rotation was triggered by
-	 * elapsed time and not something else, and (c) the computed file name is
-	 * different from what we were previously logging into.
-	 *
-	 * Note: last_file_name should never be NULL here, but if it is, append.
-	 */
-	if (time_based_rotation || (size_rotation_for & LOG_DESTINATION_STDERR))
-	{
-		if (Log_truncate_on_rotation && time_based_rotation &&
-			last_file_name != NULL &&
-			strcmp(filename, last_file_name) != 0)
-			fh = logfile_open(filename, "w", true);
-		else
-			fh = logfile_open(filename, "a", true);
-
-		if (!fh)
-		{
-			/*
-			 * ENFILE/EMFILE are not too surprising on a busy system; just
-			 * keep using the old file till we manage to get a new one.
-			 * Otherwise, assume something's wrong with Log_directory and stop
-			 * trying to create files.
-			 */
-			if (errno != ENFILE && errno != EMFILE)
-			{
-				ereport(LOG,
-						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
-				rotation_disabled = true;
-			}
-
-			if (filename)
-				pfree(filename);
-			if (csvfilename)
-				pfree(csvfilename);
-			return;
-		}
-
-		fclose(syslogFile);
-		syslogFile = fh;
-
-		/* instead of pfree'ing filename, remember it for next time */
-		if (last_file_name != NULL)
-			pfree(last_file_name);
-		last_file_name = filename;
-		filename = NULL;
-	}
-
-	/*
-	 * Same as above, but for csv file.  Note that if LOG_DESTINATION_CSVLOG
-	 * was just turned on, we might have to open csvlogFile here though it was
-	 * not open before.  In such a case we'll append not overwrite (since
-	 * last_csv_file_name will be NULL); that is consistent with the normal
-	 * rules since it's not a time-based rotation.
-	 */
-	if ((Log_destination & LOG_DESTINATION_CSVLOG) &&
-		(csvlogFile == NULL ||
-		 time_based_rotation || (size_rotation_for & LOG_DESTINATION_CSVLOG)))
-	{
-		if (Log_truncate_on_rotation && time_based_rotation &&
-			last_csv_file_name != NULL &&
-			strcmp(csvfilename, last_csv_file_name) != 0)
-			fh = logfile_open(csvfilename, "w", true);
-		else
-			fh = logfile_open(csvfilename, "a", true);
-
-		if (!fh)
-		{
-			/*
-			 * ENFILE/EMFILE are not too surprising on a busy system; just
-			 * keep using the old file till we manage to get a new one.
-			 * Otherwise, assume something's wrong with Log_directory and stop
-			 * trying to create files.
-			 */
-			if (errno != ENFILE && errno != EMFILE)
-			{
-				ereport(LOG,
-						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
-				rotation_disabled = true;
-			}
-
-			if (filename)
-				pfree(filename);
-			if (csvfilename)
-				pfree(csvfilename);
-			return;
-		}
-
-		if (csvlogFile != NULL)
-			fclose(csvlogFile);
-		csvlogFile = fh;
 
-		/* instead of pfree'ing filename, remember it for next time */
-		if (last_csv_file_name != NULL)
-			pfree(last_csv_file_name);
-		last_csv_file_name = csvfilename;
-		csvfilename = NULL;
-	}
-	else if (!(Log_destination & LOG_DESTINATION_CSVLOG) &&
-			 csvlogFile != NULL)
-	{
-		/* CSVLOG was just turned off, so close the old file */
-		fclose(csvlogFile);
-		csvlogFile = NULL;
-		if (last_csv_file_name != NULL)
-			pfree(last_csv_file_name);
-		last_csv_file_name = NULL;
+	if (!file_log_dest_rotate(&stderr_file_info, fntime, time_based_rotation, size_rotation_for) ||
+		!file_log_dest_rotate(&csvlog_file_info, fntime, time_based_rotation, size_rotation_for)) {
+		/* We failed to open a new log file so try again later */
+		return;
 	}
 
-	if (filename)
-		pfree(filename);
-	if (csvfilename)
-		pfree(csvfilename);
+	if (!(Log_destination & LOG_DESTINATION_CSVLOG))
+		file_log_dest_close(&csvlog_file_info);
 
 	update_metainfo_datafile();
 
@@ -1477,31 +1348,13 @@ update_metainfo_datafile(void)
 		return;
 	}
 
-	if (last_file_name && (Log_destination & LOG_DESTINATION_STDERR))
+	if (!file_log_dest_write_metadata(&stderr_file_info, fh) ||
+		!file_log_dest_write_metadata(&csvlog_file_info, fh))
 	{
-		if (fprintf(fh, "stderr %s\n", last_file_name) < 0)
-		{
-			ereport(LOG,
-					(errcode_for_file_access(),
-					 errmsg("could not write file \"%s\": %m",
-							LOG_METAINFO_DATAFILE_TMP)));
-			fclose(fh);
-			return;
-		}
+		fclose(fh);
+		return;
 	}
 
-	if (last_csv_file_name && (Log_destination & LOG_DESTINATION_CSVLOG))
-	{
-		if (fprintf(fh, "csvlog %s\n", last_csv_file_name) < 0)
-		{
-			ereport(LOG,
-					(errcode_for_file_access(),
-					 errmsg("could not write file \"%s\": %m",
-							LOG_METAINFO_DATAFILE_TMP)));
-			fclose(fh);
-			return;
-		}
-	}
 	fclose(fh);
 
 	if (rename(LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE) != 0)
@@ -1551,3 +1404,133 @@ sigUsr1Handler(SIGNAL_ARGS)
 
 	errno = save_errno;
 }
+
+static inline void file_log_dest_initial_open(FileLogDestination *info)
+{
+	/* We always open stderr. Otherwise only open if enabled. */
+	if (info->dest == LOG_DESTINATION_STDERR || (Log_destination & info->dest))
+	{
+		char *filename = logfile_getname(first_syslogger_file_time, info->suffix);
+		info->file = logfile_open(filename, "a", false);
+		pfree(filename);
+	}
+}
+
+static inline void file_log_dest_initial_set_last_file_name(FileLogDestination *info)
+{
+	if (info->file != NULL)
+		info->last_file_name = logfile_getname(first_syslogger_file_time, info->suffix);
+}
+
+static inline void file_log_dest_check_rotate_for_open(FileLogDestination *info)
+{
+	/*
+	* Force a rotation if a destination was just turned on or off and
+	* we need to open or close its file accordingly.
+	*/
+	if (((Log_destination & info->dest) != 0) != (info->file != NULL))
+		rotation_requested = true;
+}
+
+static inline void file_log_dest_check_rotate_for_size(FileLogDestination *info, int *p_size_rotation_for)
+{
+	if (info->file == NULL) {
+		return;
+	}
+	/* Do a rotation if file is too big */
+	if (ftell(info->file) >= Log_RotationSize * 1024L)
+	{
+		rotation_requested = true;
+		*p_size_rotation_for |= info->dest;
+	}
+}
+
+static inline void file_log_dest_close(FileLogDestination *info)
+{
+	if (info->file != NULL)
+	{
+		fclose(info->file);
+		info->file = NULL;
+	}
+	if (info->last_file_name != NULL)
+	{
+		pfree(info->last_file_name);
+		info->last_file_name = NULL;
+	}
+}
+
+static inline bool file_log_dest_should_rotate_for_size(FileLogDestination *info)
+{
+	if (info->file == NULL)
+		return false;
+
+	return ftell(info->file) >= Log_RotationSize * 1024L;
+}
+
+static inline bool file_log_dest_rotate(FileLogDestination *info, pg_time_t fntime, bool time_based_rotation, int size_rotation_for)
+{
+	/*
+	 * Decide whether to overwrite or append.  We can overwrite if (a)
+	 * Log_truncate_on_rotation is set, (b) the rotation was triggered by
+	 * elapsed time and not something else, and (c) the computed file name is
+	 * different from what we were previously logging into.
+	 *
+	 * Note: last_file_name should never be NULL here, but if it is, append.
+	 */
+	if (time_based_rotation || (size_rotation_for & info->dest))
+	{
+		FILE *file = NULL;
+		char *filename = logfile_getname(fntime, info->suffix);
+
+		if (Log_truncate_on_rotation
+			&& time_based_rotation
+			&& info->last_file_name != NULL
+			&& strcmp(filename, info->last_file_name) != 0)
+			file = logfile_open(filename, "w", true);
+		else
+			file = logfile_open(filename, "a", true);
+
+		if (file == NULL)
+		{
+			/*
+			 * ENFILE/EMFILE are not too surprising on a busy system; just
+			 * keep using the old file till we manage to get a new one.
+			 * Otherwise, assume something's wrong with Log_directory and stop
+			 * trying to create files.
+			 */
+			if (errno != ENFILE && errno != EMFILE)
+			{
+				ereport(LOG,
+						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
+				rotation_disabled = true;
+			}
+
+			if (filename)
+				pfree(filename);
+			return false;
+		}
+
+		file_log_dest_close(info);
+		info->file = file;
+		/* instead of pfree'ing filename, remember it for next time */
+		info->last_file_name = filename;
+	}
+
+	return true;
+}
+
+static bool inline file_log_dest_write_metadata(FileLogDestination *info, FILE *metadata_file)
+{
+	if (info->last_file_name != NULL && (Log_destination & info->dest))
+	{
+		if (fprintf(metadata_file, "%s %s\n", info->name, info->last_file_name) < 0)
+		{
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not write file \"%s\": %m",
+							LOG_METAINFO_DATAFILE_TMP)));
+			return false;
+		}
+	}
+	return true;
+}
-- 
2.17.1

From 0f7978566b7770465060cd497a8dd4102b313878 Mon Sep 17 00:00:00 2001
From: Sehrope Sarkuni <sehrope@jackdb.com>
Date: Thu, 16 Sep 2021 14:43:31 -0400
Subject: [PATCH 1/3] Add constant for list of log destinations that use files

---
 src/backend/postmaster/syslogger.c | 5 ++---
 src/include/utils/elog.h           | 3 +++
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index bca3883572..bc546af7ff 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -420,7 +420,7 @@ SysLoggerMain(int argc, char *argv[])
 			 * was sent by pg_rotate_logfile() or "pg_ctl logrotate".
 			 */
 			if (!time_based_rotation && size_rotation_for == 0)
-				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG;
+				size_rotation_for = LOG_DESTINATIONS_WITH_FILES;
 			logfile_rotate(time_based_rotation, size_rotation_for);
 		}
 
@@ -1465,8 +1465,7 @@ update_metainfo_datafile(void)
 	FILE	   *fh;
 	mode_t		oumask;
 
-	if (!(Log_destination & LOG_DESTINATION_STDERR) &&
-		!(Log_destination & LOG_DESTINATION_CSVLOG))
+	if (!(Log_destination & LOG_DESTINATIONS_WITH_FILES))
 	{
 		if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
 			ereport(LOG,
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index f53607e12e..bea8b93da6 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -437,6 +437,9 @@ extern bool syslog_split_messages;
 #define LOG_DESTINATION_EVENTLOG 4
 #define LOG_DESTINATION_CSVLOG	 8
 
+/* Log destinations with file handles */
+#define LOG_DESTINATIONS_WITH_FILES (LOG_DESTINATION_CSVLOG | LOG_DESTINATION_STDERR)
+
 /* Other exported functions */
 extern void DebugFileOpen(void);
 extern char *unpack_sql_state(int sql_state);
-- 
2.25.1

From a22760648dad3832869b8c67886826e7cd306e52 Mon Sep 17 00:00:00 2001
From: Sehrope Sarkuni <sehrope@jackdb.com>
Date: Thu, 16 Sep 2021 15:57:00 -0400
Subject: [PATCH 2/3] Split out syslogger EXEC_BACKEND fd serialization and
 opening into helper functions

---
 src/backend/postmaster/syslogger.c | 109 ++++++++++++-----------------
 1 file changed, 44 insertions(+), 65 deletions(-)

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index bc546af7ff..4f0477794e 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -730,9 +730,23 @@ SysLogger_Start(void)
 	return 0;
 }
 
-
 #ifdef EXEC_BACKEND
 
+static long syslogger_get_fileno(FILE *file)
+{
+#ifndef WIN32
+	if (file != NULL)
+		return (long) fileno(file);
+	else
+		return -1;
+#else							/* WIN32 */
+	if (file != NULL)
+		return (long) _get_osfhandle(_fileno(file));
+	else
+		return 0;
+#endif							/* WIN32 */
+}
+
 /*
  * syslogger_forkexec() -
  *
@@ -751,34 +765,9 @@ syslogger_forkexec(void)
 	av[ac++] = NULL;			/* filled in by postmaster_forkexec */
 
 	/* static variables (those not passed by write_backend_variables) */
-#ifndef WIN32
-	if (syslogFile != NULL)
-		snprintf(filenobuf, sizeof(filenobuf), "%d",
-				 fileno(syslogFile));
-	else
-		strcpy(filenobuf, "-1");
-#else							/* WIN32 */
-	if (syslogFile != NULL)
-		snprintf(filenobuf, sizeof(filenobuf), "%ld",
-				 (long) _get_osfhandle(_fileno(syslogFile)));
-	else
-		strcpy(filenobuf, "0");
-#endif							/* WIN32 */
+	snprintf(filenobuf, sizeof(filenobuf), "%ld", syslogger_get_fileno(syslogFile));
 	av[ac++] = filenobuf;
-
-#ifndef WIN32
-	if (csvlogFile != NULL)
-		snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%d",
-				 fileno(csvlogFile));
-	else
-		strcpy(csvfilenobuf, "-1");
-#else							/* WIN32 */
-	if (csvlogFile != NULL)
-		snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld",
-				 (long) _get_osfhandle(_fileno(csvlogFile)));
-	else
-		strcpy(csvfilenobuf, "0");
-#endif							/* WIN32 */
+	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld", syslogger_get_fileno(csvlogFile));
 	av[ac++] = csvfilenobuf;
 
 	av[ac] = NULL;
@@ -787,6 +776,31 @@ syslogger_forkexec(void)
 	return postmaster_forkexec(ac, av);
 }
 
+static FILE* syslogger_fdopen(int fd)
+{
+	FILE *file = NULL;
+
+#ifndef WIN32
+	if (fd != -1)
+	{
+		file = fdopen(fd, "a");
+		setvbuf(file, NULL, PG_IOLBF, 0);
+	}
+#else							/* WIN32 */
+	if (fd != 0)
+	{
+		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
+		if (fd > 0)
+		{
+			file = fdopen(fd, "a");
+			setvbuf(file, NULL, PG_IOLBF, 0);
+		}
+	}
+#endif							/* WIN32 */
+
+	return file;
+}
+
 /*
  * syslogger_parseArgs() -
  *
@@ -795,8 +809,6 @@ syslogger_forkexec(void)
 static void
 syslogger_parseArgs(int argc, char *argv[])
 {
-	int			fd;
-
 	Assert(argc == 5);
 	argv += 3;
 
@@ -807,41 +819,8 @@ syslogger_parseArgs(int argc, char *argv[])
 	 * fails there's not a lot we can do to report the problem anyway.  As
 	 * coded, we'll just crash on a null pointer dereference after failure...
 	 */
-#ifndef WIN32
-	fd = atoi(*argv++);
-	if (fd != -1)
-	{
-		syslogFile = fdopen(fd, "a");
-		setvbuf(syslogFile, NULL, PG_IOLBF, 0);
-	}
-	fd = atoi(*argv++);
-	if (fd != -1)
-	{
-		csvlogFile = fdopen(fd, "a");
-		setvbuf(csvlogFile, NULL, PG_IOLBF, 0);
-	}
-#else							/* WIN32 */
-	fd = atoi(*argv++);
-	if (fd != 0)
-	{
-		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
-		if (fd > 0)
-		{
-			syslogFile = fdopen(fd, "a");
-			setvbuf(syslogFile, NULL, PG_IOLBF, 0);
-		}
-	}
-	fd = atoi(*argv++);
-	if (fd != 0)
-	{
-		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
-		if (fd > 0)
-		{
-			csvlogFile = fdopen(fd, "a");
-			setvbuf(csvlogFile, NULL, PG_IOLBF, 0);
-		}
-	}
-#endif							/* WIN32 */
+	syslogFile = syslogger_fdopen(atoi(*argv++));
+	csvlogFile = syslogger_fdopen(atoi(*argv++));
 }
 #endif							/* EXEC_BACKEND */
 
-- 
2.25.1

From b4d56b497ab9412ed5a28bf5422b0905aeb4ad9f Mon Sep 17 00:00:00 2001
From: Sehrope Sarkuni <sehrope@jackdb.com>
Date: Thu, 16 Sep 2021 16:14:04 -0400
Subject: [PATCH 3/3] Refactor syslogger to consolidate common tasks for file
 based destinations

---
 src/backend/postmaster/syslogger.c | 415 ++++++++++++++---------------
 1 file changed, 199 insertions(+), 216 deletions(-)

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index 4f0477794e..720066bdca 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -84,11 +84,28 @@ extern bool redirection_done;
 static pg_time_t next_rotation_time;
 static bool pipe_eof_seen = false;
 static bool rotation_disabled = false;
-static FILE *syslogFile = NULL;
-static FILE *csvlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
-static char *last_file_name = NULL;
-static char *last_csv_file_name = NULL;
+
+typedef struct
+{
+	FILE *file;
+	char *last_file_name;
+	const int dest;
+	const char* name;
+	const char* suffix;
+} FileLogDestination;
+
+static FileLogDestination stderr_file_info = {NULL, NULL, LOG_DESTINATION_STDERR, "stderr", NULL};
+static FileLogDestination csvlog_file_info = {NULL, NULL, LOG_DESTINATION_CSVLOG, "csvlog", ".csv"};
+
+static inline void file_log_dest_initial_open(FileLogDestination *info);
+static inline void file_log_dest_initial_set_last_file_name(FileLogDestination *info);
+static inline void file_log_dest_check_rotate_for_open(FileLogDestination *info);
+static inline void file_log_dest_check_rotate_for_size(FileLogDestination *info, int *p_size_rotation_for);
+static inline void file_log_dest_close(FileLogDestination *info);
+static inline bool file_log_dest_should_rotate_for_size(FileLogDestination *info);
+static inline bool file_log_dest_rotate(FileLogDestination *info, pg_time_t fntime, bool time_based_rotation, int size_rotation_for);
+static bool inline file_log_dest_write_metadata(FileLogDestination *info, FILE *metadata_file);
 
 /*
  * Buffers for saving partial messages from different backends.
@@ -272,9 +289,8 @@ SysLoggerMain(int argc, char *argv[])
 	 * time because passing down just the pg_time_t is a lot cheaper than
 	 * passing a whole file path in the EXEC_BACKEND case.
 	 */
-	last_file_name = logfile_getname(first_syslogger_file_time, NULL);
-	if (csvlogFile != NULL)
-		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
+	file_log_dest_initial_set_last_file_name(&stderr_file_info);
+	file_log_dest_initial_set_last_file_name(&csvlog_file_info);
 
 	/* remember active logfile parameters */
 	currentLogDir = pstrdup(Log_directory);
@@ -353,13 +369,7 @@ SysLoggerMain(int argc, char *argv[])
 				rotation_requested = true;
 			}
 
-			/*
-			 * Force a rotation if CSVLOG output was just turned on or off and
-			 * we need to open or close csvlogFile accordingly.
-			 */
-			if (((Log_destination & LOG_DESTINATION_CSVLOG) != 0) !=
-				(csvlogFile != NULL))
-				rotation_requested = true;
+			file_log_dest_check_rotate_for_open(&csvlog_file_info);
 
 			/*
 			 * If rotation time parameter changed, reset next rotation time,
@@ -399,18 +409,8 @@ SysLoggerMain(int argc, char *argv[])
 
 		if (!rotation_requested && Log_RotationSize > 0 && !rotation_disabled)
 		{
-			/* Do a rotation if file is too big */
-			if (ftell(syslogFile) >= Log_RotationSize * 1024L)
-			{
-				rotation_requested = true;
-				size_rotation_for |= LOG_DESTINATION_STDERR;
-			}
-			if (csvlogFile != NULL &&
-				ftell(csvlogFile) >= Log_RotationSize * 1024L)
-			{
-				rotation_requested = true;
-				size_rotation_for |= LOG_DESTINATION_CSVLOG;
-			}
+			file_log_dest_check_rotate_for_size(&stderr_file_info, &size_rotation_for);
+			file_log_dest_check_rotate_for_size(&csvlog_file_info, &size_rotation_for);
 		}
 
 		if (rotation_requested)
@@ -541,7 +541,6 @@ int
 SysLogger_Start(void)
 {
 	pid_t		sysloggerPid;
-	char	   *filename;
 
 	if (!Logging_collector)
 		return 0;
@@ -606,25 +605,10 @@ SysLogger_Start(void)
 	 */
 	first_syslogger_file_time = time(NULL);
 
-	filename = logfile_getname(first_syslogger_file_time, NULL);
-
-	syslogFile = logfile_open(filename, "a", false);
-
-	pfree(filename);
-
-	/*
-	 * Likewise for the initial CSV log file, if that's enabled.  (Note that
-	 * we open syslogFile even when only CSV output is nominally enabled,
-	 * since some code paths will write to syslogFile anyway.)
-	 */
-	if (Log_destination & LOG_DESTINATION_CSVLOG)
-	{
-		filename = logfile_getname(first_syslogger_file_time, ".csv");
-
-		csvlogFile = logfile_open(filename, "a", false);
-
-		pfree(filename);
-	}
+	/* stderr file will always be opened */
+	file_log_dest_initial_open(&stderr_file_info);
+	/* other files are opened if destination is enabled */
+	file_log_dest_initial_open(&csvlog_file_info);
 
 #ifdef EXEC_BACKEND
 	switch ((sysloggerPid = syslogger_forkexec()))
@@ -716,13 +700,8 @@ SysLogger_Start(void)
 			}
 
 			/* postmaster will never write the file(s); close 'em */
-			fclose(syslogFile);
-			syslogFile = NULL;
-			if (csvlogFile != NULL)
-			{
-				fclose(csvlogFile);
-				csvlogFile = NULL;
-			}
+			file_log_dest_close(&stderr_file_info);
+			file_log_dest_close(&csvlog_file_info);
 			return (int) sysloggerPid;
 	}
 
@@ -765,9 +744,9 @@ syslogger_forkexec(void)
 	av[ac++] = NULL;			/* filled in by postmaster_forkexec */
 
 	/* static variables (those not passed by write_backend_variables) */
-	snprintf(filenobuf, sizeof(filenobuf), "%ld", syslogger_get_fileno(syslogFile));
+	snprintf(filenobuf, sizeof(filenobuf), "%ld", syslogger_get_fileno(stderr_file_info.file));
 	av[ac++] = filenobuf;
-	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld", syslogger_get_fileno(csvlogFile));
+	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld", syslogger_get_fileno(csvlog_file_info.file));
 	av[ac++] = csvfilenobuf;
 
 	av[ac] = NULL;
@@ -819,8 +798,8 @@ syslogger_parseArgs(int argc, char *argv[])
 	 * fails there's not a lot we can do to report the problem anyway.  As
 	 * coded, we'll just crash on a null pointer dereference after failure...
 	 */
-	syslogFile = syslogger_fdopen(atoi(*argv++));
-	csvlogFile = syslogger_fdopen(atoi(*argv++));
+	stderr_file_info.file = syslogger_fdopen(atoi(*argv++));
+	csvlog_file_info.file = syslogger_fdopen(atoi(*argv++));
 }
 #endif							/* EXEC_BACKEND */
 
@@ -1050,6 +1029,26 @@ flush_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 	*bytes_in_logbuffer = 0;
 }
 
+static inline FILE* get_syslogger_file(int dest)
+{
+	/*
+	 * If we're told to write to a logfile, but it's not open, dump the data
+	 * to stderr (which is always open) instead.  This can happen if the
+	 * output is enabled after postmaster start and we've been unable to open
+	 * outputs's file.  There are also race conditions during a parameter change
+	 * whereby backends might send us the output before we open the log file or
+	 * after we close it.  Writing formatted output to the regular log
+	 * file isn't great, but it beats dropping log output on the floor.
+	 *
+	 * Think not to improve this by trying to open a logfile on-the-fly.  Any
+	 * failure in that would lead to recursion.
+	 */
+	if (dest == LOG_DESTINATION_CSVLOG && csvlog_file_info.file != NULL) {
+		return csvlog_file_info.file;
+	}
+	return stderr_file_info.file;
+}
+
 
 /* --------------------------------
  *		logfile routines
@@ -1067,24 +1066,8 @@ void
 write_syslogger_file(const char *buffer, int count, int destination)
 {
 	int			rc;
-	FILE	   *logfile;
 
-	/*
-	 * If we're told to write to csvlogFile, but it's not open, dump the data
-	 * to syslogFile (which is always open) instead.  This can happen if CSV
-	 * output is enabled after postmaster start and we've been unable to open
-	 * csvlogFile.  There are also race conditions during a parameter change
-	 * whereby backends might send us CSV output before we open csvlogFile or
-	 * after we close it.  Writing CSV-formatted output to the regular log
-	 * file isn't great, but it beats dropping log output on the floor.
-	 *
-	 * Think not to improve this by trying to open csvlogFile on-the-fly.  Any
-	 * failure in that would lead to recursion.
-	 */
-	logfile = (destination == LOG_DESTINATION_CSVLOG &&
-			   csvlogFile != NULL) ? csvlogFile : syslogFile;
-
-	rc = fwrite(buffer, 1, count, logfile);
+	rc = fwrite(buffer, 1, count, get_syslogger_file(destination));
 
 	/*
 	 * Try to report any failure.  We mustn't use ereport because it would
@@ -1152,8 +1135,8 @@ pipeThread(void *arg)
 		 */
 		if (Log_RotationSize > 0)
 		{
-			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
-				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
+			if (file_log_dest_should_rotate_for_size(&stderr_file_info) ||
+				file_log_dest_should_rotate_for_size(&csvlog_file_info))
 				SetLatch(MyLatch);
 		}
 		LeaveCriticalSection(&sysloggerSection);
@@ -1224,10 +1207,7 @@ logfile_open(const char *filename, const char *mode, bool allow_errors)
 static void
 logfile_rotate(bool time_based_rotation, int size_rotation_for)
 {
-	char	   *filename;
-	char	   *csvfilename = NULL;
 	pg_time_t	fntime;
-	FILE	   *fh;
 
 	rotation_requested = false;
 
@@ -1240,124 +1220,15 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 		fntime = next_rotation_time;
 	else
 		fntime = time(NULL);
-	filename = logfile_getname(fntime, NULL);
-	if (Log_destination & LOG_DESTINATION_CSVLOG)
-		csvfilename = logfile_getname(fntime, ".csv");
-
-	/*
-	 * Decide whether to overwrite or append.  We can overwrite if (a)
-	 * Log_truncate_on_rotation is set, (b) the rotation was triggered by
-	 * elapsed time and not something else, and (c) the computed file name is
-	 * different from what we were previously logging into.
-	 *
-	 * Note: last_file_name should never be NULL here, but if it is, append.
-	 */
-	if (time_based_rotation || (size_rotation_for & LOG_DESTINATION_STDERR))
-	{
-		if (Log_truncate_on_rotation && time_based_rotation &&
-			last_file_name != NULL &&
-			strcmp(filename, last_file_name) != 0)
-			fh = logfile_open(filename, "w", true);
-		else
-			fh = logfile_open(filename, "a", true);
-
-		if (!fh)
-		{
-			/*
-			 * ENFILE/EMFILE are not too surprising on a busy system; just
-			 * keep using the old file till we manage to get a new one.
-			 * Otherwise, assume something's wrong with Log_directory and stop
-			 * trying to create files.
-			 */
-			if (errno != ENFILE && errno != EMFILE)
-			{
-				ereport(LOG,
-						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
-				rotation_disabled = true;
-			}
-
-			if (filename)
-				pfree(filename);
-			if (csvfilename)
-				pfree(csvfilename);
-			return;
-		}
-
-		fclose(syslogFile);
-		syslogFile = fh;
-
-		/* instead of pfree'ing filename, remember it for next time */
-		if (last_file_name != NULL)
-			pfree(last_file_name);
-		last_file_name = filename;
-		filename = NULL;
-	}
-
-	/*
-	 * Same as above, but for csv file.  Note that if LOG_DESTINATION_CSVLOG
-	 * was just turned on, we might have to open csvlogFile here though it was
-	 * not open before.  In such a case we'll append not overwrite (since
-	 * last_csv_file_name will be NULL); that is consistent with the normal
-	 * rules since it's not a time-based rotation.
-	 */
-	if ((Log_destination & LOG_DESTINATION_CSVLOG) &&
-		(csvlogFile == NULL ||
-		 time_based_rotation || (size_rotation_for & LOG_DESTINATION_CSVLOG)))
-	{
-		if (Log_truncate_on_rotation && time_based_rotation &&
-			last_csv_file_name != NULL &&
-			strcmp(csvfilename, last_csv_file_name) != 0)
-			fh = logfile_open(csvfilename, "w", true);
-		else
-			fh = logfile_open(csvfilename, "a", true);
-
-		if (!fh)
-		{
-			/*
-			 * ENFILE/EMFILE are not too surprising on a busy system; just
-			 * keep using the old file till we manage to get a new one.
-			 * Otherwise, assume something's wrong with Log_directory and stop
-			 * trying to create files.
-			 */
-			if (errno != ENFILE && errno != EMFILE)
-			{
-				ereport(LOG,
-						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
-				rotation_disabled = true;
-			}
-
-			if (filename)
-				pfree(filename);
-			if (csvfilename)
-				pfree(csvfilename);
-			return;
-		}
-
-		if (csvlogFile != NULL)
-			fclose(csvlogFile);
-		csvlogFile = fh;
 
-		/* instead of pfree'ing filename, remember it for next time */
-		if (last_csv_file_name != NULL)
-			pfree(last_csv_file_name);
-		last_csv_file_name = csvfilename;
-		csvfilename = NULL;
-	}
-	else if (!(Log_destination & LOG_DESTINATION_CSVLOG) &&
-			 csvlogFile != NULL)
-	{
-		/* CSVLOG was just turned off, so close the old file */
-		fclose(csvlogFile);
-		csvlogFile = NULL;
-		if (last_csv_file_name != NULL)
-			pfree(last_csv_file_name);
-		last_csv_file_name = NULL;
+	if (!file_log_dest_rotate(&stderr_file_info, fntime, time_based_rotation, size_rotation_for) ||
+		!file_log_dest_rotate(&csvlog_file_info, fntime, time_based_rotation, size_rotation_for)) {
+		/* We failed to open a new log file so try again later */
+		return;
 	}
 
-	if (filename)
-		pfree(filename);
-	if (csvfilename)
-		pfree(csvfilename);
+	if (!(Log_destination & LOG_DESTINATION_CSVLOG))
+		file_log_dest_close(&csvlog_file_info);
 
 	update_metainfo_datafile();
 
@@ -1477,31 +1348,13 @@ update_metainfo_datafile(void)
 		return;
 	}
 
-	if (last_file_name && (Log_destination & LOG_DESTINATION_STDERR))
+	if (!file_log_dest_write_metadata(&stderr_file_info, fh) ||
+		!file_log_dest_write_metadata(&csvlog_file_info, fh))
 	{
-		if (fprintf(fh, "stderr %s\n", last_file_name) < 0)
-		{
-			ereport(LOG,
-					(errcode_for_file_access(),
-					 errmsg("could not write file \"%s\": %m",
-							LOG_METAINFO_DATAFILE_TMP)));
-			fclose(fh);
-			return;
-		}
+		fclose(fh);
+		return;
 	}
 
-	if (last_csv_file_name && (Log_destination & LOG_DESTINATION_CSVLOG))
-	{
-		if (fprintf(fh, "csvlog %s\n", last_csv_file_name) < 0)
-		{
-			ereport(LOG,
-					(errcode_for_file_access(),
-					 errmsg("could not write file \"%s\": %m",
-							LOG_METAINFO_DATAFILE_TMP)));
-			fclose(fh);
-			return;
-		}
-	}
 	fclose(fh);
 
 	if (rename(LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE) != 0)
@@ -1551,3 +1404,133 @@ sigUsr1Handler(SIGNAL_ARGS)
 
 	errno = save_errno;
 }
+
+static inline void file_log_dest_initial_open(FileLogDestination *info)
+{
+	/* We always open stderr. Otherwise only open if enabled. */
+	if (info->dest == LOG_DESTINATION_STDERR || (Log_destination & info->dest))
+	{
+		char *filename = logfile_getname(first_syslogger_file_time, info->suffix);
+		info->file = logfile_open(filename, "a", false);
+		pfree(filename);
+	}
+}
+
+static inline void file_log_dest_initial_set_last_file_name(FileLogDestination *info)
+{
+	if (info->file != NULL)
+		info->last_file_name = logfile_getname(first_syslogger_file_time, info->suffix);
+}
+
+static inline void file_log_dest_check_rotate_for_open(FileLogDestination *info)
+{
+	/*
+	* Force a rotation if a destination was just turned on or off and
+	* we need to open or close its file accordingly.
+	*/
+	if (((Log_destination & info->dest) != 0) != (info->file != NULL))
+		rotation_requested = true;
+}
+
+static inline void file_log_dest_check_rotate_for_size(FileLogDestination *info, int *p_size_rotation_for)
+{
+	if (info->file == NULL) {
+		return;
+	}
+	/* Do a rotation if file is too big */
+	if (ftell(info->file) >= Log_RotationSize * 1024L)
+	{
+		rotation_requested = true;
+		*p_size_rotation_for |= info->dest;
+	}
+}
+
+static inline void file_log_dest_close(FileLogDestination *info)
+{
+	if (info->file != NULL)
+	{
+		fclose(info->file);
+		info->file = NULL;
+	}
+	if (info->last_file_name != NULL)
+	{
+		pfree(info->last_file_name);
+		info->last_file_name = NULL;
+	}
+}
+
+static inline bool file_log_dest_should_rotate_for_size(FileLogDestination *info)
+{
+	if (info->file == NULL)
+		return false;
+
+	return ftell(info->file) >= Log_RotationSize * 1024L;
+}
+
+static inline bool file_log_dest_rotate(FileLogDestination *info, pg_time_t fntime, bool time_based_rotation, int size_rotation_for)
+{
+	/*
+	 * Decide whether to overwrite or append.  We can overwrite if (a)
+	 * Log_truncate_on_rotation is set, (b) the rotation was triggered by
+	 * elapsed time and not something else, and (c) the computed file name is
+	 * different from what we were previously logging into.
+	 *
+	 * Note: last_file_name should never be NULL here, but if it is, append.
+	 */
+	if (time_based_rotation || (size_rotation_for & info->dest))
+	{
+		FILE *file = NULL;
+		char *filename = logfile_getname(fntime, info->suffix);
+
+		if (Log_truncate_on_rotation
+			&& time_based_rotation
+			&& info->last_file_name != NULL
+			&& strcmp(filename, info->last_file_name) != 0)
+			file = logfile_open(filename, "w", true);
+		else
+			file = logfile_open(filename, "a", true);
+
+		if (file == NULL)
+		{
+			/*
+			 * ENFILE/EMFILE are not too surprising on a busy system; just
+			 * keep using the old file till we manage to get a new one.
+			 * Otherwise, assume something's wrong with Log_directory and stop
+			 * trying to create files.
+			 */
+			if (errno != ENFILE && errno != EMFILE)
+			{
+				ereport(LOG,
+						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
+				rotation_disabled = true;
+			}
+
+			if (filename)
+				pfree(filename);
+			return false;
+		}
+
+		file_log_dest_close(info);
+		info->file = file;
+		/* instead of pfree'ing filename, remember it for next time */
+		info->last_file_name = filename;
+	}
+
+	return true;
+}
+
+static bool inline file_log_dest_write_metadata(FileLogDestination *info, FILE *metadata_file)
+{
+	if (info->last_file_name != NULL && (Log_destination & info->dest))
+	{
+		if (fprintf(metadata_file, "%s %s\n", info->name, info->last_file_name) < 0)
+		{
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not write file \"%s\": %m",
+							LOG_METAINFO_DATAFILE_TMP)));
+			return false;
+		}
+	}
+	return true;
+}
-- 
2.25.1

From c85e15ffc6a8e310c10be4c85580980d04846bf2 Mon Sep 17 00:00:00 2001
From: Sehrope Sarkuni <sehrope@jackdb.com>
Date: Thu, 16 Sep 2021 15:57:00 -0400
Subject: [PATCH 1/2] Split out syslogger EXEC_BACKEND fd serialization and
 opening into helper functions

---
 src/backend/postmaster/syslogger.c | 109 ++++++++++++-----------------
 1 file changed, 44 insertions(+), 65 deletions(-)

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index bca3883572..48b4c48a18 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -730,9 +730,23 @@ SysLogger_Start(void)
 	return 0;
 }
 
-
 #ifdef EXEC_BACKEND
 
+static long syslogger_get_fileno(FILE *file)
+{
+#ifndef WIN32
+	if (file != NULL)
+		return (long) fileno(file);
+	else
+		return -1;
+#else							/* WIN32 */
+	if (file != NULL)
+		return (long) _get_osfhandle(_fileno(file));
+	else
+		return 0;
+#endif							/* WIN32 */
+}
+
 /*
  * syslogger_forkexec() -
  *
@@ -751,34 +765,9 @@ syslogger_forkexec(void)
 	av[ac++] = NULL;			/* filled in by postmaster_forkexec */
 
 	/* static variables (those not passed by write_backend_variables) */
-#ifndef WIN32
-	if (syslogFile != NULL)
-		snprintf(filenobuf, sizeof(filenobuf), "%d",
-				 fileno(syslogFile));
-	else
-		strcpy(filenobuf, "-1");
-#else							/* WIN32 */
-	if (syslogFile != NULL)
-		snprintf(filenobuf, sizeof(filenobuf), "%ld",
-				 (long) _get_osfhandle(_fileno(syslogFile)));
-	else
-		strcpy(filenobuf, "0");
-#endif							/* WIN32 */
+	snprintf(filenobuf, sizeof(filenobuf), "%ld", syslogger_get_fileno(syslogFile));
 	av[ac++] = filenobuf;
-
-#ifndef WIN32
-	if (csvlogFile != NULL)
-		snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%d",
-				 fileno(csvlogFile));
-	else
-		strcpy(csvfilenobuf, "-1");
-#else							/* WIN32 */
-	if (csvlogFile != NULL)
-		snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld",
-				 (long) _get_osfhandle(_fileno(csvlogFile)));
-	else
-		strcpy(csvfilenobuf, "0");
-#endif							/* WIN32 */
+	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld", syslogger_get_fileno(csvlogFile));
 	av[ac++] = csvfilenobuf;
 
 	av[ac] = NULL;
@@ -787,6 +776,31 @@ syslogger_forkexec(void)
 	return postmaster_forkexec(ac, av);
 }
 
+static FILE* syslogger_fdopen(int fd)
+{
+	FILE *file = NULL;
+
+#ifndef WIN32
+	if (fd != -1)
+	{
+		file = fdopen(fd, "a");
+		setvbuf(file, NULL, PG_IOLBF, 0);
+	}
+#else							/* WIN32 */
+	if (fd != 0)
+	{
+		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
+		if (fd > 0)
+		{
+			file = fdopen(fd, "a");
+			setvbuf(file, NULL, PG_IOLBF, 0);
+		}
+	}
+#endif							/* WIN32 */
+
+	return file;
+}
+
 /*
  * syslogger_parseArgs() -
  *
@@ -795,8 +809,6 @@ syslogger_forkexec(void)
 static void
 syslogger_parseArgs(int argc, char *argv[])
 {
-	int			fd;
-
 	Assert(argc == 5);
 	argv += 3;
 
@@ -807,41 +819,8 @@ syslogger_parseArgs(int argc, char *argv[])
 	 * fails there's not a lot we can do to report the problem anyway.  As
 	 * coded, we'll just crash on a null pointer dereference after failure...
 	 */
-#ifndef WIN32
-	fd = atoi(*argv++);
-	if (fd != -1)
-	{
-		syslogFile = fdopen(fd, "a");
-		setvbuf(syslogFile, NULL, PG_IOLBF, 0);
-	}
-	fd = atoi(*argv++);
-	if (fd != -1)
-	{
-		csvlogFile = fdopen(fd, "a");
-		setvbuf(csvlogFile, NULL, PG_IOLBF, 0);
-	}
-#else							/* WIN32 */
-	fd = atoi(*argv++);
-	if (fd != 0)
-	{
-		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
-		if (fd > 0)
-		{
-			syslogFile = fdopen(fd, "a");
-			setvbuf(syslogFile, NULL, PG_IOLBF, 0);
-		}
-	}
-	fd = atoi(*argv++);
-	if (fd != 0)
-	{
-		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
-		if (fd > 0)
-		{
-			csvlogFile = fdopen(fd, "a");
-			setvbuf(csvlogFile, NULL, PG_IOLBF, 0);
-		}
-	}
-#endif							/* WIN32 */
+	syslogFile = syslogger_fdopen(atoi(*argv++));
+	csvlogFile = syslogger_fdopen(atoi(*argv++));
 }
 #endif							/* EXEC_BACKEND */
 
-- 
2.17.1

From f4836bdebdae6008de3be589e253ed64f686b2f6 Mon Sep 17 00:00:00 2001
From: Sehrope Sarkuni <sehrope@jackdb.com>
Date: Fri, 17 Sep 2021 16:14:38 -0400
Subject: [PATCH 2/2] Refactor syslogger to consolidate common tasks for file
 based destinations

---
 src/backend/postmaster/syslogger.c | 345 ++++++++++++++---------------
 1 file changed, 164 insertions(+), 181 deletions(-)

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index 48b4c48a18..2c12305992 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -84,11 +84,23 @@ extern bool redirection_done;
 static pg_time_t next_rotation_time;
 static bool pipe_eof_seen = false;
 static bool rotation_disabled = false;
-static FILE *syslogFile = NULL;
-static FILE *csvlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
-static char *last_file_name = NULL;
-static char *last_csv_file_name = NULL;
+
+typedef struct
+{
+	FILE *file;
+	char *last_file_name;
+	const int dest;
+	const char* name;
+	const char* suffix;
+} FileLogDestination;
+
+static FileLogDestination stderr_file_info = {NULL, NULL, LOG_DESTINATION_STDERR, "stderr", NULL};
+static FileLogDestination csvlog_file_info = {NULL, NULL, LOG_DESTINATION_CSVLOG, "csvlog", ".csv"};
+
+static inline bool file_log_dest_should_rotate_for_size(const FileLogDestination *info);
+static bool file_log_dest_rotate(FileLogDestination *info, pg_time_t fntime, bool time_based_rotation, int size_rotation_for);
+static inline void file_log_dest_close(FileLogDestination *info);
 
 /*
  * Buffers for saving partial messages from different backends.
@@ -138,6 +150,8 @@ static void process_pipe_input(char *logbuffer, int *bytes_in_logbuffer);
 static void flush_pipe_input(char *logbuffer, int *bytes_in_logbuffer);
 static FILE *logfile_open(const char *filename, const char *mode,
 						  bool allow_errors);
+static FILE *logfile_open_suffix(const char *filename, const char *mode,
+						  bool allow_errors);
 
 #ifdef WIN32
 static unsigned int __stdcall pipeThread(void *arg);
@@ -272,9 +286,9 @@ SysLoggerMain(int argc, char *argv[])
 	 * time because passing down just the pg_time_t is a lot cheaper than
 	 * passing a whole file path in the EXEC_BACKEND case.
 	 */
-	last_file_name = logfile_getname(first_syslogger_file_time, NULL);
-	if (csvlogFile != NULL)
-		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
+	stderr_file_info.last_file_name = logfile_getname(first_syslogger_file_time, stderr_file_info.suffix);
+	if (csvlog_file_info.file != NULL)
+		csvlog_file_info.last_file_name = logfile_getname(first_syslogger_file_time, csvlog_file_info.suffix);
 
 	/* remember active logfile parameters */
 	currentLogDir = pstrdup(Log_directory);
@@ -358,7 +372,7 @@ SysLoggerMain(int argc, char *argv[])
 			 * we need to open or close csvlogFile accordingly.
 			 */
 			if (((Log_destination & LOG_DESTINATION_CSVLOG) != 0) !=
-				(csvlogFile != NULL))
+				(csvlog_file_info.file != NULL))
 				rotation_requested = true;
 
 			/*
@@ -400,13 +414,12 @@ SysLoggerMain(int argc, char *argv[])
 		if (!rotation_requested && Log_RotationSize > 0 && !rotation_disabled)
 		{
 			/* Do a rotation if file is too big */
-			if (ftell(syslogFile) >= Log_RotationSize * 1024L)
+			if (file_log_dest_should_rotate_for_size(&stderr_file_info))
 			{
 				rotation_requested = true;
 				size_rotation_for |= LOG_DESTINATION_STDERR;
 			}
-			if (csvlogFile != NULL &&
-				ftell(csvlogFile) >= Log_RotationSize * 1024L)
+			if (file_log_dest_should_rotate_for_size(&csvlog_file_info))
 			{
 				rotation_requested = true;
 				size_rotation_for |= LOG_DESTINATION_CSVLOG;
@@ -541,7 +554,6 @@ int
 SysLogger_Start(void)
 {
 	pid_t		sysloggerPid;
-	char	   *filename;
 
 	if (!Logging_collector)
 		return 0;
@@ -606,25 +618,14 @@ SysLogger_Start(void)
 	 */
 	first_syslogger_file_time = time(NULL);
 
-	filename = logfile_getname(first_syslogger_file_time, NULL);
-
-	syslogFile = logfile_open(filename, "a", false);
-
-	pfree(filename);
-
 	/*
-	 * Likewise for the initial CSV log file, if that's enabled.  (Note that
-	 * we open syslogFile even when only CSV output is nominally enabled,
-	 * since some code paths will write to syslogFile anyway.)
+	 * stderr file will always be opened since some code paths will write there
+	 * even if only other log destinations are enabled.
 	 */
+	stderr_file_info.file = logfile_open_suffix(stderr_file_info.suffix, "a", false);
+	/* Likewise for the initial CSV log file, if that's enabled. */
 	if (Log_destination & LOG_DESTINATION_CSVLOG)
-	{
-		filename = logfile_getname(first_syslogger_file_time, ".csv");
-
-		csvlogFile = logfile_open(filename, "a", false);
-
-		pfree(filename);
-	}
+		csvlog_file_info.file = logfile_open_suffix(csvlog_file_info.suffix, "a", false);
 
 #ifdef EXEC_BACKEND
 	switch ((sysloggerPid = syslogger_forkexec()))
@@ -716,13 +717,8 @@ SysLogger_Start(void)
 			}
 
 			/* postmaster will never write the file(s); close 'em */
-			fclose(syslogFile);
-			syslogFile = NULL;
-			if (csvlogFile != NULL)
-			{
-				fclose(csvlogFile);
-				csvlogFile = NULL;
-			}
+			file_log_dest_close(&stderr_file_info);
+			file_log_dest_close(&csvlog_file_info);
 			return (int) sysloggerPid;
 	}
 
@@ -765,9 +761,9 @@ syslogger_forkexec(void)
 	av[ac++] = NULL;			/* filled in by postmaster_forkexec */
 
 	/* static variables (those not passed by write_backend_variables) */
-	snprintf(filenobuf, sizeof(filenobuf), "%ld", syslogger_get_fileno(syslogFile));
+	snprintf(filenobuf, sizeof(filenobuf), "%ld", syslogger_get_fileno(stderr_file_info.file));
 	av[ac++] = filenobuf;
-	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld", syslogger_get_fileno(csvlogFile));
+	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld", syslogger_get_fileno(csvlog_file_info.file));
 	av[ac++] = csvfilenobuf;
 
 	av[ac] = NULL;
@@ -819,8 +815,8 @@ syslogger_parseArgs(int argc, char *argv[])
 	 * fails there's not a lot we can do to report the problem anyway.  As
 	 * coded, we'll just crash on a null pointer dereference after failure...
 	 */
-	syslogFile = syslogger_fdopen(atoi(*argv++));
-	csvlogFile = syslogger_fdopen(atoi(*argv++));
+	stderr_file_info.file = syslogger_fdopen(atoi(*argv++));
+	csvlog_file_info.file = syslogger_fdopen(atoi(*argv++));
 }
 #endif							/* EXEC_BACKEND */
 
@@ -1081,8 +1077,10 @@ write_syslogger_file(const char *buffer, int count, int destination)
 	 * Think not to improve this by trying to open csvlogFile on-the-fly.  Any
 	 * failure in that would lead to recursion.
 	 */
-	logfile = (destination == LOG_DESTINATION_CSVLOG &&
-			   csvlogFile != NULL) ? csvlogFile : syslogFile;
+	if (destination == LOG_DESTINATION_CSVLOG && csvlog_file_info.file != NULL)
+		logfile = csvlog_file_info.file;
+	else
+		logfile = stderr_file_info.file;
 
 	rc = fwrite(buffer, 1, count, logfile);
 
@@ -1152,8 +1150,8 @@ pipeThread(void *arg)
 		 */
 		if (Log_RotationSize > 0)
 		{
-			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
-				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
+			if (file_log_dest_should_rotate_for_size(&stderr_file_info) ||
+				file_log_dest_should_rotate_for_size(&csvlog_file_info))
 				SetLatch(MyLatch);
 		}
 		LeaveCriticalSection(&sysloggerSection);
@@ -1218,16 +1216,29 @@ logfile_open(const char *filename, const char *mode, bool allow_errors)
 	return fh;
 }
 
+/*
+ * Generate a logfile name from a given suffix and then open it.
+ */
+static FILE *
+logfile_open_suffix(const char *suffix, const char *mode, bool allow_errors)
+{
+	FILE *file;
+	char *filename;
+
+	filename = logfile_getname(first_syslogger_file_time, suffix);
+	file = logfile_open(filename, "a", allow_errors);
+
+	pfree(filename);
+	return file;
+}
+
 /*
  * perform logfile rotation
  */
 static void
 logfile_rotate(bool time_based_rotation, int size_rotation_for)
 {
-	char	   *filename;
-	char	   *csvfilename = NULL;
 	pg_time_t	fntime;
-	FILE	   *fh;
 
 	rotation_requested = false;
 
@@ -1240,125 +1251,20 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 		fntime = next_rotation_time;
 	else
 		fntime = time(NULL);
-	filename = logfile_getname(fntime, NULL);
-	if (Log_destination & LOG_DESTINATION_CSVLOG)
-		csvfilename = logfile_getname(fntime, ".csv");
-
-	/*
-	 * Decide whether to overwrite or append.  We can overwrite if (a)
-	 * Log_truncate_on_rotation is set, (b) the rotation was triggered by
-	 * elapsed time and not something else, and (c) the computed file name is
-	 * different from what we were previously logging into.
-	 *
-	 * Note: last_file_name should never be NULL here, but if it is, append.
-	 */
-	if (time_based_rotation || (size_rotation_for & LOG_DESTINATION_STDERR))
-	{
-		if (Log_truncate_on_rotation && time_based_rotation &&
-			last_file_name != NULL &&
-			strcmp(filename, last_file_name) != 0)
-			fh = logfile_open(filename, "w", true);
-		else
-			fh = logfile_open(filename, "a", true);
 
-		if (!fh)
-		{
-			/*
-			 * ENFILE/EMFILE are not too surprising on a busy system; just
-			 * keep using the old file till we manage to get a new one.
-			 * Otherwise, assume something's wrong with Log_directory and stop
-			 * trying to create files.
-			 */
-			if (errno != ENFILE && errno != EMFILE)
-			{
-				ereport(LOG,
-						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
-				rotation_disabled = true;
-			}
-
-			if (filename)
-				pfree(filename);
-			if (csvfilename)
-				pfree(csvfilename);
-			return;
-		}
-
-		fclose(syslogFile);
-		syslogFile = fh;
-
-		/* instead of pfree'ing filename, remember it for next time */
-		if (last_file_name != NULL)
-			pfree(last_file_name);
-		last_file_name = filename;
-		filename = NULL;
-	}
-
-	/*
-	 * Same as above, but for csv file.  Note that if LOG_DESTINATION_CSVLOG
-	 * was just turned on, we might have to open csvlogFile here though it was
-	 * not open before.  In such a case we'll append not overwrite (since
-	 * last_csv_file_name will be NULL); that is consistent with the normal
-	 * rules since it's not a time-based rotation.
-	 */
-	if ((Log_destination & LOG_DESTINATION_CSVLOG) &&
-		(csvlogFile == NULL ||
-		 time_based_rotation || (size_rotation_for & LOG_DESTINATION_CSVLOG)))
-	{
-		if (Log_truncate_on_rotation && time_based_rotation &&
-			last_csv_file_name != NULL &&
-			strcmp(csvfilename, last_csv_file_name) != 0)
-			fh = logfile_open(csvfilename, "w", true);
-		else
-			fh = logfile_open(csvfilename, "a", true);
-
-		if (!fh)
-		{
-			/*
-			 * ENFILE/EMFILE are not too surprising on a busy system; just
-			 * keep using the old file till we manage to get a new one.
-			 * Otherwise, assume something's wrong with Log_directory and stop
-			 * trying to create files.
-			 */
-			if (errno != ENFILE && errno != EMFILE)
-			{
-				ereport(LOG,
-						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
-				rotation_disabled = true;
-			}
+	if (!file_log_dest_rotate(&stderr_file_info, fntime, time_based_rotation, size_rotation_for))
+		/* error rotating stderr so try again later */
+		return;
 
-			if (filename)
-				pfree(filename);
-			if (csvfilename)
-				pfree(csvfilename);
+	if (Log_destination & LOG_DESTINATION_CSVLOG) {
+		if (!file_log_dest_rotate(&csvlog_file_info, fntime, time_based_rotation, size_rotation_for))
+			/* error rotating csvlog so try again later */
 			return;
-		}
-
-		if (csvlogFile != NULL)
-			fclose(csvlogFile);
-		csvlogFile = fh;
-
-		/* instead of pfree'ing filename, remember it for next time */
-		if (last_csv_file_name != NULL)
-			pfree(last_csv_file_name);
-		last_csv_file_name = csvfilename;
-		csvfilename = NULL;
-	}
-	else if (!(Log_destination & LOG_DESTINATION_CSVLOG) &&
-			 csvlogFile != NULL)
-	{
+	} else if (csvlog_file_info.file != NULL) {
 		/* CSVLOG was just turned off, so close the old file */
-		fclose(csvlogFile);
-		csvlogFile = NULL;
-		if (last_csv_file_name != NULL)
-			pfree(last_csv_file_name);
-		last_csv_file_name = NULL;
+		file_log_dest_close(&csvlog_file_info);
 	}
 
-	if (filename)
-		pfree(filename);
-	if (csvfilename)
-		pfree(csvfilename);
-
 	update_metainfo_datafile();
 
 	set_next_rotation_time();
@@ -1430,6 +1336,22 @@ set_next_rotation_time(void)
 	next_rotation_time = now;
 }
 
+static bool inline write_metainfo_line(FILE *metadata_file, const FileLogDestination *info)
+{
+	if (info->last_file_name != NULL && (Log_destination & info->dest))
+	{
+		if (fprintf(metadata_file, "%s %s\n", info->name, info->last_file_name) < 0)
+		{
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not write file \"%s\": %m",
+							LOG_METAINFO_DATAFILE_TMP)));
+			return false;
+		}
+	}
+	return true;
+}
+
 /*
  * Store the name of the file(s) where the log collector, when enabled, writes
  * log messages.  Useful for finding the name(s) of the current log file(s)
@@ -1478,31 +1400,13 @@ update_metainfo_datafile(void)
 		return;
 	}
 
-	if (last_file_name && (Log_destination & LOG_DESTINATION_STDERR))
+	if (!write_metainfo_line(fh, &stderr_file_info) ||
+		!write_metainfo_line(fh, &csvlog_file_info))
 	{
-		if (fprintf(fh, "stderr %s\n", last_file_name) < 0)
-		{
-			ereport(LOG,
-					(errcode_for_file_access(),
-					 errmsg("could not write file \"%s\": %m",
-							LOG_METAINFO_DATAFILE_TMP)));
-			fclose(fh);
-			return;
-		}
+		fclose(fh);
+		return;
 	}
 
-	if (last_csv_file_name && (Log_destination & LOG_DESTINATION_CSVLOG))
-	{
-		if (fprintf(fh, "csvlog %s\n", last_csv_file_name) < 0)
-		{
-			ereport(LOG,
-					(errcode_for_file_access(),
-					 errmsg("could not write file \"%s\": %m",
-							LOG_METAINFO_DATAFILE_TMP)));
-			fclose(fh);
-			return;
-		}
-	}
 	fclose(fh);
 
 	if (rename(LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE) != 0)
@@ -1552,3 +1456,82 @@ sigUsr1Handler(SIGNAL_ARGS)
 
 	errno = save_errno;
 }
+
+static inline bool file_log_dest_should_rotate_for_size(const FileLogDestination *info)
+{
+	if (info->file == NULL)
+		return false;
+
+	return ftell(info->file) >= Log_RotationSize * 1024L;
+}
+
+/*
+ * Checks if a log file should be rotated and if so rotate it.
+ *
+ * If the file is to be rotated and a new log file cannot be opened then return
+ * false. Otherwise return true regardless of whether it was rotated.
+ */
+static bool file_log_dest_rotate(FileLogDestination *info, pg_time_t fntime, bool time_based_rotation, int size_rotation_for)
+{
+	/*
+	 * Decide whether to overwrite or append.  We can overwrite if (a)
+	 * Log_truncate_on_rotation is set, (b) the rotation was triggered by
+	 * elapsed time and not something else, and (c) the computed file name is
+	 * different from what we were previously logging into.
+	 *
+	 * Note: last_file_name should never be NULL here, but if it is, append.
+	 */
+	if (time_based_rotation || (size_rotation_for & info->dest))
+	{
+		FILE *file = NULL;
+		char *filename = logfile_getname(fntime, info->suffix);
+
+		if (Log_truncate_on_rotation
+			&& time_based_rotation
+			&& info->last_file_name != NULL
+			&& strcmp(filename, info->last_file_name) != 0)
+			file = logfile_open(filename, "w", true);
+		else
+			file = logfile_open(filename, "a", true);
+
+		if (file == NULL)
+		{
+			/*
+			 * ENFILE/EMFILE are not too surprising on a busy system; just
+			 * keep using the old file till we manage to get a new one.
+			 * Otherwise, assume something's wrong with Log_directory and stop
+			 * trying to create files.
+			 */
+			if (errno != ENFILE && errno != EMFILE)
+			{
+				ereport(LOG,
+						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
+				rotation_disabled = true;
+			}
+
+			pfree(filename);
+			return false;
+		}
+
+		file_log_dest_close(info);
+		info->file = file;
+		/* instead of pfree'ing filename, remember it for next time */
+		info->last_file_name = filename;
+	}
+
+	return true;
+}
+
+static inline void file_log_dest_close(FileLogDestination *info)
+{
+	if (info->file != NULL)
+	{
+		fclose(info->file);
+		info->file = NULL;
+	}
+	if (info->last_file_name != NULL)
+	{
+		pfree(info->last_file_name);
+		info->last_file_name = NULL;
+	}
+}
-- 
2.17.1

From 57bcaf49bd10ec3e6afb14f3ec384cb88a65efe6 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 28 Sep 2021 12:28:21 +0900
Subject: [PATCH v7 1/2] Refactor fd handling when forking syslogger in
 EXEC_BACKEND build

---
 src/backend/postmaster/syslogger.c | 122 +++++++++++++++--------------
 1 file changed, 62 insertions(+), 60 deletions(-)

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index bca3883572..ddb47e3cb0 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -130,6 +130,8 @@ static volatile sig_atomic_t rotation_requested = false;
 
 /* Local subroutines */
 #ifdef EXEC_BACKEND
+static long syslogger_fdget(FILE *file);
+static FILE *syslogger_fdopen(int fd);
 static pid_t syslogger_forkexec(void);
 static void syslogger_parseArgs(int argc, char *argv[]);
 #endif
@@ -733,6 +735,60 @@ SysLogger_Start(void)
 
 #ifdef EXEC_BACKEND
 
+/*
+ * syslogger_fdget() -
+ *
+ * Utility wrapper to grab the file descriptor of an opened error output
+ * file.  Used when building the command to fork the logging collector.
+ */
+static long
+syslogger_fdget(FILE *file)
+{
+#ifndef WIN32
+	if (file != NULL)
+		return (long) fileno(file);
+	else
+		return -1;
+#else							/* WIN32 */
+	if (file != NULL)
+		return (long) _get_osfhandle(_fileno(file));
+	else
+		return 0;
+#endif							/* WIN32 */
+}
+
+/*
+ * syslogger_fdopen() -
+ *
+ * Utility wrapper to re-open an error output file, using the given file
+ * descriptor.  Used when parsing arguments in a forked logging collector.
+ */
+static FILE *
+syslogger_fdopen(int fd)
+{
+	FILE	   *file = NULL;
+
+#ifndef WIN32
+	if (fd != -1)
+	{
+		file = fdopen(fd, "a");
+		setvbuf(file, NULL, PG_IOLBF, 0);
+	}
+#else							/* WIN32 */
+	if (fd != 0)
+	{
+		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
+		if (fd > 0)
+		{
+			file = fdopen(fd, "a");
+			setvbuf(file, NULL, PG_IOLBF, 0);
+		}
+	}
+#endif							/* WIN32 */
+
+	return file;
+}
+
 /*
  * syslogger_forkexec() -
  *
@@ -751,34 +807,11 @@ syslogger_forkexec(void)
 	av[ac++] = NULL;			/* filled in by postmaster_forkexec */
 
 	/* static variables (those not passed by write_backend_variables) */
-#ifndef WIN32
-	if (syslogFile != NULL)
-		snprintf(filenobuf, sizeof(filenobuf), "%d",
-				 fileno(syslogFile));
-	else
-		strcpy(filenobuf, "-1");
-#else							/* WIN32 */
-	if (syslogFile != NULL)
-		snprintf(filenobuf, sizeof(filenobuf), "%ld",
-				 (long) _get_osfhandle(_fileno(syslogFile)));
-	else
-		strcpy(filenobuf, "0");
-#endif							/* WIN32 */
+	snprintf(filenobuf, sizeof(filenobuf), "%ld",
+			 syslogger_fdget(syslogFile));
 	av[ac++] = filenobuf;
-
-#ifndef WIN32
-	if (csvlogFile != NULL)
-		snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%d",
-				 fileno(csvlogFile));
-	else
-		strcpy(csvfilenobuf, "-1");
-#else							/* WIN32 */
-	if (csvlogFile != NULL)
-		snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld",
-				 (long) _get_osfhandle(_fileno(csvlogFile)));
-	else
-		strcpy(csvfilenobuf, "0");
-#endif							/* WIN32 */
+	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%ld",
+			 syslogger_fdget(csvlogFile));
 	av[ac++] = csvfilenobuf;
 
 	av[ac] = NULL;
@@ -807,41 +840,10 @@ syslogger_parseArgs(int argc, char *argv[])
 	 * fails there's not a lot we can do to report the problem anyway.  As
 	 * coded, we'll just crash on a null pointer dereference after failure...
 	 */
-#ifndef WIN32
 	fd = atoi(*argv++);
-	if (fd != -1)
-	{
-		syslogFile = fdopen(fd, "a");
-		setvbuf(syslogFile, NULL, PG_IOLBF, 0);
-	}
+	syslogFile = syslogger_fdopen(fd);
 	fd = atoi(*argv++);
-	if (fd != -1)
-	{
-		csvlogFile = fdopen(fd, "a");
-		setvbuf(csvlogFile, NULL, PG_IOLBF, 0);
-	}
-#else							/* WIN32 */
-	fd = atoi(*argv++);
-	if (fd != 0)
-	{
-		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
-		if (fd > 0)
-		{
-			syslogFile = fdopen(fd, "a");
-			setvbuf(syslogFile, NULL, PG_IOLBF, 0);
-		}
-	}
-	fd = atoi(*argv++);
-	if (fd != 0)
-	{
-		fd = _open_osfhandle(fd, _O_APPEND | _O_TEXT);
-		if (fd > 0)
-		{
-			csvlogFile = fdopen(fd, "a");
-			setvbuf(csvlogFile, NULL, PG_IOLBF, 0);
-		}
-	}
-#endif							/* WIN32 */
+	csvlogFile = syslogger_fdopen(fd);
 }
 #endif							/* EXEC_BACKEND */
 
-- 
2.33.0

From 88d43ad72b252e9efd2c9b7f5ba84d786ad78471 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 28 Sep 2021 11:48:18 +0900
Subject: [PATCH v7 2/2] Refactor per-destination file rotation in syslogger

---
 src/backend/postmaster/syslogger.c | 242 ++++++++++++++---------------
 1 file changed, 119 insertions(+), 123 deletions(-)

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index ddb47e3cb0..2c13e7ef9f 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -87,7 +87,7 @@ static bool rotation_disabled = false;
 static FILE *syslogFile = NULL;
 static FILE *csvlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
-static char *last_file_name = NULL;
+static char *last_sys_file_name = NULL;
 static char *last_csv_file_name = NULL;
 
 /*
@@ -274,7 +274,7 @@ SysLoggerMain(int argc, char *argv[])
 	 * time because passing down just the pg_time_t is a lot cheaper than
 	 * passing a whole file path in the EXEC_BACKEND case.
 	 */
-	last_file_name = logfile_getname(first_syslogger_file_time, NULL);
+	last_sys_file_name = logfile_getname(first_syslogger_file_time, NULL);
 	if (csvlogFile != NULL)
 		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
 
@@ -1241,16 +1241,118 @@ logfile_open(const char *filename, const char *mode, bool allow_errors)
 	return fh;
 }
 
+/*
+ * Do logfile rotation for a single destination, as specified by target_dest.
+ * The information stored in *last_file_name and *logFile is updated on a
+ * successful file rotation.
+ *
+ * Returns false if the rotation has been stopped, and true to move on to
+ * the processing of other formats.
+ */
+static bool
+logfile_rotate_dest(bool time_based_rotation, int size_rotation_for,
+					pg_time_t fntime, int target_dest,
+					char **last_file_name, FILE **logFile)
+{
+	char   *logFileExt;
+	char   *filename;
+	FILE   *fh;
+
+	/*
+	 * If the target destination was just turned off, close the previous
+	 * file and unregister its data.  This cannot happen for stderr as
+	 * syslogFile is assumed to be always opened even if
+	 * LOG_DESTINATION_STDERR is disabled.
+	 */
+	if ((Log_destination & target_dest) == 0 &&
+		target_dest != LOG_DESTINATION_STDERR)
+	{
+		if (*logFile != NULL)
+			fclose(*logFile);
+		*logFile = NULL;
+		if (*last_file_name != NULL)
+			pfree(*last_file_name);
+		*last_file_name = NULL;
+		return true;
+	}
+
+	/*
+	 * Leave if it is not time for a rotation or if the target destination
+	 * has no need to do a rotation.
+	 */
+	if (!time_based_rotation &&
+		(size_rotation_for & target_dest) == 0)
+	{
+		return true;
+	}
+
+	/* file extension depends on the destination type */
+	if (target_dest == LOG_DESTINATION_STDERR)
+		logFileExt = NULL;
+	else if (target_dest == LOG_DESTINATION_CSVLOG)
+		logFileExt = ".csv";
+	else
+	{
+		/* cannot happen */
+		Assert(false);
+	}
+
+	/* build the new file name */
+	filename = logfile_getname(fntime, logFileExt);
+
+	/*
+	 * Decide whether to overwrite or append.  We can overwrite if (a)
+	 * Log_truncate_on_rotation is set, (b) the rotation was triggered by
+	 * elapsed time and not something else, and (c) the computed file name is
+	 * different from what we were previously logging into.
+	 */
+	if (Log_truncate_on_rotation && time_based_rotation &&
+		*last_file_name != NULL &&
+		strcmp(filename, *last_file_name) != 0)
+		fh = logfile_open(filename, "w", true);
+	else
+		fh = logfile_open(filename, "a", true);
+
+	if (!fh)
+	{
+		/*
+		 * ENFILE/EMFILE are not too surprising on a busy system; just keep
+		 * using the old file till we manage to get a new one.  Otherwise,
+		 * assume something's wrong with Log_directory and stop trying to
+		 * create files.
+		 */
+		if (errno != ENFILE && errno != EMFILE)
+		{
+			ereport(LOG,
+					(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
+			rotation_disabled = true;
+		}
+
+		if (filename)
+			pfree(filename);
+		return false;
+	}
+
+	/* fill in the new information */
+	if (*logFile != NULL)
+		fclose(*logFile);
+	*logFile = fh;
+
+	/* instead of pfree'ing filename, remember it for next time */
+	if (*last_file_name != NULL)
+		pfree(*last_file_name);
+	*last_file_name = filename;
+
+	return true;
+}
+
 /*
  * perform logfile rotation
  */
 static void
 logfile_rotate(bool time_based_rotation, int size_rotation_for)
 {
-	char	   *filename;
-	char	   *csvfilename = NULL;
 	pg_time_t	fntime;
-	FILE	   *fh;
 
 	rotation_requested = false;
 
@@ -1263,124 +1365,18 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 		fntime = next_rotation_time;
 	else
 		fntime = time(NULL);
-	filename = logfile_getname(fntime, NULL);
-	if (Log_destination & LOG_DESTINATION_CSVLOG)
-		csvfilename = logfile_getname(fntime, ".csv");
 
-	/*
-	 * Decide whether to overwrite or append.  We can overwrite if (a)
-	 * Log_truncate_on_rotation is set, (b) the rotation was triggered by
-	 * elapsed time and not something else, and (c) the computed file name is
-	 * different from what we were previously logging into.
-	 *
-	 * Note: last_file_name should never be NULL here, but if it is, append.
-	 */
-	if (time_based_rotation || (size_rotation_for & LOG_DESTINATION_STDERR))
-	{
-		if (Log_truncate_on_rotation && time_based_rotation &&
-			last_file_name != NULL &&
-			strcmp(filename, last_file_name) != 0)
-			fh = logfile_open(filename, "w", true);
-		else
-			fh = logfile_open(filename, "a", true);
+	/* file rotation for stderr */
+	if (!logfile_rotate_dest(time_based_rotation, size_rotation_for, fntime,
+							 LOG_DESTINATION_STDERR, &last_sys_file_name,
+							 &syslogFile))
+		return;
 
-		if (!fh)
-		{
-			/*
-			 * ENFILE/EMFILE are not too surprising on a busy system; just
-			 * keep using the old file till we manage to get a new one.
-			 * Otherwise, assume something's wrong with Log_directory and stop
-			 * trying to create files.
-			 */
-			if (errno != ENFILE && errno != EMFILE)
-			{
-				ereport(LOG,
-						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
-				rotation_disabled = true;
-			}
-
-			if (filename)
-				pfree(filename);
-			if (csvfilename)
-				pfree(csvfilename);
-			return;
-		}
-
-		fclose(syslogFile);
-		syslogFile = fh;
-
-		/* instead of pfree'ing filename, remember it for next time */
-		if (last_file_name != NULL)
-			pfree(last_file_name);
-		last_file_name = filename;
-		filename = NULL;
-	}
-
-	/*
-	 * Same as above, but for csv file.  Note that if LOG_DESTINATION_CSVLOG
-	 * was just turned on, we might have to open csvlogFile here though it was
-	 * not open before.  In such a case we'll append not overwrite (since
-	 * last_csv_file_name will be NULL); that is consistent with the normal
-	 * rules since it's not a time-based rotation.
-	 */
-	if ((Log_destination & LOG_DESTINATION_CSVLOG) &&
-		(csvlogFile == NULL ||
-		 time_based_rotation || (size_rotation_for & LOG_DESTINATION_CSVLOG)))
-	{
-		if (Log_truncate_on_rotation && time_based_rotation &&
-			last_csv_file_name != NULL &&
-			strcmp(csvfilename, last_csv_file_name) != 0)
-			fh = logfile_open(csvfilename, "w", true);
-		else
-			fh = logfile_open(csvfilename, "a", true);
-
-		if (!fh)
-		{
-			/*
-			 * ENFILE/EMFILE are not too surprising on a busy system; just
-			 * keep using the old file till we manage to get a new one.
-			 * Otherwise, assume something's wrong with Log_directory and stop
-			 * trying to create files.
-			 */
-			if (errno != ENFILE && errno != EMFILE)
-			{
-				ereport(LOG,
-						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
-				rotation_disabled = true;
-			}
-
-			if (filename)
-				pfree(filename);
-			if (csvfilename)
-				pfree(csvfilename);
-			return;
-		}
-
-		if (csvlogFile != NULL)
-			fclose(csvlogFile);
-		csvlogFile = fh;
-
-		/* instead of pfree'ing filename, remember it for next time */
-		if (last_csv_file_name != NULL)
-			pfree(last_csv_file_name);
-		last_csv_file_name = csvfilename;
-		csvfilename = NULL;
-	}
-	else if (!(Log_destination & LOG_DESTINATION_CSVLOG) &&
-			 csvlogFile != NULL)
-	{
-		/* CSVLOG was just turned off, so close the old file */
-		fclose(csvlogFile);
-		csvlogFile = NULL;
-		if (last_csv_file_name != NULL)
-			pfree(last_csv_file_name);
-		last_csv_file_name = NULL;
-	}
-
-	if (filename)
-		pfree(filename);
-	if (csvfilename)
-		pfree(csvfilename);
+	/* file rotation for csvlog */
+	if (!logfile_rotate_dest(time_based_rotation, size_rotation_for, fntime,
+							 LOG_DESTINATION_CSVLOG, &last_csv_file_name,
+							 &csvlogFile))
+		return;
 
 	update_metainfo_datafile();
 
@@ -1501,9 +1497,9 @@ update_metainfo_datafile(void)
 		return;
 	}
 
-	if (last_file_name && (Log_destination & LOG_DESTINATION_STDERR))
+	if (last_sys_file_name && (Log_destination & LOG_DESTINATION_STDERR))
 	{
-		if (fprintf(fh, "stderr %s\n", last_file_name) < 0)
+		if (fprintf(fh, "stderr %s\n", last_sys_file_name) < 0)
 		{
 			ereport(LOG,
 					(errcode_for_file_access(),
-- 
2.33.0

From 4641f8535c2be4b75285ac34d87e883bec250e48 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 28 Sep 2021 11:48:18 +0900
Subject: [PATCH v4 1/5] Refactor per-destination file rotation in syslogger

---
 src/backend/postmaster/syslogger.c | 242 ++++++++++++++---------------
 1 file changed, 119 insertions(+), 123 deletions(-)

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index c5f9c5202d..4a019db7f4 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -87,7 +87,7 @@ static bool rotation_disabled = false;
 static FILE *syslogFile = NULL;
 static FILE *csvlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
-static char *last_file_name = NULL;
+static char *last_sys_file_name = NULL;
 static char *last_csv_file_name = NULL;
 
 /*
@@ -274,7 +274,7 @@ SysLoggerMain(int argc, char *argv[])
 	 * time because passing down just the pg_time_t is a lot cheaper than
 	 * passing a whole file path in the EXEC_BACKEND case.
 	 */
-	last_file_name = logfile_getname(first_syslogger_file_time, NULL);
+	last_sys_file_name = logfile_getname(first_syslogger_file_time, NULL);
 	if (csvlogFile != NULL)
 		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
 
@@ -1241,16 +1241,118 @@ logfile_open(const char *filename, const char *mode, bool allow_errors)
 	return fh;
 }
 
+/*
+ * Do logfile rotation for a single destination, as specified by target_dest.
+ * The information stored in *last_file_name and *logFile is updated on a
+ * successful file rotation.
+ *
+ * Returns false if the rotation has been stopped, and true to move on to
+ * the processing of other formats.
+ */
+static bool
+logfile_rotate_dest(bool time_based_rotation, int size_rotation_for,
+					pg_time_t fntime, int target_dest,
+					char **last_file_name, FILE **logFile)
+{
+	char   *logFileExt;
+	char   *filename;
+	FILE   *fh;
+
+	/*
+	 * If the target destination was just turned off, close the previous
+	 * file and unregister its data.  This cannot happen for stderr as
+	 * syslogFile is assumed to be always opened even if
+	 * LOG_DESTINATION_STDERR is disabled.
+	 */
+	if ((Log_destination & target_dest) == 0 &&
+		target_dest != LOG_DESTINATION_STDERR)
+	{
+		if (*logFile != NULL)
+			fclose(*logFile);
+		*logFile = NULL;
+		if (*last_file_name != NULL)
+			pfree(*last_file_name);
+		*last_file_name = NULL;
+		return true;
+	}
+
+	/*
+	 * Leave if it is not time for a rotation or if the target destination
+	 * has no need to do a rotation.
+	 */
+	if (!time_based_rotation &&
+		(size_rotation_for & target_dest) == 0)
+	{
+		return true;
+	}
+
+	/* file extension depends on the destination type */
+	if (target_dest == LOG_DESTINATION_STDERR)
+		logFileExt = NULL;
+	else if (target_dest == LOG_DESTINATION_CSVLOG)
+		logFileExt = ".csv";
+	else
+	{
+		/* cannot happen */
+		Assert(false);
+	}
+
+	/* build the new file name */
+	filename = logfile_getname(fntime, logFileExt);
+
+	/*
+	 * Decide whether to overwrite or append.  We can overwrite if (a)
+	 * Log_truncate_on_rotation is set, (b) the rotation was triggered by
+	 * elapsed time and not something else, and (c) the computed file name is
+	 * different from what we were previously logging into.
+	 */
+	if (Log_truncate_on_rotation && time_based_rotation &&
+		*last_file_name != NULL &&
+		strcmp(filename, *last_file_name) != 0)
+		fh = logfile_open(filename, "w", true);
+	else
+		fh = logfile_open(filename, "a", true);
+
+	if (!fh)
+	{
+		/*
+		 * ENFILE/EMFILE are not too surprising on a busy system; just keep
+		 * using the old file till we manage to get a new one.  Otherwise,
+		 * assume something's wrong with Log_directory and stop trying to
+		 * create files.
+		 */
+		if (errno != ENFILE && errno != EMFILE)
+		{
+			ereport(LOG,
+					(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
+			rotation_disabled = true;
+		}
+
+		if (filename)
+			pfree(filename);
+		return false;
+	}
+
+	/* fill in the new information */
+	if (*logFile != NULL)
+		fclose(*logFile);
+	*logFile = fh;
+
+	/* instead of pfree'ing filename, remember it for next time */
+	if (*last_file_name != NULL)
+		pfree(*last_file_name);
+	*last_file_name = filename;
+
+	return true;
+}
+
 /*
  * perform logfile rotation
  */
 static void
 logfile_rotate(bool time_based_rotation, int size_rotation_for)
 {
-	char	   *filename;
-	char	   *csvfilename = NULL;
 	pg_time_t	fntime;
-	FILE	   *fh;
 
 	rotation_requested = false;
 
@@ -1263,124 +1365,18 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 		fntime = next_rotation_time;
 	else
 		fntime = time(NULL);
-	filename = logfile_getname(fntime, NULL);
-	if (Log_destination & LOG_DESTINATION_CSVLOG)
-		csvfilename = logfile_getname(fntime, ".csv");
 
-	/*
-	 * Decide whether to overwrite or append.  We can overwrite if (a)
-	 * Log_truncate_on_rotation is set, (b) the rotation was triggered by
-	 * elapsed time and not something else, and (c) the computed file name is
-	 * different from what we were previously logging into.
-	 *
-	 * Note: last_file_name should never be NULL here, but if it is, append.
-	 */
-	if (time_based_rotation || (size_rotation_for & LOG_DESTINATION_STDERR))
-	{
-		if (Log_truncate_on_rotation && time_based_rotation &&
-			last_file_name != NULL &&
-			strcmp(filename, last_file_name) != 0)
-			fh = logfile_open(filename, "w", true);
-		else
-			fh = logfile_open(filename, "a", true);
+	/* file rotation for stderr */
+	if (!logfile_rotate_dest(time_based_rotation, size_rotation_for, fntime,
+							 LOG_DESTINATION_STDERR, &last_sys_file_name,
+							 &syslogFile))
+		return;
 
-		if (!fh)
-		{
-			/*
-			 * ENFILE/EMFILE are not too surprising on a busy system; just
-			 * keep using the old file till we manage to get a new one.
-			 * Otherwise, assume something's wrong with Log_directory and stop
-			 * trying to create files.
-			 */
-			if (errno != ENFILE && errno != EMFILE)
-			{
-				ereport(LOG,
-						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
-				rotation_disabled = true;
-			}
-
-			if (filename)
-				pfree(filename);
-			if (csvfilename)
-				pfree(csvfilename);
-			return;
-		}
-
-		fclose(syslogFile);
-		syslogFile = fh;
-
-		/* instead of pfree'ing filename, remember it for next time */
-		if (last_file_name != NULL)
-			pfree(last_file_name);
-		last_file_name = filename;
-		filename = NULL;
-	}
-
-	/*
-	 * Same as above, but for csv file.  Note that if LOG_DESTINATION_CSVLOG
-	 * was just turned on, we might have to open csvlogFile here though it was
-	 * not open before.  In such a case we'll append not overwrite (since
-	 * last_csv_file_name will be NULL); that is consistent with the normal
-	 * rules since it's not a time-based rotation.
-	 */
-	if ((Log_destination & LOG_DESTINATION_CSVLOG) &&
-		(csvlogFile == NULL ||
-		 time_based_rotation || (size_rotation_for & LOG_DESTINATION_CSVLOG)))
-	{
-		if (Log_truncate_on_rotation && time_based_rotation &&
-			last_csv_file_name != NULL &&
-			strcmp(csvfilename, last_csv_file_name) != 0)
-			fh = logfile_open(csvfilename, "w", true);
-		else
-			fh = logfile_open(csvfilename, "a", true);
-
-		if (!fh)
-		{
-			/*
-			 * ENFILE/EMFILE are not too surprising on a busy system; just
-			 * keep using the old file till we manage to get a new one.
-			 * Otherwise, assume something's wrong with Log_directory and stop
-			 * trying to create files.
-			 */
-			if (errno != ENFILE && errno != EMFILE)
-			{
-				ereport(LOG,
-						(errmsg("disabling automatic rotation (use SIGHUP to re-enable)")));
-				rotation_disabled = true;
-			}
-
-			if (filename)
-				pfree(filename);
-			if (csvfilename)
-				pfree(csvfilename);
-			return;
-		}
-
-		if (csvlogFile != NULL)
-			fclose(csvlogFile);
-		csvlogFile = fh;
-
-		/* instead of pfree'ing filename, remember it for next time */
-		if (last_csv_file_name != NULL)
-			pfree(last_csv_file_name);
-		last_csv_file_name = csvfilename;
-		csvfilename = NULL;
-	}
-	else if (!(Log_destination & LOG_DESTINATION_CSVLOG) &&
-			 csvlogFile != NULL)
-	{
-		/* CSVLOG was just turned off, so close the old file */
-		fclose(csvlogFile);
-		csvlogFile = NULL;
-		if (last_csv_file_name != NULL)
-			pfree(last_csv_file_name);
-		last_csv_file_name = NULL;
-	}
-
-	if (filename)
-		pfree(filename);
-	if (csvfilename)
-		pfree(csvfilename);
+	/* file rotation for csvlog */
+	if (!logfile_rotate_dest(time_based_rotation, size_rotation_for, fntime,
+							 LOG_DESTINATION_CSVLOG, &last_csv_file_name,
+							 &csvlogFile))
+		return;
 
 	update_metainfo_datafile();
 
@@ -1501,9 +1497,9 @@ update_metainfo_datafile(void)
 		return;
 	}
 
-	if (last_file_name && (Log_destination & LOG_DESTINATION_STDERR))
+	if (last_sys_file_name && (Log_destination & LOG_DESTINATION_STDERR))
 	{
-		if (fprintf(fh, "stderr %s\n", last_file_name) < 0)
+		if (fprintf(fh, "stderr %s\n", last_sys_file_name) < 0)
 		{
 			ereport(LOG,
 					(errcode_for_file_access(),
-- 
2.33.0

From 83a5bd50da25d6a99e5804b0bd268b3a9e86644e Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 5 Oct 2021 11:19:46 +0900
Subject: [PATCH v4 2/5] Some refactoring of elog-specific routines

This refactors out the following things in elog.c, for ease of use
across multiple log destinations:
- start_timestamp
- log_timestamp
- decide if query can be logged
- backend type

This will be reused by jsonlog.
---
 src/include/utils/elog.h       |   4 +
 src/backend/utils/error/elog.c | 141 +++++++++++++++++++++------------
 2 files changed, 94 insertions(+), 51 deletions(-)

diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index f53607e12e..bc6f362b6a 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -441,6 +441,10 @@ extern bool syslog_split_messages;
 extern void DebugFileOpen(void);
 extern char *unpack_sql_state(int sql_state);
 extern bool in_error_recursion_trouble(void);
+extern char *get_formatted_start_time(void);
+extern char *get_formatted_log_time(void);
+extern bool	check_log_of_query(ErrorData *edata);
+extern const char *get_backend_type_for_log(void);
 
 #ifdef HAVE_SYSLOG
 extern void set_syslog_parameters(const char *ident, int facility);
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 2af87ee3bd..3d89937322 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -175,8 +175,6 @@ static const char *err_gettext(const char *str) pg_attribute_format_arg(1);
 static pg_noinline void set_backtrace(ErrorData *edata, int num_skip);
 static void set_errdata_field(MemoryContextData *cxt, char **ptr, const char *str);
 static void write_console(const char *line, int len);
-static void setup_formatted_log_time(void);
-static void setup_formatted_start_time(void);
 static const char *process_log_prefix_padding(const char *p, int *padding);
 static void log_line_prefix(StringInfo buf, ErrorData *edata);
 static void write_csvlog(ErrorData *edata);
@@ -2289,14 +2287,23 @@ write_console(const char *line, int len)
 }
 
 /*
- * setup formatted_log_time, for consistent times between CSV and regular logs
+ * get_formatted_log_time -- compute and get the log timestamp.
+ *
+ * The timestamp is computed if not set yet, so as it is kept consistent
+ * among all the log destinations that require it to be consistent.  Note
+ * that the computed timestamp is returned in a static buffer, not
+ * palloc()'d.
  */
-static void
-setup_formatted_log_time(void)
+char *
+get_formatted_log_time(void)
 {
 	pg_time_t	stamp_time;
 	char		msbuf[13];
 
+	/* leave if already computed */
+	if (formatted_log_time[0] != '\0')
+		return formatted_log_time;
+
 	if (!saved_timeval_set)
 	{
 		gettimeofday(&saved_timeval, NULL);
@@ -2318,16 +2325,25 @@ setup_formatted_log_time(void)
 	/* 'paste' milliseconds into place... */
 	sprintf(msbuf, ".%03d", (int) (saved_timeval.tv_usec / 1000));
 	memcpy(formatted_log_time + 19, msbuf, 4);
+
+	return formatted_log_time;
 }
 
 /*
- * setup formatted_start_time
+ * get_formatted_start_time -- compute and get the start timestamp.
+ *
+ * The timestamp is computed if not set yet.  Note that the computed
+ * timestamp is returned in a static buffer, not palloc()'d.
  */
-static void
-setup_formatted_start_time(void)
+char *
+get_formatted_start_time(void)
 {
 	pg_time_t	stamp_time = (pg_time_t) MyStartTime;
 
+	/* leave if already computed */
+	if (formatted_start_time[0] != '\0')
+		return formatted_start_time;
+
 	/*
 	 * Note: we expect that guc.c will ensure that log_timezone is set up (at
 	 * least with a minimal GMT value) before Log_line_prefix can become
@@ -2336,6 +2352,49 @@ setup_formatted_start_time(void)
 	pg_strftime(formatted_start_time, FORMATTED_TS_LEN,
 				"%Y-%m-%d %H:%M:%S %Z",
 				pg_localtime(&stamp_time, log_timezone));
+
+	return formatted_start_time;
+}
+
+/*
+ * check_log_of_query -- check if a query can be logged
+ */
+bool
+check_log_of_query(ErrorData *edata)
+{
+	/* log required? */
+	if (!is_log_level_output(edata->elevel, log_min_error_statement))
+		return false;
+
+	/* query log wanted? */
+	if (edata->hide_stmt)
+		return false;
+
+	/* query string available? */
+	if (debug_query_string == NULL)
+		return false;
+
+	return true;
+}
+
+/*
+ * get_backend_type_for_log -- backend type for log entries
+ *
+ * Returns a pointer to a static buffer, not palloc()'d.
+ */
+const char *
+get_backend_type_for_log(void)
+{
+	const char   *backend_type_str;
+
+	if (MyProcPid == PostmasterPid)
+		backend_type_str = "postmaster";
+	else if (MyBackendType == B_BG_WORKER)
+		backend_type_str = MyBgworkerEntry->bgw_type;
+	else
+		backend_type_str = GetBackendTypeDesc(MyBackendType);
+
+	return backend_type_str;
 }
 
 /*
@@ -2466,14 +2525,7 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 				break;
 			case 'b':
 				{
-					const char *backend_type_str;
-
-					if (MyProcPid == PostmasterPid)
-						backend_type_str = "postmaster";
-					else if (MyBackendType == B_BG_WORKER)
-						backend_type_str = MyBgworkerEntry->bgw_type;
-					else
-						backend_type_str = GetBackendTypeDesc(MyBackendType);
+					const char *backend_type_str = get_backend_type_for_log();
 
 					if (padding != 0)
 						appendStringInfo(buf, "%*s", padding, backend_type_str);
@@ -2561,7 +2613,10 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 					appendStringInfo(buf, "%ld", log_line_number);
 				break;
 			case 'm':
-				setup_formatted_log_time();
+				/* force a log timestamp reset */
+				formatted_log_time[0] = '\0';
+				(void) get_formatted_log_time();
+
 				if (padding != 0)
 					appendStringInfo(buf, "%*s", padding, formatted_log_time);
 				else
@@ -2602,12 +2657,14 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 				}
 				break;
 			case 's':
-				if (formatted_start_time[0] == '\0')
-					setup_formatted_start_time();
-				if (padding != 0)
-					appendStringInfo(buf, "%*s", padding, formatted_start_time);
-				else
-					appendStringInfoString(buf, formatted_start_time);
+				{
+					char   *start_time = get_formatted_start_time();
+
+					if (padding != 0)
+						appendStringInfo(buf, "%*s", padding, start_time);
+					else
+						appendStringInfoString(buf, start_time);
+				}
 				break;
 			case 'i':
 				if (MyProcPort)
@@ -2763,6 +2820,8 @@ write_csvlog(ErrorData *edata)
 {
 	StringInfoData buf;
 	bool		print_stmt = false;
+	char	   *start_time;
+	char	   *log_time;
 
 	/* static counter for line numbers */
 	static long log_line_number = 0;
@@ -2785,17 +2844,9 @@ write_csvlog(ErrorData *edata)
 
 	initStringInfo(&buf);
 
-	/*
-	 * timestamp with milliseconds
-	 *
-	 * Check if the timestamp is already calculated for the syslog message,
-	 * and use it if so.  Otherwise, get the current timestamp.  This is done
-	 * to put same timestamp in both syslog and csvlog messages.
-	 */
-	if (formatted_log_time[0] == '\0')
-		setup_formatted_log_time();
-
-	appendStringInfoString(&buf, formatted_log_time);
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+	appendStringInfoString(&buf, log_time);
 	appendStringInfoChar(&buf, ',');
 
 	/* username */
@@ -2853,9 +2904,8 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* session start timestamp */
-	if (formatted_start_time[0] == '\0')
-		setup_formatted_start_time();
-	appendStringInfoString(&buf, formatted_start_time);
+	start_time = get_formatted_start_time();
+	appendStringInfoString(&buf, start_time);
 	appendStringInfoChar(&buf, ',');
 
 	/* Virtual transaction id */
@@ -2906,10 +2956,7 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* user query --- only reported if not disabled by the caller */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
-		print_stmt = true;
+	print_stmt = check_log_of_query(edata);
 	if (print_stmt)
 		appendCSVLiteral(&buf, debug_query_string);
 	appendStringInfoChar(&buf, ',');
@@ -2943,13 +2990,7 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* backend type */
-	if (MyProcPid == PostmasterPid)
-		appendCSVLiteral(&buf, "postmaster");
-	else if (MyBackendType == B_BG_WORKER)
-		appendCSVLiteral(&buf, MyBgworkerEntry->bgw_type);
-	else
-		appendCSVLiteral(&buf, GetBackendTypeDesc(MyBackendType));
-
+	appendCSVLiteral(&buf, get_backend_type_for_log());
 	appendStringInfoChar(&buf, ',');
 
 	/* leader PID */
@@ -3100,9 +3141,7 @@ send_message_to_server_log(ErrorData *edata)
 	/*
 	 * If the user wants the query that generated this error logged, do it.
 	 */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
+	if (check_log_of_query(edata))
 	{
 		log_line_prefix(&buf, edata);
 		appendStringInfoString(&buf, _("STATEMENT:  "));
-- 
2.33.0

From b3b57f3bc30cedd59b199c2fa0178d4f7cdd1703 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 5 Oct 2021 14:24:59 +0900
Subject: [PATCH v4 3/5] Refactor fallback to stderr for some cases with csvlog

send_message_to_server_log() would force a redirection of a log entry to
stderr in some cases, like the syslogger not being available yet.  If
this happens, csvlog falls back to stderr to log something.  The code
was organized so as stderr was happening before csvlog, with csvlog
calling checking for the same conditions as the stderr code path for a
second time, with a log handling rather buggy for Windows.

Instead, move the csvlog handling to be before stderr, tracking down if
it is necessary to log something to stderr after.  The reduces the
handling of stderr to a single code path, and fixes one issue with the
case of a Windows service, where stderr is not available, where we would
lose log entries that should have been redirected from csvlog to
stderr.
---
 src/backend/utils/error/elog.c | 56 ++++++++++++++++------------------
 1 file changed, 26 insertions(+), 30 deletions(-)

diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 3d89937322..01a317ea18 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -3049,6 +3049,7 @@ static void
 send_message_to_server_log(ErrorData *edata)
 {
 	StringInfoData buf;
+	bool		fallback_to_stderr = false;
 
 	initStringInfo(&buf);
 
@@ -3198,8 +3199,29 @@ send_message_to_server_log(ErrorData *edata)
 	}
 #endif							/* WIN32 */
 
-	/* Write to stderr, if enabled */
-	if ((Log_destination & LOG_DESTINATION_STDERR) || whereToSendOutput == DestDebug)
+	/* Write to CSV log, if enabled */
+	if ((Log_destination & LOG_DESTINATION_CSVLOG) != 0)
+	{
+		/*
+		 * Send CSV data if it's safe to do so (syslogger doesn't need the
+		 * pipe).  If this is not possible, fallback to an entry written
+		 * to stderr.
+		 */
+		if (redirection_done || MyBackendType == B_LOGGER)
+		{
+			write_csvlog(edata);
+		}
+		else
+			fallback_to_stderr = true;
+	}
+
+	/*
+	 * Write to stderr, if enabled or if required because of a previous
+	 * limitation.
+	 */
+	if ((Log_destination & LOG_DESTINATION_STDERR) ||
+		whereToSendOutput == DestDebug ||
+		fallback_to_stderr)
 	{
 		/*
 		 * Use the chunking protocol if we know the syslogger should be
@@ -3228,34 +3250,8 @@ send_message_to_server_log(ErrorData *edata)
 	if (MyBackendType == B_LOGGER)
 		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_STDERR);
 
-	/* Write to CSV log if enabled */
-	if (Log_destination & LOG_DESTINATION_CSVLOG)
-	{
-		if (redirection_done || MyBackendType == B_LOGGER)
-		{
-			/*
-			 * send CSV data if it's safe to do so (syslogger doesn't need the
-			 * pipe). First get back the space in the message buffer.
-			 */
-			pfree(buf.data);
-			write_csvlog(edata);
-		}
-		else
-		{
-			/*
-			 * syslogger not up (yet), so just dump the message to stderr,
-			 * unless we already did so above.
-			 */
-			if (!(Log_destination & LOG_DESTINATION_STDERR) &&
-				whereToSendOutput != DestDebug)
-				write_console(buf.data, buf.len);
-			pfree(buf.data);
-		}
-	}
-	else
-	{
-		pfree(buf.data);
-	}
+	/* No more need of the message formatted for stderr */
+	pfree(buf.data);
 }
 
 /*
-- 
2.33.0

From 5d5eeed08377d5da0203b249b2c4042353207578 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 5 Oct 2021 15:22:24 +0900
Subject: [PATCH v4 4/5] Refactor CSV-specific code into its own file

This requires more routines of elog.c to be published.
---
 src/include/utils/elog.h         |   4 +
 src/backend/utils/error/Makefile |   1 +
 src/backend/utils/error/csvlog.c | 268 +++++++++++++++++++++++++++++++
 src/backend/utils/error/elog.c   | 251 ++---------------------------
 4 files changed, 284 insertions(+), 240 deletions(-)
 create mode 100644 src/backend/utils/error/csvlog.c

diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index bc6f362b6a..ab08e7fac8 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -441,10 +441,14 @@ extern bool syslog_split_messages;
 extern void DebugFileOpen(void);
 extern char *unpack_sql_state(int sql_state);
 extern bool in_error_recursion_trouble(void);
+extern void reset_formatted_start_time(void);
 extern char *get_formatted_start_time(void);
 extern char *get_formatted_log_time(void);
 extern bool	check_log_of_query(ErrorData *edata);
 extern const char *get_backend_type_for_log(void);
+extern const char *error_severity(int elevel);
+extern void write_csvlog(ErrorData *edata);
+extern void write_pipe_chunks(char *data, int len, int dest);
 
 #ifdef HAVE_SYSLOG
 extern void set_syslog_parameters(const char *ident, int facility);
diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index 612da215d0..ef770dd2f2 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -14,6 +14,7 @@ include $(top_builddir)/src/Makefile.global
 
 OBJS = \
 	assert.o \
+	csvlog.o \
 	elog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/csvlog.c b/src/backend/utils/error/csvlog.c
new file mode 100644
index 0000000000..443a91e168
--- /dev/null
+++ b/src/backend/utils/error/csvlog.c
@@ -0,0 +1,268 @@
+/*-------------------------------------------------------------------------
+ *
+ * csvlog.c
+ *	  CSV logging
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of Californi
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/csvlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog.h"
+#include "utils/guc.h"
+#include "utils/ps_status.h"
+
+
+/*
+ * append a CSV'd version of a string to a StringInfo
+ * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
+ * If it's NULL, append nothing.
+ */
+static inline void
+appendCSVLiteral(StringInfo buf, const char *data)
+{
+	const char *p = data;
+	char		c;
+
+	/* avoid confusing an empty string with NULL */
+	if (p == NULL)
+		return;
+
+	appendStringInfoCharMacro(buf, '"');
+	while ((c = *p++) != '\0')
+	{
+		if (c == '"')
+			appendStringInfoCharMacro(buf, '"');
+		appendStringInfoCharMacro(buf, c);
+	}
+	appendStringInfoCharMacro(buf, '"');
+}
+
+/*
+ * write_csvlog -- Generate and write CSV log entry
+ *
+ * Constructs the error message, depending on the Errordata it gets, in a CSV
+ * format which is described in doc/src/sgml/config.sgml.
+ */
+void
+write_csvlog(ErrorData *edata)
+{
+	StringInfoData buf;
+	bool		print_stmt = false;
+	char	   *start_time;
+	char	   *log_time;
+
+	/* static counter for line numbers */
+	static long log_line_number = 0;
+
+	/* has counter been reset in current process? */
+	static int	log_my_pid = 0;
+
+	/*
+	 * This is one of the few places where we'd rather not inherit a static
+	 * variable's value from the postmaster.  But since we will, reset it when
+	 * MyProcPid changes.
+	 */
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		reset_formatted_start_time();
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+	appendStringInfoString(&buf, log_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* username */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->user_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* database name */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->database_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* Process id  */
+	if (MyProcPid != 0)
+		appendStringInfo(&buf, "%d", MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendStringInfoChar(&buf, '"');
+		appendStringInfoString(&buf, MyProcPort->remote_host);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+		{
+			appendStringInfoChar(&buf, ':');
+			appendStringInfoString(&buf, MyProcPort->remote_port);
+		}
+		appendStringInfoChar(&buf, '"');
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session id */
+	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Line number */
+	appendStringInfo(&buf, "%ld", log_line_number);
+	appendStringInfoChar(&buf, ',');
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData msgbuf;
+		const char *psdisp;
+		int			displen;
+
+		initStringInfo(&msgbuf);
+
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendCSVLiteral(&buf, msgbuf.data);
+
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session start timestamp */
+	start_time = get_formatted_start_time();
+	appendStringInfoString(&buf, start_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Transaction id */
+	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
+	appendStringInfoChar(&buf, ',');
+
+	/* Error severity */
+	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
+	appendStringInfoChar(&buf, ',');
+
+	/* SQL state code */
+	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
+	appendStringInfoChar(&buf, ',');
+
+	/* errmessage */
+	appendCSVLiteral(&buf, edata->message);
+	appendStringInfoChar(&buf, ',');
+
+	/* errdetail or errdetail_log */
+	if (edata->detail_log)
+		appendCSVLiteral(&buf, edata->detail_log);
+	else
+		appendCSVLiteral(&buf, edata->detail);
+	appendStringInfoChar(&buf, ',');
+
+	/* errhint */
+	appendCSVLiteral(&buf, edata->hint);
+	appendStringInfoChar(&buf, ',');
+
+	/* internal query */
+	appendCSVLiteral(&buf, edata->internalquery);
+	appendStringInfoChar(&buf, ',');
+
+	/* if printed internal query, print internal pos too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendStringInfo(&buf, "%d", edata->internalpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* errcontext */
+	if (!edata->hide_ctx)
+		appendCSVLiteral(&buf, edata->context);
+	appendStringInfoChar(&buf, ',');
+
+	/* user query --- only reported if not disabled by the caller */
+	print_stmt = check_log_of_query(edata);
+	if (print_stmt)
+		appendCSVLiteral(&buf, debug_query_string);
+	appendStringInfoChar(&buf, ',');
+	if (print_stmt && edata->cursorpos > 0)
+		appendStringInfo(&buf, "%d", edata->cursorpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		StringInfoData msgbuf;
+
+		initStringInfo(&msgbuf);
+
+		if (edata->funcname && edata->filename)
+			appendStringInfo(&msgbuf, "%s, %s:%d",
+							 edata->funcname, edata->filename,
+							 edata->lineno);
+		else if (edata->filename)
+			appendStringInfo(&msgbuf, "%s:%d",
+							 edata->filename, edata->lineno);
+		appendCSVLiteral(&buf, msgbuf.data);
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* application name */
+	if (application_name)
+		appendCSVLiteral(&buf, application_name);
+
+	appendStringInfoChar(&buf, ',');
+
+	/* backend type */
+	appendCSVLiteral(&buf, get_backend_type_for_log());
+	appendStringInfoChar(&buf, ',');
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendStringInfo(&buf, "%d", leader->pid);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* query id */
+	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
+
+	appendStringInfoChar(&buf, '\n');
+
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+	else
+		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 01a317ea18..f99a173e15 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -177,11 +177,8 @@ static void set_errdata_field(MemoryContextData *cxt, char **ptr, const char *st
 static void write_console(const char *line, int len);
 static const char *process_log_prefix_padding(const char *p, int *padding);
 static void log_line_prefix(StringInfo buf, ErrorData *edata);
-static void write_csvlog(ErrorData *edata);
 static void send_message_to_server_log(ErrorData *edata);
-static void write_pipe_chunks(char *data, int len, int dest);
 static void send_message_to_frontend(ErrorData *edata);
-static const char *error_severity(int elevel);
 static void append_with_tabs(StringInfo buf, const char *str);
 
 
@@ -2329,6 +2326,15 @@ get_formatted_log_time(void)
 	return formatted_log_time;
 }
 
+/*
+ * reset_formatted_start_time -- reset the start timestamp
+ */
+void
+reset_formatted_start_time(void)
+{
+	formatted_start_time[0] = '\0';
+}
+
 /*
  * get_formatted_start_time -- compute and get the start timestamp.
  *
@@ -2786,241 +2792,6 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 	}
 }
 
-/*
- * append a CSV'd version of a string to a StringInfo
- * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
- * If it's NULL, append nothing.
- */
-static inline void
-appendCSVLiteral(StringInfo buf, const char *data)
-{
-	const char *p = data;
-	char		c;
-
-	/* avoid confusing an empty string with NULL */
-	if (p == NULL)
-		return;
-
-	appendStringInfoCharMacro(buf, '"');
-	while ((c = *p++) != '\0')
-	{
-		if (c == '"')
-			appendStringInfoCharMacro(buf, '"');
-		appendStringInfoCharMacro(buf, c);
-	}
-	appendStringInfoCharMacro(buf, '"');
-}
-
-/*
- * Constructs the error message, depending on the Errordata it gets, in a CSV
- * format which is described in doc/src/sgml/config.sgml.
- */
-static void
-write_csvlog(ErrorData *edata)
-{
-	StringInfoData buf;
-	bool		print_stmt = false;
-	char	   *start_time;
-	char	   *log_time;
-
-	/* static counter for line numbers */
-	static long log_line_number = 0;
-
-	/* has counter been reset in current process? */
-	static int	log_my_pid = 0;
-
-	/*
-	 * This is one of the few places where we'd rather not inherit a static
-	 * variable's value from the postmaster.  But since we will, reset it when
-	 * MyProcPid changes.
-	 */
-	if (log_my_pid != MyProcPid)
-	{
-		log_line_number = 0;
-		log_my_pid = MyProcPid;
-		formatted_start_time[0] = '\0';
-	}
-	log_line_number++;
-
-	initStringInfo(&buf);
-
-	/* timestamp with milliseconds */
-	log_time = get_formatted_log_time();
-	appendStringInfoString(&buf, log_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* username */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->user_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* database name */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->database_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* Process id  */
-	if (MyProcPid != 0)
-		appendStringInfo(&buf, "%d", MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Remote host and port */
-	if (MyProcPort && MyProcPort->remote_host)
-	{
-		appendStringInfoChar(&buf, '"');
-		appendStringInfoString(&buf, MyProcPort->remote_host);
-		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
-		{
-			appendStringInfoChar(&buf, ':');
-			appendStringInfoString(&buf, MyProcPort->remote_port);
-		}
-		appendStringInfoChar(&buf, '"');
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session id */
-	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Line number */
-	appendStringInfo(&buf, "%ld", log_line_number);
-	appendStringInfoChar(&buf, ',');
-
-	/* PS display */
-	if (MyProcPort)
-	{
-		StringInfoData msgbuf;
-		const char *psdisp;
-		int			displen;
-
-		initStringInfo(&msgbuf);
-
-		psdisp = get_ps_display(&displen);
-		appendBinaryStringInfo(&msgbuf, psdisp, displen);
-		appendCSVLiteral(&buf, msgbuf.data);
-
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session start timestamp */
-	start_time = get_formatted_start_time();
-	appendStringInfoString(&buf, start_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* Virtual transaction id */
-	/* keep VXID format in sync with lockfuncs.c */
-	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
-		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Transaction id */
-	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
-	appendStringInfoChar(&buf, ',');
-
-	/* Error severity */
-	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
-	appendStringInfoChar(&buf, ',');
-
-	/* SQL state code */
-	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
-	appendStringInfoChar(&buf, ',');
-
-	/* errmessage */
-	appendCSVLiteral(&buf, edata->message);
-	appendStringInfoChar(&buf, ',');
-
-	/* errdetail or errdetail_log */
-	if (edata->detail_log)
-		appendCSVLiteral(&buf, edata->detail_log);
-	else
-		appendCSVLiteral(&buf, edata->detail);
-	appendStringInfoChar(&buf, ',');
-
-	/* errhint */
-	appendCSVLiteral(&buf, edata->hint);
-	appendStringInfoChar(&buf, ',');
-
-	/* internal query */
-	appendCSVLiteral(&buf, edata->internalquery);
-	appendStringInfoChar(&buf, ',');
-
-	/* if printed internal query, print internal pos too */
-	if (edata->internalpos > 0 && edata->internalquery != NULL)
-		appendStringInfo(&buf, "%d", edata->internalpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* errcontext */
-	if (!edata->hide_ctx)
-		appendCSVLiteral(&buf, edata->context);
-	appendStringInfoChar(&buf, ',');
-
-	/* user query --- only reported if not disabled by the caller */
-	print_stmt = check_log_of_query(edata);
-	if (print_stmt)
-		appendCSVLiteral(&buf, debug_query_string);
-	appendStringInfoChar(&buf, ',');
-	if (print_stmt && edata->cursorpos > 0)
-		appendStringInfo(&buf, "%d", edata->cursorpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* file error location */
-	if (Log_error_verbosity >= PGERROR_VERBOSE)
-	{
-		StringInfoData msgbuf;
-
-		initStringInfo(&msgbuf);
-
-		if (edata->funcname && edata->filename)
-			appendStringInfo(&msgbuf, "%s, %s:%d",
-							 edata->funcname, edata->filename,
-							 edata->lineno);
-		else if (edata->filename)
-			appendStringInfo(&msgbuf, "%s:%d",
-							 edata->filename, edata->lineno);
-		appendCSVLiteral(&buf, msgbuf.data);
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* application name */
-	if (application_name)
-		appendCSVLiteral(&buf, application_name);
-
-	appendStringInfoChar(&buf, ',');
-
-	/* backend type */
-	appendCSVLiteral(&buf, get_backend_type_for_log());
-	appendStringInfoChar(&buf, ',');
-
-	/* leader PID */
-	if (MyProc)
-	{
-		PGPROC	   *leader = MyProc->lockGroupLeader;
-
-		/*
-		 * Show the leader only for active parallel workers.  This leaves out
-		 * the leader of a parallel group.
-		 */
-		if (leader && leader->pid != MyProcPid)
-			appendStringInfo(&buf, "%d", leader->pid);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* query id */
-	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
-
-	appendStringInfoChar(&buf, '\n');
-
-	/* If in the syslogger process, try to write messages direct to file */
-	if (MyBackendType == B_LOGGER)
-		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-	else
-		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-
-	pfree(buf.data);
-}
-
 /*
  * Unpack MAKE_SQLSTATE code. Note that this returns a pointer to a
  * static buffer.
@@ -3274,7 +3045,7 @@ send_message_to_server_log(ErrorData *edata)
  * warning from ignoring write()'s result, so do a little dance with casting
  * rc to void to shut up the compiler.
  */
-static void
+void
 write_pipe_chunks(char *data, int len, int dest)
 {
 	PipeProtoChunk p;
@@ -3510,7 +3281,7 @@ send_message_to_frontend(ErrorData *edata)
  * The string is not localized here, but we mark the strings for translation
  * so that callers can invoke _() on the result.
  */
-static const char *
+const char *
 error_severity(int elevel)
 {
 	const char *prefix;
-- 
2.33.0

From 77687eb0fa733cc6990265d1918b79a82a185e24 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 5 Oct 2021 15:59:44 +0900
Subject: [PATCH v4 5/5] JSON logging

---
 src/include/postmaster/syslogger.h |   1 +
 src/include/utils/elog.h           |   2 +
 src/backend/postmaster/syslogger.c | 107 ++++++++--
 src/backend/utils/adt/misc.c       |   5 +-
 src/backend/utils/error/Makefile   |   3 +-
 src/backend/utils/error/elog.c     |  18 ++
 src/backend/utils/error/jsonlog.c  | 323 +++++++++++++++++++++++++++++
 src/backend/utils/misc/guc.c       |   2 +
 src/bin/pg_ctl/t/004_logrotate.pl  |  12 +-
 doc/src/sgml/config.sgml           |  67 +++++-
 10 files changed, 514 insertions(+), 26 deletions(-)
 create mode 100644 src/backend/utils/error/jsonlog.c

diff --git a/src/include/postmaster/syslogger.h b/src/include/postmaster/syslogger.h
index c79dfbeba2..18448b76e5 100644
--- a/src/include/postmaster/syslogger.h
+++ b/src/include/postmaster/syslogger.h
@@ -64,6 +64,7 @@ typedef union
 /* log destinations */
 #define PIPE_PROTO_DEST_STDERR	0x10
 #define PIPE_PROTO_DEST_CSVLOG	0x20
+#define PIPE_PROTO_DEST_JSONLOG	0x40
 
 /* GUC options */
 extern bool Logging_collector;
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index ab08e7fac8..87b3398ca6 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -436,6 +436,7 @@ extern bool syslog_split_messages;
 #define LOG_DESTINATION_SYSLOG	 2
 #define LOG_DESTINATION_EVENTLOG 4
 #define LOG_DESTINATION_CSVLOG	 8
+#define LOG_DESTINATION_JSONLOG	16
 
 /* Other exported functions */
 extern void DebugFileOpen(void);
@@ -448,6 +449,7 @@ extern bool	check_log_of_query(ErrorData *edata);
 extern const char *get_backend_type_for_log(void);
 extern const char *error_severity(int elevel);
 extern void write_csvlog(ErrorData *edata);
+extern void write_jsonlog(ErrorData *edata);
 extern void write_pipe_chunks(char *data, int len, int dest);
 
 #ifdef HAVE_SYSLOG
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index 4a019db7f4..9d5de35a44 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -86,9 +86,11 @@ static bool pipe_eof_seen = false;
 static bool rotation_disabled = false;
 static FILE *syslogFile = NULL;
 static FILE *csvlogFile = NULL;
+static FILE *jsonlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
 static char *last_sys_file_name = NULL;
 static char *last_csv_file_name = NULL;
+static char *last_json_file_name = NULL;
 
 /*
  * Buffers for saving partial messages from different backends.
@@ -277,6 +279,8 @@ SysLoggerMain(int argc, char *argv[])
 	last_sys_file_name = logfile_getname(first_syslogger_file_time, NULL);
 	if (csvlogFile != NULL)
 		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
+	if (jsonlogFile != NULL)
+		last_json_file_name = logfile_getname(first_syslogger_file_time, ".json");
 
 	/* remember active logfile parameters */
 	currentLogDir = pstrdup(Log_directory);
@@ -363,6 +367,14 @@ SysLoggerMain(int argc, char *argv[])
 				(csvlogFile != NULL))
 				rotation_requested = true;
 
+			/*
+			 * Force a rotation if JSONLOG output was just turned on or off and
+			 * we need to open or close jsonlogFile accordingly.
+			 */
+			if (((Log_destination & LOG_DESTINATION_JSONLOG) != 0) !=
+				(jsonlogFile != NULL))
+				rotation_requested = true;
+
 			/*
 			 * If rotation time parameter changed, reset next rotation time,
 			 * but don't immediately force a rotation.
@@ -413,6 +425,12 @@ SysLoggerMain(int argc, char *argv[])
 				rotation_requested = true;
 				size_rotation_for |= LOG_DESTINATION_CSVLOG;
 			}
+			if (jsonlogFile != NULL &&
+				ftell(jsonlogFile) >= Log_RotationSize * 1024L)
+			{
+				rotation_requested = true;
+				size_rotation_for |= LOG_DESTINATION_JSONLOG;
+			}
 		}
 
 		if (rotation_requested)
@@ -422,7 +440,7 @@ SysLoggerMain(int argc, char *argv[])
 			 * was sent by pg_rotate_logfile() or "pg_ctl logrotate".
 			 */
 			if (!time_based_rotation && size_rotation_for == 0)
-				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG;
+				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG | LOG_DESTINATION_JSONLOG;
 			logfile_rotate(time_based_rotation, size_rotation_for);
 		}
 
@@ -628,6 +646,20 @@ SysLogger_Start(void)
 		pfree(filename);
 	}
 
+	/*
+	 * Likewise for the initial JSON log file, if that's enabled.  (Note that
+	 * we open syslogFile even when only JSON output is nominally enabled,
+	 * since some code paths will write to syslogFile anyway.)
+	 */
+	if (Log_destination & LOG_DESTINATION_JSONLOG)
+	{
+		filename = logfile_getname(first_syslogger_file_time, ".json");
+
+		jsonlogFile = logfile_open(filename, "a", false);
+
+		pfree(filename);
+	}
+
 #ifdef EXEC_BACKEND
 	switch ((sysloggerPid = syslogger_forkexec()))
 #else
@@ -725,6 +757,11 @@ SysLogger_Start(void)
 				fclose(csvlogFile);
 				csvlogFile = NULL;
 			}
+			if (jsonlogFile != NULL)
+			{
+				fclose(jsonlogFile);
+				jsonlogFile = NULL;
+			}
 			return (int) sysloggerPid;
 	}
 
@@ -801,6 +838,7 @@ syslogger_forkexec(void)
 	int			ac = 0;
 	char		filenobuf[32];
 	char		csvfilenobuf[32];
+	char		jsonfilenobuf[32];
 
 	av[ac++] = "postgres";
 	av[ac++] = "--forklog";
@@ -813,6 +851,9 @@ syslogger_forkexec(void)
 	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%d",
 			 syslogger_fdget(csvlogFile));
 	av[ac++] = csvfilenobuf;
+	snprintf(jsonfilenobuf, sizeof(jsonfilenobuf), "%d",
+			 syslogger_fdget(jsonlogFile));
+	av[ac++] = jsonfilenobuf;
 
 	av[ac] = NULL;
 	Assert(ac < lengthof(av));
@@ -830,8 +871,8 @@ syslogger_parseArgs(int argc, char *argv[])
 {
 	int			fd;
 
-	Assert(argc == 5);
-	argv += 3;
+	Assert(argc == 6);
+	argv += 4;
 
 	/*
 	 * Re-open the error output files that were opened by SysLogger_Start().
@@ -844,6 +885,8 @@ syslogger_parseArgs(int argc, char *argv[])
 	syslogFile = syslogger_fdopen(fd);
 	fd = atoi(*argv++);
 	csvlogFile = syslogger_fdopen(fd);
+	fd = atoi(*argv++);
+	jsonlogFile = syslogger_fdopen(fd);
 }
 #endif							/* EXEC_BACKEND */
 
@@ -892,7 +935,9 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 
 		/* Do we have a valid header? */
 		memcpy(&p, cursor, offsetof(PipeProtoHeader, data));
-		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR | PIPE_PROTO_DEST_CSVLOG);
+		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR |
+								PIPE_PROTO_DEST_CSVLOG |
+								PIPE_PROTO_DEST_JSONLOG);
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&
@@ -914,6 +959,8 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 				dest = LOG_DESTINATION_STDERR;
 			else if ((p.flags & PIPE_PROTO_DEST_CSVLOG) != 0)
 				dest = LOG_DESTINATION_CSVLOG;
+			else if ((p.flags & PIPE_PROTO_DEST_JSONLOG) != 0)
+				dest = LOG_DESTINATION_JSONLOG;
 			else
 			{
 				/* this should never happen as of the header validation */
@@ -1093,19 +1140,24 @@ write_syslogger_file(const char *buffer, int count, int destination)
 	FILE	   *logfile;
 
 	/*
-	 * If we're told to write to csvlogFile, but it's not open, dump the data
-	 * to syslogFile (which is always open) instead.  This can happen if CSV
-	 * output is enabled after postmaster start and we've been unable to open
-	 * csvlogFile.  There are also race conditions during a parameter change
-	 * whereby backends might send us CSV output before we open csvlogFile or
-	 * after we close it.  Writing CSV-formatted output to the regular log
-	 * file isn't great, but it beats dropping log output on the floor.
+	 * If we're told to write to a structured log file, but it's not open,
+	 * dump the data to syslogFile (which is always open) instead.  This can
+	 * happen if structured output is enabled after postmaster start and
+	 * we've been unable to open logFile.  There are also race conditions
+	 * during a parameter change whereby backends might send us structured
+	 * output before we open the logFile or after we close it.  Writing
+	 * formatted output to the regular log file isn't great, but it beats
+	 * dropping log output on the floor.
 	 *
-	 * Think not to improve this by trying to open csvlogFile on-the-fly.  Any
+	 * Think not to improve this by trying to open logFile on-the-fly.  Any
 	 * failure in that would lead to recursion.
 	 */
-	logfile = (destination == LOG_DESTINATION_CSVLOG &&
-			   csvlogFile != NULL) ? csvlogFile : syslogFile;
+	if ((destination & LOG_DESTINATION_CSVLOG) && csvlogFile != NULL)
+		logfile = csvlogFile;
+	else if ((destination & LOG_DESTINATION_JSONLOG) && jsonlogFile != NULL)
+		logfile = jsonlogFile;
+	else
+		logfile = syslogFile;
 
 	rc = fwrite(buffer, 1, count, logfile);
 
@@ -1176,7 +1228,8 @@ pipeThread(void *arg)
 		if (Log_RotationSize > 0)
 		{
 			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
-				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
+				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L) ||
+				(jsonlogFile != NULL && ftell(jsonlogFile) >= Log_RotationSize * 1024L))
 				SetLatch(MyLatch);
 		}
 		LeaveCriticalSection(&sysloggerSection);
@@ -1291,6 +1344,8 @@ logfile_rotate_dest(bool time_based_rotation, int size_rotation_for,
 		logFileExt = NULL;
 	else if (target_dest == LOG_DESTINATION_CSVLOG)
 		logFileExt = ".csv";
+	else if (target_dest == LOG_DESTINATION_JSONLOG)
+		logFileExt = ".json";
 	else
 	{
 		/* cannot happen */
@@ -1378,6 +1433,12 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 							 &csvlogFile))
 		return;
 
+	/* file rotation for csvlog */
+	if (!logfile_rotate_dest(time_based_rotation, size_rotation_for, fntime,
+							 LOG_DESTINATION_JSONLOG, &last_json_file_name,
+							 &jsonlogFile))
+		return;
+
 	update_metainfo_datafile();
 
 	set_next_rotation_time();
@@ -1464,7 +1525,8 @@ update_metainfo_datafile(void)
 	mode_t		oumask;
 
 	if (!(Log_destination & LOG_DESTINATION_STDERR) &&
-		!(Log_destination & LOG_DESTINATION_CSVLOG))
+		!(Log_destination & LOG_DESTINATION_CSVLOG) &&
+		!(Log_destination & LOG_DESTINATION_JSONLOG))
 	{
 		if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
 			ereport(LOG,
@@ -1522,6 +1584,19 @@ update_metainfo_datafile(void)
 			return;
 		}
 	}
+
+	if (last_json_file_name && (Log_destination & LOG_DESTINATION_JSONLOG))
+	{
+		if (fprintf(fh, "jsonlog %s\n", last_json_file_name) < 0)
+		{
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not write file \"%s\": %m",
+							LOG_METAINFO_DATAFILE_TMP)));
+			fclose(fh);
+			return;
+		}
+	}
 	fclose(fh);
 
 	if (rename(LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE) != 0)
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 88faf4dfd7..4931859627 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -843,11 +843,12 @@ pg_current_logfile(PG_FUNCTION_ARGS)
 	{
 		logfmt = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
-		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0)
+		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0 &&
+				strcmp(logfmt, "jsonlog") != 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("log format \"%s\" is not supported", logfmt),
-					 errhint("The supported log formats are \"stderr\" and \"csvlog\".")));
+					 errhint("The supported log formats are \"stderr\", \"csvlog\", and \"jsonlog\".")));
 	}
 
 	fd = AllocateFile(LOG_METAINFO_DATAFILE, "r");
diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index ef770dd2f2..65ba61fb3c 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -15,6 +15,7 @@ include $(top_builddir)/src/Makefile.global
 OBJS = \
 	assert.o \
 	csvlog.o \
-	elog.o
+	elog.o \
+	jsonlog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index f99a173e15..c96bb3d527 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2986,6 +2986,22 @@ send_message_to_server_log(ErrorData *edata)
 			fallback_to_stderr = true;
 	}
 
+	/* Write to JSON log, if enabled */
+	if ((Log_destination & LOG_DESTINATION_JSONLOG) != 0)
+	{
+		/*
+		 * Send JSON data if it's safe to do so (syslogger doesn't need the
+		 * pipe).  If this is not possible, fallback to an entry written
+		 * to stderr.
+		 */
+		if (redirection_done || MyBackendType == B_LOGGER)
+		{
+			write_jsonlog(edata);
+		}
+		else
+			fallback_to_stderr = true;
+	}
+
 	/*
 	 * Write to stderr, if enabled or if required because of a previous
 	 * limitation.
@@ -3061,6 +3077,8 @@ write_pipe_chunks(char *data, int len, int dest)
 		p.proto.flags |= PIPE_PROTO_DEST_STDERR;
 	else if (dest == LOG_DESTINATION_CSVLOG)
 		p.proto.flags |= PIPE_PROTO_DEST_CSVLOG;
+	else if (dest == LOG_DESTINATION_JSONLOG)
+		p.proto.flags |= PIPE_PROTO_DEST_JSONLOG;
 
 	/* write all but the last chunk */
 	while (len > PIPE_MAX_PAYLOAD)
diff --git a/src/backend/utils/error/jsonlog.c b/src/backend/utils/error/jsonlog.c
new file mode 100644
index 0000000000..f92ee64a47
--- /dev/null
+++ b/src/backend/utils/error/jsonlog.c
@@ -0,0 +1,323 @@
+/*-------------------------------------------------------------------------
+ *
+ * jsonlog.c
+ *	  JSON logging
+ *
+ * Copyright (c) 2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/jsonlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog.h"
+#include "utils/guc.h"
+#include "utils/json.h"
+#include "utils/ps_status.h"
+
+static void appendJSONKeyValueFmt(StringInfo buf, const char *key,
+								  const char *fmt,...) pg_attribute_printf(3, 4);
+
+/*
+ * appendJSONKeyValue
+ * Append to given StringInfo a comma followed by a JSON key and value.
+ * Both the key and value will be escaped as JSON string literals.
+ */
+static void
+appendJSONKeyValue(StringInfo buf, const char *key, const char *value)
+{
+	if (value == NULL)
+		return;
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	escape_json(buf, value);
+}
+
+/*
+ * appendJSONKeyValueFmt
+ *
+ * Evaluate the fmt string and then invoke appendJSONKeyValue as the
+ * value of the JSON property. Both the key and value will be escaped by
+ * appendJSONKeyValue.
+ */
+static void
+appendJSONKeyValueFmt(StringInfo buf, const char *key, const char *fmt,...)
+{
+	int			save_errno = errno;
+	size_t		len = 128;		/* initial assumption about buffer size */
+	char	    *value;
+
+	for (;;)
+	{
+		va_list		args;
+		size_t		newlen;
+
+		/*
+		 * Allocate result buffer.  Note that in frontend this maps to malloc
+		 * with exit-on-error.
+		 */
+		value = (char *) palloc(len);
+
+		/* Try to format the data. */
+		errno = save_errno;
+		va_start(args, fmt);
+		newlen = pvsnprintf(value, len, fmt, args);
+		va_end(args);
+
+		if (newlen < len)
+			break; /* success */
+
+		/* Release buffer and loop around to try again with larger len. */
+		pfree(value);
+		len = newlen;
+	}
+	appendJSONKeyValue(buf, key, value);
+
+	/* Clean up */
+	pfree(value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as a signed integer (a JSON number).
+ */
+static void
+appendJSONKeyValueAsInt(StringInfo buf, const char *key, int value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%d", value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as an unsigned integer (a JSON number).
+ */
+static void
+appendJSONKeyValueAsUInt(StringInfo buf, const char *key, int value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%u", value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as a long (a JSON number).
+ */
+static void
+appendJSONKeyValueAsLong(StringInfo buf, const char *key, long value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%ld", value);
+}
+
+/*
+ * Write logs in json format.
+ */
+void
+write_jsonlog(ErrorData *edata)
+{
+	StringInfoData	buf;
+	char	   *start_time;
+	char	   *log_time;
+
+	/* static counter for line numbers */
+	static long	log_line_number = 0;
+
+	/* Has the counter been reset in the current process? */
+	static int	log_my_pid = 0;
+
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		reset_formatted_start_time();
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* Initialize string */
+	appendStringInfoChar(&buf, '{');
+
+	/*
+	 * timestamp with milliseconds
+	 *
+	 * Check if the timestamp is already calculated for the syslog message,
+	 * and use it if so.  Otherwise, get the current timestamp.  This is done
+	 * to put same timestamp in both syslog and jsonlog messages.
+	 */
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+
+	/*
+	 * First property does not use appendJSONKeyValue as it does not have
+	 * comma prefix.
+	 */
+	escape_json(&buf, "timestamp");
+	appendStringInfoChar(&buf, ':');
+	escape_json(&buf, log_time);
+
+	/* username */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "user", MyProcPort->user_name);
+
+	/* database name */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "dbname", MyProcPort->database_name);
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendJSONKeyValueAsInt(&buf, "leader_pid", leader->pid);
+	}
+
+	/* Process ID */
+	if (MyProcPid != 0)
+		appendJSONKeyValueAsInt(&buf, "pid", MyProcPid);
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendJSONKeyValue(&buf, "remote_host", MyProcPort->remote_host);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+			appendJSONKeyValue(&buf, "remote_port", MyProcPort->remote_port);
+	}
+
+	/* Session id */
+	appendJSONKeyValueFmt(&buf, "session_id", "%lx.%x", (long) MyStartTime, MyProcPid);
+
+	/* Line number */
+	appendJSONKeyValueAsLong(&buf, "line_num", log_line_number);
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData	msgbuf;
+		const char	   *psdisp;
+		int				displen;
+
+		initStringInfo(&msgbuf);
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendJSONKeyValue(&buf, "ps", msgbuf.data);
+
+		pfree(msgbuf.data);
+	}
+
+	/* session start timestamp */
+	start_time = get_formatted_start_time();
+	appendJSONKeyValue(&buf, "session_start", start_time);
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendJSONKeyValueFmt(&buf, "vxid", "%d/%u", MyProc->backendId, MyProc->lxid);
+
+	/* Transaction id */
+	appendJSONKeyValueFmt(&buf, "txid", "%u", GetTopTransactionIdIfAny());
+
+	/* Error severity */
+	if (edata->elevel)
+		appendJSONKeyValue(&buf, "error_severity", (char *) error_severity(edata->elevel));
+
+	/* query id */
+	appendJSONKeyValueFmt(&buf,  "query_id", "%lld", (long long) pgstat_get_my_query_id());
+
+	/* SQL state code */
+	if (edata->sqlerrcode)
+		appendJSONKeyValue(&buf, "state_code", unpack_sql_state(edata->sqlerrcode));
+
+	/* errdetail or error_detail log */
+	if (edata->detail_log)
+		appendJSONKeyValue(&buf, "detail", edata->detail_log);
+	else if (edata->detail)
+		appendJSONKeyValue(&buf, "detail", edata->detail);
+
+	/* errhint */
+	if (edata->hint)
+		appendJSONKeyValue(&buf, "hint", edata->hint);
+
+	/* Internal query */
+	if (edata->internalquery)
+		appendJSONKeyValue(&buf, "internal_query", edata->internalquery);
+
+	/* If the internal query got printed, print internal pos, too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendJSONKeyValueAsUInt(&buf, "internal_position", edata->internalpos);
+
+	/* errcontext */
+	if (edata->context && !edata->hide_ctx)
+		appendJSONKeyValue(&buf, "context", edata->context);
+
+	/* user query --- only reported if not disabled by the caller */
+	if (check_log_of_query(edata))
+	{
+		appendJSONKeyValue(&buf, "statement", debug_query_string);
+		if (edata->cursorpos > 0)
+			appendJSONKeyValueAsInt(&buf, "cursor_position", edata->cursorpos);
+	}
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		if (edata->funcname)
+			appendJSONKeyValue(&buf, "func_name", edata->funcname);
+		if (edata->filename)
+		{
+			appendJSONKeyValue(&buf, "file_name", edata->filename);
+			appendJSONKeyValueAsInt(&buf, "file_line_num", edata->lineno);
+		}
+	}
+
+	/* Application name */
+	if (application_name && application_name[0] != '\0')
+		appendJSONKeyValue(&buf, "application_name", application_name);
+
+	/* backend type */
+	appendJSONKeyValue(&buf, "backend_type", get_backend_type_for_log());
+
+	/* Error message */
+	appendJSONKeyValue(&buf, "message", edata->message);
+
+	/* Finish string */
+	appendStringInfoChar(&buf, '}');
+	appendStringInfoChar(&buf, '\n');
+
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+	else
+		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index d2ce4a8450..0b79753ec3 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -11714,6 +11714,8 @@ check_log_destination(char **newval, void **extra, GucSource source)
 			newlogdest |= LOG_DESTINATION_STDERR;
 		else if (pg_strcasecmp(tok, "csvlog") == 0)
 			newlogdest |= LOG_DESTINATION_CSVLOG;
+		else if (pg_strcasecmp(tok, "jsonlog") == 0)
+			newlogdest |= LOG_DESTINATION_JSONLOG;
 #ifdef HAVE_SYSLOG
 		else if (pg_strcasecmp(tok, "syslog") == 0)
 			newlogdest |= LOG_DESTINATION_SYSLOG;
diff --git a/src/bin/pg_ctl/t/004_logrotate.pl b/src/bin/pg_ctl/t/004_logrotate.pl
index aa0d64a4f7..caa5740254 100644
--- a/src/bin/pg_ctl/t/004_logrotate.pl
+++ b/src/bin/pg_ctl/t/004_logrotate.pl
@@ -6,7 +6,7 @@ use warnings;
 
 use PostgresNode;
 use TestLib;
-use Test::More tests => 10;
+use Test::More tests => 14;
 use Time::HiRes qw(usleep);
 
 # Extract the file name of a $format from the contents of
@@ -63,7 +63,7 @@ $node->init();
 $node->append_conf(
 	'postgresql.conf', qq(
 logging_collector = on
-log_destination = 'stderr, csvlog'
+log_destination = 'stderr, csvlog, jsonlog'
 # these ensure stability of test results:
 log_rotation_age = 0
 lc_messages = 'C'
@@ -94,11 +94,13 @@ note "current_logfiles = $current_logfiles";
 like(
 	$current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'current_logfiles is sane');
 
 check_log_pattern('stderr', $current_logfiles, 'division by zero', $node);
 check_log_pattern('csvlog', $current_logfiles, 'division by zero', $node);
+check_log_pattern('jsonlog', $current_logfiles, 'division by zero', $node);
 
 # Sleep 2 seconds and ask for log rotation; this should result in
 # output into a different log file name.
@@ -120,7 +122,8 @@ note "now current_logfiles = $new_current_logfiles";
 like(
 	$new_current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'new current_logfiles is sane');
 
 # Verify that log output gets to this file, too
@@ -128,5 +131,6 @@ $node->psql('postgres', 'fee fi fo fum');
 
 check_log_pattern('stderr', $new_current_logfiles, 'syntax error', $node);
 check_log_pattern('csvlog', $new_current_logfiles, 'syntax error', $node);
+check_log_pattern('jsonlog', $new_current_logfiles, 'syntax error', $node);
 
 $node->stop();
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 0a8e35c59f..7723e11cf7 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5926,7 +5926,8 @@ SELECT * FROM parent WHERE key = 2400;
        <para>
         <productname>PostgreSQL</productname> supports several methods
          for logging server messages, including
-         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem> and
+         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem>,
+         <systemitem>jsonlog</systemitem>, and
          <systemitem>syslog</systemitem>. On Windows,
          <systemitem>eventlog</systemitem> is also supported. Set this
          parameter to a list of desired log destinations separated by
@@ -5944,6 +5945,14 @@ SELECT * FROM parent WHERE key = 2400;
         <xref linkend="guc-logging-collector"/> must be enabled to generate
         CSV-format log output.
        </para>
+       <para>
+        If <systemitem>jsonlog</systemitem> is included in <varname>log_destination</varname>,
+        log entries are output in <acronym>JSON</acronym> format, which is convenient for
+        loading logs into programs.
+        See <xref linkend="runtime-config-logging-jsonlog"/> for details.
+        <xref linkend="guc-logging-collector"/> must be enabled to generate
+        CSV-format log output.
+       </para>
        <para>
         When either <systemitem>stderr</systemitem> or
         <systemitem>csvlog</systemitem> are included, the file
@@ -5955,13 +5964,14 @@ SELECT * FROM parent WHERE key = 2400;
 <programlisting>
 stderr log/postgresql.log
 csvlog log/postgresql.csv
+jsonlog log/postgresql.json
 </programlisting>
 
         <filename>current_logfiles</filename> is recreated when a new log file
         is created as an effect of rotation, and
         when <varname>log_destination</varname> is reloaded.  It is removed when
-        neither <systemitem>stderr</systemitem>
-        nor <systemitem>csvlog</systemitem> are included
+        none of <systemitem>stderr</systemitem>,
+        <systemitem>csvlog</systemitem>, <systemitem>jsonlog</systemitem> are included
         in <varname>log_destination</varname>, and when the logging collector is
         disabled.
        </para>
@@ -6101,6 +6111,13 @@ local0.*    /var/log/postgresql
         (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
         replaced instead.)
        </para>
+       <para>
+        If JSON-format output is enabled in <varname>log_destination</varname>,
+        <literal>.json</literal> will be appended to the timestamped
+        log file name to create the file name for JSON-format output.
+        (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
+        replaced instead.)
+       </para>
        <para>
         This parameter can only be set in the <filename>postgresql.conf</filename>
         file or on the server command line.
@@ -7433,6 +7450,50 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         </orderedlist>
       </para>
     </sect2>
+     <sect2 id="runtime-config-logging-jsonlog">
+     <title>Using JSON-Format Log Output</title>
+
+       <para>
+        Including <literal>jsonlog</literal> in the <varname>log_destination</varname> list
+        provides a convenient way to import log files into many different programs.
+        This option emits log lines in (<acronym>JSON</acronym>) format.
+        Each log line is serialized as a JSON object with the following fields:
+<programlisting>
+        {
+            "timestamp": time stamp with milliseconds (string),
+            "user": user name (string),
+            "dbname": database name (string),
+            "pid": process ID (number),
+            "remote_host": client host (string)
+            "remote_port": port number (string),
+            "session_id": session ID (string),
+            "line_num": per-session line number (number),
+            "ps": current ps display (string),
+            "session_start": session start time (string),
+            "vxid": virtual transaction ID (string),
+            "txid": regular transaction ID (string),
+            "error_severity": error severity (string),
+            "state_code": SQLSTATE code (string),
+            "detail": error message detail (string),
+            "hint": hint (string),
+            "internal_query": internal query that led to the error (string),
+            "internal_position": cursor index into internal query (number),
+            "context": error context (string),
+            "statement": client supplied query string (string),
+            "cursor_position": cursor index into query string (string),
+            "func_name": error location function name (string),
+            "file_name": error location file name (string),
+            "file_line_num": error location file line number (number),
+            "application_name": client application name (string),
+            "message": error message (string)
+        }
+</programlisting>
+        String fields with null values are excluded from output.
+        Additional fields may be added in the future. User applications that process jsonlog
+        output should ignore unknown fields.
+       </para>
+
+    </sect2>
 
    <sect2>
     <title>Process Title</title>
-- 
2.33.0

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index 34b16ba3bb..d1f56b95a4 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -1258,7 +1258,7 @@ logfile_rotate_dest(bool time_based_rotation, int size_rotation_for,
 					pg_time_t fntime, int target_dest,
 					char **last_file_name, FILE **logFile)
 {
-	char	   *logFileExt;
+	char	   *logFileExt = NULL;
 	char	   *filename;
 	FILE	   *fh;
 

From 70317f6603923347d95e22404fdd53842c6fc1a5 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 5 Oct 2021 11:19:46 +0900
Subject: [PATCH v5 1/3] Some refactoring of elog-specific routines

This refactors out the following things in elog.c, for ease of use
across multiple log destinations:
- start_timestamp
- log_timestamp
- decide if query can be logged
- backend type

This will be reused by jsonlog.
---
 src/include/utils/elog.h       |   4 +
 src/backend/utils/error/elog.c | 141 +++++++++++++++++++++------------
 2 files changed, 94 insertions(+), 51 deletions(-)

diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index f53607e12e..bc6f362b6a 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -441,6 +441,10 @@ extern bool syslog_split_messages;
 extern void DebugFileOpen(void);
 extern char *unpack_sql_state(int sql_state);
 extern bool in_error_recursion_trouble(void);
+extern char *get_formatted_start_time(void);
+extern char *get_formatted_log_time(void);
+extern bool	check_log_of_query(ErrorData *edata);
+extern const char *get_backend_type_for_log(void);
 
 #ifdef HAVE_SYSLOG
 extern void set_syslog_parameters(const char *ident, int facility);
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index f33729513a..87e911ad28 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -175,8 +175,6 @@ static const char *err_gettext(const char *str) pg_attribute_format_arg(1);
 static pg_noinline void set_backtrace(ErrorData *edata, int num_skip);
 static void set_errdata_field(MemoryContextData *cxt, char **ptr, const char *str);
 static void write_console(const char *line, int len);
-static void setup_formatted_log_time(void);
-static void setup_formatted_start_time(void);
 static const char *process_log_prefix_padding(const char *p, int *padding);
 static void log_line_prefix(StringInfo buf, ErrorData *edata);
 static void write_csvlog(ErrorData *edata);
@@ -2289,14 +2287,23 @@ write_console(const char *line, int len)
 }
 
 /*
- * setup formatted_log_time, for consistent times between CSV and regular logs
+ * get_formatted_log_time -- compute and get the log timestamp.
+ *
+ * The timestamp is computed if not set yet, so as it is kept consistent
+ * among all the log destinations that require it to be consistent.  Note
+ * that the computed timestamp is returned in a static buffer, not
+ * palloc()'d.
  */
-static void
-setup_formatted_log_time(void)
+char *
+get_formatted_log_time(void)
 {
 	pg_time_t	stamp_time;
 	char		msbuf[13];
 
+	/* leave if already computed */
+	if (formatted_log_time[0] != '\0')
+		return formatted_log_time;
+
 	if (!saved_timeval_set)
 	{
 		gettimeofday(&saved_timeval, NULL);
@@ -2318,16 +2325,25 @@ setup_formatted_log_time(void)
 	/* 'paste' milliseconds into place... */
 	sprintf(msbuf, ".%03d", (int) (saved_timeval.tv_usec / 1000));
 	memcpy(formatted_log_time + 19, msbuf, 4);
+
+	return formatted_log_time;
 }
 
 /*
- * setup formatted_start_time
+ * get_formatted_start_time -- compute and get the start timestamp.
+ *
+ * The timestamp is computed if not set yet.  Note that the computed
+ * timestamp is returned in a static buffer, not palloc()'d.
  */
-static void
-setup_formatted_start_time(void)
+char *
+get_formatted_start_time(void)
 {
 	pg_time_t	stamp_time = (pg_time_t) MyStartTime;
 
+	/* leave if already computed */
+	if (formatted_start_time[0] != '\0')
+		return formatted_start_time;
+
 	/*
 	 * Note: we expect that guc.c will ensure that log_timezone is set up (at
 	 * least with a minimal GMT value) before Log_line_prefix can become
@@ -2336,6 +2352,49 @@ setup_formatted_start_time(void)
 	pg_strftime(formatted_start_time, FORMATTED_TS_LEN,
 				"%Y-%m-%d %H:%M:%S %Z",
 				pg_localtime(&stamp_time, log_timezone));
+
+	return formatted_start_time;
+}
+
+/*
+ * check_log_of_query -- check if a query can be logged
+ */
+bool
+check_log_of_query(ErrorData *edata)
+{
+	/* log required? */
+	if (!is_log_level_output(edata->elevel, log_min_error_statement))
+		return false;
+
+	/* query log wanted? */
+	if (edata->hide_stmt)
+		return false;
+
+	/* query string available? */
+	if (debug_query_string == NULL)
+		return false;
+
+	return true;
+}
+
+/*
+ * get_backend_type_for_log -- backend type for log entries
+ *
+ * Returns a pointer to a static buffer, not palloc()'d.
+ */
+const char *
+get_backend_type_for_log(void)
+{
+	const char   *backend_type_str;
+
+	if (MyProcPid == PostmasterPid)
+		backend_type_str = "postmaster";
+	else if (MyBackendType == B_BG_WORKER)
+		backend_type_str = MyBgworkerEntry->bgw_type;
+	else
+		backend_type_str = GetBackendTypeDesc(MyBackendType);
+
+	return backend_type_str;
 }
 
 /*
@@ -2466,14 +2525,7 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 				break;
 			case 'b':
 				{
-					const char *backend_type_str;
-
-					if (MyProcPid == PostmasterPid)
-						backend_type_str = "postmaster";
-					else if (MyBackendType == B_BG_WORKER)
-						backend_type_str = MyBgworkerEntry->bgw_type;
-					else
-						backend_type_str = GetBackendTypeDesc(MyBackendType);
+					const char *backend_type_str = get_backend_type_for_log();
 
 					if (padding != 0)
 						appendStringInfo(buf, "%*s", padding, backend_type_str);
@@ -2561,7 +2613,10 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 					appendStringInfo(buf, "%ld", log_line_number);
 				break;
 			case 'm':
-				setup_formatted_log_time();
+				/* force a log timestamp reset */
+				formatted_log_time[0] = '\0';
+				(void) get_formatted_log_time();
+
 				if (padding != 0)
 					appendStringInfo(buf, "%*s", padding, formatted_log_time);
 				else
@@ -2602,12 +2657,14 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 				}
 				break;
 			case 's':
-				if (formatted_start_time[0] == '\0')
-					setup_formatted_start_time();
-				if (padding != 0)
-					appendStringInfo(buf, "%*s", padding, formatted_start_time);
-				else
-					appendStringInfoString(buf, formatted_start_time);
+				{
+					char   *start_time = get_formatted_start_time();
+
+					if (padding != 0)
+						appendStringInfo(buf, "%*s", padding, start_time);
+					else
+						appendStringInfoString(buf, start_time);
+				}
 				break;
 			case 'i':
 				if (MyProcPort)
@@ -2763,6 +2820,8 @@ write_csvlog(ErrorData *edata)
 {
 	StringInfoData buf;
 	bool		print_stmt = false;
+	char	   *start_time;
+	char	   *log_time;
 
 	/* static counter for line numbers */
 	static long log_line_number = 0;
@@ -2785,17 +2844,9 @@ write_csvlog(ErrorData *edata)
 
 	initStringInfo(&buf);
 
-	/*
-	 * timestamp with milliseconds
-	 *
-	 * Check if the timestamp is already calculated for the syslog message,
-	 * and use it if so.  Otherwise, get the current timestamp.  This is done
-	 * to put same timestamp in both syslog and csvlog messages.
-	 */
-	if (formatted_log_time[0] == '\0')
-		setup_formatted_log_time();
-
-	appendStringInfoString(&buf, formatted_log_time);
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+	appendStringInfoString(&buf, log_time);
 	appendStringInfoChar(&buf, ',');
 
 	/* username */
@@ -2853,9 +2904,8 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* session start timestamp */
-	if (formatted_start_time[0] == '\0')
-		setup_formatted_start_time();
-	appendStringInfoString(&buf, formatted_start_time);
+	start_time = get_formatted_start_time();
+	appendStringInfoString(&buf, start_time);
 	appendStringInfoChar(&buf, ',');
 
 	/* Virtual transaction id */
@@ -2906,10 +2956,7 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* user query --- only reported if not disabled by the caller */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
-		print_stmt = true;
+	print_stmt = check_log_of_query(edata);
 	if (print_stmt)
 		appendCSVLiteral(&buf, debug_query_string);
 	appendStringInfoChar(&buf, ',');
@@ -2943,13 +2990,7 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* backend type */
-	if (MyProcPid == PostmasterPid)
-		appendCSVLiteral(&buf, "postmaster");
-	else if (MyBackendType == B_BG_WORKER)
-		appendCSVLiteral(&buf, MyBgworkerEntry->bgw_type);
-	else
-		appendCSVLiteral(&buf, GetBackendTypeDesc(MyBackendType));
-
+	appendCSVLiteral(&buf, get_backend_type_for_log());
 	appendStringInfoChar(&buf, ',');
 
 	/* leader PID */
@@ -3101,9 +3142,7 @@ send_message_to_server_log(ErrorData *edata)
 	/*
 	 * If the user wants the query that generated this error logged, do it.
 	 */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
+	if (check_log_of_query(edata))
 	{
 		log_line_prefix(&buf, edata);
 		appendStringInfoString(&buf, _("STATEMENT:  "));
-- 
2.33.0

From ebf79e3275609d93f5145fed5a7d3909a39946b4 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 5 Oct 2021 15:22:24 +0900
Subject: [PATCH v5 2/3] Refactor CSV-specific code into its own file

This requires more routines of elog.c to be published.
---
 src/include/utils/elog.h         |   4 +
 src/backend/utils/error/Makefile |   1 +
 src/backend/utils/error/csvlog.c | 268 +++++++++++++++++++++++++++++++
 src/backend/utils/error/elog.c   | 251 ++---------------------------
 4 files changed, 284 insertions(+), 240 deletions(-)
 create mode 100644 src/backend/utils/error/csvlog.c

diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index bc6f362b6a..ab08e7fac8 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -441,10 +441,14 @@ extern bool syslog_split_messages;
 extern void DebugFileOpen(void);
 extern char *unpack_sql_state(int sql_state);
 extern bool in_error_recursion_trouble(void);
+extern void reset_formatted_start_time(void);
 extern char *get_formatted_start_time(void);
 extern char *get_formatted_log_time(void);
 extern bool	check_log_of_query(ErrorData *edata);
 extern const char *get_backend_type_for_log(void);
+extern const char *error_severity(int elevel);
+extern void write_csvlog(ErrorData *edata);
+extern void write_pipe_chunks(char *data, int len, int dest);
 
 #ifdef HAVE_SYSLOG
 extern void set_syslog_parameters(const char *ident, int facility);
diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index 612da215d0..ef770dd2f2 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -14,6 +14,7 @@ include $(top_builddir)/src/Makefile.global
 
 OBJS = \
 	assert.o \
+	csvlog.o \
 	elog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/csvlog.c b/src/backend/utils/error/csvlog.c
new file mode 100644
index 0000000000..443a91e168
--- /dev/null
+++ b/src/backend/utils/error/csvlog.c
@@ -0,0 +1,268 @@
+/*-------------------------------------------------------------------------
+ *
+ * csvlog.c
+ *	  CSV logging
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of Californi
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/csvlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog.h"
+#include "utils/guc.h"
+#include "utils/ps_status.h"
+
+
+/*
+ * append a CSV'd version of a string to a StringInfo
+ * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
+ * If it's NULL, append nothing.
+ */
+static inline void
+appendCSVLiteral(StringInfo buf, const char *data)
+{
+	const char *p = data;
+	char		c;
+
+	/* avoid confusing an empty string with NULL */
+	if (p == NULL)
+		return;
+
+	appendStringInfoCharMacro(buf, '"');
+	while ((c = *p++) != '\0')
+	{
+		if (c == '"')
+			appendStringInfoCharMacro(buf, '"');
+		appendStringInfoCharMacro(buf, c);
+	}
+	appendStringInfoCharMacro(buf, '"');
+}
+
+/*
+ * write_csvlog -- Generate and write CSV log entry
+ *
+ * Constructs the error message, depending on the Errordata it gets, in a CSV
+ * format which is described in doc/src/sgml/config.sgml.
+ */
+void
+write_csvlog(ErrorData *edata)
+{
+	StringInfoData buf;
+	bool		print_stmt = false;
+	char	   *start_time;
+	char	   *log_time;
+
+	/* static counter for line numbers */
+	static long log_line_number = 0;
+
+	/* has counter been reset in current process? */
+	static int	log_my_pid = 0;
+
+	/*
+	 * This is one of the few places where we'd rather not inherit a static
+	 * variable's value from the postmaster.  But since we will, reset it when
+	 * MyProcPid changes.
+	 */
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		reset_formatted_start_time();
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+	appendStringInfoString(&buf, log_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* username */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->user_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* database name */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->database_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* Process id  */
+	if (MyProcPid != 0)
+		appendStringInfo(&buf, "%d", MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendStringInfoChar(&buf, '"');
+		appendStringInfoString(&buf, MyProcPort->remote_host);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+		{
+			appendStringInfoChar(&buf, ':');
+			appendStringInfoString(&buf, MyProcPort->remote_port);
+		}
+		appendStringInfoChar(&buf, '"');
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session id */
+	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Line number */
+	appendStringInfo(&buf, "%ld", log_line_number);
+	appendStringInfoChar(&buf, ',');
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData msgbuf;
+		const char *psdisp;
+		int			displen;
+
+		initStringInfo(&msgbuf);
+
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendCSVLiteral(&buf, msgbuf.data);
+
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session start timestamp */
+	start_time = get_formatted_start_time();
+	appendStringInfoString(&buf, start_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Transaction id */
+	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
+	appendStringInfoChar(&buf, ',');
+
+	/* Error severity */
+	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
+	appendStringInfoChar(&buf, ',');
+
+	/* SQL state code */
+	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
+	appendStringInfoChar(&buf, ',');
+
+	/* errmessage */
+	appendCSVLiteral(&buf, edata->message);
+	appendStringInfoChar(&buf, ',');
+
+	/* errdetail or errdetail_log */
+	if (edata->detail_log)
+		appendCSVLiteral(&buf, edata->detail_log);
+	else
+		appendCSVLiteral(&buf, edata->detail);
+	appendStringInfoChar(&buf, ',');
+
+	/* errhint */
+	appendCSVLiteral(&buf, edata->hint);
+	appendStringInfoChar(&buf, ',');
+
+	/* internal query */
+	appendCSVLiteral(&buf, edata->internalquery);
+	appendStringInfoChar(&buf, ',');
+
+	/* if printed internal query, print internal pos too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendStringInfo(&buf, "%d", edata->internalpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* errcontext */
+	if (!edata->hide_ctx)
+		appendCSVLiteral(&buf, edata->context);
+	appendStringInfoChar(&buf, ',');
+
+	/* user query --- only reported if not disabled by the caller */
+	print_stmt = check_log_of_query(edata);
+	if (print_stmt)
+		appendCSVLiteral(&buf, debug_query_string);
+	appendStringInfoChar(&buf, ',');
+	if (print_stmt && edata->cursorpos > 0)
+		appendStringInfo(&buf, "%d", edata->cursorpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		StringInfoData msgbuf;
+
+		initStringInfo(&msgbuf);
+
+		if (edata->funcname && edata->filename)
+			appendStringInfo(&msgbuf, "%s, %s:%d",
+							 edata->funcname, edata->filename,
+							 edata->lineno);
+		else if (edata->filename)
+			appendStringInfo(&msgbuf, "%s:%d",
+							 edata->filename, edata->lineno);
+		appendCSVLiteral(&buf, msgbuf.data);
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* application name */
+	if (application_name)
+		appendCSVLiteral(&buf, application_name);
+
+	appendStringInfoChar(&buf, ',');
+
+	/* backend type */
+	appendCSVLiteral(&buf, get_backend_type_for_log());
+	appendStringInfoChar(&buf, ',');
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendStringInfo(&buf, "%d", leader->pid);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* query id */
+	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
+
+	appendStringInfoChar(&buf, '\n');
+
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+	else
+		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 87e911ad28..4406d8deff 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -177,11 +177,8 @@ static void set_errdata_field(MemoryContextData *cxt, char **ptr, const char *st
 static void write_console(const char *line, int len);
 static const char *process_log_prefix_padding(const char *p, int *padding);
 static void log_line_prefix(StringInfo buf, ErrorData *edata);
-static void write_csvlog(ErrorData *edata);
 static void send_message_to_server_log(ErrorData *edata);
-static void write_pipe_chunks(char *data, int len, int dest);
 static void send_message_to_frontend(ErrorData *edata);
-static const char *error_severity(int elevel);
 static void append_with_tabs(StringInfo buf, const char *str);
 
 
@@ -2329,6 +2326,15 @@ get_formatted_log_time(void)
 	return formatted_log_time;
 }
 
+/*
+ * reset_formatted_start_time -- reset the start timestamp
+ */
+void
+reset_formatted_start_time(void)
+{
+	formatted_start_time[0] = '\0';
+}
+
 /*
  * get_formatted_start_time -- compute and get the start timestamp.
  *
@@ -2786,241 +2792,6 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 	}
 }
 
-/*
- * append a CSV'd version of a string to a StringInfo
- * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
- * If it's NULL, append nothing.
- */
-static inline void
-appendCSVLiteral(StringInfo buf, const char *data)
-{
-	const char *p = data;
-	char		c;
-
-	/* avoid confusing an empty string with NULL */
-	if (p == NULL)
-		return;
-
-	appendStringInfoCharMacro(buf, '"');
-	while ((c = *p++) != '\0')
-	{
-		if (c == '"')
-			appendStringInfoCharMacro(buf, '"');
-		appendStringInfoCharMacro(buf, c);
-	}
-	appendStringInfoCharMacro(buf, '"');
-}
-
-/*
- * Constructs the error message, depending on the Errordata it gets, in a CSV
- * format which is described in doc/src/sgml/config.sgml.
- */
-static void
-write_csvlog(ErrorData *edata)
-{
-	StringInfoData buf;
-	bool		print_stmt = false;
-	char	   *start_time;
-	char	   *log_time;
-
-	/* static counter for line numbers */
-	static long log_line_number = 0;
-
-	/* has counter been reset in current process? */
-	static int	log_my_pid = 0;
-
-	/*
-	 * This is one of the few places where we'd rather not inherit a static
-	 * variable's value from the postmaster.  But since we will, reset it when
-	 * MyProcPid changes.
-	 */
-	if (log_my_pid != MyProcPid)
-	{
-		log_line_number = 0;
-		log_my_pid = MyProcPid;
-		formatted_start_time[0] = '\0';
-	}
-	log_line_number++;
-
-	initStringInfo(&buf);
-
-	/* timestamp with milliseconds */
-	log_time = get_formatted_log_time();
-	appendStringInfoString(&buf, log_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* username */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->user_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* database name */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->database_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* Process id  */
-	if (MyProcPid != 0)
-		appendStringInfo(&buf, "%d", MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Remote host and port */
-	if (MyProcPort && MyProcPort->remote_host)
-	{
-		appendStringInfoChar(&buf, '"');
-		appendStringInfoString(&buf, MyProcPort->remote_host);
-		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
-		{
-			appendStringInfoChar(&buf, ':');
-			appendStringInfoString(&buf, MyProcPort->remote_port);
-		}
-		appendStringInfoChar(&buf, '"');
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session id */
-	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Line number */
-	appendStringInfo(&buf, "%ld", log_line_number);
-	appendStringInfoChar(&buf, ',');
-
-	/* PS display */
-	if (MyProcPort)
-	{
-		StringInfoData msgbuf;
-		const char *psdisp;
-		int			displen;
-
-		initStringInfo(&msgbuf);
-
-		psdisp = get_ps_display(&displen);
-		appendBinaryStringInfo(&msgbuf, psdisp, displen);
-		appendCSVLiteral(&buf, msgbuf.data);
-
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session start timestamp */
-	start_time = get_formatted_start_time();
-	appendStringInfoString(&buf, start_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* Virtual transaction id */
-	/* keep VXID format in sync with lockfuncs.c */
-	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
-		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Transaction id */
-	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
-	appendStringInfoChar(&buf, ',');
-
-	/* Error severity */
-	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
-	appendStringInfoChar(&buf, ',');
-
-	/* SQL state code */
-	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
-	appendStringInfoChar(&buf, ',');
-
-	/* errmessage */
-	appendCSVLiteral(&buf, edata->message);
-	appendStringInfoChar(&buf, ',');
-
-	/* errdetail or errdetail_log */
-	if (edata->detail_log)
-		appendCSVLiteral(&buf, edata->detail_log);
-	else
-		appendCSVLiteral(&buf, edata->detail);
-	appendStringInfoChar(&buf, ',');
-
-	/* errhint */
-	appendCSVLiteral(&buf, edata->hint);
-	appendStringInfoChar(&buf, ',');
-
-	/* internal query */
-	appendCSVLiteral(&buf, edata->internalquery);
-	appendStringInfoChar(&buf, ',');
-
-	/* if printed internal query, print internal pos too */
-	if (edata->internalpos > 0 && edata->internalquery != NULL)
-		appendStringInfo(&buf, "%d", edata->internalpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* errcontext */
-	if (!edata->hide_ctx)
-		appendCSVLiteral(&buf, edata->context);
-	appendStringInfoChar(&buf, ',');
-
-	/* user query --- only reported if not disabled by the caller */
-	print_stmt = check_log_of_query(edata);
-	if (print_stmt)
-		appendCSVLiteral(&buf, debug_query_string);
-	appendStringInfoChar(&buf, ',');
-	if (print_stmt && edata->cursorpos > 0)
-		appendStringInfo(&buf, "%d", edata->cursorpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* file error location */
-	if (Log_error_verbosity >= PGERROR_VERBOSE)
-	{
-		StringInfoData msgbuf;
-
-		initStringInfo(&msgbuf);
-
-		if (edata->funcname && edata->filename)
-			appendStringInfo(&msgbuf, "%s, %s:%d",
-							 edata->funcname, edata->filename,
-							 edata->lineno);
-		else if (edata->filename)
-			appendStringInfo(&msgbuf, "%s:%d",
-							 edata->filename, edata->lineno);
-		appendCSVLiteral(&buf, msgbuf.data);
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* application name */
-	if (application_name)
-		appendCSVLiteral(&buf, application_name);
-
-	appendStringInfoChar(&buf, ',');
-
-	/* backend type */
-	appendCSVLiteral(&buf, get_backend_type_for_log());
-	appendStringInfoChar(&buf, ',');
-
-	/* leader PID */
-	if (MyProc)
-	{
-		PGPROC	   *leader = MyProc->lockGroupLeader;
-
-		/*
-		 * Show the leader only for active parallel workers.  This leaves out
-		 * the leader of a parallel group.
-		 */
-		if (leader && leader->pid != MyProcPid)
-			appendStringInfo(&buf, "%d", leader->pid);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* query id */
-	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
-
-	appendStringInfoChar(&buf, '\n');
-
-	/* If in the syslogger process, try to write messages direct to file */
-	if (MyBackendType == B_LOGGER)
-		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-	else
-		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-
-	pfree(buf.data);
-}
-
 /*
  * Unpack MAKE_SQLSTATE code. Note that this returns a pointer to a
  * static buffer.
@@ -3272,7 +3043,7 @@ send_message_to_server_log(ErrorData *edata)
  * warning from ignoring write()'s result, so do a little dance with casting
  * rc to void to shut up the compiler.
  */
-static void
+void
 write_pipe_chunks(char *data, int len, int dest)
 {
 	PipeProtoChunk p;
@@ -3508,7 +3279,7 @@ send_message_to_frontend(ErrorData *edata)
  * The string is not localized here, but we mark the strings for translation
  * so that callers can invoke _() on the result.
  */
-static const char *
+const char *
 error_severity(int elevel)
 {
 	const char *prefix;
-- 
2.33.0

From 7a0d22829d0aff3c53d4bc95bce8a3af0f19d02a Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 5 Oct 2021 15:59:44 +0900
Subject: [PATCH v5 3/3] JSON logging

---
 src/include/postmaster/syslogger.h |   1 +
 src/include/utils/elog.h           |   2 +
 src/backend/postmaster/syslogger.c | 107 ++++++++--
 src/backend/utils/adt/misc.c       |   5 +-
 src/backend/utils/error/Makefile   |   3 +-
 src/backend/utils/error/elog.c     |  18 ++
 src/backend/utils/error/jsonlog.c  | 323 +++++++++++++++++++++++++++++
 src/backend/utils/misc/guc.c       |   2 +
 src/bin/pg_ctl/t/004_logrotate.pl  |  12 +-
 doc/src/sgml/config.sgml           |  67 +++++-
 10 files changed, 514 insertions(+), 26 deletions(-)
 create mode 100644 src/backend/utils/error/jsonlog.c

diff --git a/src/include/postmaster/syslogger.h b/src/include/postmaster/syslogger.h
index c79dfbeba2..18448b76e5 100644
--- a/src/include/postmaster/syslogger.h
+++ b/src/include/postmaster/syslogger.h
@@ -64,6 +64,7 @@ typedef union
 /* log destinations */
 #define PIPE_PROTO_DEST_STDERR	0x10
 #define PIPE_PROTO_DEST_CSVLOG	0x20
+#define PIPE_PROTO_DEST_JSONLOG	0x40
 
 /* GUC options */
 extern bool Logging_collector;
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index ab08e7fac8..87b3398ca6 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -436,6 +436,7 @@ extern bool syslog_split_messages;
 #define LOG_DESTINATION_SYSLOG	 2
 #define LOG_DESTINATION_EVENTLOG 4
 #define LOG_DESTINATION_CSVLOG	 8
+#define LOG_DESTINATION_JSONLOG	16
 
 /* Other exported functions */
 extern void DebugFileOpen(void);
@@ -448,6 +449,7 @@ extern bool	check_log_of_query(ErrorData *edata);
 extern const char *get_backend_type_for_log(void);
 extern const char *error_severity(int elevel);
 extern void write_csvlog(ErrorData *edata);
+extern void write_jsonlog(ErrorData *edata);
 extern void write_pipe_chunks(char *data, int len, int dest);
 
 #ifdef HAVE_SYSLOG
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index d1f56b95a4..449d327268 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -86,9 +86,11 @@ static bool pipe_eof_seen = false;
 static bool rotation_disabled = false;
 static FILE *syslogFile = NULL;
 static FILE *csvlogFile = NULL;
+static FILE *jsonlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
 static char *last_sys_file_name = NULL;
 static char *last_csv_file_name = NULL;
+static char *last_json_file_name = NULL;
 
 /*
  * Buffers for saving partial messages from different backends.
@@ -281,6 +283,8 @@ SysLoggerMain(int argc, char *argv[])
 	last_sys_file_name = logfile_getname(first_syslogger_file_time, NULL);
 	if (csvlogFile != NULL)
 		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
+	if (jsonlogFile != NULL)
+		last_json_file_name = logfile_getname(first_syslogger_file_time, ".json");
 
 	/* remember active logfile parameters */
 	currentLogDir = pstrdup(Log_directory);
@@ -367,6 +371,14 @@ SysLoggerMain(int argc, char *argv[])
 				(csvlogFile != NULL))
 				rotation_requested = true;
 
+			/*
+			 * Force a rotation if JSONLOG output was just turned on or off and
+			 * we need to open or close jsonlogFile accordingly.
+			 */
+			if (((Log_destination & LOG_DESTINATION_JSONLOG) != 0) !=
+				(jsonlogFile != NULL))
+				rotation_requested = true;
+
 			/*
 			 * If rotation time parameter changed, reset next rotation time,
 			 * but don't immediately force a rotation.
@@ -417,6 +429,12 @@ SysLoggerMain(int argc, char *argv[])
 				rotation_requested = true;
 				size_rotation_for |= LOG_DESTINATION_CSVLOG;
 			}
+			if (jsonlogFile != NULL &&
+				ftell(jsonlogFile) >= Log_RotationSize * 1024L)
+			{
+				rotation_requested = true;
+				size_rotation_for |= LOG_DESTINATION_JSONLOG;
+			}
 		}
 
 		if (rotation_requested)
@@ -426,7 +444,7 @@ SysLoggerMain(int argc, char *argv[])
 			 * was sent by pg_rotate_logfile() or "pg_ctl logrotate".
 			 */
 			if (!time_based_rotation && size_rotation_for == 0)
-				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG;
+				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG | LOG_DESTINATION_JSONLOG;
 			logfile_rotate(time_based_rotation, size_rotation_for);
 		}
 
@@ -632,6 +650,20 @@ SysLogger_Start(void)
 		pfree(filename);
 	}
 
+	/*
+	 * Likewise for the initial JSON log file, if that's enabled.  (Note that
+	 * we open syslogFile even when only JSON output is nominally enabled,
+	 * since some code paths will write to syslogFile anyway.)
+	 */
+	if (Log_destination & LOG_DESTINATION_JSONLOG)
+	{
+		filename = logfile_getname(first_syslogger_file_time, ".json");
+
+		jsonlogFile = logfile_open(filename, "a", false);
+
+		pfree(filename);
+	}
+
 #ifdef EXEC_BACKEND
 	switch ((sysloggerPid = syslogger_forkexec()))
 #else
@@ -729,6 +761,11 @@ SysLogger_Start(void)
 				fclose(csvlogFile);
 				csvlogFile = NULL;
 			}
+			if (jsonlogFile != NULL)
+			{
+				fclose(jsonlogFile);
+				jsonlogFile = NULL;
+			}
 			return (int) sysloggerPid;
 	}
 
@@ -805,6 +842,7 @@ syslogger_forkexec(void)
 	int			ac = 0;
 	char		filenobuf[32];
 	char		csvfilenobuf[32];
+	char		jsonfilenobuf[32];
 
 	av[ac++] = "postgres";
 	av[ac++] = "--forklog";
@@ -817,6 +855,9 @@ syslogger_forkexec(void)
 	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%d",
 			 syslogger_fdget(csvlogFile));
 	av[ac++] = csvfilenobuf;
+	snprintf(jsonfilenobuf, sizeof(jsonfilenobuf), "%d",
+			 syslogger_fdget(jsonlogFile));
+	av[ac++] = jsonfilenobuf;
 
 	av[ac] = NULL;
 	Assert(ac < lengthof(av));
@@ -834,8 +875,8 @@ syslogger_parseArgs(int argc, char *argv[])
 {
 	int			fd;
 
-	Assert(argc == 5);
-	argv += 3;
+	Assert(argc == 6);
+	argv += 4;
 
 	/*
 	 * Re-open the error output files that were opened by SysLogger_Start().
@@ -848,6 +889,8 @@ syslogger_parseArgs(int argc, char *argv[])
 	syslogFile = syslogger_fdopen(fd);
 	fd = atoi(*argv++);
 	csvlogFile = syslogger_fdopen(fd);
+	fd = atoi(*argv++);
+	jsonlogFile = syslogger_fdopen(fd);
 }
 #endif							/* EXEC_BACKEND */
 
@@ -896,7 +939,9 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 
 		/* Do we have a valid header? */
 		memcpy(&p, cursor, offsetof(PipeProtoHeader, data));
-		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR | PIPE_PROTO_DEST_CSVLOG);
+		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR |
+								PIPE_PROTO_DEST_CSVLOG |
+								PIPE_PROTO_DEST_JSONLOG);
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&
@@ -918,6 +963,8 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 				dest = LOG_DESTINATION_STDERR;
 			else if ((p.flags & PIPE_PROTO_DEST_CSVLOG) != 0)
 				dest = LOG_DESTINATION_CSVLOG;
+			else if ((p.flags & PIPE_PROTO_DEST_JSONLOG) != 0)
+				dest = LOG_DESTINATION_JSONLOG;
 			else
 			{
 				/* this should never happen as of the header validation */
@@ -1097,19 +1144,24 @@ write_syslogger_file(const char *buffer, int count, int destination)
 	FILE	   *logfile;
 
 	/*
-	 * If we're told to write to csvlogFile, but it's not open, dump the data
-	 * to syslogFile (which is always open) instead.  This can happen if CSV
-	 * output is enabled after postmaster start and we've been unable to open
-	 * csvlogFile.  There are also race conditions during a parameter change
-	 * whereby backends might send us CSV output before we open csvlogFile or
-	 * after we close it.  Writing CSV-formatted output to the regular log
-	 * file isn't great, but it beats dropping log output on the floor.
+	 * If we're told to write to a structured log file, but it's not open,
+	 * dump the data to syslogFile (which is always open) instead.  This can
+	 * happen if structured output is enabled after postmaster start and
+	 * we've been unable to open logFile.  There are also race conditions
+	 * during a parameter change whereby backends might send us structured
+	 * output before we open the logFile or after we close it.  Writing
+	 * formatted output to the regular log file isn't great, but it beats
+	 * dropping log output on the floor.
 	 *
-	 * Think not to improve this by trying to open csvlogFile on-the-fly.  Any
+	 * Think not to improve this by trying to open logFile on-the-fly.  Any
 	 * failure in that would lead to recursion.
 	 */
-	logfile = (destination == LOG_DESTINATION_CSVLOG &&
-			   csvlogFile != NULL) ? csvlogFile : syslogFile;
+	if ((destination & LOG_DESTINATION_CSVLOG) && csvlogFile != NULL)
+		logfile = csvlogFile;
+	else if ((destination & LOG_DESTINATION_JSONLOG) && jsonlogFile != NULL)
+		logfile = jsonlogFile;
+	else
+		logfile = syslogFile;
 
 	rc = fwrite(buffer, 1, count, logfile);
 
@@ -1180,7 +1232,8 @@ pipeThread(void *arg)
 		if (Log_RotationSize > 0)
 		{
 			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
-				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
+				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L) ||
+				(jsonlogFile != NULL && ftell(jsonlogFile) >= Log_RotationSize * 1024L))
 				SetLatch(MyLatch);
 		}
 		LeaveCriticalSection(&sysloggerSection);
@@ -1292,6 +1345,8 @@ logfile_rotate_dest(bool time_based_rotation, int size_rotation_for,
 		logFileExt = NULL;
 	else if (target_dest == LOG_DESTINATION_CSVLOG)
 		logFileExt = ".csv";
+	else if (target_dest == LOG_DESTINATION_JSONLOG)
+		logFileExt = ".json";
 	else
 	{
 		/* cannot happen */
@@ -1379,6 +1434,12 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 							 &csvlogFile))
 		return;
 
+	/* file rotation for csvlog */
+	if (!logfile_rotate_dest(time_based_rotation, size_rotation_for, fntime,
+							 LOG_DESTINATION_JSONLOG, &last_json_file_name,
+							 &jsonlogFile))
+		return;
+
 	update_metainfo_datafile();
 
 	set_next_rotation_time();
@@ -1465,7 +1526,8 @@ update_metainfo_datafile(void)
 	mode_t		oumask;
 
 	if (!(Log_destination & LOG_DESTINATION_STDERR) &&
-		!(Log_destination & LOG_DESTINATION_CSVLOG))
+		!(Log_destination & LOG_DESTINATION_CSVLOG) &&
+		!(Log_destination & LOG_DESTINATION_JSONLOG))
 	{
 		if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
 			ereport(LOG,
@@ -1523,6 +1585,19 @@ update_metainfo_datafile(void)
 			return;
 		}
 	}
+
+	if (last_json_file_name && (Log_destination & LOG_DESTINATION_JSONLOG))
+	{
+		if (fprintf(fh, "jsonlog %s\n", last_json_file_name) < 0)
+		{
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not write file \"%s\": %m",
+							LOG_METAINFO_DATAFILE_TMP)));
+			fclose(fh);
+			return;
+		}
+	}
 	fclose(fh);
 
 	if (rename(LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE) != 0)
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 88faf4dfd7..4931859627 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -843,11 +843,12 @@ pg_current_logfile(PG_FUNCTION_ARGS)
 	{
 		logfmt = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
-		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0)
+		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0 &&
+				strcmp(logfmt, "jsonlog") != 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("log format \"%s\" is not supported", logfmt),
-					 errhint("The supported log formats are \"stderr\" and \"csvlog\".")));
+					 errhint("The supported log formats are \"stderr\", \"csvlog\", and \"jsonlog\".")));
 	}
 
 	fd = AllocateFile(LOG_METAINFO_DATAFILE, "r");
diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index ef770dd2f2..65ba61fb3c 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -15,6 +15,7 @@ include $(top_builddir)/src/Makefile.global
 OBJS = \
 	assert.o \
 	csvlog.o \
-	elog.o
+	elog.o \
+	jsonlog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 4406d8deff..39467be917 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2984,6 +2984,22 @@ send_message_to_server_log(ErrorData *edata)
 			fallback_to_stderr = true;
 	}
 
+	/* Write to JSON log, if enabled */
+	if ((Log_destination & LOG_DESTINATION_JSONLOG) != 0)
+	{
+		/*
+		 * Send JSON data if it's safe to do so (syslogger doesn't need the
+		 * pipe).  If this is not possible, fallback to an entry written
+		 * to stderr.
+		 */
+		if (redirection_done || MyBackendType == B_LOGGER)
+		{
+			write_jsonlog(edata);
+		}
+		else
+			fallback_to_stderr = true;
+	}
+
 	/*
 	 * Write to stderr, if enabled or if required because of a previous
 	 * limitation.
@@ -3059,6 +3075,8 @@ write_pipe_chunks(char *data, int len, int dest)
 		p.proto.flags |= PIPE_PROTO_DEST_STDERR;
 	else if (dest == LOG_DESTINATION_CSVLOG)
 		p.proto.flags |= PIPE_PROTO_DEST_CSVLOG;
+	else if (dest == LOG_DESTINATION_JSONLOG)
+		p.proto.flags |= PIPE_PROTO_DEST_JSONLOG;
 
 	/* write all but the last chunk */
 	while (len > PIPE_MAX_PAYLOAD)
diff --git a/src/backend/utils/error/jsonlog.c b/src/backend/utils/error/jsonlog.c
new file mode 100644
index 0000000000..f92ee64a47
--- /dev/null
+++ b/src/backend/utils/error/jsonlog.c
@@ -0,0 +1,323 @@
+/*-------------------------------------------------------------------------
+ *
+ * jsonlog.c
+ *	  JSON logging
+ *
+ * Copyright (c) 2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/jsonlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog.h"
+#include "utils/guc.h"
+#include "utils/json.h"
+#include "utils/ps_status.h"
+
+static void appendJSONKeyValueFmt(StringInfo buf, const char *key,
+								  const char *fmt,...) pg_attribute_printf(3, 4);
+
+/*
+ * appendJSONKeyValue
+ * Append to given StringInfo a comma followed by a JSON key and value.
+ * Both the key and value will be escaped as JSON string literals.
+ */
+static void
+appendJSONKeyValue(StringInfo buf, const char *key, const char *value)
+{
+	if (value == NULL)
+		return;
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	escape_json(buf, value);
+}
+
+/*
+ * appendJSONKeyValueFmt
+ *
+ * Evaluate the fmt string and then invoke appendJSONKeyValue as the
+ * value of the JSON property. Both the key and value will be escaped by
+ * appendJSONKeyValue.
+ */
+static void
+appendJSONKeyValueFmt(StringInfo buf, const char *key, const char *fmt,...)
+{
+	int			save_errno = errno;
+	size_t		len = 128;		/* initial assumption about buffer size */
+	char	    *value;
+
+	for (;;)
+	{
+		va_list		args;
+		size_t		newlen;
+
+		/*
+		 * Allocate result buffer.  Note that in frontend this maps to malloc
+		 * with exit-on-error.
+		 */
+		value = (char *) palloc(len);
+
+		/* Try to format the data. */
+		errno = save_errno;
+		va_start(args, fmt);
+		newlen = pvsnprintf(value, len, fmt, args);
+		va_end(args);
+
+		if (newlen < len)
+			break; /* success */
+
+		/* Release buffer and loop around to try again with larger len. */
+		pfree(value);
+		len = newlen;
+	}
+	appendJSONKeyValue(buf, key, value);
+
+	/* Clean up */
+	pfree(value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as a signed integer (a JSON number).
+ */
+static void
+appendJSONKeyValueAsInt(StringInfo buf, const char *key, int value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%d", value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as an unsigned integer (a JSON number).
+ */
+static void
+appendJSONKeyValueAsUInt(StringInfo buf, const char *key, int value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%u", value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as a long (a JSON number).
+ */
+static void
+appendJSONKeyValueAsLong(StringInfo buf, const char *key, long value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%ld", value);
+}
+
+/*
+ * Write logs in json format.
+ */
+void
+write_jsonlog(ErrorData *edata)
+{
+	StringInfoData	buf;
+	char	   *start_time;
+	char	   *log_time;
+
+	/* static counter for line numbers */
+	static long	log_line_number = 0;
+
+	/* Has the counter been reset in the current process? */
+	static int	log_my_pid = 0;
+
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		reset_formatted_start_time();
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* Initialize string */
+	appendStringInfoChar(&buf, '{');
+
+	/*
+	 * timestamp with milliseconds
+	 *
+	 * Check if the timestamp is already calculated for the syslog message,
+	 * and use it if so.  Otherwise, get the current timestamp.  This is done
+	 * to put same timestamp in both syslog and jsonlog messages.
+	 */
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+
+	/*
+	 * First property does not use appendJSONKeyValue as it does not have
+	 * comma prefix.
+	 */
+	escape_json(&buf, "timestamp");
+	appendStringInfoChar(&buf, ':');
+	escape_json(&buf, log_time);
+
+	/* username */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "user", MyProcPort->user_name);
+
+	/* database name */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "dbname", MyProcPort->database_name);
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendJSONKeyValueAsInt(&buf, "leader_pid", leader->pid);
+	}
+
+	/* Process ID */
+	if (MyProcPid != 0)
+		appendJSONKeyValueAsInt(&buf, "pid", MyProcPid);
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendJSONKeyValue(&buf, "remote_host", MyProcPort->remote_host);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+			appendJSONKeyValue(&buf, "remote_port", MyProcPort->remote_port);
+	}
+
+	/* Session id */
+	appendJSONKeyValueFmt(&buf, "session_id", "%lx.%x", (long) MyStartTime, MyProcPid);
+
+	/* Line number */
+	appendJSONKeyValueAsLong(&buf, "line_num", log_line_number);
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData	msgbuf;
+		const char	   *psdisp;
+		int				displen;
+
+		initStringInfo(&msgbuf);
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendJSONKeyValue(&buf, "ps", msgbuf.data);
+
+		pfree(msgbuf.data);
+	}
+
+	/* session start timestamp */
+	start_time = get_formatted_start_time();
+	appendJSONKeyValue(&buf, "session_start", start_time);
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendJSONKeyValueFmt(&buf, "vxid", "%d/%u", MyProc->backendId, MyProc->lxid);
+
+	/* Transaction id */
+	appendJSONKeyValueFmt(&buf, "txid", "%u", GetTopTransactionIdIfAny());
+
+	/* Error severity */
+	if (edata->elevel)
+		appendJSONKeyValue(&buf, "error_severity", (char *) error_severity(edata->elevel));
+
+	/* query id */
+	appendJSONKeyValueFmt(&buf,  "query_id", "%lld", (long long) pgstat_get_my_query_id());
+
+	/* SQL state code */
+	if (edata->sqlerrcode)
+		appendJSONKeyValue(&buf, "state_code", unpack_sql_state(edata->sqlerrcode));
+
+	/* errdetail or error_detail log */
+	if (edata->detail_log)
+		appendJSONKeyValue(&buf, "detail", edata->detail_log);
+	else if (edata->detail)
+		appendJSONKeyValue(&buf, "detail", edata->detail);
+
+	/* errhint */
+	if (edata->hint)
+		appendJSONKeyValue(&buf, "hint", edata->hint);
+
+	/* Internal query */
+	if (edata->internalquery)
+		appendJSONKeyValue(&buf, "internal_query", edata->internalquery);
+
+	/* If the internal query got printed, print internal pos, too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendJSONKeyValueAsUInt(&buf, "internal_position", edata->internalpos);
+
+	/* errcontext */
+	if (edata->context && !edata->hide_ctx)
+		appendJSONKeyValue(&buf, "context", edata->context);
+
+	/* user query --- only reported if not disabled by the caller */
+	if (check_log_of_query(edata))
+	{
+		appendJSONKeyValue(&buf, "statement", debug_query_string);
+		if (edata->cursorpos > 0)
+			appendJSONKeyValueAsInt(&buf, "cursor_position", edata->cursorpos);
+	}
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		if (edata->funcname)
+			appendJSONKeyValue(&buf, "func_name", edata->funcname);
+		if (edata->filename)
+		{
+			appendJSONKeyValue(&buf, "file_name", edata->filename);
+			appendJSONKeyValueAsInt(&buf, "file_line_num", edata->lineno);
+		}
+	}
+
+	/* Application name */
+	if (application_name && application_name[0] != '\0')
+		appendJSONKeyValue(&buf, "application_name", application_name);
+
+	/* backend type */
+	appendJSONKeyValue(&buf, "backend_type", get_backend_type_for_log());
+
+	/* Error message */
+	appendJSONKeyValue(&buf, "message", edata->message);
+
+	/* Finish string */
+	appendStringInfoChar(&buf, '}');
+	appendStringInfoChar(&buf, '\n');
+
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+	else
+		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index d2ce4a8450..0b79753ec3 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -11714,6 +11714,8 @@ check_log_destination(char **newval, void **extra, GucSource source)
 			newlogdest |= LOG_DESTINATION_STDERR;
 		else if (pg_strcasecmp(tok, "csvlog") == 0)
 			newlogdest |= LOG_DESTINATION_CSVLOG;
+		else if (pg_strcasecmp(tok, "jsonlog") == 0)
+			newlogdest |= LOG_DESTINATION_JSONLOG;
 #ifdef HAVE_SYSLOG
 		else if (pg_strcasecmp(tok, "syslog") == 0)
 			newlogdest |= LOG_DESTINATION_SYSLOG;
diff --git a/src/bin/pg_ctl/t/004_logrotate.pl b/src/bin/pg_ctl/t/004_logrotate.pl
index aa0d64a4f7..caa5740254 100644
--- a/src/bin/pg_ctl/t/004_logrotate.pl
+++ b/src/bin/pg_ctl/t/004_logrotate.pl
@@ -6,7 +6,7 @@ use warnings;
 
 use PostgresNode;
 use TestLib;
-use Test::More tests => 10;
+use Test::More tests => 14;
 use Time::HiRes qw(usleep);
 
 # Extract the file name of a $format from the contents of
@@ -63,7 +63,7 @@ $node->init();
 $node->append_conf(
 	'postgresql.conf', qq(
 logging_collector = on
-log_destination = 'stderr, csvlog'
+log_destination = 'stderr, csvlog, jsonlog'
 # these ensure stability of test results:
 log_rotation_age = 0
 lc_messages = 'C'
@@ -94,11 +94,13 @@ note "current_logfiles = $current_logfiles";
 like(
 	$current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'current_logfiles is sane');
 
 check_log_pattern('stderr', $current_logfiles, 'division by zero', $node);
 check_log_pattern('csvlog', $current_logfiles, 'division by zero', $node);
+check_log_pattern('jsonlog', $current_logfiles, 'division by zero', $node);
 
 # Sleep 2 seconds and ask for log rotation; this should result in
 # output into a different log file name.
@@ -120,7 +122,8 @@ note "now current_logfiles = $new_current_logfiles";
 like(
 	$new_current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'new current_logfiles is sane');
 
 # Verify that log output gets to this file, too
@@ -128,5 +131,6 @@ $node->psql('postgres', 'fee fi fo fum');
 
 check_log_pattern('stderr', $new_current_logfiles, 'syntax error', $node);
 check_log_pattern('csvlog', $new_current_logfiles, 'syntax error', $node);
+check_log_pattern('jsonlog', $new_current_logfiles, 'syntax error', $node);
 
 $node->stop();
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 0a8e35c59f..7723e11cf7 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5926,7 +5926,8 @@ SELECT * FROM parent WHERE key = 2400;
        <para>
         <productname>PostgreSQL</productname> supports several methods
          for logging server messages, including
-         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem> and
+         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem>,
+         <systemitem>jsonlog</systemitem>, and
          <systemitem>syslog</systemitem>. On Windows,
          <systemitem>eventlog</systemitem> is also supported. Set this
          parameter to a list of desired log destinations separated by
@@ -5944,6 +5945,14 @@ SELECT * FROM parent WHERE key = 2400;
         <xref linkend="guc-logging-collector"/> must be enabled to generate
         CSV-format log output.
        </para>
+       <para>
+        If <systemitem>jsonlog</systemitem> is included in <varname>log_destination</varname>,
+        log entries are output in <acronym>JSON</acronym> format, which is convenient for
+        loading logs into programs.
+        See <xref linkend="runtime-config-logging-jsonlog"/> for details.
+        <xref linkend="guc-logging-collector"/> must be enabled to generate
+        CSV-format log output.
+       </para>
        <para>
         When either <systemitem>stderr</systemitem> or
         <systemitem>csvlog</systemitem> are included, the file
@@ -5955,13 +5964,14 @@ SELECT * FROM parent WHERE key = 2400;
 <programlisting>
 stderr log/postgresql.log
 csvlog log/postgresql.csv
+jsonlog log/postgresql.json
 </programlisting>
 
         <filename>current_logfiles</filename> is recreated when a new log file
         is created as an effect of rotation, and
         when <varname>log_destination</varname> is reloaded.  It is removed when
-        neither <systemitem>stderr</systemitem>
-        nor <systemitem>csvlog</systemitem> are included
+        none of <systemitem>stderr</systemitem>,
+        <systemitem>csvlog</systemitem>, <systemitem>jsonlog</systemitem> are included
         in <varname>log_destination</varname>, and when the logging collector is
         disabled.
        </para>
@@ -6101,6 +6111,13 @@ local0.*    /var/log/postgresql
         (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
         replaced instead.)
        </para>
+       <para>
+        If JSON-format output is enabled in <varname>log_destination</varname>,
+        <literal>.json</literal> will be appended to the timestamped
+        log file name to create the file name for JSON-format output.
+        (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
+        replaced instead.)
+       </para>
        <para>
         This parameter can only be set in the <filename>postgresql.conf</filename>
         file or on the server command line.
@@ -7433,6 +7450,50 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         </orderedlist>
       </para>
     </sect2>
+     <sect2 id="runtime-config-logging-jsonlog">
+     <title>Using JSON-Format Log Output</title>
+
+       <para>
+        Including <literal>jsonlog</literal> in the <varname>log_destination</varname> list
+        provides a convenient way to import log files into many different programs.
+        This option emits log lines in (<acronym>JSON</acronym>) format.
+        Each log line is serialized as a JSON object with the following fields:
+<programlisting>
+        {
+            "timestamp": time stamp with milliseconds (string),
+            "user": user name (string),
+            "dbname": database name (string),
+            "pid": process ID (number),
+            "remote_host": client host (string)
+            "remote_port": port number (string),
+            "session_id": session ID (string),
+            "line_num": per-session line number (number),
+            "ps": current ps display (string),
+            "session_start": session start time (string),
+            "vxid": virtual transaction ID (string),
+            "txid": regular transaction ID (string),
+            "error_severity": error severity (string),
+            "state_code": SQLSTATE code (string),
+            "detail": error message detail (string),
+            "hint": hint (string),
+            "internal_query": internal query that led to the error (string),
+            "internal_position": cursor index into internal query (number),
+            "context": error context (string),
+            "statement": client supplied query string (string),
+            "cursor_position": cursor index into query string (string),
+            "func_name": error location function name (string),
+            "file_name": error location file name (string),
+            "file_line_num": error location file line number (number),
+            "application_name": client application name (string),
+            "message": error message (string)
+        }
+</programlisting>
+        String fields with null values are excluded from output.
+        Additional fields may be added in the future. User applications that process jsonlog
+        output should ignore unknown fields.
+       </para>
+
+    </sect2>
 
    <sect2>
     <title>Process Title</title>
-- 
2.33.0

From 74a4d36e5f6cac1318a14168321c34edcd7d9b86 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 19 Oct 2021 16:25:45 +0900
Subject: [PATCH v6 1/3] Some refactoring of elog-specific routines

This refactors out the following things in elog.c, for ease of use
across multiple log destinations:
- start_timestamp (including reset)
- log_timestamp
- decide if query can be logged
- backend type
- write using the elog piped protocol
- Error severity to string.

These will be reused by csvlog and jsonlog.
---
 src/include/utils/elog.h       |  12 +++
 src/backend/utils/error/elog.c | 159 +++++++++++++++++++++------------
 2 files changed, 114 insertions(+), 57 deletions(-)

diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index f53607e12e..731f3e3cd8 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -442,6 +442,18 @@ extern void DebugFileOpen(void);
 extern char *unpack_sql_state(int sql_state);
 extern bool in_error_recursion_trouble(void);
 
+/* Common functions shared across destinations */
+extern void reset_formatted_start_time(void);
+extern char *get_formatted_start_time(void);
+extern char *get_formatted_log_time(void);
+extern const char *get_backend_type_for_log(void);
+extern bool	check_log_of_query(ErrorData *edata);
+extern const char *error_severity(int elevel);
+extern void write_pipe_chunks(char *data, int len, int dest);
+
+/* Destination-specific functions */
+extern void write_csvlog(ErrorData *edata);
+
 #ifdef HAVE_SYSLOG
 extern void set_syslog_parameters(const char *ident, int facility);
 #endif
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index f33729513a..a162258bab 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -175,15 +175,10 @@ static const char *err_gettext(const char *str) pg_attribute_format_arg(1);
 static pg_noinline void set_backtrace(ErrorData *edata, int num_skip);
 static void set_errdata_field(MemoryContextData *cxt, char **ptr, const char *str);
 static void write_console(const char *line, int len);
-static void setup_formatted_log_time(void);
-static void setup_formatted_start_time(void);
 static const char *process_log_prefix_padding(const char *p, int *padding);
 static void log_line_prefix(StringInfo buf, ErrorData *edata);
-static void write_csvlog(ErrorData *edata);
 static void send_message_to_server_log(ErrorData *edata);
-static void write_pipe_chunks(char *data, int len, int dest);
 static void send_message_to_frontend(ErrorData *edata);
-static const char *error_severity(int elevel);
 static void append_with_tabs(StringInfo buf, const char *str);
 
 
@@ -2289,14 +2284,23 @@ write_console(const char *line, int len)
 }
 
 /*
- * setup formatted_log_time, for consistent times between CSV and regular logs
+ * get_formatted_log_time -- compute and get the log timestamp.
+ *
+ * The timestamp is computed if not set yet, so as it is kept consistent
+ * among all the log destinations that require it to be consistent.  Note
+ * that the computed timestamp is returned in a static buffer, not
+ * palloc()'d.
  */
-static void
-setup_formatted_log_time(void)
+char *
+get_formatted_log_time(void)
 {
 	pg_time_t	stamp_time;
 	char		msbuf[13];
 
+	/* leave if already computed */
+	if (formatted_log_time[0] != '\0')
+		return formatted_log_time;
+
 	if (!saved_timeval_set)
 	{
 		gettimeofday(&saved_timeval, NULL);
@@ -2318,16 +2322,34 @@ setup_formatted_log_time(void)
 	/* 'paste' milliseconds into place... */
 	sprintf(msbuf, ".%03d", (int) (saved_timeval.tv_usec / 1000));
 	memcpy(formatted_log_time + 19, msbuf, 4);
+
+	return formatted_log_time;
 }
 
 /*
- * setup formatted_start_time
+ * reset_formatted_start_time -- reset the start timestamp
  */
-static void
-setup_formatted_start_time(void)
+void
+reset_formatted_start_time(void)
+{
+	formatted_start_time[0] = '\0';
+}
+
+/*
+ * get_formatted_start_time -- compute and get the start timestamp.
+ *
+ * The timestamp is computed if not set yet.  Note that the computed
+ * timestamp is returned in a static buffer, not palloc()'d.
+ */
+char *
+get_formatted_start_time(void)
 {
 	pg_time_t	stamp_time = (pg_time_t) MyStartTime;
 
+	/* leave if already computed */
+	if (formatted_start_time[0] != '\0')
+		return formatted_start_time;
+
 	/*
 	 * Note: we expect that guc.c will ensure that log_timezone is set up (at
 	 * least with a minimal GMT value) before Log_line_prefix can become
@@ -2336,6 +2358,49 @@ setup_formatted_start_time(void)
 	pg_strftime(formatted_start_time, FORMATTED_TS_LEN,
 				"%Y-%m-%d %H:%M:%S %Z",
 				pg_localtime(&stamp_time, log_timezone));
+
+	return formatted_start_time;
+}
+
+/*
+ * check_log_of_query -- check if a query can be logged
+ */
+bool
+check_log_of_query(ErrorData *edata)
+{
+	/* log required? */
+	if (!is_log_level_output(edata->elevel, log_min_error_statement))
+		return false;
+
+	/* query log wanted? */
+	if (edata->hide_stmt)
+		return false;
+
+	/* query string available? */
+	if (debug_query_string == NULL)
+		return false;
+
+	return true;
+}
+
+/*
+ * get_backend_type_for_log -- backend type for log entries
+ *
+ * Returns a pointer to a static buffer, not palloc()'d.
+ */
+const char *
+get_backend_type_for_log(void)
+{
+	const char   *backend_type_str;
+
+	if (MyProcPid == PostmasterPid)
+		backend_type_str = "postmaster";
+	else if (MyBackendType == B_BG_WORKER)
+		backend_type_str = MyBgworkerEntry->bgw_type;
+	else
+		backend_type_str = GetBackendTypeDesc(MyBackendType);
+
+	return backend_type_str;
 }
 
 /*
@@ -2466,14 +2531,7 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 				break;
 			case 'b':
 				{
-					const char *backend_type_str;
-
-					if (MyProcPid == PostmasterPid)
-						backend_type_str = "postmaster";
-					else if (MyBackendType == B_BG_WORKER)
-						backend_type_str = MyBgworkerEntry->bgw_type;
-					else
-						backend_type_str = GetBackendTypeDesc(MyBackendType);
+					const char *backend_type_str = get_backend_type_for_log();
 
 					if (padding != 0)
 						appendStringInfo(buf, "%*s", padding, backend_type_str);
@@ -2561,7 +2619,10 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 					appendStringInfo(buf, "%ld", log_line_number);
 				break;
 			case 'm':
-				setup_formatted_log_time();
+				/* force a log timestamp reset */
+				formatted_log_time[0] = '\0';
+				(void) get_formatted_log_time();
+
 				if (padding != 0)
 					appendStringInfo(buf, "%*s", padding, formatted_log_time);
 				else
@@ -2602,12 +2663,14 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 				}
 				break;
 			case 's':
-				if (formatted_start_time[0] == '\0')
-					setup_formatted_start_time();
-				if (padding != 0)
-					appendStringInfo(buf, "%*s", padding, formatted_start_time);
-				else
-					appendStringInfoString(buf, formatted_start_time);
+				{
+					char   *start_time = get_formatted_start_time();
+
+					if (padding != 0)
+						appendStringInfo(buf, "%*s", padding, start_time);
+					else
+						appendStringInfoString(buf, start_time);
+				}
 				break;
 			case 'i':
 				if (MyProcPort)
@@ -2758,11 +2821,13 @@ appendCSVLiteral(StringInfo buf, const char *data)
  * Constructs the error message, depending on the Errordata it gets, in a CSV
  * format which is described in doc/src/sgml/config.sgml.
  */
-static void
+void
 write_csvlog(ErrorData *edata)
 {
 	StringInfoData buf;
 	bool		print_stmt = false;
+	char	   *start_time;
+	char	   *log_time;
 
 	/* static counter for line numbers */
 	static long log_line_number = 0;
@@ -2785,17 +2850,9 @@ write_csvlog(ErrorData *edata)
 
 	initStringInfo(&buf);
 
-	/*
-	 * timestamp with milliseconds
-	 *
-	 * Check if the timestamp is already calculated for the syslog message,
-	 * and use it if so.  Otherwise, get the current timestamp.  This is done
-	 * to put same timestamp in both syslog and csvlog messages.
-	 */
-	if (formatted_log_time[0] == '\0')
-		setup_formatted_log_time();
-
-	appendStringInfoString(&buf, formatted_log_time);
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+	appendStringInfoString(&buf, log_time);
 	appendStringInfoChar(&buf, ',');
 
 	/* username */
@@ -2853,9 +2910,8 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* session start timestamp */
-	if (formatted_start_time[0] == '\0')
-		setup_formatted_start_time();
-	appendStringInfoString(&buf, formatted_start_time);
+	start_time = get_formatted_start_time();
+	appendStringInfoString(&buf, start_time);
 	appendStringInfoChar(&buf, ',');
 
 	/* Virtual transaction id */
@@ -2906,10 +2962,7 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* user query --- only reported if not disabled by the caller */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
-		print_stmt = true;
+	print_stmt = check_log_of_query(edata);
 	if (print_stmt)
 		appendCSVLiteral(&buf, debug_query_string);
 	appendStringInfoChar(&buf, ',');
@@ -2943,13 +2996,7 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* backend type */
-	if (MyProcPid == PostmasterPid)
-		appendCSVLiteral(&buf, "postmaster");
-	else if (MyBackendType == B_BG_WORKER)
-		appendCSVLiteral(&buf, MyBgworkerEntry->bgw_type);
-	else
-		appendCSVLiteral(&buf, GetBackendTypeDesc(MyBackendType));
-
+	appendCSVLiteral(&buf, get_backend_type_for_log());
 	appendStringInfoChar(&buf, ',');
 
 	/* leader PID */
@@ -3101,9 +3148,7 @@ send_message_to_server_log(ErrorData *edata)
 	/*
 	 * If the user wants the query that generated this error logged, do it.
 	 */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
+	if (check_log_of_query(edata))
 	{
 		log_line_prefix(&buf, edata);
 		appendStringInfoString(&buf, _("STATEMENT:  "));
@@ -3233,7 +3278,7 @@ send_message_to_server_log(ErrorData *edata)
  * warning from ignoring write()'s result, so do a little dance with casting
  * rc to void to shut up the compiler.
  */
-static void
+void
 write_pipe_chunks(char *data, int len, int dest)
 {
 	PipeProtoChunk p;
@@ -3469,7 +3514,7 @@ send_message_to_frontend(ErrorData *edata)
  * The string is not localized here, but we mark the strings for translation
  * so that callers can invoke _() on the result.
  */
-static const char *
+const char *
 error_severity(int elevel)
 {
 	const char *prefix;
-- 
2.33.0

From 17af8a58c8286c7af347a95329769dd7d6c805c0 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 5 Oct 2021 15:22:24 +0900
Subject: [PATCH v6 2/3] Refactor CSV-specific code into its own file

---
 src/backend/utils/error/Makefile |   1 +
 src/backend/utils/error/csvlog.c | 268 +++++++++++++++++++++++++++++++
 src/backend/utils/error/elog.c   | 235 ---------------------------
 3 files changed, 269 insertions(+), 235 deletions(-)
 create mode 100644 src/backend/utils/error/csvlog.c

diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index 612da215d0..ef770dd2f2 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -14,6 +14,7 @@ include $(top_builddir)/src/Makefile.global
 
 OBJS = \
 	assert.o \
+	csvlog.o \
 	elog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/csvlog.c b/src/backend/utils/error/csvlog.c
new file mode 100644
index 0000000000..443a91e168
--- /dev/null
+++ b/src/backend/utils/error/csvlog.c
@@ -0,0 +1,268 @@
+/*-------------------------------------------------------------------------
+ *
+ * csvlog.c
+ *	  CSV logging
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of Californi
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/csvlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog.h"
+#include "utils/guc.h"
+#include "utils/ps_status.h"
+
+
+/*
+ * append a CSV'd version of a string to a StringInfo
+ * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
+ * If it's NULL, append nothing.
+ */
+static inline void
+appendCSVLiteral(StringInfo buf, const char *data)
+{
+	const char *p = data;
+	char		c;
+
+	/* avoid confusing an empty string with NULL */
+	if (p == NULL)
+		return;
+
+	appendStringInfoCharMacro(buf, '"');
+	while ((c = *p++) != '\0')
+	{
+		if (c == '"')
+			appendStringInfoCharMacro(buf, '"');
+		appendStringInfoCharMacro(buf, c);
+	}
+	appendStringInfoCharMacro(buf, '"');
+}
+
+/*
+ * write_csvlog -- Generate and write CSV log entry
+ *
+ * Constructs the error message, depending on the Errordata it gets, in a CSV
+ * format which is described in doc/src/sgml/config.sgml.
+ */
+void
+write_csvlog(ErrorData *edata)
+{
+	StringInfoData buf;
+	bool		print_stmt = false;
+	char	   *start_time;
+	char	   *log_time;
+
+	/* static counter for line numbers */
+	static long log_line_number = 0;
+
+	/* has counter been reset in current process? */
+	static int	log_my_pid = 0;
+
+	/*
+	 * This is one of the few places where we'd rather not inherit a static
+	 * variable's value from the postmaster.  But since we will, reset it when
+	 * MyProcPid changes.
+	 */
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		reset_formatted_start_time();
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+	appendStringInfoString(&buf, log_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* username */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->user_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* database name */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->database_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* Process id  */
+	if (MyProcPid != 0)
+		appendStringInfo(&buf, "%d", MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendStringInfoChar(&buf, '"');
+		appendStringInfoString(&buf, MyProcPort->remote_host);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+		{
+			appendStringInfoChar(&buf, ':');
+			appendStringInfoString(&buf, MyProcPort->remote_port);
+		}
+		appendStringInfoChar(&buf, '"');
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session id */
+	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Line number */
+	appendStringInfo(&buf, "%ld", log_line_number);
+	appendStringInfoChar(&buf, ',');
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData msgbuf;
+		const char *psdisp;
+		int			displen;
+
+		initStringInfo(&msgbuf);
+
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendCSVLiteral(&buf, msgbuf.data);
+
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session start timestamp */
+	start_time = get_formatted_start_time();
+	appendStringInfoString(&buf, start_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Transaction id */
+	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
+	appendStringInfoChar(&buf, ',');
+
+	/* Error severity */
+	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
+	appendStringInfoChar(&buf, ',');
+
+	/* SQL state code */
+	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
+	appendStringInfoChar(&buf, ',');
+
+	/* errmessage */
+	appendCSVLiteral(&buf, edata->message);
+	appendStringInfoChar(&buf, ',');
+
+	/* errdetail or errdetail_log */
+	if (edata->detail_log)
+		appendCSVLiteral(&buf, edata->detail_log);
+	else
+		appendCSVLiteral(&buf, edata->detail);
+	appendStringInfoChar(&buf, ',');
+
+	/* errhint */
+	appendCSVLiteral(&buf, edata->hint);
+	appendStringInfoChar(&buf, ',');
+
+	/* internal query */
+	appendCSVLiteral(&buf, edata->internalquery);
+	appendStringInfoChar(&buf, ',');
+
+	/* if printed internal query, print internal pos too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendStringInfo(&buf, "%d", edata->internalpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* errcontext */
+	if (!edata->hide_ctx)
+		appendCSVLiteral(&buf, edata->context);
+	appendStringInfoChar(&buf, ',');
+
+	/* user query --- only reported if not disabled by the caller */
+	print_stmt = check_log_of_query(edata);
+	if (print_stmt)
+		appendCSVLiteral(&buf, debug_query_string);
+	appendStringInfoChar(&buf, ',');
+	if (print_stmt && edata->cursorpos > 0)
+		appendStringInfo(&buf, "%d", edata->cursorpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		StringInfoData msgbuf;
+
+		initStringInfo(&msgbuf);
+
+		if (edata->funcname && edata->filename)
+			appendStringInfo(&msgbuf, "%s, %s:%d",
+							 edata->funcname, edata->filename,
+							 edata->lineno);
+		else if (edata->filename)
+			appendStringInfo(&msgbuf, "%s:%d",
+							 edata->filename, edata->lineno);
+		appendCSVLiteral(&buf, msgbuf.data);
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* application name */
+	if (application_name)
+		appendCSVLiteral(&buf, application_name);
+
+	appendStringInfoChar(&buf, ',');
+
+	/* backend type */
+	appendCSVLiteral(&buf, get_backend_type_for_log());
+	appendStringInfoChar(&buf, ',');
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendStringInfo(&buf, "%d", leader->pid);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* query id */
+	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
+
+	appendStringInfoChar(&buf, '\n');
+
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+	else
+		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index a162258bab..4406d8deff 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2792,241 +2792,6 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 	}
 }
 
-/*
- * append a CSV'd version of a string to a StringInfo
- * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
- * If it's NULL, append nothing.
- */
-static inline void
-appendCSVLiteral(StringInfo buf, const char *data)
-{
-	const char *p = data;
-	char		c;
-
-	/* avoid confusing an empty string with NULL */
-	if (p == NULL)
-		return;
-
-	appendStringInfoCharMacro(buf, '"');
-	while ((c = *p++) != '\0')
-	{
-		if (c == '"')
-			appendStringInfoCharMacro(buf, '"');
-		appendStringInfoCharMacro(buf, c);
-	}
-	appendStringInfoCharMacro(buf, '"');
-}
-
-/*
- * Constructs the error message, depending on the Errordata it gets, in a CSV
- * format which is described in doc/src/sgml/config.sgml.
- */
-void
-write_csvlog(ErrorData *edata)
-{
-	StringInfoData buf;
-	bool		print_stmt = false;
-	char	   *start_time;
-	char	   *log_time;
-
-	/* static counter for line numbers */
-	static long log_line_number = 0;
-
-	/* has counter been reset in current process? */
-	static int	log_my_pid = 0;
-
-	/*
-	 * This is one of the few places where we'd rather not inherit a static
-	 * variable's value from the postmaster.  But since we will, reset it when
-	 * MyProcPid changes.
-	 */
-	if (log_my_pid != MyProcPid)
-	{
-		log_line_number = 0;
-		log_my_pid = MyProcPid;
-		formatted_start_time[0] = '\0';
-	}
-	log_line_number++;
-
-	initStringInfo(&buf);
-
-	/* timestamp with milliseconds */
-	log_time = get_formatted_log_time();
-	appendStringInfoString(&buf, log_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* username */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->user_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* database name */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->database_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* Process id  */
-	if (MyProcPid != 0)
-		appendStringInfo(&buf, "%d", MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Remote host and port */
-	if (MyProcPort && MyProcPort->remote_host)
-	{
-		appendStringInfoChar(&buf, '"');
-		appendStringInfoString(&buf, MyProcPort->remote_host);
-		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
-		{
-			appendStringInfoChar(&buf, ':');
-			appendStringInfoString(&buf, MyProcPort->remote_port);
-		}
-		appendStringInfoChar(&buf, '"');
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session id */
-	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Line number */
-	appendStringInfo(&buf, "%ld", log_line_number);
-	appendStringInfoChar(&buf, ',');
-
-	/* PS display */
-	if (MyProcPort)
-	{
-		StringInfoData msgbuf;
-		const char *psdisp;
-		int			displen;
-
-		initStringInfo(&msgbuf);
-
-		psdisp = get_ps_display(&displen);
-		appendBinaryStringInfo(&msgbuf, psdisp, displen);
-		appendCSVLiteral(&buf, msgbuf.data);
-
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session start timestamp */
-	start_time = get_formatted_start_time();
-	appendStringInfoString(&buf, start_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* Virtual transaction id */
-	/* keep VXID format in sync with lockfuncs.c */
-	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
-		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Transaction id */
-	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
-	appendStringInfoChar(&buf, ',');
-
-	/* Error severity */
-	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
-	appendStringInfoChar(&buf, ',');
-
-	/* SQL state code */
-	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
-	appendStringInfoChar(&buf, ',');
-
-	/* errmessage */
-	appendCSVLiteral(&buf, edata->message);
-	appendStringInfoChar(&buf, ',');
-
-	/* errdetail or errdetail_log */
-	if (edata->detail_log)
-		appendCSVLiteral(&buf, edata->detail_log);
-	else
-		appendCSVLiteral(&buf, edata->detail);
-	appendStringInfoChar(&buf, ',');
-
-	/* errhint */
-	appendCSVLiteral(&buf, edata->hint);
-	appendStringInfoChar(&buf, ',');
-
-	/* internal query */
-	appendCSVLiteral(&buf, edata->internalquery);
-	appendStringInfoChar(&buf, ',');
-
-	/* if printed internal query, print internal pos too */
-	if (edata->internalpos > 0 && edata->internalquery != NULL)
-		appendStringInfo(&buf, "%d", edata->internalpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* errcontext */
-	if (!edata->hide_ctx)
-		appendCSVLiteral(&buf, edata->context);
-	appendStringInfoChar(&buf, ',');
-
-	/* user query --- only reported if not disabled by the caller */
-	print_stmt = check_log_of_query(edata);
-	if (print_stmt)
-		appendCSVLiteral(&buf, debug_query_string);
-	appendStringInfoChar(&buf, ',');
-	if (print_stmt && edata->cursorpos > 0)
-		appendStringInfo(&buf, "%d", edata->cursorpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* file error location */
-	if (Log_error_verbosity >= PGERROR_VERBOSE)
-	{
-		StringInfoData msgbuf;
-
-		initStringInfo(&msgbuf);
-
-		if (edata->funcname && edata->filename)
-			appendStringInfo(&msgbuf, "%s, %s:%d",
-							 edata->funcname, edata->filename,
-							 edata->lineno);
-		else if (edata->filename)
-			appendStringInfo(&msgbuf, "%s:%d",
-							 edata->filename, edata->lineno);
-		appendCSVLiteral(&buf, msgbuf.data);
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* application name */
-	if (application_name)
-		appendCSVLiteral(&buf, application_name);
-
-	appendStringInfoChar(&buf, ',');
-
-	/* backend type */
-	appendCSVLiteral(&buf, get_backend_type_for_log());
-	appendStringInfoChar(&buf, ',');
-
-	/* leader PID */
-	if (MyProc)
-	{
-		PGPROC	   *leader = MyProc->lockGroupLeader;
-
-		/*
-		 * Show the leader only for active parallel workers.  This leaves out
-		 * the leader of a parallel group.
-		 */
-		if (leader && leader->pid != MyProcPid)
-			appendStringInfo(&buf, "%d", leader->pid);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* query id */
-	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
-
-	appendStringInfoChar(&buf, '\n');
-
-	/* If in the syslogger process, try to write messages direct to file */
-	if (MyBackendType == B_LOGGER)
-		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-	else
-		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-
-	pfree(buf.data);
-}
-
 /*
  * Unpack MAKE_SQLSTATE code. Note that this returns a pointer to a
  * static buffer.
-- 
2.33.0

From c3a46da88ed75090d8582961c9c05e1ca887af5a Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 5 Oct 2021 15:59:44 +0900
Subject: [PATCH v6 3/3] JSON logging

---
 src/include/postmaster/syslogger.h |   1 +
 src/include/utils/elog.h           |   2 +
 src/backend/postmaster/syslogger.c | 107 ++++++++--
 src/backend/utils/adt/misc.c       |   5 +-
 src/backend/utils/error/Makefile   |   3 +-
 src/backend/utils/error/elog.c     |  18 ++
 src/backend/utils/error/jsonlog.c  | 323 +++++++++++++++++++++++++++++
 src/backend/utils/misc/guc.c       |   2 +
 src/bin/pg_ctl/t/004_logrotate.pl  |  12 +-
 doc/src/sgml/config.sgml           |  67 +++++-
 10 files changed, 514 insertions(+), 26 deletions(-)
 create mode 100644 src/backend/utils/error/jsonlog.c

diff --git a/src/include/postmaster/syslogger.h b/src/include/postmaster/syslogger.h
index c79dfbeba2..18448b76e5 100644
--- a/src/include/postmaster/syslogger.h
+++ b/src/include/postmaster/syslogger.h
@@ -64,6 +64,7 @@ typedef union
 /* log destinations */
 #define PIPE_PROTO_DEST_STDERR	0x10
 #define PIPE_PROTO_DEST_CSVLOG	0x20
+#define PIPE_PROTO_DEST_JSONLOG	0x40
 
 /* GUC options */
 extern bool Logging_collector;
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 731f3e3cd8..a32c790421 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -436,6 +436,7 @@ extern bool syslog_split_messages;
 #define LOG_DESTINATION_SYSLOG	 2
 #define LOG_DESTINATION_EVENTLOG 4
 #define LOG_DESTINATION_CSVLOG	 8
+#define LOG_DESTINATION_JSONLOG	16
 
 /* Other exported functions */
 extern void DebugFileOpen(void);
@@ -453,6 +454,7 @@ extern void write_pipe_chunks(char *data, int len, int dest);
 
 /* Destination-specific functions */
 extern void write_csvlog(ErrorData *edata);
+extern void write_jsonlog(ErrorData *edata);
 
 #ifdef HAVE_SYSLOG
 extern void set_syslog_parameters(const char *ident, int facility);
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index d1f56b95a4..449d327268 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -86,9 +86,11 @@ static bool pipe_eof_seen = false;
 static bool rotation_disabled = false;
 static FILE *syslogFile = NULL;
 static FILE *csvlogFile = NULL;
+static FILE *jsonlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
 static char *last_sys_file_name = NULL;
 static char *last_csv_file_name = NULL;
+static char *last_json_file_name = NULL;
 
 /*
  * Buffers for saving partial messages from different backends.
@@ -281,6 +283,8 @@ SysLoggerMain(int argc, char *argv[])
 	last_sys_file_name = logfile_getname(first_syslogger_file_time, NULL);
 	if (csvlogFile != NULL)
 		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
+	if (jsonlogFile != NULL)
+		last_json_file_name = logfile_getname(first_syslogger_file_time, ".json");
 
 	/* remember active logfile parameters */
 	currentLogDir = pstrdup(Log_directory);
@@ -367,6 +371,14 @@ SysLoggerMain(int argc, char *argv[])
 				(csvlogFile != NULL))
 				rotation_requested = true;
 
+			/*
+			 * Force a rotation if JSONLOG output was just turned on or off and
+			 * we need to open or close jsonlogFile accordingly.
+			 */
+			if (((Log_destination & LOG_DESTINATION_JSONLOG) != 0) !=
+				(jsonlogFile != NULL))
+				rotation_requested = true;
+
 			/*
 			 * If rotation time parameter changed, reset next rotation time,
 			 * but don't immediately force a rotation.
@@ -417,6 +429,12 @@ SysLoggerMain(int argc, char *argv[])
 				rotation_requested = true;
 				size_rotation_for |= LOG_DESTINATION_CSVLOG;
 			}
+			if (jsonlogFile != NULL &&
+				ftell(jsonlogFile) >= Log_RotationSize * 1024L)
+			{
+				rotation_requested = true;
+				size_rotation_for |= LOG_DESTINATION_JSONLOG;
+			}
 		}
 
 		if (rotation_requested)
@@ -426,7 +444,7 @@ SysLoggerMain(int argc, char *argv[])
 			 * was sent by pg_rotate_logfile() or "pg_ctl logrotate".
 			 */
 			if (!time_based_rotation && size_rotation_for == 0)
-				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG;
+				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG | LOG_DESTINATION_JSONLOG;
 			logfile_rotate(time_based_rotation, size_rotation_for);
 		}
 
@@ -632,6 +650,20 @@ SysLogger_Start(void)
 		pfree(filename);
 	}
 
+	/*
+	 * Likewise for the initial JSON log file, if that's enabled.  (Note that
+	 * we open syslogFile even when only JSON output is nominally enabled,
+	 * since some code paths will write to syslogFile anyway.)
+	 */
+	if (Log_destination & LOG_DESTINATION_JSONLOG)
+	{
+		filename = logfile_getname(first_syslogger_file_time, ".json");
+
+		jsonlogFile = logfile_open(filename, "a", false);
+
+		pfree(filename);
+	}
+
 #ifdef EXEC_BACKEND
 	switch ((sysloggerPid = syslogger_forkexec()))
 #else
@@ -729,6 +761,11 @@ SysLogger_Start(void)
 				fclose(csvlogFile);
 				csvlogFile = NULL;
 			}
+			if (jsonlogFile != NULL)
+			{
+				fclose(jsonlogFile);
+				jsonlogFile = NULL;
+			}
 			return (int) sysloggerPid;
 	}
 
@@ -805,6 +842,7 @@ syslogger_forkexec(void)
 	int			ac = 0;
 	char		filenobuf[32];
 	char		csvfilenobuf[32];
+	char		jsonfilenobuf[32];
 
 	av[ac++] = "postgres";
 	av[ac++] = "--forklog";
@@ -817,6 +855,9 @@ syslogger_forkexec(void)
 	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%d",
 			 syslogger_fdget(csvlogFile));
 	av[ac++] = csvfilenobuf;
+	snprintf(jsonfilenobuf, sizeof(jsonfilenobuf), "%d",
+			 syslogger_fdget(jsonlogFile));
+	av[ac++] = jsonfilenobuf;
 
 	av[ac] = NULL;
 	Assert(ac < lengthof(av));
@@ -834,8 +875,8 @@ syslogger_parseArgs(int argc, char *argv[])
 {
 	int			fd;
 
-	Assert(argc == 5);
-	argv += 3;
+	Assert(argc == 6);
+	argv += 4;
 
 	/*
 	 * Re-open the error output files that were opened by SysLogger_Start().
@@ -848,6 +889,8 @@ syslogger_parseArgs(int argc, char *argv[])
 	syslogFile = syslogger_fdopen(fd);
 	fd = atoi(*argv++);
 	csvlogFile = syslogger_fdopen(fd);
+	fd = atoi(*argv++);
+	jsonlogFile = syslogger_fdopen(fd);
 }
 #endif							/* EXEC_BACKEND */
 
@@ -896,7 +939,9 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 
 		/* Do we have a valid header? */
 		memcpy(&p, cursor, offsetof(PipeProtoHeader, data));
-		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR | PIPE_PROTO_DEST_CSVLOG);
+		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR |
+								PIPE_PROTO_DEST_CSVLOG |
+								PIPE_PROTO_DEST_JSONLOG);
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&
@@ -918,6 +963,8 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 				dest = LOG_DESTINATION_STDERR;
 			else if ((p.flags & PIPE_PROTO_DEST_CSVLOG) != 0)
 				dest = LOG_DESTINATION_CSVLOG;
+			else if ((p.flags & PIPE_PROTO_DEST_JSONLOG) != 0)
+				dest = LOG_DESTINATION_JSONLOG;
 			else
 			{
 				/* this should never happen as of the header validation */
@@ -1097,19 +1144,24 @@ write_syslogger_file(const char *buffer, int count, int destination)
 	FILE	   *logfile;
 
 	/*
-	 * If we're told to write to csvlogFile, but it's not open, dump the data
-	 * to syslogFile (which is always open) instead.  This can happen if CSV
-	 * output is enabled after postmaster start and we've been unable to open
-	 * csvlogFile.  There are also race conditions during a parameter change
-	 * whereby backends might send us CSV output before we open csvlogFile or
-	 * after we close it.  Writing CSV-formatted output to the regular log
-	 * file isn't great, but it beats dropping log output on the floor.
+	 * If we're told to write to a structured log file, but it's not open,
+	 * dump the data to syslogFile (which is always open) instead.  This can
+	 * happen if structured output is enabled after postmaster start and
+	 * we've been unable to open logFile.  There are also race conditions
+	 * during a parameter change whereby backends might send us structured
+	 * output before we open the logFile or after we close it.  Writing
+	 * formatted output to the regular log file isn't great, but it beats
+	 * dropping log output on the floor.
 	 *
-	 * Think not to improve this by trying to open csvlogFile on-the-fly.  Any
+	 * Think not to improve this by trying to open logFile on-the-fly.  Any
 	 * failure in that would lead to recursion.
 	 */
-	logfile = (destination == LOG_DESTINATION_CSVLOG &&
-			   csvlogFile != NULL) ? csvlogFile : syslogFile;
+	if ((destination & LOG_DESTINATION_CSVLOG) && csvlogFile != NULL)
+		logfile = csvlogFile;
+	else if ((destination & LOG_DESTINATION_JSONLOG) && jsonlogFile != NULL)
+		logfile = jsonlogFile;
+	else
+		logfile = syslogFile;
 
 	rc = fwrite(buffer, 1, count, logfile);
 
@@ -1180,7 +1232,8 @@ pipeThread(void *arg)
 		if (Log_RotationSize > 0)
 		{
 			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
-				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
+				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L) ||
+				(jsonlogFile != NULL && ftell(jsonlogFile) >= Log_RotationSize * 1024L))
 				SetLatch(MyLatch);
 		}
 		LeaveCriticalSection(&sysloggerSection);
@@ -1292,6 +1345,8 @@ logfile_rotate_dest(bool time_based_rotation, int size_rotation_for,
 		logFileExt = NULL;
 	else if (target_dest == LOG_DESTINATION_CSVLOG)
 		logFileExt = ".csv";
+	else if (target_dest == LOG_DESTINATION_JSONLOG)
+		logFileExt = ".json";
 	else
 	{
 		/* cannot happen */
@@ -1379,6 +1434,12 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 							 &csvlogFile))
 		return;
 
+	/* file rotation for csvlog */
+	if (!logfile_rotate_dest(time_based_rotation, size_rotation_for, fntime,
+							 LOG_DESTINATION_JSONLOG, &last_json_file_name,
+							 &jsonlogFile))
+		return;
+
 	update_metainfo_datafile();
 
 	set_next_rotation_time();
@@ -1465,7 +1526,8 @@ update_metainfo_datafile(void)
 	mode_t		oumask;
 
 	if (!(Log_destination & LOG_DESTINATION_STDERR) &&
-		!(Log_destination & LOG_DESTINATION_CSVLOG))
+		!(Log_destination & LOG_DESTINATION_CSVLOG) &&
+		!(Log_destination & LOG_DESTINATION_JSONLOG))
 	{
 		if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
 			ereport(LOG,
@@ -1523,6 +1585,19 @@ update_metainfo_datafile(void)
 			return;
 		}
 	}
+
+	if (last_json_file_name && (Log_destination & LOG_DESTINATION_JSONLOG))
+	{
+		if (fprintf(fh, "jsonlog %s\n", last_json_file_name) < 0)
+		{
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not write file \"%s\": %m",
+							LOG_METAINFO_DATAFILE_TMP)));
+			fclose(fh);
+			return;
+		}
+	}
 	fclose(fh);
 
 	if (rename(LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE) != 0)
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 88faf4dfd7..4931859627 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -843,11 +843,12 @@ pg_current_logfile(PG_FUNCTION_ARGS)
 	{
 		logfmt = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
-		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0)
+		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0 &&
+				strcmp(logfmt, "jsonlog") != 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("log format \"%s\" is not supported", logfmt),
-					 errhint("The supported log formats are \"stderr\" and \"csvlog\".")));
+					 errhint("The supported log formats are \"stderr\", \"csvlog\", and \"jsonlog\".")));
 	}
 
 	fd = AllocateFile(LOG_METAINFO_DATAFILE, "r");
diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index ef770dd2f2..65ba61fb3c 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -15,6 +15,7 @@ include $(top_builddir)/src/Makefile.global
 OBJS = \
 	assert.o \
 	csvlog.o \
-	elog.o
+	elog.o \
+	jsonlog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 4406d8deff..39467be917 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2984,6 +2984,22 @@ send_message_to_server_log(ErrorData *edata)
 			fallback_to_stderr = true;
 	}
 
+	/* Write to JSON log, if enabled */
+	if ((Log_destination & LOG_DESTINATION_JSONLOG) != 0)
+	{
+		/*
+		 * Send JSON data if it's safe to do so (syslogger doesn't need the
+		 * pipe).  If this is not possible, fallback to an entry written
+		 * to stderr.
+		 */
+		if (redirection_done || MyBackendType == B_LOGGER)
+		{
+			write_jsonlog(edata);
+		}
+		else
+			fallback_to_stderr = true;
+	}
+
 	/*
 	 * Write to stderr, if enabled or if required because of a previous
 	 * limitation.
@@ -3059,6 +3075,8 @@ write_pipe_chunks(char *data, int len, int dest)
 		p.proto.flags |= PIPE_PROTO_DEST_STDERR;
 	else if (dest == LOG_DESTINATION_CSVLOG)
 		p.proto.flags |= PIPE_PROTO_DEST_CSVLOG;
+	else if (dest == LOG_DESTINATION_JSONLOG)
+		p.proto.flags |= PIPE_PROTO_DEST_JSONLOG;
 
 	/* write all but the last chunk */
 	while (len > PIPE_MAX_PAYLOAD)
diff --git a/src/backend/utils/error/jsonlog.c b/src/backend/utils/error/jsonlog.c
new file mode 100644
index 0000000000..f92ee64a47
--- /dev/null
+++ b/src/backend/utils/error/jsonlog.c
@@ -0,0 +1,323 @@
+/*-------------------------------------------------------------------------
+ *
+ * jsonlog.c
+ *	  JSON logging
+ *
+ * Copyright (c) 2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/jsonlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog.h"
+#include "utils/guc.h"
+#include "utils/json.h"
+#include "utils/ps_status.h"
+
+static void appendJSONKeyValueFmt(StringInfo buf, const char *key,
+								  const char *fmt,...) pg_attribute_printf(3, 4);
+
+/*
+ * appendJSONKeyValue
+ * Append to given StringInfo a comma followed by a JSON key and value.
+ * Both the key and value will be escaped as JSON string literals.
+ */
+static void
+appendJSONKeyValue(StringInfo buf, const char *key, const char *value)
+{
+	if (value == NULL)
+		return;
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	escape_json(buf, value);
+}
+
+/*
+ * appendJSONKeyValueFmt
+ *
+ * Evaluate the fmt string and then invoke appendJSONKeyValue as the
+ * value of the JSON property. Both the key and value will be escaped by
+ * appendJSONKeyValue.
+ */
+static void
+appendJSONKeyValueFmt(StringInfo buf, const char *key, const char *fmt,...)
+{
+	int			save_errno = errno;
+	size_t		len = 128;		/* initial assumption about buffer size */
+	char	    *value;
+
+	for (;;)
+	{
+		va_list		args;
+		size_t		newlen;
+
+		/*
+		 * Allocate result buffer.  Note that in frontend this maps to malloc
+		 * with exit-on-error.
+		 */
+		value = (char *) palloc(len);
+
+		/* Try to format the data. */
+		errno = save_errno;
+		va_start(args, fmt);
+		newlen = pvsnprintf(value, len, fmt, args);
+		va_end(args);
+
+		if (newlen < len)
+			break; /* success */
+
+		/* Release buffer and loop around to try again with larger len. */
+		pfree(value);
+		len = newlen;
+	}
+	appendJSONKeyValue(buf, key, value);
+
+	/* Clean up */
+	pfree(value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as a signed integer (a JSON number).
+ */
+static void
+appendJSONKeyValueAsInt(StringInfo buf, const char *key, int value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%d", value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as an unsigned integer (a JSON number).
+ */
+static void
+appendJSONKeyValueAsUInt(StringInfo buf, const char *key, int value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%u", value);
+}
+
+/*
+ * appendJSONKeyValueAsInt
+ * Append to given StringInfo a comma followed by a JSON key and value with
+ * value being formatted as a long (a JSON number).
+ */
+static void
+appendJSONKeyValueAsLong(StringInfo buf, const char *key, long value)
+{
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+	appendStringInfo(buf, "%ld", value);
+}
+
+/*
+ * Write logs in json format.
+ */
+void
+write_jsonlog(ErrorData *edata)
+{
+	StringInfoData	buf;
+	char	   *start_time;
+	char	   *log_time;
+
+	/* static counter for line numbers */
+	static long	log_line_number = 0;
+
+	/* Has the counter been reset in the current process? */
+	static int	log_my_pid = 0;
+
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		reset_formatted_start_time();
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* Initialize string */
+	appendStringInfoChar(&buf, '{');
+
+	/*
+	 * timestamp with milliseconds
+	 *
+	 * Check if the timestamp is already calculated for the syslog message,
+	 * and use it if so.  Otherwise, get the current timestamp.  This is done
+	 * to put same timestamp in both syslog and jsonlog messages.
+	 */
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+
+	/*
+	 * First property does not use appendJSONKeyValue as it does not have
+	 * comma prefix.
+	 */
+	escape_json(&buf, "timestamp");
+	appendStringInfoChar(&buf, ':');
+	escape_json(&buf, log_time);
+
+	/* username */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "user", MyProcPort->user_name);
+
+	/* database name */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "dbname", MyProcPort->database_name);
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendJSONKeyValueAsInt(&buf, "leader_pid", leader->pid);
+	}
+
+	/* Process ID */
+	if (MyProcPid != 0)
+		appendJSONKeyValueAsInt(&buf, "pid", MyProcPid);
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendJSONKeyValue(&buf, "remote_host", MyProcPort->remote_host);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+			appendJSONKeyValue(&buf, "remote_port", MyProcPort->remote_port);
+	}
+
+	/* Session id */
+	appendJSONKeyValueFmt(&buf, "session_id", "%lx.%x", (long) MyStartTime, MyProcPid);
+
+	/* Line number */
+	appendJSONKeyValueAsLong(&buf, "line_num", log_line_number);
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData	msgbuf;
+		const char	   *psdisp;
+		int				displen;
+
+		initStringInfo(&msgbuf);
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendJSONKeyValue(&buf, "ps", msgbuf.data);
+
+		pfree(msgbuf.data);
+	}
+
+	/* session start timestamp */
+	start_time = get_formatted_start_time();
+	appendJSONKeyValue(&buf, "session_start", start_time);
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendJSONKeyValueFmt(&buf, "vxid", "%d/%u", MyProc->backendId, MyProc->lxid);
+
+	/* Transaction id */
+	appendJSONKeyValueFmt(&buf, "txid", "%u", GetTopTransactionIdIfAny());
+
+	/* Error severity */
+	if (edata->elevel)
+		appendJSONKeyValue(&buf, "error_severity", (char *) error_severity(edata->elevel));
+
+	/* query id */
+	appendJSONKeyValueFmt(&buf,  "query_id", "%lld", (long long) pgstat_get_my_query_id());
+
+	/* SQL state code */
+	if (edata->sqlerrcode)
+		appendJSONKeyValue(&buf, "state_code", unpack_sql_state(edata->sqlerrcode));
+
+	/* errdetail or error_detail log */
+	if (edata->detail_log)
+		appendJSONKeyValue(&buf, "detail", edata->detail_log);
+	else if (edata->detail)
+		appendJSONKeyValue(&buf, "detail", edata->detail);
+
+	/* errhint */
+	if (edata->hint)
+		appendJSONKeyValue(&buf, "hint", edata->hint);
+
+	/* Internal query */
+	if (edata->internalquery)
+		appendJSONKeyValue(&buf, "internal_query", edata->internalquery);
+
+	/* If the internal query got printed, print internal pos, too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendJSONKeyValueAsUInt(&buf, "internal_position", edata->internalpos);
+
+	/* errcontext */
+	if (edata->context && !edata->hide_ctx)
+		appendJSONKeyValue(&buf, "context", edata->context);
+
+	/* user query --- only reported if not disabled by the caller */
+	if (check_log_of_query(edata))
+	{
+		appendJSONKeyValue(&buf, "statement", debug_query_string);
+		if (edata->cursorpos > 0)
+			appendJSONKeyValueAsInt(&buf, "cursor_position", edata->cursorpos);
+	}
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		if (edata->funcname)
+			appendJSONKeyValue(&buf, "func_name", edata->funcname);
+		if (edata->filename)
+		{
+			appendJSONKeyValue(&buf, "file_name", edata->filename);
+			appendJSONKeyValueAsInt(&buf, "file_line_num", edata->lineno);
+		}
+	}
+
+	/* Application name */
+	if (application_name && application_name[0] != '\0')
+		appendJSONKeyValue(&buf, "application_name", application_name);
+
+	/* backend type */
+	appendJSONKeyValue(&buf, "backend_type", get_backend_type_for_log());
+
+	/* Error message */
+	appendJSONKeyValue(&buf, "message", edata->message);
+
+	/* Finish string */
+	appendStringInfoChar(&buf, '}');
+	appendStringInfoChar(&buf, '\n');
+
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+	else
+		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index d2ce4a8450..0b79753ec3 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -11714,6 +11714,8 @@ check_log_destination(char **newval, void **extra, GucSource source)
 			newlogdest |= LOG_DESTINATION_STDERR;
 		else if (pg_strcasecmp(tok, "csvlog") == 0)
 			newlogdest |= LOG_DESTINATION_CSVLOG;
+		else if (pg_strcasecmp(tok, "jsonlog") == 0)
+			newlogdest |= LOG_DESTINATION_JSONLOG;
 #ifdef HAVE_SYSLOG
 		else if (pg_strcasecmp(tok, "syslog") == 0)
 			newlogdest |= LOG_DESTINATION_SYSLOG;
diff --git a/src/bin/pg_ctl/t/004_logrotate.pl b/src/bin/pg_ctl/t/004_logrotate.pl
index 13e91f3bc9..5f05fd2bad 100644
--- a/src/bin/pg_ctl/t/004_logrotate.pl
+++ b/src/bin/pg_ctl/t/004_logrotate.pl
@@ -6,7 +6,7 @@ use warnings;
 
 use PostgresNode;
 use TestLib;
-use Test::More tests => 10;
+use Test::More tests => 14;
 use Time::HiRes qw(usleep);
 
 # Extract the file name of a $format from the contents of
@@ -65,7 +65,7 @@ $node->init();
 $node->append_conf(
 	'postgresql.conf', qq(
 logging_collector = on
-log_destination = 'stderr, csvlog'
+log_destination = 'stderr, csvlog, jsonlog'
 # these ensure stability of test results:
 log_rotation_age = 0
 lc_messages = 'C'
@@ -96,11 +96,13 @@ note "current_logfiles = $current_logfiles";
 like(
 	$current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'current_logfiles is sane');
 
 check_log_pattern('stderr', $current_logfiles, 'division by zero', $node);
 check_log_pattern('csvlog', $current_logfiles, 'division by zero', $node);
+check_log_pattern('jsonlog', $current_logfiles, 'division by zero', $node);
 
 # Sleep 2 seconds and ask for log rotation; this should result in
 # output into a different log file name.
@@ -122,7 +124,8 @@ note "now current_logfiles = $new_current_logfiles";
 like(
 	$new_current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'new current_logfiles is sane');
 
 # Verify that log output gets to this file, too
@@ -130,5 +133,6 @@ $node->psql('postgres', 'fee fi fo fum');
 
 check_log_pattern('stderr', $new_current_logfiles, 'syntax error', $node);
 check_log_pattern('csvlog', $new_current_logfiles, 'syntax error', $node);
+check_log_pattern('jsonlog', $new_current_logfiles, 'syntax error', $node);
 
 $node->stop();
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 0bcc6fd322..72a8204818 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5926,7 +5926,8 @@ SELECT * FROM parent WHERE key = 2400;
        <para>
         <productname>PostgreSQL</productname> supports several methods
          for logging server messages, including
-         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem> and
+         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem>,
+         <systemitem>jsonlog</systemitem>, and
          <systemitem>syslog</systemitem>. On Windows,
          <systemitem>eventlog</systemitem> is also supported. Set this
          parameter to a list of desired log destinations separated by
@@ -5944,6 +5945,14 @@ SELECT * FROM parent WHERE key = 2400;
         <xref linkend="guc-logging-collector"/> must be enabled to generate
         CSV-format log output.
        </para>
+       <para>
+        If <systemitem>jsonlog</systemitem> is included in <varname>log_destination</varname>,
+        log entries are output in <acronym>JSON</acronym> format, which is convenient for
+        loading logs into programs.
+        See <xref linkend="runtime-config-logging-jsonlog"/> for details.
+        <xref linkend="guc-logging-collector"/> must be enabled to generate
+        CSV-format log output.
+       </para>
        <para>
         When either <systemitem>stderr</systemitem> or
         <systemitem>csvlog</systemitem> are included, the file
@@ -5955,13 +5964,14 @@ SELECT * FROM parent WHERE key = 2400;
 <programlisting>
 stderr log/postgresql.log
 csvlog log/postgresql.csv
+jsonlog log/postgresql.json
 </programlisting>
 
         <filename>current_logfiles</filename> is recreated when a new log file
         is created as an effect of rotation, and
         when <varname>log_destination</varname> is reloaded.  It is removed when
-        neither <systemitem>stderr</systemitem>
-        nor <systemitem>csvlog</systemitem> are included
+        none of <systemitem>stderr</systemitem>,
+        <systemitem>csvlog</systemitem>, <systemitem>jsonlog</systemitem> are included
         in <varname>log_destination</varname>, and when the logging collector is
         disabled.
        </para>
@@ -6101,6 +6111,13 @@ local0.*    /var/log/postgresql
         (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
         replaced instead.)
        </para>
+       <para>
+        If JSON-format output is enabled in <varname>log_destination</varname>,
+        <literal>.json</literal> will be appended to the timestamped
+        log file name to create the file name for JSON-format output.
+        (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
+        replaced instead.)
+       </para>
        <para>
         This parameter can only be set in the <filename>postgresql.conf</filename>
         file or on the server command line.
@@ -7433,6 +7450,50 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         </orderedlist>
       </para>
     </sect2>
+     <sect2 id="runtime-config-logging-jsonlog">
+     <title>Using JSON-Format Log Output</title>
+
+       <para>
+        Including <literal>jsonlog</literal> in the <varname>log_destination</varname> list
+        provides a convenient way to import log files into many different programs.
+        This option emits log lines in (<acronym>JSON</acronym>) format.
+        Each log line is serialized as a JSON object with the following fields:
+<programlisting>
+        {
+            "timestamp": time stamp with milliseconds (string),
+            "user": user name (string),
+            "dbname": database name (string),
+            "pid": process ID (number),
+            "remote_host": client host (string)
+            "remote_port": port number (string),
+            "session_id": session ID (string),
+            "line_num": per-session line number (number),
+            "ps": current ps display (string),
+            "session_start": session start time (string),
+            "vxid": virtual transaction ID (string),
+            "txid": regular transaction ID (string),
+            "error_severity": error severity (string),
+            "state_code": SQLSTATE code (string),
+            "detail": error message detail (string),
+            "hint": hint (string),
+            "internal_query": internal query that led to the error (string),
+            "internal_position": cursor index into internal query (number),
+            "context": error context (string),
+            "statement": client supplied query string (string),
+            "cursor_position": cursor index into query string (string),
+            "func_name": error location function name (string),
+            "file_name": error location file name (string),
+            "file_line_num": error location file line number (number),
+            "application_name": client application name (string),
+            "message": error message (string)
+        }
+</programlisting>
+        String fields with null values are excluded from output.
+        Additional fields may be added in the future. User applications that process jsonlog
+        output should ignore unknown fields.
+       </para>
+
+    </sect2>
 
    <sect2>
     <title>Process Title</title>
-- 
2.33.0

From 6d71178c0809a5ed9bc131f6d601411ec2f2ec9f Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 19 Oct 2021 16:25:45 +0900
Subject: [PATCH v7 1/3] Some refactoring of elog-specific routines

This refactors out the following things in elog.c, for ease of use
across multiple log destinations:
- start_timestamp (including reset)
- log_timestamp
- decide if query can be logged
- backend type
- write using the elog piped protocol
- Error severity to string.

These will be reused by csvlog and jsonlog.
---
 src/include/utils/elog.h       |  12 +++
 src/backend/utils/error/elog.c | 159 +++++++++++++++++++++------------
 2 files changed, 114 insertions(+), 57 deletions(-)

diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index f53607e12e..731f3e3cd8 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -442,6 +442,18 @@ extern void DebugFileOpen(void);
 extern char *unpack_sql_state(int sql_state);
 extern bool in_error_recursion_trouble(void);
 
+/* Common functions shared across destinations */
+extern void reset_formatted_start_time(void);
+extern char *get_formatted_start_time(void);
+extern char *get_formatted_log_time(void);
+extern const char *get_backend_type_for_log(void);
+extern bool	check_log_of_query(ErrorData *edata);
+extern const char *error_severity(int elevel);
+extern void write_pipe_chunks(char *data, int len, int dest);
+
+/* Destination-specific functions */
+extern void write_csvlog(ErrorData *edata);
+
 #ifdef HAVE_SYSLOG
 extern void set_syslog_parameters(const char *ident, int facility);
 #endif
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index f33729513a..a162258bab 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -175,15 +175,10 @@ static const char *err_gettext(const char *str) pg_attribute_format_arg(1);
 static pg_noinline void set_backtrace(ErrorData *edata, int num_skip);
 static void set_errdata_field(MemoryContextData *cxt, char **ptr, const char *str);
 static void write_console(const char *line, int len);
-static void setup_formatted_log_time(void);
-static void setup_formatted_start_time(void);
 static const char *process_log_prefix_padding(const char *p, int *padding);
 static void log_line_prefix(StringInfo buf, ErrorData *edata);
-static void write_csvlog(ErrorData *edata);
 static void send_message_to_server_log(ErrorData *edata);
-static void write_pipe_chunks(char *data, int len, int dest);
 static void send_message_to_frontend(ErrorData *edata);
-static const char *error_severity(int elevel);
 static void append_with_tabs(StringInfo buf, const char *str);
 
 
@@ -2289,14 +2284,23 @@ write_console(const char *line, int len)
 }
 
 /*
- * setup formatted_log_time, for consistent times between CSV and regular logs
+ * get_formatted_log_time -- compute and get the log timestamp.
+ *
+ * The timestamp is computed if not set yet, so as it is kept consistent
+ * among all the log destinations that require it to be consistent.  Note
+ * that the computed timestamp is returned in a static buffer, not
+ * palloc()'d.
  */
-static void
-setup_formatted_log_time(void)
+char *
+get_formatted_log_time(void)
 {
 	pg_time_t	stamp_time;
 	char		msbuf[13];
 
+	/* leave if already computed */
+	if (formatted_log_time[0] != '\0')
+		return formatted_log_time;
+
 	if (!saved_timeval_set)
 	{
 		gettimeofday(&saved_timeval, NULL);
@@ -2318,16 +2322,34 @@ setup_formatted_log_time(void)
 	/* 'paste' milliseconds into place... */
 	sprintf(msbuf, ".%03d", (int) (saved_timeval.tv_usec / 1000));
 	memcpy(formatted_log_time + 19, msbuf, 4);
+
+	return formatted_log_time;
 }
 
 /*
- * setup formatted_start_time
+ * reset_formatted_start_time -- reset the start timestamp
  */
-static void
-setup_formatted_start_time(void)
+void
+reset_formatted_start_time(void)
+{
+	formatted_start_time[0] = '\0';
+}
+
+/*
+ * get_formatted_start_time -- compute and get the start timestamp.
+ *
+ * The timestamp is computed if not set yet.  Note that the computed
+ * timestamp is returned in a static buffer, not palloc()'d.
+ */
+char *
+get_formatted_start_time(void)
 {
 	pg_time_t	stamp_time = (pg_time_t) MyStartTime;
 
+	/* leave if already computed */
+	if (formatted_start_time[0] != '\0')
+		return formatted_start_time;
+
 	/*
 	 * Note: we expect that guc.c will ensure that log_timezone is set up (at
 	 * least with a minimal GMT value) before Log_line_prefix can become
@@ -2336,6 +2358,49 @@ setup_formatted_start_time(void)
 	pg_strftime(formatted_start_time, FORMATTED_TS_LEN,
 				"%Y-%m-%d %H:%M:%S %Z",
 				pg_localtime(&stamp_time, log_timezone));
+
+	return formatted_start_time;
+}
+
+/*
+ * check_log_of_query -- check if a query can be logged
+ */
+bool
+check_log_of_query(ErrorData *edata)
+{
+	/* log required? */
+	if (!is_log_level_output(edata->elevel, log_min_error_statement))
+		return false;
+
+	/* query log wanted? */
+	if (edata->hide_stmt)
+		return false;
+
+	/* query string available? */
+	if (debug_query_string == NULL)
+		return false;
+
+	return true;
+}
+
+/*
+ * get_backend_type_for_log -- backend type for log entries
+ *
+ * Returns a pointer to a static buffer, not palloc()'d.
+ */
+const char *
+get_backend_type_for_log(void)
+{
+	const char   *backend_type_str;
+
+	if (MyProcPid == PostmasterPid)
+		backend_type_str = "postmaster";
+	else if (MyBackendType == B_BG_WORKER)
+		backend_type_str = MyBgworkerEntry->bgw_type;
+	else
+		backend_type_str = GetBackendTypeDesc(MyBackendType);
+
+	return backend_type_str;
 }
 
 /*
@@ -2466,14 +2531,7 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 				break;
 			case 'b':
 				{
-					const char *backend_type_str;
-
-					if (MyProcPid == PostmasterPid)
-						backend_type_str = "postmaster";
-					else if (MyBackendType == B_BG_WORKER)
-						backend_type_str = MyBgworkerEntry->bgw_type;
-					else
-						backend_type_str = GetBackendTypeDesc(MyBackendType);
+					const char *backend_type_str = get_backend_type_for_log();
 
 					if (padding != 0)
 						appendStringInfo(buf, "%*s", padding, backend_type_str);
@@ -2561,7 +2619,10 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 					appendStringInfo(buf, "%ld", log_line_number);
 				break;
 			case 'm':
-				setup_formatted_log_time();
+				/* force a log timestamp reset */
+				formatted_log_time[0] = '\0';
+				(void) get_formatted_log_time();
+
 				if (padding != 0)
 					appendStringInfo(buf, "%*s", padding, formatted_log_time);
 				else
@@ -2602,12 +2663,14 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 				}
 				break;
 			case 's':
-				if (formatted_start_time[0] == '\0')
-					setup_formatted_start_time();
-				if (padding != 0)
-					appendStringInfo(buf, "%*s", padding, formatted_start_time);
-				else
-					appendStringInfoString(buf, formatted_start_time);
+				{
+					char   *start_time = get_formatted_start_time();
+
+					if (padding != 0)
+						appendStringInfo(buf, "%*s", padding, start_time);
+					else
+						appendStringInfoString(buf, start_time);
+				}
 				break;
 			case 'i':
 				if (MyProcPort)
@@ -2758,11 +2821,13 @@ appendCSVLiteral(StringInfo buf, const char *data)
  * Constructs the error message, depending on the Errordata it gets, in a CSV
  * format which is described in doc/src/sgml/config.sgml.
  */
-static void
+void
 write_csvlog(ErrorData *edata)
 {
 	StringInfoData buf;
 	bool		print_stmt = false;
+	char	   *start_time;
+	char	   *log_time;
 
 	/* static counter for line numbers */
 	static long log_line_number = 0;
@@ -2785,17 +2850,9 @@ write_csvlog(ErrorData *edata)
 
 	initStringInfo(&buf);
 
-	/*
-	 * timestamp with milliseconds
-	 *
-	 * Check if the timestamp is already calculated for the syslog message,
-	 * and use it if so.  Otherwise, get the current timestamp.  This is done
-	 * to put same timestamp in both syslog and csvlog messages.
-	 */
-	if (formatted_log_time[0] == '\0')
-		setup_formatted_log_time();
-
-	appendStringInfoString(&buf, formatted_log_time);
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+	appendStringInfoString(&buf, log_time);
 	appendStringInfoChar(&buf, ',');
 
 	/* username */
@@ -2853,9 +2910,8 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* session start timestamp */
-	if (formatted_start_time[0] == '\0')
-		setup_formatted_start_time();
-	appendStringInfoString(&buf, formatted_start_time);
+	start_time = get_formatted_start_time();
+	appendStringInfoString(&buf, start_time);
 	appendStringInfoChar(&buf, ',');
 
 	/* Virtual transaction id */
@@ -2906,10 +2962,7 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* user query --- only reported if not disabled by the caller */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
-		print_stmt = true;
+	print_stmt = check_log_of_query(edata);
 	if (print_stmt)
 		appendCSVLiteral(&buf, debug_query_string);
 	appendStringInfoChar(&buf, ',');
@@ -2943,13 +2996,7 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* backend type */
-	if (MyProcPid == PostmasterPid)
-		appendCSVLiteral(&buf, "postmaster");
-	else if (MyBackendType == B_BG_WORKER)
-		appendCSVLiteral(&buf, MyBgworkerEntry->bgw_type);
-	else
-		appendCSVLiteral(&buf, GetBackendTypeDesc(MyBackendType));
-
+	appendCSVLiteral(&buf, get_backend_type_for_log());
 	appendStringInfoChar(&buf, ',');
 
 	/* leader PID */
@@ -3101,9 +3148,7 @@ send_message_to_server_log(ErrorData *edata)
 	/*
 	 * If the user wants the query that generated this error logged, do it.
 	 */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
+	if (check_log_of_query(edata))
 	{
 		log_line_prefix(&buf, edata);
 		appendStringInfoString(&buf, _("STATEMENT:  "));
@@ -3233,7 +3278,7 @@ send_message_to_server_log(ErrorData *edata)
  * warning from ignoring write()'s result, so do a little dance with casting
  * rc to void to shut up the compiler.
  */
-static void
+void
 write_pipe_chunks(char *data, int len, int dest)
 {
 	PipeProtoChunk p;
@@ -3469,7 +3514,7 @@ send_message_to_frontend(ErrorData *edata)
  * The string is not localized here, but we mark the strings for translation
  * so that callers can invoke _() on the result.
  */
-static const char *
+const char *
 error_severity(int elevel)
 {
 	const char *prefix;
-- 
2.33.1

From a0ab2f6c420a08c65b042ba183394c40dee0d4bb Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 5 Oct 2021 15:22:24 +0900
Subject: [PATCH v7 2/3] Refactor CSV-specific code into its own file

---
 src/backend/utils/error/Makefile |   1 +
 src/backend/utils/error/csvlog.c | 268 +++++++++++++++++++++++++++++++
 src/backend/utils/error/elog.c   | 235 ---------------------------
 3 files changed, 269 insertions(+), 235 deletions(-)
 create mode 100644 src/backend/utils/error/csvlog.c

diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index 612da215d0..ef770dd2f2 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -14,6 +14,7 @@ include $(top_builddir)/src/Makefile.global
 
 OBJS = \
 	assert.o \
+	csvlog.o \
 	elog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/csvlog.c b/src/backend/utils/error/csvlog.c
new file mode 100644
index 0000000000..443a91e168
--- /dev/null
+++ b/src/backend/utils/error/csvlog.c
@@ -0,0 +1,268 @@
+/*-------------------------------------------------------------------------
+ *
+ * csvlog.c
+ *	  CSV logging
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of Californi
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/csvlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog.h"
+#include "utils/guc.h"
+#include "utils/ps_status.h"
+
+
+/*
+ * append a CSV'd version of a string to a StringInfo
+ * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
+ * If it's NULL, append nothing.
+ */
+static inline void
+appendCSVLiteral(StringInfo buf, const char *data)
+{
+	const char *p = data;
+	char		c;
+
+	/* avoid confusing an empty string with NULL */
+	if (p == NULL)
+		return;
+
+	appendStringInfoCharMacro(buf, '"');
+	while ((c = *p++) != '\0')
+	{
+		if (c == '"')
+			appendStringInfoCharMacro(buf, '"');
+		appendStringInfoCharMacro(buf, c);
+	}
+	appendStringInfoCharMacro(buf, '"');
+}
+
+/*
+ * write_csvlog -- Generate and write CSV log entry
+ *
+ * Constructs the error message, depending on the Errordata it gets, in a CSV
+ * format which is described in doc/src/sgml/config.sgml.
+ */
+void
+write_csvlog(ErrorData *edata)
+{
+	StringInfoData buf;
+	bool		print_stmt = false;
+	char	   *start_time;
+	char	   *log_time;
+
+	/* static counter for line numbers */
+	static long log_line_number = 0;
+
+	/* has counter been reset in current process? */
+	static int	log_my_pid = 0;
+
+	/*
+	 * This is one of the few places where we'd rather not inherit a static
+	 * variable's value from the postmaster.  But since we will, reset it when
+	 * MyProcPid changes.
+	 */
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		reset_formatted_start_time();
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+	appendStringInfoString(&buf, log_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* username */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->user_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* database name */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->database_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* Process id  */
+	if (MyProcPid != 0)
+		appendStringInfo(&buf, "%d", MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendStringInfoChar(&buf, '"');
+		appendStringInfoString(&buf, MyProcPort->remote_host);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+		{
+			appendStringInfoChar(&buf, ':');
+			appendStringInfoString(&buf, MyProcPort->remote_port);
+		}
+		appendStringInfoChar(&buf, '"');
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session id */
+	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Line number */
+	appendStringInfo(&buf, "%ld", log_line_number);
+	appendStringInfoChar(&buf, ',');
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData msgbuf;
+		const char *psdisp;
+		int			displen;
+
+		initStringInfo(&msgbuf);
+
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendCSVLiteral(&buf, msgbuf.data);
+
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session start timestamp */
+	start_time = get_formatted_start_time();
+	appendStringInfoString(&buf, start_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Transaction id */
+	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
+	appendStringInfoChar(&buf, ',');
+
+	/* Error severity */
+	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
+	appendStringInfoChar(&buf, ',');
+
+	/* SQL state code */
+	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
+	appendStringInfoChar(&buf, ',');
+
+	/* errmessage */
+	appendCSVLiteral(&buf, edata->message);
+	appendStringInfoChar(&buf, ',');
+
+	/* errdetail or errdetail_log */
+	if (edata->detail_log)
+		appendCSVLiteral(&buf, edata->detail_log);
+	else
+		appendCSVLiteral(&buf, edata->detail);
+	appendStringInfoChar(&buf, ',');
+
+	/* errhint */
+	appendCSVLiteral(&buf, edata->hint);
+	appendStringInfoChar(&buf, ',');
+
+	/* internal query */
+	appendCSVLiteral(&buf, edata->internalquery);
+	appendStringInfoChar(&buf, ',');
+
+	/* if printed internal query, print internal pos too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendStringInfo(&buf, "%d", edata->internalpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* errcontext */
+	if (!edata->hide_ctx)
+		appendCSVLiteral(&buf, edata->context);
+	appendStringInfoChar(&buf, ',');
+
+	/* user query --- only reported if not disabled by the caller */
+	print_stmt = check_log_of_query(edata);
+	if (print_stmt)
+		appendCSVLiteral(&buf, debug_query_string);
+	appendStringInfoChar(&buf, ',');
+	if (print_stmt && edata->cursorpos > 0)
+		appendStringInfo(&buf, "%d", edata->cursorpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		StringInfoData msgbuf;
+
+		initStringInfo(&msgbuf);
+
+		if (edata->funcname && edata->filename)
+			appendStringInfo(&msgbuf, "%s, %s:%d",
+							 edata->funcname, edata->filename,
+							 edata->lineno);
+		else if (edata->filename)
+			appendStringInfo(&msgbuf, "%s:%d",
+							 edata->filename, edata->lineno);
+		appendCSVLiteral(&buf, msgbuf.data);
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* application name */
+	if (application_name)
+		appendCSVLiteral(&buf, application_name);
+
+	appendStringInfoChar(&buf, ',');
+
+	/* backend type */
+	appendCSVLiteral(&buf, get_backend_type_for_log());
+	appendStringInfoChar(&buf, ',');
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendStringInfo(&buf, "%d", leader->pid);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* query id */
+	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
+
+	appendStringInfoChar(&buf, '\n');
+
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+	else
+		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index a162258bab..4406d8deff 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2792,241 +2792,6 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 	}
 }
 
-/*
- * append a CSV'd version of a string to a StringInfo
- * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
- * If it's NULL, append nothing.
- */
-static inline void
-appendCSVLiteral(StringInfo buf, const char *data)
-{
-	const char *p = data;
-	char		c;
-
-	/* avoid confusing an empty string with NULL */
-	if (p == NULL)
-		return;
-
-	appendStringInfoCharMacro(buf, '"');
-	while ((c = *p++) != '\0')
-	{
-		if (c == '"')
-			appendStringInfoCharMacro(buf, '"');
-		appendStringInfoCharMacro(buf, c);
-	}
-	appendStringInfoCharMacro(buf, '"');
-}
-
-/*
- * Constructs the error message, depending on the Errordata it gets, in a CSV
- * format which is described in doc/src/sgml/config.sgml.
- */
-void
-write_csvlog(ErrorData *edata)
-{
-	StringInfoData buf;
-	bool		print_stmt = false;
-	char	   *start_time;
-	char	   *log_time;
-
-	/* static counter for line numbers */
-	static long log_line_number = 0;
-
-	/* has counter been reset in current process? */
-	static int	log_my_pid = 0;
-
-	/*
-	 * This is one of the few places where we'd rather not inherit a static
-	 * variable's value from the postmaster.  But since we will, reset it when
-	 * MyProcPid changes.
-	 */
-	if (log_my_pid != MyProcPid)
-	{
-		log_line_number = 0;
-		log_my_pid = MyProcPid;
-		formatted_start_time[0] = '\0';
-	}
-	log_line_number++;
-
-	initStringInfo(&buf);
-
-	/* timestamp with milliseconds */
-	log_time = get_formatted_log_time();
-	appendStringInfoString(&buf, log_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* username */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->user_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* database name */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->database_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* Process id  */
-	if (MyProcPid != 0)
-		appendStringInfo(&buf, "%d", MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Remote host and port */
-	if (MyProcPort && MyProcPort->remote_host)
-	{
-		appendStringInfoChar(&buf, '"');
-		appendStringInfoString(&buf, MyProcPort->remote_host);
-		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
-		{
-			appendStringInfoChar(&buf, ':');
-			appendStringInfoString(&buf, MyProcPort->remote_port);
-		}
-		appendStringInfoChar(&buf, '"');
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session id */
-	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Line number */
-	appendStringInfo(&buf, "%ld", log_line_number);
-	appendStringInfoChar(&buf, ',');
-
-	/* PS display */
-	if (MyProcPort)
-	{
-		StringInfoData msgbuf;
-		const char *psdisp;
-		int			displen;
-
-		initStringInfo(&msgbuf);
-
-		psdisp = get_ps_display(&displen);
-		appendBinaryStringInfo(&msgbuf, psdisp, displen);
-		appendCSVLiteral(&buf, msgbuf.data);
-
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session start timestamp */
-	start_time = get_formatted_start_time();
-	appendStringInfoString(&buf, start_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* Virtual transaction id */
-	/* keep VXID format in sync with lockfuncs.c */
-	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
-		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Transaction id */
-	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
-	appendStringInfoChar(&buf, ',');
-
-	/* Error severity */
-	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
-	appendStringInfoChar(&buf, ',');
-
-	/* SQL state code */
-	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
-	appendStringInfoChar(&buf, ',');
-
-	/* errmessage */
-	appendCSVLiteral(&buf, edata->message);
-	appendStringInfoChar(&buf, ',');
-
-	/* errdetail or errdetail_log */
-	if (edata->detail_log)
-		appendCSVLiteral(&buf, edata->detail_log);
-	else
-		appendCSVLiteral(&buf, edata->detail);
-	appendStringInfoChar(&buf, ',');
-
-	/* errhint */
-	appendCSVLiteral(&buf, edata->hint);
-	appendStringInfoChar(&buf, ',');
-
-	/* internal query */
-	appendCSVLiteral(&buf, edata->internalquery);
-	appendStringInfoChar(&buf, ',');
-
-	/* if printed internal query, print internal pos too */
-	if (edata->internalpos > 0 && edata->internalquery != NULL)
-		appendStringInfo(&buf, "%d", edata->internalpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* errcontext */
-	if (!edata->hide_ctx)
-		appendCSVLiteral(&buf, edata->context);
-	appendStringInfoChar(&buf, ',');
-
-	/* user query --- only reported if not disabled by the caller */
-	print_stmt = check_log_of_query(edata);
-	if (print_stmt)
-		appendCSVLiteral(&buf, debug_query_string);
-	appendStringInfoChar(&buf, ',');
-	if (print_stmt && edata->cursorpos > 0)
-		appendStringInfo(&buf, "%d", edata->cursorpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* file error location */
-	if (Log_error_verbosity >= PGERROR_VERBOSE)
-	{
-		StringInfoData msgbuf;
-
-		initStringInfo(&msgbuf);
-
-		if (edata->funcname && edata->filename)
-			appendStringInfo(&msgbuf, "%s, %s:%d",
-							 edata->funcname, edata->filename,
-							 edata->lineno);
-		else if (edata->filename)
-			appendStringInfo(&msgbuf, "%s:%d",
-							 edata->filename, edata->lineno);
-		appendCSVLiteral(&buf, msgbuf.data);
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* application name */
-	if (application_name)
-		appendCSVLiteral(&buf, application_name);
-
-	appendStringInfoChar(&buf, ',');
-
-	/* backend type */
-	appendCSVLiteral(&buf, get_backend_type_for_log());
-	appendStringInfoChar(&buf, ',');
-
-	/* leader PID */
-	if (MyProc)
-	{
-		PGPROC	   *leader = MyProc->lockGroupLeader;
-
-		/*
-		 * Show the leader only for active parallel workers.  This leaves out
-		 * the leader of a parallel group.
-		 */
-		if (leader && leader->pid != MyProcPid)
-			appendStringInfo(&buf, "%d", leader->pid);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* query id */
-	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
-
-	appendStringInfoChar(&buf, '\n');
-
-	/* If in the syslogger process, try to write messages direct to file */
-	if (MyBackendType == B_LOGGER)
-		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-	else
-		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-
-	pfree(buf.data);
-}
-
 /*
  * Unpack MAKE_SQLSTATE code. Note that this returns a pointer to a
  * static buffer.
-- 
2.33.1

From c393518a927d08fd82b6063620f25728edd6131e Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Wed, 10 Nov 2021 22:40:33 +0900
Subject: [PATCH v7 3/3] JSON logging

---
 src/include/postmaster/syslogger.h            |   1 +
 src/include/utils/elog.h                      |   2 +
 src/backend/postmaster/syslogger.c            | 107 ++++++-
 src/backend/utils/adt/misc.c                  |   5 +-
 src/backend/utils/error/Makefile              |   3 +-
 src/backend/utils/error/elog.c                |  18 ++
 src/backend/utils/error/jsonlog.c             | 294 ++++++++++++++++++
 src/backend/utils/misc/guc.c                  |   2 +
 src/backend/utils/misc/postgresql.conf.sample |  13 +-
 src/bin/pg_ctl/t/004_logrotate.pl             |  12 +-
 doc/src/sgml/config.sgml                      | 203 +++++++++++-
 11 files changed, 628 insertions(+), 32 deletions(-)
 create mode 100644 src/backend/utils/error/jsonlog.c

diff --git a/src/include/postmaster/syslogger.h b/src/include/postmaster/syslogger.h
index c79dfbeba2..18448b76e5 100644
--- a/src/include/postmaster/syslogger.h
+++ b/src/include/postmaster/syslogger.h
@@ -64,6 +64,7 @@ typedef union
 /* log destinations */
 #define PIPE_PROTO_DEST_STDERR	0x10
 #define PIPE_PROTO_DEST_CSVLOG	0x20
+#define PIPE_PROTO_DEST_JSONLOG	0x40
 
 /* GUC options */
 extern bool Logging_collector;
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 731f3e3cd8..a32c790421 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -436,6 +436,7 @@ extern bool syslog_split_messages;
 #define LOG_DESTINATION_SYSLOG	 2
 #define LOG_DESTINATION_EVENTLOG 4
 #define LOG_DESTINATION_CSVLOG	 8
+#define LOG_DESTINATION_JSONLOG	16
 
 /* Other exported functions */
 extern void DebugFileOpen(void);
@@ -453,6 +454,7 @@ extern void write_pipe_chunks(char *data, int len, int dest);
 
 /* Destination-specific functions */
 extern void write_csvlog(ErrorData *edata);
+extern void write_jsonlog(ErrorData *edata);
 
 #ifdef HAVE_SYSLOG
 extern void set_syslog_parameters(const char *ident, int facility);
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index d1f56b95a4..449d327268 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -86,9 +86,11 @@ static bool pipe_eof_seen = false;
 static bool rotation_disabled = false;
 static FILE *syslogFile = NULL;
 static FILE *csvlogFile = NULL;
+static FILE *jsonlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
 static char *last_sys_file_name = NULL;
 static char *last_csv_file_name = NULL;
+static char *last_json_file_name = NULL;
 
 /*
  * Buffers for saving partial messages from different backends.
@@ -281,6 +283,8 @@ SysLoggerMain(int argc, char *argv[])
 	last_sys_file_name = logfile_getname(first_syslogger_file_time, NULL);
 	if (csvlogFile != NULL)
 		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
+	if (jsonlogFile != NULL)
+		last_json_file_name = logfile_getname(first_syslogger_file_time, ".json");
 
 	/* remember active logfile parameters */
 	currentLogDir = pstrdup(Log_directory);
@@ -367,6 +371,14 @@ SysLoggerMain(int argc, char *argv[])
 				(csvlogFile != NULL))
 				rotation_requested = true;
 
+			/*
+			 * Force a rotation if JSONLOG output was just turned on or off and
+			 * we need to open or close jsonlogFile accordingly.
+			 */
+			if (((Log_destination & LOG_DESTINATION_JSONLOG) != 0) !=
+				(jsonlogFile != NULL))
+				rotation_requested = true;
+
 			/*
 			 * If rotation time parameter changed, reset next rotation time,
 			 * but don't immediately force a rotation.
@@ -417,6 +429,12 @@ SysLoggerMain(int argc, char *argv[])
 				rotation_requested = true;
 				size_rotation_for |= LOG_DESTINATION_CSVLOG;
 			}
+			if (jsonlogFile != NULL &&
+				ftell(jsonlogFile) >= Log_RotationSize * 1024L)
+			{
+				rotation_requested = true;
+				size_rotation_for |= LOG_DESTINATION_JSONLOG;
+			}
 		}
 
 		if (rotation_requested)
@@ -426,7 +444,7 @@ SysLoggerMain(int argc, char *argv[])
 			 * was sent by pg_rotate_logfile() or "pg_ctl logrotate".
 			 */
 			if (!time_based_rotation && size_rotation_for == 0)
-				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG;
+				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG | LOG_DESTINATION_JSONLOG;
 			logfile_rotate(time_based_rotation, size_rotation_for);
 		}
 
@@ -632,6 +650,20 @@ SysLogger_Start(void)
 		pfree(filename);
 	}
 
+	/*
+	 * Likewise for the initial JSON log file, if that's enabled.  (Note that
+	 * we open syslogFile even when only JSON output is nominally enabled,
+	 * since some code paths will write to syslogFile anyway.)
+	 */
+	if (Log_destination & LOG_DESTINATION_JSONLOG)
+	{
+		filename = logfile_getname(first_syslogger_file_time, ".json");
+
+		jsonlogFile = logfile_open(filename, "a", false);
+
+		pfree(filename);
+	}
+
 #ifdef EXEC_BACKEND
 	switch ((sysloggerPid = syslogger_forkexec()))
 #else
@@ -729,6 +761,11 @@ SysLogger_Start(void)
 				fclose(csvlogFile);
 				csvlogFile = NULL;
 			}
+			if (jsonlogFile != NULL)
+			{
+				fclose(jsonlogFile);
+				jsonlogFile = NULL;
+			}
 			return (int) sysloggerPid;
 	}
 
@@ -805,6 +842,7 @@ syslogger_forkexec(void)
 	int			ac = 0;
 	char		filenobuf[32];
 	char		csvfilenobuf[32];
+	char		jsonfilenobuf[32];
 
 	av[ac++] = "postgres";
 	av[ac++] = "--forklog";
@@ -817,6 +855,9 @@ syslogger_forkexec(void)
 	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%d",
 			 syslogger_fdget(csvlogFile));
 	av[ac++] = csvfilenobuf;
+	snprintf(jsonfilenobuf, sizeof(jsonfilenobuf), "%d",
+			 syslogger_fdget(jsonlogFile));
+	av[ac++] = jsonfilenobuf;
 
 	av[ac] = NULL;
 	Assert(ac < lengthof(av));
@@ -834,8 +875,8 @@ syslogger_parseArgs(int argc, char *argv[])
 {
 	int			fd;
 
-	Assert(argc == 5);
-	argv += 3;
+	Assert(argc == 6);
+	argv += 4;
 
 	/*
 	 * Re-open the error output files that were opened by SysLogger_Start().
@@ -848,6 +889,8 @@ syslogger_parseArgs(int argc, char *argv[])
 	syslogFile = syslogger_fdopen(fd);
 	fd = atoi(*argv++);
 	csvlogFile = syslogger_fdopen(fd);
+	fd = atoi(*argv++);
+	jsonlogFile = syslogger_fdopen(fd);
 }
 #endif							/* EXEC_BACKEND */
 
@@ -896,7 +939,9 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 
 		/* Do we have a valid header? */
 		memcpy(&p, cursor, offsetof(PipeProtoHeader, data));
-		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR | PIPE_PROTO_DEST_CSVLOG);
+		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR |
+								PIPE_PROTO_DEST_CSVLOG |
+								PIPE_PROTO_DEST_JSONLOG);
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&
@@ -918,6 +963,8 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 				dest = LOG_DESTINATION_STDERR;
 			else if ((p.flags & PIPE_PROTO_DEST_CSVLOG) != 0)
 				dest = LOG_DESTINATION_CSVLOG;
+			else if ((p.flags & PIPE_PROTO_DEST_JSONLOG) != 0)
+				dest = LOG_DESTINATION_JSONLOG;
 			else
 			{
 				/* this should never happen as of the header validation */
@@ -1097,19 +1144,24 @@ write_syslogger_file(const char *buffer, int count, int destination)
 	FILE	   *logfile;
 
 	/*
-	 * If we're told to write to csvlogFile, but it's not open, dump the data
-	 * to syslogFile (which is always open) instead.  This can happen if CSV
-	 * output is enabled after postmaster start and we've been unable to open
-	 * csvlogFile.  There are also race conditions during a parameter change
-	 * whereby backends might send us CSV output before we open csvlogFile or
-	 * after we close it.  Writing CSV-formatted output to the regular log
-	 * file isn't great, but it beats dropping log output on the floor.
+	 * If we're told to write to a structured log file, but it's not open,
+	 * dump the data to syslogFile (which is always open) instead.  This can
+	 * happen if structured output is enabled after postmaster start and
+	 * we've been unable to open logFile.  There are also race conditions
+	 * during a parameter change whereby backends might send us structured
+	 * output before we open the logFile or after we close it.  Writing
+	 * formatted output to the regular log file isn't great, but it beats
+	 * dropping log output on the floor.
 	 *
-	 * Think not to improve this by trying to open csvlogFile on-the-fly.  Any
+	 * Think not to improve this by trying to open logFile on-the-fly.  Any
 	 * failure in that would lead to recursion.
 	 */
-	logfile = (destination == LOG_DESTINATION_CSVLOG &&
-			   csvlogFile != NULL) ? csvlogFile : syslogFile;
+	if ((destination & LOG_DESTINATION_CSVLOG) && csvlogFile != NULL)
+		logfile = csvlogFile;
+	else if ((destination & LOG_DESTINATION_JSONLOG) && jsonlogFile != NULL)
+		logfile = jsonlogFile;
+	else
+		logfile = syslogFile;
 
 	rc = fwrite(buffer, 1, count, logfile);
 
@@ -1180,7 +1232,8 @@ pipeThread(void *arg)
 		if (Log_RotationSize > 0)
 		{
 			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
-				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
+				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L) ||
+				(jsonlogFile != NULL && ftell(jsonlogFile) >= Log_RotationSize * 1024L))
 				SetLatch(MyLatch);
 		}
 		LeaveCriticalSection(&sysloggerSection);
@@ -1292,6 +1345,8 @@ logfile_rotate_dest(bool time_based_rotation, int size_rotation_for,
 		logFileExt = NULL;
 	else if (target_dest == LOG_DESTINATION_CSVLOG)
 		logFileExt = ".csv";
+	else if (target_dest == LOG_DESTINATION_JSONLOG)
+		logFileExt = ".json";
 	else
 	{
 		/* cannot happen */
@@ -1379,6 +1434,12 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 							 &csvlogFile))
 		return;
 
+	/* file rotation for csvlog */
+	if (!logfile_rotate_dest(time_based_rotation, size_rotation_for, fntime,
+							 LOG_DESTINATION_JSONLOG, &last_json_file_name,
+							 &jsonlogFile))
+		return;
+
 	update_metainfo_datafile();
 
 	set_next_rotation_time();
@@ -1465,7 +1526,8 @@ update_metainfo_datafile(void)
 	mode_t		oumask;
 
 	if (!(Log_destination & LOG_DESTINATION_STDERR) &&
-		!(Log_destination & LOG_DESTINATION_CSVLOG))
+		!(Log_destination & LOG_DESTINATION_CSVLOG) &&
+		!(Log_destination & LOG_DESTINATION_JSONLOG))
 	{
 		if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
 			ereport(LOG,
@@ -1523,6 +1585,19 @@ update_metainfo_datafile(void)
 			return;
 		}
 	}
+
+	if (last_json_file_name && (Log_destination & LOG_DESTINATION_JSONLOG))
+	{
+		if (fprintf(fh, "jsonlog %s\n", last_json_file_name) < 0)
+		{
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not write file \"%s\": %m",
+							LOG_METAINFO_DATAFILE_TMP)));
+			fclose(fh);
+			return;
+		}
+	}
 	fclose(fh);
 
 	if (rename(LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE) != 0)
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 88faf4dfd7..4931859627 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -843,11 +843,12 @@ pg_current_logfile(PG_FUNCTION_ARGS)
 	{
 		logfmt = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
-		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0)
+		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0 &&
+				strcmp(logfmt, "jsonlog") != 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("log format \"%s\" is not supported", logfmt),
-					 errhint("The supported log formats are \"stderr\" and \"csvlog\".")));
+					 errhint("The supported log formats are \"stderr\", \"csvlog\", and \"jsonlog\".")));
 	}
 
 	fd = AllocateFile(LOG_METAINFO_DATAFILE, "r");
diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index ef770dd2f2..65ba61fb3c 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -15,6 +15,7 @@ include $(top_builddir)/src/Makefile.global
 OBJS = \
 	assert.o \
 	csvlog.o \
-	elog.o
+	elog.o \
+	jsonlog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 4406d8deff..39467be917 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2984,6 +2984,22 @@ send_message_to_server_log(ErrorData *edata)
 			fallback_to_stderr = true;
 	}
 
+	/* Write to JSON log, if enabled */
+	if ((Log_destination & LOG_DESTINATION_JSONLOG) != 0)
+	{
+		/*
+		 * Send JSON data if it's safe to do so (syslogger doesn't need the
+		 * pipe).  If this is not possible, fallback to an entry written
+		 * to stderr.
+		 */
+		if (redirection_done || MyBackendType == B_LOGGER)
+		{
+			write_jsonlog(edata);
+		}
+		else
+			fallback_to_stderr = true;
+	}
+
 	/*
 	 * Write to stderr, if enabled or if required because of a previous
 	 * limitation.
@@ -3059,6 +3075,8 @@ write_pipe_chunks(char *data, int len, int dest)
 		p.proto.flags |= PIPE_PROTO_DEST_STDERR;
 	else if (dest == LOG_DESTINATION_CSVLOG)
 		p.proto.flags |= PIPE_PROTO_DEST_CSVLOG;
+	else if (dest == LOG_DESTINATION_JSONLOG)
+		p.proto.flags |= PIPE_PROTO_DEST_JSONLOG;
 
 	/* write all but the last chunk */
 	while (len > PIPE_MAX_PAYLOAD)
diff --git a/src/backend/utils/error/jsonlog.c b/src/backend/utils/error/jsonlog.c
new file mode 100644
index 0000000000..f2101b59ff
--- /dev/null
+++ b/src/backend/utils/error/jsonlog.c
@@ -0,0 +1,294 @@
+/*-------------------------------------------------------------------------
+ *
+ * jsonlog.c
+ *	  JSON logging
+ *
+ * Copyright (c) 2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/jsonlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog.h"
+#include "utils/guc.h"
+#include "utils/json.h"
+#include "utils/ps_status.h"
+
+static void appendJSONKeyValueFmt(StringInfo buf, const char *key,
+								  bool escape_key,
+								  const char *fmt,...) pg_attribute_printf(4, 5);
+
+/*
+ * appendJSONKeyValue
+ * Append to a StringInfo a comma followed by a JSON key and value.
+ * The key is always escaped. The value can be escaped optionally.
+ */
+static void
+appendJSONKeyValue(StringInfo buf, const char *key, const char *value,
+				   bool escape_value)
+{
+	Assert(key != NULL);
+
+	if (value == NULL)
+		return;
+
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+
+	if (escape_value)
+		escape_json(buf, value);
+	else
+		appendStringInfoString(buf, value);
+}
+
+
+/*
+ * appendJSONKeyValueFmt
+ *
+ * Evaluate the fmt string and then invoke appendJSONKeyValue as the
+ * value of the JSON property. Both the key and value will be escaped by
+ * appendJSONKeyValue.
+ */
+static void
+appendJSONKeyValueFmt(StringInfo buf, const char *key,
+					  bool escape_key, const char *fmt,...)
+{
+	int			save_errno = errno;
+	size_t		len = 128;		/* initial assumption about buffer size */
+	char	    *value;
+
+	for (;;)
+	{
+		va_list		args;
+		size_t		newlen;
+
+		/* Allocate result buffer */
+		value = (char *) palloc(len);
+
+		/* Try to format the data. */
+		errno = save_errno;
+		va_start(args, fmt);
+		newlen = pvsnprintf(value, len, fmt, args);
+		va_end(args);
+
+		if (newlen < len)
+			break; /* success */
+
+		/* Release buffer and loop around to try again with larger len. */
+		pfree(value);
+		len = newlen;
+	}
+
+	appendJSONKeyValue(buf, key, value, escape_key);
+
+	/* Clean up */
+	pfree(value);
+}
+
+/*
+ * Write logs in json format.
+ */
+void
+write_jsonlog(ErrorData *edata)
+{
+	StringInfoData	buf;
+	char	   *start_time;
+	char	   *log_time;
+
+	/* static counter for line numbers */
+	static long	log_line_number = 0;
+
+	/* Has the counter been reset in the current process? */
+	static int	log_my_pid = 0;
+
+	/*
+	 * This is one of the few places where we'd rather not inherit a static
+	 * variable's value from the postmaster.  But since we will, reset it when
+	 * MyProcPid changes.
+	 */
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		reset_formatted_start_time();
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* Initialize string */
+	appendStringInfoChar(&buf, '{');
+
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+
+	/*
+	 * First property does not use appendJSONKeyValue as it does not have
+	 * comma prefix.
+	 */
+	escape_json(&buf, "timestamp");
+	appendStringInfoChar(&buf, ':');
+	escape_json(&buf, log_time);
+
+	/* username */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "user", MyProcPort->user_name, true);
+
+	/* database name */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "dbname", MyProcPort->database_name, true);
+
+	/* Process ID */
+	if (MyProcPid != 0)
+		appendJSONKeyValueFmt(&buf, "pid", false, "%d", MyProcPid);
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendJSONKeyValue(&buf, "remote_host", MyProcPort->remote_host, true);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+			appendJSONKeyValue(&buf, "remote_port", MyProcPort->remote_port, false);
+	}
+
+	/* Session id */
+	appendJSONKeyValueFmt(&buf, "session_id", true, "%lx.%x", (long) MyStartTime, MyProcPid);
+
+	/* Line number */
+	appendJSONKeyValueFmt(&buf, "line_num", false, "%ld", log_line_number);
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData	msgbuf;
+		const char	   *psdisp;
+		int				displen;
+
+		initStringInfo(&msgbuf);
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendJSONKeyValue(&buf, "ps", msgbuf.data, true);
+
+		pfree(msgbuf.data);
+	}
+
+	/* session start timestamp */
+	start_time = get_formatted_start_time();
+	appendJSONKeyValue(&buf, "session_start", start_time, true);
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendJSONKeyValueFmt(&buf, "vxid", true, "%d/%u", MyProc->backendId, MyProc->lxid);
+
+	/* Transaction id */
+	appendJSONKeyValueFmt(&buf, "txid", false, "%u", GetTopTransactionIdIfAny());
+
+	/* Error severity */
+	if (edata->elevel)
+		appendJSONKeyValue(&buf, "error_severity",
+						   (char *) error_severity(edata->elevel), true);
+
+	/* SQL state code */
+	if (edata->sqlerrcode)
+		appendJSONKeyValue(&buf, "state_code",
+						   unpack_sql_state(edata->sqlerrcode), true);
+
+	/* errmessage */
+	appendJSONKeyValue(&buf, "message", edata->message, true);
+
+	/* errdetail or error_detail log */
+	if (edata->detail_log)
+		appendJSONKeyValue(&buf, "detail", edata->detail_log, true);
+	else
+		appendJSONKeyValue(&buf, "detail", edata->detail, true);
+
+	/* errhint */
+	if (edata->hint)
+		appendJSONKeyValue(&buf, "hint", edata->hint, true);
+
+	/* internal query */
+	if (edata->internalquery)
+		appendJSONKeyValue(&buf, "internal_query", edata->internalquery, true);
+
+	/* if printed internal query, print internal pos too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendJSONKeyValueFmt(&buf, "internal_position", false, "%u",
+							  edata->internalpos);
+
+	/* errcontext */
+	if (edata->context && !edata->hide_ctx)
+		appendJSONKeyValue(&buf, "context", edata->context, true);
+
+	/* user query --- only reported if not disabled by the caller */
+	if (check_log_of_query(edata))
+	{
+		appendJSONKeyValue(&buf, "statement", debug_query_string, true);
+		if (edata->cursorpos > 0)
+			appendJSONKeyValueFmt(&buf, "cursor_position", false, "%d",
+								  edata->cursorpos);
+	}
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		if (edata->funcname)
+			appendJSONKeyValue(&buf, "func_name", edata->funcname, true);
+		if (edata->filename)
+		{
+			appendJSONKeyValue(&buf, "file_name", edata->filename, true);
+			appendJSONKeyValueFmt(&buf, "file_line_num", false, "%d",
+								  edata->lineno);
+		}
+	}
+
+	/* Application name */
+	if (application_name && application_name[0] != '\0')
+		appendJSONKeyValue(&buf, "application_name", application_name, true);
+
+	/* backend type */
+	appendJSONKeyValue(&buf, "backend_type", get_backend_type_for_log(), true);
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendJSONKeyValueFmt(&buf, "leader_pid", false, "%d", leader->pid);
+	}
+
+	/* query id */
+	appendJSONKeyValueFmt(&buf, "query_id", false, "%lld",
+						  (long long) pgstat_get_my_query_id());
+
+	/* Finish string */
+	appendStringInfoChar(&buf, '}');
+	appendStringInfoChar(&buf, '\n');
+
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+	else
+		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index e91d5a3cfd..f1f8be805c 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -11727,6 +11727,8 @@ check_log_destination(char **newval, void **extra, GucSource source)
 			newlogdest |= LOG_DESTINATION_STDERR;
 		else if (pg_strcasecmp(tok, "csvlog") == 0)
 			newlogdest |= LOG_DESTINATION_CSVLOG;
+		else if (pg_strcasecmp(tok, "jsonlog") == 0)
+			newlogdest |= LOG_DESTINATION_JSONLOG;
 #ifdef HAVE_SYSLOG
 		else if (pg_strcasecmp(tok, "syslog") == 0)
 			newlogdest |= LOG_DESTINATION_SYSLOG;
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 1cbc9feeb6..137827d134 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -432,14 +432,15 @@
 # - Where to Log -
 
 #log_destination = 'stderr'		# Valid values are combinations of
-					# stderr, csvlog, syslog, and eventlog,
-					# depending on platform.  csvlog
-					# requires logging_collector to be on.
+					# stderr, csvlog, jsonlog, syslog, and
+					# eventlog, depending on platform.
+					# csvlog and jsonlog require
+					# logging_collector to be on.
 
 # This is used when logging to stderr:
-#logging_collector = off		# Enable capturing of stderr and csvlog
-					# into log files. Required to be on for
-					# csvlogs.
+#logging_collector = off		# Enable capturing of stderr, jsonlog
+					# and csvlog into log files. Required
+					# to be on for csvlogs and jsonlogs.
 					# (change requires restart)
 
 # These are only used if logging_collector is on:
diff --git a/src/bin/pg_ctl/t/004_logrotate.pl b/src/bin/pg_ctl/t/004_logrotate.pl
index 3813a3b1fd..e2e0a27d73 100644
--- a/src/bin/pg_ctl/t/004_logrotate.pl
+++ b/src/bin/pg_ctl/t/004_logrotate.pl
@@ -6,7 +6,7 @@ use warnings;
 
 use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
-use Test::More tests => 10;
+use Test::More tests => 14;
 use Time::HiRes qw(usleep);
 
 # Extract the file name of a $format from the contents of
@@ -65,7 +65,7 @@ $node->init();
 $node->append_conf(
 	'postgresql.conf', qq(
 logging_collector = on
-log_destination = 'stderr, csvlog'
+log_destination = 'stderr, csvlog, jsonlog'
 # these ensure stability of test results:
 log_rotation_age = 0
 lc_messages = 'C'
@@ -96,11 +96,13 @@ note "current_logfiles = $current_logfiles";
 like(
 	$current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'current_logfiles is sane');
 
 check_log_pattern('stderr', $current_logfiles, 'division by zero', $node);
 check_log_pattern('csvlog', $current_logfiles, 'division by zero', $node);
+check_log_pattern('jsonlog', $current_logfiles, 'division by zero', $node);
 
 # Sleep 2 seconds and ask for log rotation; this should result in
 # output into a different log file name.
@@ -122,7 +124,8 @@ note "now current_logfiles = $new_current_logfiles";
 like(
 	$new_current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'new current_logfiles is sane');
 
 # Verify that log output gets to this file, too
@@ -130,5 +133,6 @@ $node->psql('postgres', 'fee fi fo fum');
 
 check_log_pattern('stderr', $new_current_logfiles, 'syntax error', $node);
 check_log_pattern('csvlog', $new_current_logfiles, 'syntax error', $node);
+check_log_pattern('jsonlog', $new_current_logfiles, 'syntax error', $node);
 
 $node->stop();
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 3f806740d5..7e00cdc988 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5928,7 +5928,8 @@ SELECT * FROM parent WHERE key = 2400;
        <para>
         <productname>PostgreSQL</productname> supports several methods
          for logging server messages, including
-         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem> and
+         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem>,
+         <systemitem>jsonlog</systemitem>, and
          <systemitem>syslog</systemitem>. On Windows,
          <systemitem>eventlog</systemitem> is also supported. Set this
          parameter to a list of desired log destinations separated by
@@ -5946,6 +5947,14 @@ SELECT * FROM parent WHERE key = 2400;
         <xref linkend="guc-logging-collector"/> must be enabled to generate
         CSV-format log output.
        </para>
+       <para>
+        If <systemitem>jsonlog</systemitem> is included in <varname>log_destination</varname>,
+        log entries are output in <acronym>JSON</acronym> format, which is convenient for
+        loading logs into programs.
+        See <xref linkend="runtime-config-logging-jsonlog"/> for details.
+        <xref linkend="guc-logging-collector"/> must be enabled to generate
+        JSON-format log output.
+       </para>
        <para>
         When either <systemitem>stderr</systemitem> or
         <systemitem>csvlog</systemitem> are included, the file
@@ -5957,13 +5966,14 @@ SELECT * FROM parent WHERE key = 2400;
 <programlisting>
 stderr log/postgresql.log
 csvlog log/postgresql.csv
+jsonlog log/postgresql.json
 </programlisting>
 
         <filename>current_logfiles</filename> is recreated when a new log file
         is created as an effect of rotation, and
         when <varname>log_destination</varname> is reloaded.  It is removed when
-        neither <systemitem>stderr</systemitem>
-        nor <systemitem>csvlog</systemitem> are included
+        none of <systemitem>stderr</systemitem>,
+        <systemitem>csvlog</systemitem>, <systemitem>jsonlog</systemitem> are included
         in <varname>log_destination</varname>, and when the logging collector is
         disabled.
        </para>
@@ -6103,6 +6113,13 @@ local0.*    /var/log/postgresql
         (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
         replaced instead.)
        </para>
+       <para>
+        If JSON-format output is enabled in <varname>log_destination</varname>,
+        <literal>.json</literal> will be appended to the timestamped
+        log file name to create the file name for JSON-format output.
+        (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
+        replaced instead.)
+       </para>
        <para>
         This parameter can only be set in the <filename>postgresql.conf</filename>
         file or on the server command line.
@@ -7465,6 +7482,186 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         </orderedlist>
       </para>
     </sect2>
+     <sect2 id="runtime-config-logging-jsonlog">
+     <title>Using JSON-Format Log Output</title>
+
+     <para>
+      Including <literal>jsonlog</literal> in the <varname>log_destination</varname> list
+      provides a convenient way to import log files into many different programs.
+      This option emits log lines in (<acronym>JSON</acronym>) format.
+     </para>
+
+     <para>
+      String fields with null values are excluded from output.
+      Additional fields may be added in the future. User applications that process jsonlog
+      output should ignore unknown fields.
+     </para>
+
+     <para>
+      Each log line is serialized as a JSON object as of the following
+      set of keys with their values.
+     </para>
+
+     <table>
+      <title>Keys and values of JSON log entries</title>
+      <tgroup cols="3">
+       <thead>
+        <row>
+         <entry>Key name</entry>
+         <entry>Type</entry>
+         <entry>Description</entry>
+        </row>
+       </thead>
+       <tbody>
+        <row>
+         <entry><literal>timestamp</literal></entry>
+         <entry>string</entry>
+         <entry>Time stamp with milliseconds</entry>
+        </row>
+        <row>
+         <entry><literal>user</literal></entry>
+         <entry>string</entry>
+         <entry>User name</entry>
+        </row>
+        <row>
+         <entry><literal>dbname</literal></entry>
+         <entry>string</entry>
+         <entry>Database name</entry>
+        </row>
+        <row>
+         <entry><literal>pid</literal></entry>
+         <entry>number</entry>
+         <entry>Process ID</entry>
+        </row>
+        <row>
+         <entry><literal>remote_host</literal></entry>
+         <entry>string</entry>
+         <entry>Client host</entry>
+        </row>
+        <row>
+         <entry><literal>remote_port</literal></entry>
+         <entry>number</entry>
+         <entry>Client port</entry>
+        </row>
+        <row>
+         <entry><literal>session_id</literal></entry>
+         <entry>string</entry>
+         <entry>Session ID</entry>
+        </row>
+        <row>
+         <entry><literal>line_num</literal></entry>
+         <entry>number</entry>
+         <entry>Per-session line number</entry>
+        </row>
+        <row>
+         <entry><literal>ps</literal></entry>
+         <entry>string</entry>
+         <entry>Current ps display</entry>
+        </row>
+        <row>
+         <entry><literal>session_start</literal></entry>
+         <entry>string</entry>
+         <entry>Session start time</entry>
+        </row>
+        <row>
+         <entry><literal>vxid</literal></entry>
+         <entry>string</entry>
+         <entry>Virtual transaction ID</entry>
+        </row>
+        <row>
+         <entry><literal>txid</literal></entry>
+         <entry>string</entry>
+         <entry>Regular transaction ID</entry>
+        </row>
+        <row>
+         <entry><literal>error_severity</literal></entry>
+         <entry>string</entry>
+         <entry>Error severity</entry>
+        </row>
+        <row>
+         <entry><literal>state_code</literal></entry>
+         <entry>string</entry>
+         <entry>SQLSTATE code</entry>
+        </row>
+        <row>
+         <entry><literal>message</literal></entry>
+         <entry>string</entry>
+         <entry>Error message</entry>
+        </row>
+        <row>
+         <entry><literal>detail</literal></entry>
+         <entry>string</entry>
+         <entry>Error message detail</entry>
+        </row>
+        <row>
+         <entry><literal>hint</literal></entry>
+         <entry>string</entry>
+         <entry>Error message hint</entry>
+        </row>
+        <row>
+         <entry><literal>internal_query</literal></entry>
+         <entry>string</entry>
+         <entry>Internal query that led to the error</entry>
+        </row>
+        <row>
+         <entry><literal>internal_position</literal></entry>
+         <entry>number</entry>
+         <entry>Cursor index into internal query</entry>
+        </row>
+        <row>
+         <entry><literal>context</literal></entry>
+         <entry>string</entry>
+         <entry>Error context</entry>
+        </row>
+        <row>
+         <entry><literal>statement</literal></entry>
+         <entry>string</entry>
+         <entry>Client-supplied query string</entry>
+        </row>
+        <row>
+         <entry><literal>cursor_position</literal></entry>
+         <entry>string</entry>
+         <entry>Cursor index into query string</entry>
+        </row>
+        <row>
+         <entry><literal>func_name</literal></entry>
+         <entry>string</entry>
+         <entry>Error location function name</entry>
+        </row>
+        <row>
+         <entry><literal>file_name</literal></entry>
+         <entry>string</entry>
+         <entry>File name of error location</entry>
+        </row>
+        <row>
+         <entry><literal>file_line_num</literal></entry>
+         <entry>number</entry>
+         <entry>File line number of the error location</entry>
+        </row>
+        <row>
+         <entry><literal>application_name</literal></entry>
+         <entry>string</entry>
+         <entry>Client application name</entry>
+        </row>
+        <row>
+         <entry><literal>backend_type</literal></entry>
+         <entry>string</entry>
+         <entry>Type of backend</entry>
+        </row>
+        <row>
+         <entry><literal>leader_pid</literal></entry>
+         <entry>number</entry>
+         <entry>Process ID of leader for active parallel workers</entry>
+        </row>
+        <row>
+         <entry><literal>query_id</literal></entry>
+         <entry>number</entry>
+         <entry>Query ID</entry>
+        </row>
+       </tbody>
+      </tgroup>
+     </table>
+    </sect2>
 
    <sect2>
     <title>Process Title</title>
-- 
2.33.1

From 7417ee1ac6e6ee4d95f9b2e5f0b411c94515a957 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Thu, 11 Nov 2021 09:02:33 +0900
Subject: [PATCH v8 3/3] JSON logging

---
 src/include/postmaster/syslogger.h            |   1 +
 src/include/utils/elog.h                      |   2 +
 src/backend/postmaster/syslogger.c            | 107 ++++++-
 src/backend/utils/adt/misc.c                  |   5 +-
 src/backend/utils/error/Makefile              |   3 +-
 src/backend/utils/error/elog.c                |  18 ++
 src/backend/utils/error/jsonlog.c             | 294 ++++++++++++++++++
 src/backend/utils/misc/guc.c                  |   4 +-
 src/backend/utils/misc/postgresql.conf.sample |  13 +-
 src/bin/pg_ctl/t/004_logrotate.pl             |  16 +-
 doc/src/sgml/config.sgml                      | 203 +++++++++++-
 11 files changed, 631 insertions(+), 35 deletions(-)
 create mode 100644 src/backend/utils/error/jsonlog.c

diff --git a/src/include/postmaster/syslogger.h b/src/include/postmaster/syslogger.h
index c79dfbeba2..18448b76e5 100644
--- a/src/include/postmaster/syslogger.h
+++ b/src/include/postmaster/syslogger.h
@@ -64,6 +64,7 @@ typedef union
 /* log destinations */
 #define PIPE_PROTO_DEST_STDERR	0x10
 #define PIPE_PROTO_DEST_CSVLOG	0x20
+#define PIPE_PROTO_DEST_JSONLOG	0x40
 
 /* GUC options */
 extern bool Logging_collector;
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 731f3e3cd8..a32c790421 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -436,6 +436,7 @@ extern bool syslog_split_messages;
 #define LOG_DESTINATION_SYSLOG	 2
 #define LOG_DESTINATION_EVENTLOG 4
 #define LOG_DESTINATION_CSVLOG	 8
+#define LOG_DESTINATION_JSONLOG	16
 
 /* Other exported functions */
 extern void DebugFileOpen(void);
@@ -453,6 +454,7 @@ extern void write_pipe_chunks(char *data, int len, int dest);
 
 /* Destination-specific functions */
 extern void write_csvlog(ErrorData *edata);
+extern void write_jsonlog(ErrorData *edata);
 
 #ifdef HAVE_SYSLOG
 extern void set_syslog_parameters(const char *ident, int facility);
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index d1f56b95a4..0cf03bcdef 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -86,9 +86,11 @@ static bool pipe_eof_seen = false;
 static bool rotation_disabled = false;
 static FILE *syslogFile = NULL;
 static FILE *csvlogFile = NULL;
+static FILE *jsonlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
 static char *last_sys_file_name = NULL;
 static char *last_csv_file_name = NULL;
+static char *last_json_file_name = NULL;
 
 /*
  * Buffers for saving partial messages from different backends.
@@ -281,6 +283,8 @@ SysLoggerMain(int argc, char *argv[])
 	last_sys_file_name = logfile_getname(first_syslogger_file_time, NULL);
 	if (csvlogFile != NULL)
 		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
+	if (jsonlogFile != NULL)
+		last_json_file_name = logfile_getname(first_syslogger_file_time, ".json");
 
 	/* remember active logfile parameters */
 	currentLogDir = pstrdup(Log_directory);
@@ -367,6 +371,14 @@ SysLoggerMain(int argc, char *argv[])
 				(csvlogFile != NULL))
 				rotation_requested = true;
 
+			/*
+			 * Force a rotation if JSONLOG output was just turned on or off and
+			 * we need to open or close jsonlogFile accordingly.
+			 */
+			if (((Log_destination & LOG_DESTINATION_JSONLOG) != 0) !=
+				(jsonlogFile != NULL))
+				rotation_requested = true;
+
 			/*
 			 * If rotation time parameter changed, reset next rotation time,
 			 * but don't immediately force a rotation.
@@ -417,6 +429,12 @@ SysLoggerMain(int argc, char *argv[])
 				rotation_requested = true;
 				size_rotation_for |= LOG_DESTINATION_CSVLOG;
 			}
+			if (jsonlogFile != NULL &&
+				ftell(jsonlogFile) >= Log_RotationSize * 1024L)
+			{
+				rotation_requested = true;
+				size_rotation_for |= LOG_DESTINATION_JSONLOG;
+			}
 		}
 
 		if (rotation_requested)
@@ -426,7 +444,7 @@ SysLoggerMain(int argc, char *argv[])
 			 * was sent by pg_rotate_logfile() or "pg_ctl logrotate".
 			 */
 			if (!time_based_rotation && size_rotation_for == 0)
-				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG;
+				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG | LOG_DESTINATION_JSONLOG;
 			logfile_rotate(time_based_rotation, size_rotation_for);
 		}
 
@@ -632,6 +650,20 @@ SysLogger_Start(void)
 		pfree(filename);
 	}
 
+	/*
+	 * Likewise for the initial JSON log file, if that's enabled.  (Note that
+	 * we open syslogFile even when only JSON output is nominally enabled,
+	 * since some code paths will write to syslogFile anyway.)
+	 */
+	if (Log_destination & LOG_DESTINATION_JSONLOG)
+	{
+		filename = logfile_getname(first_syslogger_file_time, ".json");
+
+		jsonlogFile = logfile_open(filename, "a", false);
+
+		pfree(filename);
+	}
+
 #ifdef EXEC_BACKEND
 	switch ((sysloggerPid = syslogger_forkexec()))
 #else
@@ -729,6 +761,11 @@ SysLogger_Start(void)
 				fclose(csvlogFile);
 				csvlogFile = NULL;
 			}
+			if (jsonlogFile != NULL)
+			{
+				fclose(jsonlogFile);
+				jsonlogFile = NULL;
+			}
 			return (int) sysloggerPid;
 	}
 
@@ -805,6 +842,7 @@ syslogger_forkexec(void)
 	int			ac = 0;
 	char		filenobuf[32];
 	char		csvfilenobuf[32];
+	char		jsonfilenobuf[32];
 
 	av[ac++] = "postgres";
 	av[ac++] = "--forklog";
@@ -817,6 +855,9 @@ syslogger_forkexec(void)
 	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%d",
 			 syslogger_fdget(csvlogFile));
 	av[ac++] = csvfilenobuf;
+	snprintf(jsonfilenobuf, sizeof(jsonfilenobuf), "%d",
+			 syslogger_fdget(jsonlogFile));
+	av[ac++] = jsonfilenobuf;
 
 	av[ac] = NULL;
 	Assert(ac < lengthof(av));
@@ -834,8 +875,8 @@ syslogger_parseArgs(int argc, char *argv[])
 {
 	int			fd;
 
-	Assert(argc == 5);
-	argv += 3;
+	Assert(argc == 6);
+	argv += 4;
 
 	/*
 	 * Re-open the error output files that were opened by SysLogger_Start().
@@ -848,6 +889,8 @@ syslogger_parseArgs(int argc, char *argv[])
 	syslogFile = syslogger_fdopen(fd);
 	fd = atoi(*argv++);
 	csvlogFile = syslogger_fdopen(fd);
+	fd = atoi(*argv++);
+	jsonlogFile = syslogger_fdopen(fd);
 }
 #endif							/* EXEC_BACKEND */
 
@@ -896,7 +939,9 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 
 		/* Do we have a valid header? */
 		memcpy(&p, cursor, offsetof(PipeProtoHeader, data));
-		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR | PIPE_PROTO_DEST_CSVLOG);
+		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR |
+								PIPE_PROTO_DEST_CSVLOG |
+								PIPE_PROTO_DEST_JSONLOG);
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&
@@ -918,6 +963,8 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 				dest = LOG_DESTINATION_STDERR;
 			else if ((p.flags & PIPE_PROTO_DEST_CSVLOG) != 0)
 				dest = LOG_DESTINATION_CSVLOG;
+			else if ((p.flags & PIPE_PROTO_DEST_JSONLOG) != 0)
+				dest = LOG_DESTINATION_JSONLOG;
 			else
 			{
 				/* this should never happen as of the header validation */
@@ -1097,19 +1144,24 @@ write_syslogger_file(const char *buffer, int count, int destination)
 	FILE	   *logfile;
 
 	/*
-	 * If we're told to write to csvlogFile, but it's not open, dump the data
-	 * to syslogFile (which is always open) instead.  This can happen if CSV
-	 * output is enabled after postmaster start and we've been unable to open
-	 * csvlogFile.  There are also race conditions during a parameter change
-	 * whereby backends might send us CSV output before we open csvlogFile or
-	 * after we close it.  Writing CSV-formatted output to the regular log
-	 * file isn't great, but it beats dropping log output on the floor.
+	 * If we're told to write to a structured log file, but it's not open,
+	 * dump the data to syslogFile (which is always open) instead.  This can
+	 * happen if structured output is enabled after postmaster start and
+	 * we've been unable to open logFile.  There are also race conditions
+	 * during a parameter change whereby backends might send us structured
+	 * output before we open the logFile or after we close it.  Writing
+	 * formatted output to the regular log file isn't great, but it beats
+	 * dropping log output on the floor.
 	 *
-	 * Think not to improve this by trying to open csvlogFile on-the-fly.  Any
+	 * Think not to improve this by trying to open logFile on-the-fly.  Any
 	 * failure in that would lead to recursion.
 	 */
-	logfile = (destination == LOG_DESTINATION_CSVLOG &&
-			   csvlogFile != NULL) ? csvlogFile : syslogFile;
+	if ((destination & LOG_DESTINATION_CSVLOG) && csvlogFile != NULL)
+		logfile = csvlogFile;
+	else if ((destination & LOG_DESTINATION_JSONLOG) && jsonlogFile != NULL)
+		logfile = jsonlogFile;
+	else
+		logfile = syslogFile;
 
 	rc = fwrite(buffer, 1, count, logfile);
 
@@ -1180,7 +1232,8 @@ pipeThread(void *arg)
 		if (Log_RotationSize > 0)
 		{
 			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
-				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
+				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L) ||
+				(jsonlogFile != NULL && ftell(jsonlogFile) >= Log_RotationSize * 1024L))
 				SetLatch(MyLatch);
 		}
 		LeaveCriticalSection(&sysloggerSection);
@@ -1292,6 +1345,8 @@ logfile_rotate_dest(bool time_based_rotation, int size_rotation_for,
 		logFileExt = NULL;
 	else if (target_dest == LOG_DESTINATION_CSVLOG)
 		logFileExt = ".csv";
+	else if (target_dest == LOG_DESTINATION_JSONLOG)
+		logFileExt = ".json";
 	else
 	{
 		/* cannot happen */
@@ -1379,6 +1434,12 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 							 &csvlogFile))
 		return;
 
+	/* file rotation for jsonlog */
+	if (!logfile_rotate_dest(time_based_rotation, size_rotation_for, fntime,
+							 LOG_DESTINATION_JSONLOG, &last_json_file_name,
+							 &jsonlogFile))
+		return;
+
 	update_metainfo_datafile();
 
 	set_next_rotation_time();
@@ -1465,7 +1526,8 @@ update_metainfo_datafile(void)
 	mode_t		oumask;
 
 	if (!(Log_destination & LOG_DESTINATION_STDERR) &&
-		!(Log_destination & LOG_DESTINATION_CSVLOG))
+		!(Log_destination & LOG_DESTINATION_CSVLOG) &&
+		!(Log_destination & LOG_DESTINATION_JSONLOG))
 	{
 		if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
 			ereport(LOG,
@@ -1523,6 +1585,19 @@ update_metainfo_datafile(void)
 			return;
 		}
 	}
+
+	if (last_json_file_name && (Log_destination & LOG_DESTINATION_JSONLOG))
+	{
+		if (fprintf(fh, "jsonlog %s\n", last_json_file_name) < 0)
+		{
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not write file \"%s\": %m",
+							LOG_METAINFO_DATAFILE_TMP)));
+			fclose(fh);
+			return;
+		}
+	}
 	fclose(fh);
 
 	if (rename(LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE) != 0)
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 88faf4dfd7..4931859627 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -843,11 +843,12 @@ pg_current_logfile(PG_FUNCTION_ARGS)
 	{
 		logfmt = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
-		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0)
+		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0 &&
+				strcmp(logfmt, "jsonlog") != 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("log format \"%s\" is not supported", logfmt),
-					 errhint("The supported log formats are \"stderr\" and \"csvlog\".")));
+					 errhint("The supported log formats are \"stderr\", \"csvlog\", and \"jsonlog\".")));
 	}
 
 	fd = AllocateFile(LOG_METAINFO_DATAFILE, "r");
diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index ef770dd2f2..65ba61fb3c 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -15,6 +15,7 @@ include $(top_builddir)/src/Makefile.global
 OBJS = \
 	assert.o \
 	csvlog.o \
-	elog.o
+	elog.o \
+	jsonlog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 4406d8deff..39467be917 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2984,6 +2984,22 @@ send_message_to_server_log(ErrorData *edata)
 			fallback_to_stderr = true;
 	}
 
+	/* Write to JSON log, if enabled */
+	if ((Log_destination & LOG_DESTINATION_JSONLOG) != 0)
+	{
+		/*
+		 * Send JSON data if it's safe to do so (syslogger doesn't need the
+		 * pipe).  If this is not possible, fallback to an entry written
+		 * to stderr.
+		 */
+		if (redirection_done || MyBackendType == B_LOGGER)
+		{
+			write_jsonlog(edata);
+		}
+		else
+			fallback_to_stderr = true;
+	}
+
 	/*
 	 * Write to stderr, if enabled or if required because of a previous
 	 * limitation.
@@ -3059,6 +3075,8 @@ write_pipe_chunks(char *data, int len, int dest)
 		p.proto.flags |= PIPE_PROTO_DEST_STDERR;
 	else if (dest == LOG_DESTINATION_CSVLOG)
 		p.proto.flags |= PIPE_PROTO_DEST_CSVLOG;
+	else if (dest == LOG_DESTINATION_JSONLOG)
+		p.proto.flags |= PIPE_PROTO_DEST_JSONLOG;
 
 	/* write all but the last chunk */
 	while (len > PIPE_MAX_PAYLOAD)
diff --git a/src/backend/utils/error/jsonlog.c b/src/backend/utils/error/jsonlog.c
new file mode 100644
index 0000000000..f2101b59ff
--- /dev/null
+++ b/src/backend/utils/error/jsonlog.c
@@ -0,0 +1,294 @@
+/*-------------------------------------------------------------------------
+ *
+ * jsonlog.c
+ *	  JSON logging
+ *
+ * Copyright (c) 2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/jsonlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog.h"
+#include "utils/guc.h"
+#include "utils/json.h"
+#include "utils/ps_status.h"
+
+static void appendJSONKeyValueFmt(StringInfo buf, const char *key,
+								  bool escape_key,
+								  const char *fmt,...) pg_attribute_printf(4, 5);
+
+/*
+ * appendJSONKeyValue
+ * Append to a StringInfo a comma followed by a JSON key and value.
+ * The key is always escaped. The value can be escaped optionally.
+ */
+static void
+appendJSONKeyValue(StringInfo buf, const char *key, const char *value,
+				   bool escape_value)
+{
+	Assert(key != NULL);
+
+	if (value == NULL)
+		return;
+
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+
+	if (escape_value)
+		escape_json(buf, value);
+	else
+		appendStringInfoString(buf, value);
+}
+
+
+/*
+ * appendJSONKeyValueFmt
+ *
+ * Evaluate the fmt string and then invoke appendJSONKeyValue as the
+ * value of the JSON property. Both the key and value will be escaped by
+ * appendJSONKeyValue.
+ */
+static void
+appendJSONKeyValueFmt(StringInfo buf, const char *key,
+					  bool escape_key, const char *fmt,...)
+{
+	int			save_errno = errno;
+	size_t		len = 128;		/* initial assumption about buffer size */
+	char	    *value;
+
+	for (;;)
+	{
+		va_list		args;
+		size_t		newlen;
+
+		/* Allocate result buffer */
+		value = (char *) palloc(len);
+
+		/* Try to format the data. */
+		errno = save_errno;
+		va_start(args, fmt);
+		newlen = pvsnprintf(value, len, fmt, args);
+		va_end(args);
+
+		if (newlen < len)
+			break; /* success */
+
+		/* Release buffer and loop around to try again with larger len. */
+		pfree(value);
+		len = newlen;
+	}
+
+	appendJSONKeyValue(buf, key, value, escape_key);
+
+	/* Clean up */
+	pfree(value);
+}
+
+/*
+ * Write logs in json format.
+ */
+void
+write_jsonlog(ErrorData *edata)
+{
+	StringInfoData	buf;
+	char	   *start_time;
+	char	   *log_time;
+
+	/* static counter for line numbers */
+	static long	log_line_number = 0;
+
+	/* Has the counter been reset in the current process? */
+	static int	log_my_pid = 0;
+
+	/*
+	 * This is one of the few places where we'd rather not inherit a static
+	 * variable's value from the postmaster.  But since we will, reset it when
+	 * MyProcPid changes.
+	 */
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		reset_formatted_start_time();
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* Initialize string */
+	appendStringInfoChar(&buf, '{');
+
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+
+	/*
+	 * First property does not use appendJSONKeyValue as it does not have
+	 * comma prefix.
+	 */
+	escape_json(&buf, "timestamp");
+	appendStringInfoChar(&buf, ':');
+	escape_json(&buf, log_time);
+
+	/* username */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "user", MyProcPort->user_name, true);
+
+	/* database name */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "dbname", MyProcPort->database_name, true);
+
+	/* Process ID */
+	if (MyProcPid != 0)
+		appendJSONKeyValueFmt(&buf, "pid", false, "%d", MyProcPid);
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendJSONKeyValue(&buf, "remote_host", MyProcPort->remote_host, true);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+			appendJSONKeyValue(&buf, "remote_port", MyProcPort->remote_port, false);
+	}
+
+	/* Session id */
+	appendJSONKeyValueFmt(&buf, "session_id", true, "%lx.%x", (long) MyStartTime, MyProcPid);
+
+	/* Line number */
+	appendJSONKeyValueFmt(&buf, "line_num", false, "%ld", log_line_number);
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData	msgbuf;
+		const char	   *psdisp;
+		int				displen;
+
+		initStringInfo(&msgbuf);
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendJSONKeyValue(&buf, "ps", msgbuf.data, true);
+
+		pfree(msgbuf.data);
+	}
+
+	/* session start timestamp */
+	start_time = get_formatted_start_time();
+	appendJSONKeyValue(&buf, "session_start", start_time, true);
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendJSONKeyValueFmt(&buf, "vxid", true, "%d/%u", MyProc->backendId, MyProc->lxid);
+
+	/* Transaction id */
+	appendJSONKeyValueFmt(&buf, "txid", false, "%u", GetTopTransactionIdIfAny());
+
+	/* Error severity */
+	if (edata->elevel)
+		appendJSONKeyValue(&buf, "error_severity",
+						   (char *) error_severity(edata->elevel), true);
+
+	/* SQL state code */
+	if (edata->sqlerrcode)
+		appendJSONKeyValue(&buf, "state_code",
+						   unpack_sql_state(edata->sqlerrcode), true);
+
+	/* errmessage */
+	appendJSONKeyValue(&buf, "message", edata->message, true);
+
+	/* errdetail or error_detail log */
+	if (edata->detail_log)
+		appendJSONKeyValue(&buf, "detail", edata->detail_log, true);
+	else
+		appendJSONKeyValue(&buf, "detail", edata->detail, true);
+
+	/* errhint */
+	if (edata->hint)
+		appendJSONKeyValue(&buf, "hint", edata->hint, true);
+
+	/* internal query */
+	if (edata->internalquery)
+		appendJSONKeyValue(&buf, "internal_query", edata->internalquery, true);
+
+	/* if printed internal query, print internal pos too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendJSONKeyValueFmt(&buf, "internal_position", false, "%u",
+							  edata->internalpos);
+
+	/* errcontext */
+	if (edata->context && !edata->hide_ctx)
+		appendJSONKeyValue(&buf, "context", edata->context, true);
+
+	/* user query --- only reported if not disabled by the caller */
+	if (check_log_of_query(edata))
+	{
+		appendJSONKeyValue(&buf, "statement", debug_query_string, true);
+		if (edata->cursorpos > 0)
+			appendJSONKeyValueFmt(&buf, "cursor_position", false, "%d",
+								  edata->cursorpos);
+	}
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		if (edata->funcname)
+			appendJSONKeyValue(&buf, "func_name", edata->funcname, true);
+		if (edata->filename)
+		{
+			appendJSONKeyValue(&buf, "file_name", edata->filename, true);
+			appendJSONKeyValueFmt(&buf, "file_line_num", false, "%d",
+								  edata->lineno);
+		}
+	}
+
+	/* Application name */
+	if (application_name && application_name[0] != '\0')
+		appendJSONKeyValue(&buf, "application_name", application_name, true);
+
+	/* backend type */
+	appendJSONKeyValue(&buf, "backend_type", get_backend_type_for_log(), true);
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendJSONKeyValueFmt(&buf, "leader_pid", false, "%d", leader->pid);
+	}
+
+	/* query id */
+	appendJSONKeyValueFmt(&buf, "query_id", false, "%lld",
+						  (long long) pgstat_get_my_query_id());
+
+	/* Finish string */
+	appendStringInfoChar(&buf, '}');
+	appendStringInfoChar(&buf, '\n');
+
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+	else
+		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index f9504d3aec..2c70804fae 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4264,7 +4264,7 @@ static struct config_string ConfigureNamesString[] =
 		{"log_destination", PGC_SIGHUP, LOGGING_WHERE,
 			gettext_noop("Sets the destination for server log output."),
 			gettext_noop("Valid values are combinations of \"stderr\", "
-						 "\"syslog\", \"csvlog\", and \"eventlog\", "
+						 "\"syslog\", \"csvlog\", \"jsonlog\" and \"eventlog\", "
 						 "depending on the platform."),
 			GUC_LIST_INPUT
 		},
@@ -11740,6 +11740,8 @@ check_log_destination(char **newval, void **extra, GucSource source)
 			newlogdest |= LOG_DESTINATION_STDERR;
 		else if (pg_strcasecmp(tok, "csvlog") == 0)
 			newlogdest |= LOG_DESTINATION_CSVLOG;
+		else if (pg_strcasecmp(tok, "jsonlog") == 0)
+			newlogdest |= LOG_DESTINATION_JSONLOG;
 #ifdef HAVE_SYSLOG
 		else if (pg_strcasecmp(tok, "syslog") == 0)
 			newlogdest |= LOG_DESTINATION_SYSLOG;
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index a1acd46b61..817d5f5324 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -432,14 +432,15 @@
 # - Where to Log -
 
 #log_destination = 'stderr'		# Valid values are combinations of
-					# stderr, csvlog, syslog, and eventlog,
-					# depending on platform.  csvlog
-					# requires logging_collector to be on.
+					# stderr, csvlog, jsonlog, syslog, and
+					# eventlog, depending on platform.
+					# csvlog and jsonlog require
+					# logging_collector to be on.
 
 # This is used when logging to stderr:
-#logging_collector = off		# Enable capturing of stderr and csvlog
-					# into log files. Required to be on for
-					# csvlogs.
+#logging_collector = off		# Enable capturing of stderr, jsonlog
+					# and csvlog into log files. Required
+					# to be on for csvlogs and jsonlogs.
 					# (change requires restart)
 
 # These are only used if logging_collector is on:
diff --git a/src/bin/pg_ctl/t/004_logrotate.pl b/src/bin/pg_ctl/t/004_logrotate.pl
index 3813a3b1fd..4b6ccd8e9b 100644
--- a/src/bin/pg_ctl/t/004_logrotate.pl
+++ b/src/bin/pg_ctl/t/004_logrotate.pl
@@ -6,7 +6,7 @@ use warnings;
 
 use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
-use Test::More tests => 10;
+use Test::More tests => 14;
 use Time::HiRes qw(usleep);
 
 # Extract the file name of a $format from the contents of
@@ -39,7 +39,7 @@ sub check_log_pattern
 	my $node     = shift;
 	my $lfname   = fetch_file_name($logfiles, $format);
 
-	my $max_attempts = 180 * 10;
+	my $max_attempts = 360 * 10;
 
 	my $logcontents;
 	for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
@@ -65,7 +65,7 @@ $node->init();
 $node->append_conf(
 	'postgresql.conf', qq(
 logging_collector = on
-log_destination = 'stderr, csvlog'
+log_destination = 'stderr, csvlog, jsonlog'
 # these ensure stability of test results:
 log_rotation_age = 0
 lc_messages = 'C'
@@ -78,7 +78,7 @@ $node->start();
 $node->psql('postgres', 'SELECT 1/0');
 
 # might need to retry if logging collector process is slow...
-my $max_attempts = 180 * 10;
+my $max_attempts = 360 * 10;
 
 my $current_logfiles;
 for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
@@ -96,11 +96,13 @@ note "current_logfiles = $current_logfiles";
 like(
 	$current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'current_logfiles is sane');
 
 check_log_pattern('stderr', $current_logfiles, 'division by zero', $node);
 check_log_pattern('csvlog', $current_logfiles, 'division by zero', $node);
+check_log_pattern('jsonlog', $current_logfiles, 'division by zero', $node);
 
 # Sleep 2 seconds and ask for log rotation; this should result in
 # output into a different log file name.
@@ -122,7 +124,8 @@ note "now current_logfiles = $new_current_logfiles";
 like(
 	$new_current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'new current_logfiles is sane');
 
 # Verify that log output gets to this file, too
@@ -130,5 +133,6 @@ $node->psql('postgres', 'fee fi fo fum');
 
 check_log_pattern('stderr', $new_current_logfiles, 'syntax error', $node);
 check_log_pattern('csvlog', $new_current_logfiles, 'syntax error', $node);
+check_log_pattern('jsonlog', $new_current_logfiles, 'syntax error', $node);
 
 $node->stop();
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index afbb6c35e3..c29ced427c 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5931,7 +5931,8 @@ SELECT * FROM parent WHERE key = 2400;
        <para>
         <productname>PostgreSQL</productname> supports several methods
          for logging server messages, including
-         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem> and
+         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem>,
+         <systemitem>jsonlog</systemitem>, and
          <systemitem>syslog</systemitem>. On Windows,
          <systemitem>eventlog</systemitem> is also supported. Set this
          parameter to a list of desired log destinations separated by
@@ -5949,6 +5950,14 @@ SELECT * FROM parent WHERE key = 2400;
         <xref linkend="guc-logging-collector"/> must be enabled to generate
         CSV-format log output.
        </para>
+       <para>
+        If <systemitem>jsonlog</systemitem> is included in <varname>log_destination</varname>,
+        log entries are output in <acronym>JSON</acronym> format, which is convenient for
+        loading logs into programs.
+        See <xref linkend="runtime-config-logging-jsonlog"/> for details.
+        <xref linkend="guc-logging-collector"/> must be enabled to generate
+        JSON-format log output.
+       </para>
        <para>
         When either <systemitem>stderr</systemitem> or
         <systemitem>csvlog</systemitem> are included, the file
@@ -5960,13 +5969,14 @@ SELECT * FROM parent WHERE key = 2400;
 <programlisting>
 stderr log/postgresql.log
 csvlog log/postgresql.csv
+jsonlog log/postgresql.json
 </programlisting>
 
         <filename>current_logfiles</filename> is recreated when a new log file
         is created as an effect of rotation, and
         when <varname>log_destination</varname> is reloaded.  It is removed when
-        neither <systemitem>stderr</systemitem>
-        nor <systemitem>csvlog</systemitem> are included
+        none of <systemitem>stderr</systemitem>,
+        <systemitem>csvlog</systemitem>, <systemitem>jsonlog</systemitem> are included
         in <varname>log_destination</varname>, and when the logging collector is
         disabled.
        </para>
@@ -6106,6 +6116,13 @@ local0.*    /var/log/postgresql
         (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
         replaced instead.)
        </para>
+       <para>
+        If JSON-format output is enabled in <varname>log_destination</varname>,
+        <literal>.json</literal> will be appended to the timestamped
+        log file name to create the file name for JSON-format output.
+        (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
+        replaced instead.)
+       </para>
        <para>
         This parameter can only be set in the <filename>postgresql.conf</filename>
         file or on the server command line.
@@ -7467,6 +7484,186 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         </orderedlist>
       </para>
     </sect2>
+     <sect2 id="runtime-config-logging-jsonlog">
+     <title>Using JSON-Format Log Output</title>
+
+     <para>
+      Including <literal>jsonlog</literal> in the <varname>log_destination</varname> list
+      provides a convenient way to import log files into many different programs.
+      This option emits log lines in (<acronym>JSON</acronym>) format.
+     </para>
+
+     <para>
+      String fields with null values are excluded from output.
+      Additional fields may be added in the future. User applications that process jsonlog
+      output should ignore unknown fields.
+     </para>
+
+     <para>
+      Each log line is serialized as a JSON object as of the following
+      set of keys with their values.
+     </para>
+
+     <table>
+      <title>Keys and values of JSON log entries</title>
+      <tgroup cols="3">
+       <thead>
+        <row>
+         <entry>Key name</entry>
+         <entry>Type</entry>
+         <entry>Description</entry>
+        </row>
+       </thead>
+       <tbody>
+        <row>
+         <entry><literal>timestamp</literal></entry>
+         <entry>string</entry>
+         <entry>Time stamp with milliseconds</entry>
+        </row>
+        <row>
+         <entry><literal>user</literal></entry>
+         <entry>string</entry>
+         <entry>User name</entry>
+        </row>
+        <row>
+         <entry><literal>dbname</literal></entry>
+         <entry>string</entry>
+         <entry>Database name</entry>
+        </row>
+        <row>
+         <entry><literal>pid</literal></entry>
+         <entry>number</entry>
+         <entry>Process ID</entry>
+        </row>
+        <row>
+         <entry><literal>remote_host</literal></entry>
+         <entry>string</entry>
+         <entry>Client host</entry>
+        </row>
+        <row>
+         <entry><literal>remote_port</literal></entry>
+         <entry>number</entry>
+         <entry>Client port</entry>
+        </row>
+        <row>
+         <entry><literal>session_id</literal></entry>
+         <entry>string</entry>
+         <entry>Session ID</entry>
+        </row>
+        <row>
+         <entry><literal>line_num</literal></entry>
+         <entry>number</entry>
+         <entry>Per-session line number</entry>
+        </row>
+        <row>
+         <entry><literal>ps</literal></entry>
+         <entry>string</entry>
+         <entry>Current ps display</entry>
+        </row>
+        <row>
+         <entry><literal>session_start</literal></entry>
+         <entry>string</entry>
+         <entry>Session start time</entry>
+        </row>
+        <row>
+         <entry><literal>vxid</literal></entry>
+         <entry>string</entry>
+         <entry>Virtual transaction ID</entry>
+        </row>
+        <row>
+         <entry><literal>txid</literal></entry>
+         <entry>string</entry>
+         <entry>Regular transaction ID</entry>
+        </row>
+        <row>
+         <entry><literal>error_severity</literal></entry>
+         <entry>string</entry>
+         <entry>Error severity</entry>
+        </row>
+        <row>
+         <entry><literal>state_code</literal></entry>
+         <entry>string</entry>
+         <entry>SQLSTATE code</entry>
+        </row>
+        <row>
+         <entry><literal>message</literal></entry>
+         <entry>string</entry>
+         <entry>Error message</entry>
+        </row>
+        <row>
+         <entry><literal>detail</literal></entry>
+         <entry>string</entry>
+         <entry>Error message detail</entry>
+        </row>
+        <row>
+         <entry><literal>hint</literal></entry>
+         <entry>string</entry>
+         <entry>Error message hint</entry>
+        </row>
+        <row>
+         <entry><literal>internal_query</literal></entry>
+         <entry>string</entry>
+         <entry>Internal query that led to the error</entry>
+        </row>
+        <row>
+         <entry><literal>internal_position</literal></entry>
+         <entry>number</entry>
+         <entry>Cursor index into internal query</entry>
+        </row>
+        <row>
+         <entry><literal>context</literal></entry>
+         <entry>string</entry>
+         <entry>Error context</entry>
+        </row>
+        <row>
+         <entry><literal>statement</literal></entry>
+         <entry>string</entry>
+         <entry>Client-supplied query string</entry>
+        </row>
+        <row>
+         <entry><literal>cursor_position</literal></entry>
+         <entry>string</entry>
+         <entry>Cursor index into query string</entry>
+        </row>
+        <row>
+         <entry><literal>func_name</literal></entry>
+         <entry>string</entry>
+         <entry>Error location function name</entry>
+        </row>
+        <row>
+         <entry><literal>file_name</literal></entry>
+         <entry>string</entry>
+         <entry>File name of error location</entry>
+        </row>
+        <row>
+         <entry><literal>file_line_num</literal></entry>
+         <entry>number</entry>
+         <entry>File line number of the error location</entry>
+        </row>
+        <row>
+         <entry><literal>application_name</literal></entry>
+         <entry>string</entry>
+         <entry>Client application name</entry>
+        </row>
+        <row>
+         <entry><literal>backend_type</literal></entry>
+         <entry>string</entry>
+         <entry>Type of backend</entry>
+        </row>
+        <row>
+         <entry><literal>leader_pid</literal></entry>
+         <entry>number</entry>
+         <entry>Process ID of leader for active parallel workers</entry>
+        </row>
+        <row>
+         <entry><literal>query_id</literal></entry>
+         <entry>number</entry>
+         <entry>Query ID</entry>
+        </row>
+       </tbody>
+      </tgroup>
+     </table>
+    </sect2>
 
    <sect2>
     <title>Process Title</title>
-- 
2.34.1

From 33fbcbe4c8d4ac43a10d6f9362a961352a8df8ca Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 19 Oct 2021 16:25:45 +0900
Subject: [PATCH v8 1/3] Some refactoring of elog-specific routines

This refactors out the following things in elog.c, for ease of use
across multiple log destinations:
- start_timestamp (including reset)
- log_timestamp
- decide if query can be logged
- backend type
- write using the elog piped protocol
- Error severity to string.

These will be reused by csvlog and jsonlog.
---
 src/include/utils/elog.h       |  12 +++
 src/backend/utils/error/elog.c | 159 +++++++++++++++++++++------------
 2 files changed, 114 insertions(+), 57 deletions(-)

diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index f53607e12e..731f3e3cd8 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -442,6 +442,18 @@ extern void DebugFileOpen(void);
 extern char *unpack_sql_state(int sql_state);
 extern bool in_error_recursion_trouble(void);
 
+/* Common functions shared across destinations */
+extern void reset_formatted_start_time(void);
+extern char *get_formatted_start_time(void);
+extern char *get_formatted_log_time(void);
+extern const char *get_backend_type_for_log(void);
+extern bool	check_log_of_query(ErrorData *edata);
+extern const char *error_severity(int elevel);
+extern void write_pipe_chunks(char *data, int len, int dest);
+
+/* Destination-specific functions */
+extern void write_csvlog(ErrorData *edata);
+
 #ifdef HAVE_SYSLOG
 extern void set_syslog_parameters(const char *ident, int facility);
 #endif
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index f33729513a..a162258bab 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -175,15 +175,10 @@ static const char *err_gettext(const char *str) pg_attribute_format_arg(1);
 static pg_noinline void set_backtrace(ErrorData *edata, int num_skip);
 static void set_errdata_field(MemoryContextData *cxt, char **ptr, const char *str);
 static void write_console(const char *line, int len);
-static void setup_formatted_log_time(void);
-static void setup_formatted_start_time(void);
 static const char *process_log_prefix_padding(const char *p, int *padding);
 static void log_line_prefix(StringInfo buf, ErrorData *edata);
-static void write_csvlog(ErrorData *edata);
 static void send_message_to_server_log(ErrorData *edata);
-static void write_pipe_chunks(char *data, int len, int dest);
 static void send_message_to_frontend(ErrorData *edata);
-static const char *error_severity(int elevel);
 static void append_with_tabs(StringInfo buf, const char *str);
 
 
@@ -2289,14 +2284,23 @@ write_console(const char *line, int len)
 }
 
 /*
- * setup formatted_log_time, for consistent times between CSV and regular logs
+ * get_formatted_log_time -- compute and get the log timestamp.
+ *
+ * The timestamp is computed if not set yet, so as it is kept consistent
+ * among all the log destinations that require it to be consistent.  Note
+ * that the computed timestamp is returned in a static buffer, not
+ * palloc()'d.
  */
-static void
-setup_formatted_log_time(void)
+char *
+get_formatted_log_time(void)
 {
 	pg_time_t	stamp_time;
 	char		msbuf[13];
 
+	/* leave if already computed */
+	if (formatted_log_time[0] != '\0')
+		return formatted_log_time;
+
 	if (!saved_timeval_set)
 	{
 		gettimeofday(&saved_timeval, NULL);
@@ -2318,16 +2322,34 @@ setup_formatted_log_time(void)
 	/* 'paste' milliseconds into place... */
 	sprintf(msbuf, ".%03d", (int) (saved_timeval.tv_usec / 1000));
 	memcpy(formatted_log_time + 19, msbuf, 4);
+
+	return formatted_log_time;
 }
 
 /*
- * setup formatted_start_time
+ * reset_formatted_start_time -- reset the start timestamp
  */
-static void
-setup_formatted_start_time(void)
+void
+reset_formatted_start_time(void)
+{
+	formatted_start_time[0] = '\0';
+}
+
+/*
+ * get_formatted_start_time -- compute and get the start timestamp.
+ *
+ * The timestamp is computed if not set yet.  Note that the computed
+ * timestamp is returned in a static buffer, not palloc()'d.
+ */
+char *
+get_formatted_start_time(void)
 {
 	pg_time_t	stamp_time = (pg_time_t) MyStartTime;
 
+	/* leave if already computed */
+	if (formatted_start_time[0] != '\0')
+		return formatted_start_time;
+
 	/*
 	 * Note: we expect that guc.c will ensure that log_timezone is set up (at
 	 * least with a minimal GMT value) before Log_line_prefix can become
@@ -2336,6 +2358,49 @@ setup_formatted_start_time(void)
 	pg_strftime(formatted_start_time, FORMATTED_TS_LEN,
 				"%Y-%m-%d %H:%M:%S %Z",
 				pg_localtime(&stamp_time, log_timezone));
+
+	return formatted_start_time;
+}
+
+/*
+ * check_log_of_query -- check if a query can be logged
+ */
+bool
+check_log_of_query(ErrorData *edata)
+{
+	/* log required? */
+	if (!is_log_level_output(edata->elevel, log_min_error_statement))
+		return false;
+
+	/* query log wanted? */
+	if (edata->hide_stmt)
+		return false;
+
+	/* query string available? */
+	if (debug_query_string == NULL)
+		return false;
+
+	return true;
+}
+
+/*
+ * get_backend_type_for_log -- backend type for log entries
+ *
+ * Returns a pointer to a static buffer, not palloc()'d.
+ */
+const char *
+get_backend_type_for_log(void)
+{
+	const char   *backend_type_str;
+
+	if (MyProcPid == PostmasterPid)
+		backend_type_str = "postmaster";
+	else if (MyBackendType == B_BG_WORKER)
+		backend_type_str = MyBgworkerEntry->bgw_type;
+	else
+		backend_type_str = GetBackendTypeDesc(MyBackendType);
+
+	return backend_type_str;
 }
 
 /*
@@ -2466,14 +2531,7 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 				break;
 			case 'b':
 				{
-					const char *backend_type_str;
-
-					if (MyProcPid == PostmasterPid)
-						backend_type_str = "postmaster";
-					else if (MyBackendType == B_BG_WORKER)
-						backend_type_str = MyBgworkerEntry->bgw_type;
-					else
-						backend_type_str = GetBackendTypeDesc(MyBackendType);
+					const char *backend_type_str = get_backend_type_for_log();
 
 					if (padding != 0)
 						appendStringInfo(buf, "%*s", padding, backend_type_str);
@@ -2561,7 +2619,10 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 					appendStringInfo(buf, "%ld", log_line_number);
 				break;
 			case 'm':
-				setup_formatted_log_time();
+				/* force a log timestamp reset */
+				formatted_log_time[0] = '\0';
+				(void) get_formatted_log_time();
+
 				if (padding != 0)
 					appendStringInfo(buf, "%*s", padding, formatted_log_time);
 				else
@@ -2602,12 +2663,14 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 				}
 				break;
 			case 's':
-				if (formatted_start_time[0] == '\0')
-					setup_formatted_start_time();
-				if (padding != 0)
-					appendStringInfo(buf, "%*s", padding, formatted_start_time);
-				else
-					appendStringInfoString(buf, formatted_start_time);
+				{
+					char   *start_time = get_formatted_start_time();
+
+					if (padding != 0)
+						appendStringInfo(buf, "%*s", padding, start_time);
+					else
+						appendStringInfoString(buf, start_time);
+				}
 				break;
 			case 'i':
 				if (MyProcPort)
@@ -2758,11 +2821,13 @@ appendCSVLiteral(StringInfo buf, const char *data)
  * Constructs the error message, depending on the Errordata it gets, in a CSV
  * format which is described in doc/src/sgml/config.sgml.
  */
-static void
+void
 write_csvlog(ErrorData *edata)
 {
 	StringInfoData buf;
 	bool		print_stmt = false;
+	char	   *start_time;
+	char	   *log_time;
 
 	/* static counter for line numbers */
 	static long log_line_number = 0;
@@ -2785,17 +2850,9 @@ write_csvlog(ErrorData *edata)
 
 	initStringInfo(&buf);
 
-	/*
-	 * timestamp with milliseconds
-	 *
-	 * Check if the timestamp is already calculated for the syslog message,
-	 * and use it if so.  Otherwise, get the current timestamp.  This is done
-	 * to put same timestamp in both syslog and csvlog messages.
-	 */
-	if (formatted_log_time[0] == '\0')
-		setup_formatted_log_time();
-
-	appendStringInfoString(&buf, formatted_log_time);
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+	appendStringInfoString(&buf, log_time);
 	appendStringInfoChar(&buf, ',');
 
 	/* username */
@@ -2853,9 +2910,8 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* session start timestamp */
-	if (formatted_start_time[0] == '\0')
-		setup_formatted_start_time();
-	appendStringInfoString(&buf, formatted_start_time);
+	start_time = get_formatted_start_time();
+	appendStringInfoString(&buf, start_time);
 	appendStringInfoChar(&buf, ',');
 
 	/* Virtual transaction id */
@@ -2906,10 +2962,7 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* user query --- only reported if not disabled by the caller */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
-		print_stmt = true;
+	print_stmt = check_log_of_query(edata);
 	if (print_stmt)
 		appendCSVLiteral(&buf, debug_query_string);
 	appendStringInfoChar(&buf, ',');
@@ -2943,13 +2996,7 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* backend type */
-	if (MyProcPid == PostmasterPid)
-		appendCSVLiteral(&buf, "postmaster");
-	else if (MyBackendType == B_BG_WORKER)
-		appendCSVLiteral(&buf, MyBgworkerEntry->bgw_type);
-	else
-		appendCSVLiteral(&buf, GetBackendTypeDesc(MyBackendType));
-
+	appendCSVLiteral(&buf, get_backend_type_for_log());
 	appendStringInfoChar(&buf, ',');
 
 	/* leader PID */
@@ -3101,9 +3148,7 @@ send_message_to_server_log(ErrorData *edata)
 	/*
 	 * If the user wants the query that generated this error logged, do it.
 	 */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
+	if (check_log_of_query(edata))
 	{
 		log_line_prefix(&buf, edata);
 		appendStringInfoString(&buf, _("STATEMENT:  "));
@@ -3233,7 +3278,7 @@ send_message_to_server_log(ErrorData *edata)
  * warning from ignoring write()'s result, so do a little dance with casting
  * rc to void to shut up the compiler.
  */
-static void
+void
 write_pipe_chunks(char *data, int len, int dest)
 {
 	PipeProtoChunk p;
@@ -3469,7 +3514,7 @@ send_message_to_frontend(ErrorData *edata)
  * The string is not localized here, but we mark the strings for translation
  * so that callers can invoke _() on the result.
  */
-static const char *
+const char *
 error_severity(int elevel)
 {
 	const char *prefix;
-- 
2.34.1

From 85d9fbee22f56e342ffcf8082a320764b0ad1237 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 5 Oct 2021 15:22:24 +0900
Subject: [PATCH v8 2/3] Refactor CSV-specific code into its own file

---
 src/backend/utils/error/Makefile |   1 +
 src/backend/utils/error/csvlog.c | 268 +++++++++++++++++++++++++++++++
 src/backend/utils/error/elog.c   | 235 ---------------------------
 3 files changed, 269 insertions(+), 235 deletions(-)
 create mode 100644 src/backend/utils/error/csvlog.c

diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index 612da215d0..ef770dd2f2 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -14,6 +14,7 @@ include $(top_builddir)/src/Makefile.global
 
 OBJS = \
 	assert.o \
+	csvlog.o \
 	elog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/csvlog.c b/src/backend/utils/error/csvlog.c
new file mode 100644
index 0000000000..443a91e168
--- /dev/null
+++ b/src/backend/utils/error/csvlog.c
@@ -0,0 +1,268 @@
+/*-------------------------------------------------------------------------
+ *
+ * csvlog.c
+ *	  CSV logging
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of Californi
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/csvlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog.h"
+#include "utils/guc.h"
+#include "utils/ps_status.h"
+
+
+/*
+ * append a CSV'd version of a string to a StringInfo
+ * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
+ * If it's NULL, append nothing.
+ */
+static inline void
+appendCSVLiteral(StringInfo buf, const char *data)
+{
+	const char *p = data;
+	char		c;
+
+	/* avoid confusing an empty string with NULL */
+	if (p == NULL)
+		return;
+
+	appendStringInfoCharMacro(buf, '"');
+	while ((c = *p++) != '\0')
+	{
+		if (c == '"')
+			appendStringInfoCharMacro(buf, '"');
+		appendStringInfoCharMacro(buf, c);
+	}
+	appendStringInfoCharMacro(buf, '"');
+}
+
+/*
+ * write_csvlog -- Generate and write CSV log entry
+ *
+ * Constructs the error message, depending on the Errordata it gets, in a CSV
+ * format which is described in doc/src/sgml/config.sgml.
+ */
+void
+write_csvlog(ErrorData *edata)
+{
+	StringInfoData buf;
+	bool		print_stmt = false;
+	char	   *start_time;
+	char	   *log_time;
+
+	/* static counter for line numbers */
+	static long log_line_number = 0;
+
+	/* has counter been reset in current process? */
+	static int	log_my_pid = 0;
+
+	/*
+	 * This is one of the few places where we'd rather not inherit a static
+	 * variable's value from the postmaster.  But since we will, reset it when
+	 * MyProcPid changes.
+	 */
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		reset_formatted_start_time();
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+	appendStringInfoString(&buf, log_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* username */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->user_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* database name */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->database_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* Process id  */
+	if (MyProcPid != 0)
+		appendStringInfo(&buf, "%d", MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendStringInfoChar(&buf, '"');
+		appendStringInfoString(&buf, MyProcPort->remote_host);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+		{
+			appendStringInfoChar(&buf, ':');
+			appendStringInfoString(&buf, MyProcPort->remote_port);
+		}
+		appendStringInfoChar(&buf, '"');
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session id */
+	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Line number */
+	appendStringInfo(&buf, "%ld", log_line_number);
+	appendStringInfoChar(&buf, ',');
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData msgbuf;
+		const char *psdisp;
+		int			displen;
+
+		initStringInfo(&msgbuf);
+
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendCSVLiteral(&buf, msgbuf.data);
+
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session start timestamp */
+	start_time = get_formatted_start_time();
+	appendStringInfoString(&buf, start_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Transaction id */
+	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
+	appendStringInfoChar(&buf, ',');
+
+	/* Error severity */
+	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
+	appendStringInfoChar(&buf, ',');
+
+	/* SQL state code */
+	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
+	appendStringInfoChar(&buf, ',');
+
+	/* errmessage */
+	appendCSVLiteral(&buf, edata->message);
+	appendStringInfoChar(&buf, ',');
+
+	/* errdetail or errdetail_log */
+	if (edata->detail_log)
+		appendCSVLiteral(&buf, edata->detail_log);
+	else
+		appendCSVLiteral(&buf, edata->detail);
+	appendStringInfoChar(&buf, ',');
+
+	/* errhint */
+	appendCSVLiteral(&buf, edata->hint);
+	appendStringInfoChar(&buf, ',');
+
+	/* internal query */
+	appendCSVLiteral(&buf, edata->internalquery);
+	appendStringInfoChar(&buf, ',');
+
+	/* if printed internal query, print internal pos too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendStringInfo(&buf, "%d", edata->internalpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* errcontext */
+	if (!edata->hide_ctx)
+		appendCSVLiteral(&buf, edata->context);
+	appendStringInfoChar(&buf, ',');
+
+	/* user query --- only reported if not disabled by the caller */
+	print_stmt = check_log_of_query(edata);
+	if (print_stmt)
+		appendCSVLiteral(&buf, debug_query_string);
+	appendStringInfoChar(&buf, ',');
+	if (print_stmt && edata->cursorpos > 0)
+		appendStringInfo(&buf, "%d", edata->cursorpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		StringInfoData msgbuf;
+
+		initStringInfo(&msgbuf);
+
+		if (edata->funcname && edata->filename)
+			appendStringInfo(&msgbuf, "%s, %s:%d",
+							 edata->funcname, edata->filename,
+							 edata->lineno);
+		else if (edata->filename)
+			appendStringInfo(&msgbuf, "%s:%d",
+							 edata->filename, edata->lineno);
+		appendCSVLiteral(&buf, msgbuf.data);
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* application name */
+	if (application_name)
+		appendCSVLiteral(&buf, application_name);
+
+	appendStringInfoChar(&buf, ',');
+
+	/* backend type */
+	appendCSVLiteral(&buf, get_backend_type_for_log());
+	appendStringInfoChar(&buf, ',');
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendStringInfo(&buf, "%d", leader->pid);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* query id */
+	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
+
+	appendStringInfoChar(&buf, '\n');
+
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+	else
+		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index a162258bab..4406d8deff 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2792,241 +2792,6 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 	}
 }
 
-/*
- * append a CSV'd version of a string to a StringInfo
- * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
- * If it's NULL, append nothing.
- */
-static inline void
-appendCSVLiteral(StringInfo buf, const char *data)
-{
-	const char *p = data;
-	char		c;
-
-	/* avoid confusing an empty string with NULL */
-	if (p == NULL)
-		return;
-
-	appendStringInfoCharMacro(buf, '"');
-	while ((c = *p++) != '\0')
-	{
-		if (c == '"')
-			appendStringInfoCharMacro(buf, '"');
-		appendStringInfoCharMacro(buf, c);
-	}
-	appendStringInfoCharMacro(buf, '"');
-}
-
-/*
- * Constructs the error message, depending on the Errordata it gets, in a CSV
- * format which is described in doc/src/sgml/config.sgml.
- */
-void
-write_csvlog(ErrorData *edata)
-{
-	StringInfoData buf;
-	bool		print_stmt = false;
-	char	   *start_time;
-	char	   *log_time;
-
-	/* static counter for line numbers */
-	static long log_line_number = 0;
-
-	/* has counter been reset in current process? */
-	static int	log_my_pid = 0;
-
-	/*
-	 * This is one of the few places where we'd rather not inherit a static
-	 * variable's value from the postmaster.  But since we will, reset it when
-	 * MyProcPid changes.
-	 */
-	if (log_my_pid != MyProcPid)
-	{
-		log_line_number = 0;
-		log_my_pid = MyProcPid;
-		formatted_start_time[0] = '\0';
-	}
-	log_line_number++;
-
-	initStringInfo(&buf);
-
-	/* timestamp with milliseconds */
-	log_time = get_formatted_log_time();
-	appendStringInfoString(&buf, log_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* username */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->user_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* database name */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->database_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* Process id  */
-	if (MyProcPid != 0)
-		appendStringInfo(&buf, "%d", MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Remote host and port */
-	if (MyProcPort && MyProcPort->remote_host)
-	{
-		appendStringInfoChar(&buf, '"');
-		appendStringInfoString(&buf, MyProcPort->remote_host);
-		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
-		{
-			appendStringInfoChar(&buf, ':');
-			appendStringInfoString(&buf, MyProcPort->remote_port);
-		}
-		appendStringInfoChar(&buf, '"');
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session id */
-	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Line number */
-	appendStringInfo(&buf, "%ld", log_line_number);
-	appendStringInfoChar(&buf, ',');
-
-	/* PS display */
-	if (MyProcPort)
-	{
-		StringInfoData msgbuf;
-		const char *psdisp;
-		int			displen;
-
-		initStringInfo(&msgbuf);
-
-		psdisp = get_ps_display(&displen);
-		appendBinaryStringInfo(&msgbuf, psdisp, displen);
-		appendCSVLiteral(&buf, msgbuf.data);
-
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session start timestamp */
-	start_time = get_formatted_start_time();
-	appendStringInfoString(&buf, start_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* Virtual transaction id */
-	/* keep VXID format in sync with lockfuncs.c */
-	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
-		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Transaction id */
-	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
-	appendStringInfoChar(&buf, ',');
-
-	/* Error severity */
-	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
-	appendStringInfoChar(&buf, ',');
-
-	/* SQL state code */
-	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
-	appendStringInfoChar(&buf, ',');
-
-	/* errmessage */
-	appendCSVLiteral(&buf, edata->message);
-	appendStringInfoChar(&buf, ',');
-
-	/* errdetail or errdetail_log */
-	if (edata->detail_log)
-		appendCSVLiteral(&buf, edata->detail_log);
-	else
-		appendCSVLiteral(&buf, edata->detail);
-	appendStringInfoChar(&buf, ',');
-
-	/* errhint */
-	appendCSVLiteral(&buf, edata->hint);
-	appendStringInfoChar(&buf, ',');
-
-	/* internal query */
-	appendCSVLiteral(&buf, edata->internalquery);
-	appendStringInfoChar(&buf, ',');
-
-	/* if printed internal query, print internal pos too */
-	if (edata->internalpos > 0 && edata->internalquery != NULL)
-		appendStringInfo(&buf, "%d", edata->internalpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* errcontext */
-	if (!edata->hide_ctx)
-		appendCSVLiteral(&buf, edata->context);
-	appendStringInfoChar(&buf, ',');
-
-	/* user query --- only reported if not disabled by the caller */
-	print_stmt = check_log_of_query(edata);
-	if (print_stmt)
-		appendCSVLiteral(&buf, debug_query_string);
-	appendStringInfoChar(&buf, ',');
-	if (print_stmt && edata->cursorpos > 0)
-		appendStringInfo(&buf, "%d", edata->cursorpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* file error location */
-	if (Log_error_verbosity >= PGERROR_VERBOSE)
-	{
-		StringInfoData msgbuf;
-
-		initStringInfo(&msgbuf);
-
-		if (edata->funcname && edata->filename)
-			appendStringInfo(&msgbuf, "%s, %s:%d",
-							 edata->funcname, edata->filename,
-							 edata->lineno);
-		else if (edata->filename)
-			appendStringInfo(&msgbuf, "%s:%d",
-							 edata->filename, edata->lineno);
-		appendCSVLiteral(&buf, msgbuf.data);
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* application name */
-	if (application_name)
-		appendCSVLiteral(&buf, application_name);
-
-	appendStringInfoChar(&buf, ',');
-
-	/* backend type */
-	appendCSVLiteral(&buf, get_backend_type_for_log());
-	appendStringInfoChar(&buf, ',');
-
-	/* leader PID */
-	if (MyProc)
-	{
-		PGPROC	   *leader = MyProc->lockGroupLeader;
-
-		/*
-		 * Show the leader only for active parallel workers.  This leaves out
-		 * the leader of a parallel group.
-		 */
-		if (leader && leader->pid != MyProcPid)
-			appendStringInfo(&buf, "%d", leader->pid);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* query id */
-	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
-
-	appendStringInfoChar(&buf, '\n');
-
-	/* If in the syslogger process, try to write messages direct to file */
-	if (MyBackendType == B_LOGGER)
-		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-	else
-		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-
-	pfree(buf.data);
-}
-
 /*
  * Unpack MAKE_SQLSTATE code. Note that this returns a pointer to a
  * static buffer.
-- 
2.34.1

From 6ab52532b232bc3314cef5c9c4ac38110957ab34 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 19 Oct 2021 16:25:45 +0900
Subject: [PATCH v9 1/3] Some refactoring of elog-specific routines

This refactors out the following things in elog.c, for ease of use
across multiple log destinations:
- start_timestamp (including reset)
- log_timestamp
- decide if query can be logged
- backend type
- write using the elog piped protocol
- Error severity to string.

These will be reused by csvlog and jsonlog.
---
 src/include/utils/elog.h       |  12 +++
 src/backend/utils/error/elog.c | 159 +++++++++++++++++++++------------
 2 files changed, 114 insertions(+), 57 deletions(-)

diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 8df2799dc2..f37956f100 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -442,6 +442,18 @@ extern void DebugFileOpen(void);
 extern char *unpack_sql_state(int sql_state);
 extern bool in_error_recursion_trouble(void);
 
+/* Common functions shared across destinations */
+extern void reset_formatted_start_time(void);
+extern char *get_formatted_start_time(void);
+extern char *get_formatted_log_time(void);
+extern const char *get_backend_type_for_log(void);
+extern bool	check_log_of_query(ErrorData *edata);
+extern const char *error_severity(int elevel);
+extern void write_pipe_chunks(char *data, int len, int dest);
+
+/* Destination-specific functions */
+extern void write_csvlog(ErrorData *edata);
+
 #ifdef HAVE_SYSLOG
 extern void set_syslog_parameters(const char *ident, int facility);
 #endif
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 2f2c3ba41b..4ccad9bac1 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -175,15 +175,10 @@ static const char *err_gettext(const char *str) pg_attribute_format_arg(1);
 static pg_noinline void set_backtrace(ErrorData *edata, int num_skip);
 static void set_errdata_field(MemoryContextData *cxt, char **ptr, const char *str);
 static void write_console(const char *line, int len);
-static void setup_formatted_log_time(void);
-static void setup_formatted_start_time(void);
 static const char *process_log_prefix_padding(const char *p, int *padding);
 static void log_line_prefix(StringInfo buf, ErrorData *edata);
-static void write_csvlog(ErrorData *edata);
 static void send_message_to_server_log(ErrorData *edata);
-static void write_pipe_chunks(char *data, int len, int dest);
 static void send_message_to_frontend(ErrorData *edata);
-static const char *error_severity(int elevel);
 static void append_with_tabs(StringInfo buf, const char *str);
 
 
@@ -2289,14 +2284,23 @@ write_console(const char *line, int len)
 }
 
 /*
- * setup formatted_log_time, for consistent times between CSV and regular logs
+ * get_formatted_log_time -- compute and get the log timestamp.
+ *
+ * The timestamp is computed if not set yet, so as it is kept consistent
+ * among all the log destinations that require it to be consistent.  Note
+ * that the computed timestamp is returned in a static buffer, not
+ * palloc()'d.
  */
-static void
-setup_formatted_log_time(void)
+char *
+get_formatted_log_time(void)
 {
 	pg_time_t	stamp_time;
 	char		msbuf[13];
 
+	/* leave if already computed */
+	if (formatted_log_time[0] != '\0')
+		return formatted_log_time;
+
 	if (!saved_timeval_set)
 	{
 		gettimeofday(&saved_timeval, NULL);
@@ -2318,16 +2322,34 @@ setup_formatted_log_time(void)
 	/* 'paste' milliseconds into place... */
 	sprintf(msbuf, ".%03d", (int) (saved_timeval.tv_usec / 1000));
 	memcpy(formatted_log_time + 19, msbuf, 4);
+
+	return formatted_log_time;
 }
 
 /*
- * setup formatted_start_time
+ * reset_formatted_start_time -- reset the start timestamp
  */
-static void
-setup_formatted_start_time(void)
+void
+reset_formatted_start_time(void)
+{
+	formatted_start_time[0] = '\0';
+}
+
+/*
+ * get_formatted_start_time -- compute and get the start timestamp.
+ *
+ * The timestamp is computed if not set yet.  Note that the computed
+ * timestamp is returned in a static buffer, not palloc()'d.
+ */
+char *
+get_formatted_start_time(void)
 {
 	pg_time_t	stamp_time = (pg_time_t) MyStartTime;
 
+	/* leave if already computed */
+	if (formatted_start_time[0] != '\0')
+		return formatted_start_time;
+
 	/*
 	 * Note: we expect that guc.c will ensure that log_timezone is set up (at
 	 * least with a minimal GMT value) before Log_line_prefix can become
@@ -2336,6 +2358,49 @@ setup_formatted_start_time(void)
 	pg_strftime(formatted_start_time, FORMATTED_TS_LEN,
 				"%Y-%m-%d %H:%M:%S %Z",
 				pg_localtime(&stamp_time, log_timezone));
+
+	return formatted_start_time;
+}
+
+/*
+ * check_log_of_query -- check if a query can be logged
+ */
+bool
+check_log_of_query(ErrorData *edata)
+{
+	/* log required? */
+	if (!is_log_level_output(edata->elevel, log_min_error_statement))
+		return false;
+
+	/* query log wanted? */
+	if (edata->hide_stmt)
+		return false;
+
+	/* query string available? */
+	if (debug_query_string == NULL)
+		return false;
+
+	return true;
+}
+
+/*
+ * get_backend_type_for_log -- backend type for log entries
+ *
+ * Returns a pointer to a static buffer, not palloc()'d.
+ */
+const char *
+get_backend_type_for_log(void)
+{
+	const char   *backend_type_str;
+
+	if (MyProcPid == PostmasterPid)
+		backend_type_str = "postmaster";
+	else if (MyBackendType == B_BG_WORKER)
+		backend_type_str = MyBgworkerEntry->bgw_type;
+	else
+		backend_type_str = GetBackendTypeDesc(MyBackendType);
+
+	return backend_type_str;
 }
 
 /*
@@ -2466,14 +2531,7 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 				break;
 			case 'b':
 				{
-					const char *backend_type_str;
-
-					if (MyProcPid == PostmasterPid)
-						backend_type_str = "postmaster";
-					else if (MyBackendType == B_BG_WORKER)
-						backend_type_str = MyBgworkerEntry->bgw_type;
-					else
-						backend_type_str = GetBackendTypeDesc(MyBackendType);
+					const char *backend_type_str = get_backend_type_for_log();
 
 					if (padding != 0)
 						appendStringInfo(buf, "%*s", padding, backend_type_str);
@@ -2561,7 +2619,10 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 					appendStringInfo(buf, "%ld", log_line_number);
 				break;
 			case 'm':
-				setup_formatted_log_time();
+				/* force a log timestamp reset */
+				formatted_log_time[0] = '\0';
+				(void) get_formatted_log_time();
+
 				if (padding != 0)
 					appendStringInfo(buf, "%*s", padding, formatted_log_time);
 				else
@@ -2602,12 +2663,14 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 				}
 				break;
 			case 's':
-				if (formatted_start_time[0] == '\0')
-					setup_formatted_start_time();
-				if (padding != 0)
-					appendStringInfo(buf, "%*s", padding, formatted_start_time);
-				else
-					appendStringInfoString(buf, formatted_start_time);
+				{
+					char   *start_time = get_formatted_start_time();
+
+					if (padding != 0)
+						appendStringInfo(buf, "%*s", padding, start_time);
+					else
+						appendStringInfoString(buf, start_time);
+				}
 				break;
 			case 'i':
 				if (MyProcPort)
@@ -2758,11 +2821,13 @@ appendCSVLiteral(StringInfo buf, const char *data)
  * Constructs the error message, depending on the Errordata it gets, in a CSV
  * format which is described in doc/src/sgml/config.sgml.
  */
-static void
+void
 write_csvlog(ErrorData *edata)
 {
 	StringInfoData buf;
 	bool		print_stmt = false;
+	char	   *start_time;
+	char	   *log_time;
 
 	/* static counter for line numbers */
 	static long log_line_number = 0;
@@ -2785,17 +2850,9 @@ write_csvlog(ErrorData *edata)
 
 	initStringInfo(&buf);
 
-	/*
-	 * timestamp with milliseconds
-	 *
-	 * Check if the timestamp is already calculated for the syslog message,
-	 * and use it if so.  Otherwise, get the current timestamp.  This is done
-	 * to put same timestamp in both syslog and csvlog messages.
-	 */
-	if (formatted_log_time[0] == '\0')
-		setup_formatted_log_time();
-
-	appendStringInfoString(&buf, formatted_log_time);
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+	appendStringInfoString(&buf, log_time);
 	appendStringInfoChar(&buf, ',');
 
 	/* username */
@@ -2853,9 +2910,8 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* session start timestamp */
-	if (formatted_start_time[0] == '\0')
-		setup_formatted_start_time();
-	appendStringInfoString(&buf, formatted_start_time);
+	start_time = get_formatted_start_time();
+	appendStringInfoString(&buf, start_time);
 	appendStringInfoChar(&buf, ',');
 
 	/* Virtual transaction id */
@@ -2906,10 +2962,7 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* user query --- only reported if not disabled by the caller */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
-		print_stmt = true;
+	print_stmt = check_log_of_query(edata);
 	if (print_stmt)
 		appendCSVLiteral(&buf, debug_query_string);
 	appendStringInfoChar(&buf, ',');
@@ -2943,13 +2996,7 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, ',');
 
 	/* backend type */
-	if (MyProcPid == PostmasterPid)
-		appendCSVLiteral(&buf, "postmaster");
-	else if (MyBackendType == B_BG_WORKER)
-		appendCSVLiteral(&buf, MyBgworkerEntry->bgw_type);
-	else
-		appendCSVLiteral(&buf, GetBackendTypeDesc(MyBackendType));
-
+	appendCSVLiteral(&buf, get_backend_type_for_log());
 	appendStringInfoChar(&buf, ',');
 
 	/* leader PID */
@@ -3101,9 +3148,7 @@ send_message_to_server_log(ErrorData *edata)
 	/*
 	 * If the user wants the query that generated this error logged, do it.
 	 */
-	if (is_log_level_output(edata->elevel, log_min_error_statement) &&
-		debug_query_string != NULL &&
-		!edata->hide_stmt)
+	if (check_log_of_query(edata))
 	{
 		log_line_prefix(&buf, edata);
 		appendStringInfoString(&buf, _("STATEMENT:  "));
@@ -3233,7 +3278,7 @@ send_message_to_server_log(ErrorData *edata)
  * warning from ignoring write()'s result, so do a little dance with casting
  * rc to void to shut up the compiler.
  */
-static void
+void
 write_pipe_chunks(char *data, int len, int dest)
 {
 	PipeProtoChunk p;
@@ -3469,7 +3514,7 @@ send_message_to_frontend(ErrorData *edata)
  * The string is not localized here, but we mark the strings for translation
  * so that callers can invoke _() on the result.
  */
-static const char *
+const char *
 error_severity(int elevel)
 {
 	const char *prefix;
-- 
2.34.1

From 6bd32c8a49fd4b6a1b08b39593c1e610c711f761 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 5 Oct 2021 15:22:24 +0900
Subject: [PATCH v9 2/3] Refactor CSV-specific code into its own file

---
 src/backend/utils/error/Makefile |   1 +
 src/backend/utils/error/csvlog.c | 268 +++++++++++++++++++++++++++++++
 src/backend/utils/error/elog.c   | 235 ---------------------------
 3 files changed, 269 insertions(+), 235 deletions(-)
 create mode 100644 src/backend/utils/error/csvlog.c

diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index 612da215d0..ef770dd2f2 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -14,6 +14,7 @@ include $(top_builddir)/src/Makefile.global
 
 OBJS = \
 	assert.o \
+	csvlog.o \
 	elog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/csvlog.c b/src/backend/utils/error/csvlog.c
new file mode 100644
index 0000000000..443a91e168
--- /dev/null
+++ b/src/backend/utils/error/csvlog.c
@@ -0,0 +1,268 @@
+/*-------------------------------------------------------------------------
+ *
+ * csvlog.c
+ *	  CSV logging
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of Californi
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/csvlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog.h"
+#include "utils/guc.h"
+#include "utils/ps_status.h"
+
+
+/*
+ * append a CSV'd version of a string to a StringInfo
+ * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
+ * If it's NULL, append nothing.
+ */
+static inline void
+appendCSVLiteral(StringInfo buf, const char *data)
+{
+	const char *p = data;
+	char		c;
+
+	/* avoid confusing an empty string with NULL */
+	if (p == NULL)
+		return;
+
+	appendStringInfoCharMacro(buf, '"');
+	while ((c = *p++) != '\0')
+	{
+		if (c == '"')
+			appendStringInfoCharMacro(buf, '"');
+		appendStringInfoCharMacro(buf, c);
+	}
+	appendStringInfoCharMacro(buf, '"');
+}
+
+/*
+ * write_csvlog -- Generate and write CSV log entry
+ *
+ * Constructs the error message, depending on the Errordata it gets, in a CSV
+ * format which is described in doc/src/sgml/config.sgml.
+ */
+void
+write_csvlog(ErrorData *edata)
+{
+	StringInfoData buf;
+	bool		print_stmt = false;
+	char	   *start_time;
+	char	   *log_time;
+
+	/* static counter for line numbers */
+	static long log_line_number = 0;
+
+	/* has counter been reset in current process? */
+	static int	log_my_pid = 0;
+
+	/*
+	 * This is one of the few places where we'd rather not inherit a static
+	 * variable's value from the postmaster.  But since we will, reset it when
+	 * MyProcPid changes.
+	 */
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		reset_formatted_start_time();
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+	appendStringInfoString(&buf, log_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* username */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->user_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* database name */
+	if (MyProcPort)
+		appendCSVLiteral(&buf, MyProcPort->database_name);
+	appendStringInfoChar(&buf, ',');
+
+	/* Process id  */
+	if (MyProcPid != 0)
+		appendStringInfo(&buf, "%d", MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendStringInfoChar(&buf, '"');
+		appendStringInfoString(&buf, MyProcPort->remote_host);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+		{
+			appendStringInfoChar(&buf, ':');
+			appendStringInfoString(&buf, MyProcPort->remote_port);
+		}
+		appendStringInfoChar(&buf, '"');
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session id */
+	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Line number */
+	appendStringInfo(&buf, "%ld", log_line_number);
+	appendStringInfoChar(&buf, ',');
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData msgbuf;
+		const char *psdisp;
+		int			displen;
+
+		initStringInfo(&msgbuf);
+
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendCSVLiteral(&buf, msgbuf.data);
+
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* session start timestamp */
+	start_time = get_formatted_start_time();
+	appendStringInfoString(&buf, start_time);
+	appendStringInfoChar(&buf, ',');
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
+	appendStringInfoChar(&buf, ',');
+
+	/* Transaction id */
+	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
+	appendStringInfoChar(&buf, ',');
+
+	/* Error severity */
+	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
+	appendStringInfoChar(&buf, ',');
+
+	/* SQL state code */
+	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
+	appendStringInfoChar(&buf, ',');
+
+	/* errmessage */
+	appendCSVLiteral(&buf, edata->message);
+	appendStringInfoChar(&buf, ',');
+
+	/* errdetail or errdetail_log */
+	if (edata->detail_log)
+		appendCSVLiteral(&buf, edata->detail_log);
+	else
+		appendCSVLiteral(&buf, edata->detail);
+	appendStringInfoChar(&buf, ',');
+
+	/* errhint */
+	appendCSVLiteral(&buf, edata->hint);
+	appendStringInfoChar(&buf, ',');
+
+	/* internal query */
+	appendCSVLiteral(&buf, edata->internalquery);
+	appendStringInfoChar(&buf, ',');
+
+	/* if printed internal query, print internal pos too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendStringInfo(&buf, "%d", edata->internalpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* errcontext */
+	if (!edata->hide_ctx)
+		appendCSVLiteral(&buf, edata->context);
+	appendStringInfoChar(&buf, ',');
+
+	/* user query --- only reported if not disabled by the caller */
+	print_stmt = check_log_of_query(edata);
+	if (print_stmt)
+		appendCSVLiteral(&buf, debug_query_string);
+	appendStringInfoChar(&buf, ',');
+	if (print_stmt && edata->cursorpos > 0)
+		appendStringInfo(&buf, "%d", edata->cursorpos);
+	appendStringInfoChar(&buf, ',');
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		StringInfoData msgbuf;
+
+		initStringInfo(&msgbuf);
+
+		if (edata->funcname && edata->filename)
+			appendStringInfo(&msgbuf, "%s, %s:%d",
+							 edata->funcname, edata->filename,
+							 edata->lineno);
+		else if (edata->filename)
+			appendStringInfo(&msgbuf, "%s:%d",
+							 edata->filename, edata->lineno);
+		appendCSVLiteral(&buf, msgbuf.data);
+		pfree(msgbuf.data);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* application name */
+	if (application_name)
+		appendCSVLiteral(&buf, application_name);
+
+	appendStringInfoChar(&buf, ',');
+
+	/* backend type */
+	appendCSVLiteral(&buf, get_backend_type_for_log());
+	appendStringInfoChar(&buf, ',');
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendStringInfo(&buf, "%d", leader->pid);
+	}
+	appendStringInfoChar(&buf, ',');
+
+	/* query id */
+	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
+
+	appendStringInfoChar(&buf, '\n');
+
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+	else
+		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 4ccad9bac1..511b43e4ac 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2792,241 +2792,6 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 	}
 }
 
-/*
- * append a CSV'd version of a string to a StringInfo
- * We use the PostgreSQL defaults for CSV, i.e. quote = escape = '"'
- * If it's NULL, append nothing.
- */
-static inline void
-appendCSVLiteral(StringInfo buf, const char *data)
-{
-	const char *p = data;
-	char		c;
-
-	/* avoid confusing an empty string with NULL */
-	if (p == NULL)
-		return;
-
-	appendStringInfoCharMacro(buf, '"');
-	while ((c = *p++) != '\0')
-	{
-		if (c == '"')
-			appendStringInfoCharMacro(buf, '"');
-		appendStringInfoCharMacro(buf, c);
-	}
-	appendStringInfoCharMacro(buf, '"');
-}
-
-/*
- * Constructs the error message, depending on the Errordata it gets, in a CSV
- * format which is described in doc/src/sgml/config.sgml.
- */
-void
-write_csvlog(ErrorData *edata)
-{
-	StringInfoData buf;
-	bool		print_stmt = false;
-	char	   *start_time;
-	char	   *log_time;
-
-	/* static counter for line numbers */
-	static long log_line_number = 0;
-
-	/* has counter been reset in current process? */
-	static int	log_my_pid = 0;
-
-	/*
-	 * This is one of the few places where we'd rather not inherit a static
-	 * variable's value from the postmaster.  But since we will, reset it when
-	 * MyProcPid changes.
-	 */
-	if (log_my_pid != MyProcPid)
-	{
-		log_line_number = 0;
-		log_my_pid = MyProcPid;
-		formatted_start_time[0] = '\0';
-	}
-	log_line_number++;
-
-	initStringInfo(&buf);
-
-	/* timestamp with milliseconds */
-	log_time = get_formatted_log_time();
-	appendStringInfoString(&buf, log_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* username */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->user_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* database name */
-	if (MyProcPort)
-		appendCSVLiteral(&buf, MyProcPort->database_name);
-	appendStringInfoChar(&buf, ',');
-
-	/* Process id  */
-	if (MyProcPid != 0)
-		appendStringInfo(&buf, "%d", MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Remote host and port */
-	if (MyProcPort && MyProcPort->remote_host)
-	{
-		appendStringInfoChar(&buf, '"');
-		appendStringInfoString(&buf, MyProcPort->remote_host);
-		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
-		{
-			appendStringInfoChar(&buf, ':');
-			appendStringInfoString(&buf, MyProcPort->remote_port);
-		}
-		appendStringInfoChar(&buf, '"');
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session id */
-	appendStringInfo(&buf, "%lx.%x", (long) MyStartTime, MyProcPid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Line number */
-	appendStringInfo(&buf, "%ld", log_line_number);
-	appendStringInfoChar(&buf, ',');
-
-	/* PS display */
-	if (MyProcPort)
-	{
-		StringInfoData msgbuf;
-		const char *psdisp;
-		int			displen;
-
-		initStringInfo(&msgbuf);
-
-		psdisp = get_ps_display(&displen);
-		appendBinaryStringInfo(&msgbuf, psdisp, displen);
-		appendCSVLiteral(&buf, msgbuf.data);
-
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* session start timestamp */
-	start_time = get_formatted_start_time();
-	appendStringInfoString(&buf, start_time);
-	appendStringInfoChar(&buf, ',');
-
-	/* Virtual transaction id */
-	/* keep VXID format in sync with lockfuncs.c */
-	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
-		appendStringInfo(&buf, "%d/%u", MyProc->backendId, MyProc->lxid);
-	appendStringInfoChar(&buf, ',');
-
-	/* Transaction id */
-	appendStringInfo(&buf, "%u", GetTopTransactionIdIfAny());
-	appendStringInfoChar(&buf, ',');
-
-	/* Error severity */
-	appendStringInfoString(&buf, _(error_severity(edata->elevel)));
-	appendStringInfoChar(&buf, ',');
-
-	/* SQL state code */
-	appendStringInfoString(&buf, unpack_sql_state(edata->sqlerrcode));
-	appendStringInfoChar(&buf, ',');
-
-	/* errmessage */
-	appendCSVLiteral(&buf, edata->message);
-	appendStringInfoChar(&buf, ',');
-
-	/* errdetail or errdetail_log */
-	if (edata->detail_log)
-		appendCSVLiteral(&buf, edata->detail_log);
-	else
-		appendCSVLiteral(&buf, edata->detail);
-	appendStringInfoChar(&buf, ',');
-
-	/* errhint */
-	appendCSVLiteral(&buf, edata->hint);
-	appendStringInfoChar(&buf, ',');
-
-	/* internal query */
-	appendCSVLiteral(&buf, edata->internalquery);
-	appendStringInfoChar(&buf, ',');
-
-	/* if printed internal query, print internal pos too */
-	if (edata->internalpos > 0 && edata->internalquery != NULL)
-		appendStringInfo(&buf, "%d", edata->internalpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* errcontext */
-	if (!edata->hide_ctx)
-		appendCSVLiteral(&buf, edata->context);
-	appendStringInfoChar(&buf, ',');
-
-	/* user query --- only reported if not disabled by the caller */
-	print_stmt = check_log_of_query(edata);
-	if (print_stmt)
-		appendCSVLiteral(&buf, debug_query_string);
-	appendStringInfoChar(&buf, ',');
-	if (print_stmt && edata->cursorpos > 0)
-		appendStringInfo(&buf, "%d", edata->cursorpos);
-	appendStringInfoChar(&buf, ',');
-
-	/* file error location */
-	if (Log_error_verbosity >= PGERROR_VERBOSE)
-	{
-		StringInfoData msgbuf;
-
-		initStringInfo(&msgbuf);
-
-		if (edata->funcname && edata->filename)
-			appendStringInfo(&msgbuf, "%s, %s:%d",
-							 edata->funcname, edata->filename,
-							 edata->lineno);
-		else if (edata->filename)
-			appendStringInfo(&msgbuf, "%s:%d",
-							 edata->filename, edata->lineno);
-		appendCSVLiteral(&buf, msgbuf.data);
-		pfree(msgbuf.data);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* application name */
-	if (application_name)
-		appendCSVLiteral(&buf, application_name);
-
-	appendStringInfoChar(&buf, ',');
-
-	/* backend type */
-	appendCSVLiteral(&buf, get_backend_type_for_log());
-	appendStringInfoChar(&buf, ',');
-
-	/* leader PID */
-	if (MyProc)
-	{
-		PGPROC	   *leader = MyProc->lockGroupLeader;
-
-		/*
-		 * Show the leader only for active parallel workers.  This leaves out
-		 * the leader of a parallel group.
-		 */
-		if (leader && leader->pid != MyProcPid)
-			appendStringInfo(&buf, "%d", leader->pid);
-	}
-	appendStringInfoChar(&buf, ',');
-
-	/* query id */
-	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
-
-	appendStringInfoChar(&buf, '\n');
-
-	/* If in the syslogger process, try to write messages direct to file */
-	if (MyBackendType == B_LOGGER)
-		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-	else
-		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
-
-	pfree(buf.data);
-}
-
 /*
  * Unpack MAKE_SQLSTATE code. Note that this returns a pointer to a
  * static buffer.
-- 
2.34.1

From 077656335da1aaf12b543f5d05c493804adfa4d5 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Mon, 10 Jan 2022 21:44:53 +0900
Subject: [PATCH v9 3/3] JSON logging

---
 src/include/postmaster/syslogger.h            |   1 +
 src/include/utils/elog.h                      |   2 +
 src/backend/postmaster/syslogger.c            | 105 ++++++-
 src/backend/utils/adt/misc.c                  |   5 +-
 src/backend/utils/error/Makefile              |   3 +-
 src/backend/utils/error/elog.c                |  18 ++
 src/backend/utils/error/jsonlog.c             | 294 ++++++++++++++++++
 src/backend/utils/misc/guc.c                  |   4 +-
 src/backend/utils/misc/postgresql.conf.sample |  13 +-
 src/bin/pg_ctl/t/004_logrotate.pl             |  16 +-
 doc/src/sgml/config.sgml                      | 203 +++++++++++-
 11 files changed, 630 insertions(+), 34 deletions(-)
 create mode 100644 src/backend/utils/error/jsonlog.c

diff --git a/src/include/postmaster/syslogger.h b/src/include/postmaster/syslogger.h
index 2df68a196e..1ca326e52e 100644
--- a/src/include/postmaster/syslogger.h
+++ b/src/include/postmaster/syslogger.h
@@ -64,6 +64,7 @@ typedef union
 /* log destinations */
 #define PIPE_PROTO_DEST_STDERR	0x10
 #define PIPE_PROTO_DEST_CSVLOG	0x20
+#define PIPE_PROTO_DEST_JSONLOG	0x40
 
 /* GUC options */
 extern bool Logging_collector;
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index f37956f100..77c5a6b9a3 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -436,6 +436,7 @@ extern bool syslog_split_messages;
 #define LOG_DESTINATION_SYSLOG	 2
 #define LOG_DESTINATION_EVENTLOG 4
 #define LOG_DESTINATION_CSVLOG	 8
+#define LOG_DESTINATION_JSONLOG	16
 
 /* Other exported functions */
 extern void DebugFileOpen(void);
@@ -453,6 +454,7 @@ extern void write_pipe_chunks(char *data, int len, int dest);
 
 /* Destination-specific functions */
 extern void write_csvlog(ErrorData *edata);
+extern void write_jsonlog(ErrorData *edata);
 
 #ifdef HAVE_SYSLOG
 extern void set_syslog_parameters(const char *ident, int facility);
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index 2256f072aa..eb53260943 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -86,9 +86,11 @@ static bool pipe_eof_seen = false;
 static bool rotation_disabled = false;
 static FILE *syslogFile = NULL;
 static FILE *csvlogFile = NULL;
+static FILE *jsonlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
 static char *last_sys_file_name = NULL;
 static char *last_csv_file_name = NULL;
+static char *last_json_file_name = NULL;
 
 /*
  * Buffers for saving partial messages from different backends.
@@ -281,6 +283,8 @@ SysLoggerMain(int argc, char *argv[])
 	last_sys_file_name = logfile_getname(first_syslogger_file_time, NULL);
 	if (csvlogFile != NULL)
 		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
+	if (jsonlogFile != NULL)
+		last_json_file_name = logfile_getname(first_syslogger_file_time, ".json");
 
 	/* remember active logfile parameters */
 	currentLogDir = pstrdup(Log_directory);
@@ -367,6 +371,14 @@ SysLoggerMain(int argc, char *argv[])
 				(csvlogFile != NULL))
 				rotation_requested = true;
 
+			/*
+			 * Force a rotation if JSONLOG output was just turned on or off and
+			 * we need to open or close jsonlogFile accordingly.
+			 */
+			if (((Log_destination & LOG_DESTINATION_JSONLOG) != 0) !=
+				(jsonlogFile != NULL))
+				rotation_requested = true;
+
 			/*
 			 * If rotation time parameter changed, reset next rotation time,
 			 * but don't immediately force a rotation.
@@ -417,6 +429,12 @@ SysLoggerMain(int argc, char *argv[])
 				rotation_requested = true;
 				size_rotation_for |= LOG_DESTINATION_CSVLOG;
 			}
+			if (jsonlogFile != NULL &&
+				ftell(jsonlogFile) >= Log_RotationSize * 1024L)
+			{
+				rotation_requested = true;
+				size_rotation_for |= LOG_DESTINATION_JSONLOG;
+			}
 		}
 
 		if (rotation_requested)
@@ -426,7 +444,7 @@ SysLoggerMain(int argc, char *argv[])
 			 * was sent by pg_rotate_logfile() or "pg_ctl logrotate".
 			 */
 			if (!time_based_rotation && size_rotation_for == 0)
-				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG;
+				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG | LOG_DESTINATION_JSONLOG;
 			logfile_rotate(time_based_rotation, size_rotation_for);
 		}
 
@@ -632,6 +650,20 @@ SysLogger_Start(void)
 		pfree(filename);
 	}
 
+	/*
+	 * Likewise for the initial JSON log file, if that's enabled.  (Note that
+	 * we open syslogFile even when only JSON output is nominally enabled,
+	 * since some code paths will write to syslogFile anyway.)
+	 */
+	if (Log_destination & LOG_DESTINATION_JSONLOG)
+	{
+		filename = logfile_getname(first_syslogger_file_time, ".json");
+
+		jsonlogFile = logfile_open(filename, "a", false);
+
+		pfree(filename);
+	}
+
 #ifdef EXEC_BACKEND
 	switch ((sysloggerPid = syslogger_forkexec()))
 #else
@@ -729,6 +761,11 @@ SysLogger_Start(void)
 				fclose(csvlogFile);
 				csvlogFile = NULL;
 			}
+			if (jsonlogFile != NULL)
+			{
+				fclose(jsonlogFile);
+				jsonlogFile = NULL;
+			}
 			return (int) sysloggerPid;
 	}
 
@@ -805,6 +842,7 @@ syslogger_forkexec(void)
 	int			ac = 0;
 	char		filenobuf[32];
 	char		csvfilenobuf[32];
+	char		jsonfilenobuf[32];
 
 	av[ac++] = "postgres";
 	av[ac++] = "--forklog";
@@ -817,6 +855,9 @@ syslogger_forkexec(void)
 	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%d",
 			 syslogger_fdget(csvlogFile));
 	av[ac++] = csvfilenobuf;
+	snprintf(jsonfilenobuf, sizeof(jsonfilenobuf), "%d",
+			 syslogger_fdget(jsonlogFile));
+	av[ac++] = jsonfilenobuf;
 
 	av[ac] = NULL;
 	Assert(ac < lengthof(av));
@@ -834,7 +875,7 @@ syslogger_parseArgs(int argc, char *argv[])
 {
 	int			fd;
 
-	Assert(argc == 5);
+	Assert(argc == 6);
 	argv += 3;
 
 	/*
@@ -848,6 +889,8 @@ syslogger_parseArgs(int argc, char *argv[])
 	syslogFile = syslogger_fdopen(fd);
 	fd = atoi(*argv++);
 	csvlogFile = syslogger_fdopen(fd);
+	fd = atoi(*argv++);
+	jsonlogFile = syslogger_fdopen(fd);
 }
 #endif							/* EXEC_BACKEND */
 
@@ -896,7 +939,9 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 
 		/* Do we have a valid header? */
 		memcpy(&p, cursor, offsetof(PipeProtoHeader, data));
-		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR | PIPE_PROTO_DEST_CSVLOG);
+		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR |
+								PIPE_PROTO_DEST_CSVLOG |
+								PIPE_PROTO_DEST_JSONLOG);
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&
@@ -918,6 +963,8 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 				dest = LOG_DESTINATION_STDERR;
 			else if ((p.flags & PIPE_PROTO_DEST_CSVLOG) != 0)
 				dest = LOG_DESTINATION_CSVLOG;
+			else if ((p.flags & PIPE_PROTO_DEST_JSONLOG) != 0)
+				dest = LOG_DESTINATION_JSONLOG;
 			else
 			{
 				/* this should never happen as of the header validation */
@@ -1097,19 +1144,24 @@ write_syslogger_file(const char *buffer, int count, int destination)
 	FILE	   *logfile;
 
 	/*
-	 * If we're told to write to csvlogFile, but it's not open, dump the data
-	 * to syslogFile (which is always open) instead.  This can happen if CSV
-	 * output is enabled after postmaster start and we've been unable to open
-	 * csvlogFile.  There are also race conditions during a parameter change
-	 * whereby backends might send us CSV output before we open csvlogFile or
-	 * after we close it.  Writing CSV-formatted output to the regular log
-	 * file isn't great, but it beats dropping log output on the floor.
+	 * If we're told to write to a structured log file, but it's not open,
+	 * dump the data to syslogFile (which is always open) instead.  This can
+	 * happen if structured output is enabled after postmaster start and
+	 * we've been unable to open logFile.  There are also race conditions
+	 * during a parameter change whereby backends might send us structured
+	 * output before we open the logFile or after we close it.  Writing
+	 * formatted output to the regular log file isn't great, but it beats
+	 * dropping log output on the floor.
 	 *
-	 * Think not to improve this by trying to open csvlogFile on-the-fly.  Any
+	 * Think not to improve this by trying to open logFile on-the-fly.  Any
 	 * failure in that would lead to recursion.
 	 */
-	logfile = (destination == LOG_DESTINATION_CSVLOG &&
-			   csvlogFile != NULL) ? csvlogFile : syslogFile;
+	if ((destination & LOG_DESTINATION_CSVLOG) && csvlogFile != NULL)
+		logfile = csvlogFile;
+	else if ((destination & LOG_DESTINATION_JSONLOG) && jsonlogFile != NULL)
+		logfile = jsonlogFile;
+	else
+		logfile = syslogFile;
 
 	rc = fwrite(buffer, 1, count, logfile);
 
@@ -1180,7 +1232,8 @@ pipeThread(void *arg)
 		if (Log_RotationSize > 0)
 		{
 			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
-				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
+				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L) ||
+				(jsonlogFile != NULL && ftell(jsonlogFile) >= Log_RotationSize * 1024L))
 				SetLatch(MyLatch);
 		}
 		LeaveCriticalSection(&sysloggerSection);
@@ -1292,6 +1345,8 @@ logfile_rotate_dest(bool time_based_rotation, int size_rotation_for,
 		logFileExt = NULL;
 	else if (target_dest == LOG_DESTINATION_CSVLOG)
 		logFileExt = ".csv";
+	else if (target_dest == LOG_DESTINATION_JSONLOG)
+		logFileExt = ".json";
 	else
 	{
 		/* cannot happen */
@@ -1379,6 +1434,12 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 							 &csvlogFile))
 		return;
 
+	/* file rotation for jsonlog */
+	if (!logfile_rotate_dest(time_based_rotation, size_rotation_for, fntime,
+							 LOG_DESTINATION_JSONLOG, &last_json_file_name,
+							 &jsonlogFile))
+		return;
+
 	update_metainfo_datafile();
 
 	set_next_rotation_time();
@@ -1465,7 +1526,8 @@ update_metainfo_datafile(void)
 	mode_t		oumask;
 
 	if (!(Log_destination & LOG_DESTINATION_STDERR) &&
-		!(Log_destination & LOG_DESTINATION_CSVLOG))
+		!(Log_destination & LOG_DESTINATION_CSVLOG) &&
+		!(Log_destination & LOG_DESTINATION_JSONLOG))
 	{
 		if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
 			ereport(LOG,
@@ -1523,6 +1585,19 @@ update_metainfo_datafile(void)
 			return;
 		}
 	}
+
+	if (last_json_file_name && (Log_destination & LOG_DESTINATION_JSONLOG))
+	{
+		if (fprintf(fh, "jsonlog %s\n", last_json_file_name) < 0)
+		{
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not write file \"%s\": %m",
+							LOG_METAINFO_DATAFILE_TMP)));
+			fclose(fh);
+			return;
+		}
+	}
 	fclose(fh);
 
 	if (rename(LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE) != 0)
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index fe4f180b6f..b3e1453bed 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -843,11 +843,12 @@ pg_current_logfile(PG_FUNCTION_ARGS)
 	{
 		logfmt = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
-		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0)
+		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0 &&
+				strcmp(logfmt, "jsonlog") != 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("log format \"%s\" is not supported", logfmt),
-					 errhint("The supported log formats are \"stderr\" and \"csvlog\".")));
+					 errhint("The supported log formats are \"stderr\", \"csvlog\", and \"jsonlog\".")));
 	}
 
 	fd = AllocateFile(LOG_METAINFO_DATAFILE, "r");
diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index ef770dd2f2..65ba61fb3c 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -15,6 +15,7 @@ include $(top_builddir)/src/Makefile.global
 OBJS = \
 	assert.o \
 	csvlog.o \
-	elog.o
+	elog.o \
+	jsonlog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 511b43e4ac..680497de46 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2984,6 +2984,22 @@ send_message_to_server_log(ErrorData *edata)
 			fallback_to_stderr = true;
 	}
 
+	/* Write to JSON log, if enabled */
+	if ((Log_destination & LOG_DESTINATION_JSONLOG) != 0)
+	{
+		/*
+		 * Send JSON data if it's safe to do so (syslogger doesn't need the
+		 * pipe).  If this is not possible, fallback to an entry written
+		 * to stderr.
+		 */
+		if (redirection_done || MyBackendType == B_LOGGER)
+		{
+			write_jsonlog(edata);
+		}
+		else
+			fallback_to_stderr = true;
+	}
+
 	/*
 	 * Write to stderr, if enabled or if required because of a previous
 	 * limitation.
@@ -3059,6 +3075,8 @@ write_pipe_chunks(char *data, int len, int dest)
 		p.proto.flags |= PIPE_PROTO_DEST_STDERR;
 	else if (dest == LOG_DESTINATION_CSVLOG)
 		p.proto.flags |= PIPE_PROTO_DEST_CSVLOG;
+	else if (dest == LOG_DESTINATION_JSONLOG)
+		p.proto.flags |= PIPE_PROTO_DEST_JSONLOG;
 
 	/* write all but the last chunk */
 	while (len > PIPE_MAX_PAYLOAD)
diff --git a/src/backend/utils/error/jsonlog.c b/src/backend/utils/error/jsonlog.c
new file mode 100644
index 0000000000..f2101b59ff
--- /dev/null
+++ b/src/backend/utils/error/jsonlog.c
@@ -0,0 +1,294 @@
+/*-------------------------------------------------------------------------
+ *
+ * jsonlog.c
+ *	  JSON logging
+ *
+ * Copyright (c) 2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/jsonlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog.h"
+#include "utils/guc.h"
+#include "utils/json.h"
+#include "utils/ps_status.h"
+
+static void appendJSONKeyValueFmt(StringInfo buf, const char *key,
+								  bool escape_key,
+								  const char *fmt,...) pg_attribute_printf(4, 5);
+
+/*
+ * appendJSONKeyValue
+ * Append to a StringInfo a comma followed by a JSON key and value.
+ * The key is always escaped. The value can be escaped optionally.
+ */
+static void
+appendJSONKeyValue(StringInfo buf, const char *key, const char *value,
+				   bool escape_value)
+{
+	Assert(key != NULL);
+
+	if (value == NULL)
+		return;
+
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+
+	if (escape_value)
+		escape_json(buf, value);
+	else
+		appendStringInfoString(buf, value);
+}
+
+
+/*
+ * appendJSONKeyValueFmt
+ *
+ * Evaluate the fmt string and then invoke appendJSONKeyValue as the
+ * value of the JSON property. Both the key and value will be escaped by
+ * appendJSONKeyValue.
+ */
+static void
+appendJSONKeyValueFmt(StringInfo buf, const char *key,
+					  bool escape_key, const char *fmt,...)
+{
+	int			save_errno = errno;
+	size_t		len = 128;		/* initial assumption about buffer size */
+	char	    *value;
+
+	for (;;)
+	{
+		va_list		args;
+		size_t		newlen;
+
+		/* Allocate result buffer */
+		value = (char *) palloc(len);
+
+		/* Try to format the data. */
+		errno = save_errno;
+		va_start(args, fmt);
+		newlen = pvsnprintf(value, len, fmt, args);
+		va_end(args);
+
+		if (newlen < len)
+			break; /* success */
+
+		/* Release buffer and loop around to try again with larger len. */
+		pfree(value);
+		len = newlen;
+	}
+
+	appendJSONKeyValue(buf, key, value, escape_key);
+
+	/* Clean up */
+	pfree(value);
+}
+
+/*
+ * Write logs in json format.
+ */
+void
+write_jsonlog(ErrorData *edata)
+{
+	StringInfoData	buf;
+	char	   *start_time;
+	char	   *log_time;
+
+	/* static counter for line numbers */
+	static long	log_line_number = 0;
+
+	/* Has the counter been reset in the current process? */
+	static int	log_my_pid = 0;
+
+	/*
+	 * This is one of the few places where we'd rather not inherit a static
+	 * variable's value from the postmaster.  But since we will, reset it when
+	 * MyProcPid changes.
+	 */
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		reset_formatted_start_time();
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* Initialize string */
+	appendStringInfoChar(&buf, '{');
+
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+
+	/*
+	 * First property does not use appendJSONKeyValue as it does not have
+	 * comma prefix.
+	 */
+	escape_json(&buf, "timestamp");
+	appendStringInfoChar(&buf, ':');
+	escape_json(&buf, log_time);
+
+	/* username */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "user", MyProcPort->user_name, true);
+
+	/* database name */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "dbname", MyProcPort->database_name, true);
+
+	/* Process ID */
+	if (MyProcPid != 0)
+		appendJSONKeyValueFmt(&buf, "pid", false, "%d", MyProcPid);
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendJSONKeyValue(&buf, "remote_host", MyProcPort->remote_host, true);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+			appendJSONKeyValue(&buf, "remote_port", MyProcPort->remote_port, false);
+	}
+
+	/* Session id */
+	appendJSONKeyValueFmt(&buf, "session_id", true, "%lx.%x", (long) MyStartTime, MyProcPid);
+
+	/* Line number */
+	appendJSONKeyValueFmt(&buf, "line_num", false, "%ld", log_line_number);
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData	msgbuf;
+		const char	   *psdisp;
+		int				displen;
+
+		initStringInfo(&msgbuf);
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendJSONKeyValue(&buf, "ps", msgbuf.data, true);
+
+		pfree(msgbuf.data);
+	}
+
+	/* session start timestamp */
+	start_time = get_formatted_start_time();
+	appendJSONKeyValue(&buf, "session_start", start_time, true);
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendJSONKeyValueFmt(&buf, "vxid", true, "%d/%u", MyProc->backendId, MyProc->lxid);
+
+	/* Transaction id */
+	appendJSONKeyValueFmt(&buf, "txid", false, "%u", GetTopTransactionIdIfAny());
+
+	/* Error severity */
+	if (edata->elevel)
+		appendJSONKeyValue(&buf, "error_severity",
+						   (char *) error_severity(edata->elevel), true);
+
+	/* SQL state code */
+	if (edata->sqlerrcode)
+		appendJSONKeyValue(&buf, "state_code",
+						   unpack_sql_state(edata->sqlerrcode), true);
+
+	/* errmessage */
+	appendJSONKeyValue(&buf, "message", edata->message, true);
+
+	/* errdetail or error_detail log */
+	if (edata->detail_log)
+		appendJSONKeyValue(&buf, "detail", edata->detail_log, true);
+	else
+		appendJSONKeyValue(&buf, "detail", edata->detail, true);
+
+	/* errhint */
+	if (edata->hint)
+		appendJSONKeyValue(&buf, "hint", edata->hint, true);
+
+	/* internal query */
+	if (edata->internalquery)
+		appendJSONKeyValue(&buf, "internal_query", edata->internalquery, true);
+
+	/* if printed internal query, print internal pos too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendJSONKeyValueFmt(&buf, "internal_position", false, "%u",
+							  edata->internalpos);
+
+	/* errcontext */
+	if (edata->context && !edata->hide_ctx)
+		appendJSONKeyValue(&buf, "context", edata->context, true);
+
+	/* user query --- only reported if not disabled by the caller */
+	if (check_log_of_query(edata))
+	{
+		appendJSONKeyValue(&buf, "statement", debug_query_string, true);
+		if (edata->cursorpos > 0)
+			appendJSONKeyValueFmt(&buf, "cursor_position", false, "%d",
+								  edata->cursorpos);
+	}
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		if (edata->funcname)
+			appendJSONKeyValue(&buf, "func_name", edata->funcname, true);
+		if (edata->filename)
+		{
+			appendJSONKeyValue(&buf, "file_name", edata->filename, true);
+			appendJSONKeyValueFmt(&buf, "file_line_num", false, "%d",
+								  edata->lineno);
+		}
+	}
+
+	/* Application name */
+	if (application_name && application_name[0] != '\0')
+		appendJSONKeyValue(&buf, "application_name", application_name, true);
+
+	/* backend type */
+	appendJSONKeyValue(&buf, "backend_type", get_backend_type_for_log(), true);
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendJSONKeyValueFmt(&buf, "leader_pid", false, "%d", leader->pid);
+	}
+
+	/* query id */
+	appendJSONKeyValueFmt(&buf, "query_id", false, "%lld",
+						  (long long) pgstat_get_my_query_id());
+
+	/* Finish string */
+	appendStringInfoChar(&buf, '}');
+	appendStringInfoChar(&buf, '\n');
+
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+	else
+		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 6fc5cbc09a..b651429ed6 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4264,7 +4264,7 @@ static struct config_string ConfigureNamesString[] =
 		{"log_destination", PGC_SIGHUP, LOGGING_WHERE,
 			gettext_noop("Sets the destination for server log output."),
 			gettext_noop("Valid values are combinations of \"stderr\", "
-						 "\"syslog\", \"csvlog\", and \"eventlog\", "
+						 "\"syslog\", \"csvlog\", \"jsonlog\" and \"eventlog\", "
 						 "depending on the platform."),
 			GUC_LIST_INPUT
 		},
@@ -11740,6 +11740,8 @@ check_log_destination(char **newval, void **extra, GucSource source)
 			newlogdest |= LOG_DESTINATION_STDERR;
 		else if (pg_strcasecmp(tok, "csvlog") == 0)
 			newlogdest |= LOG_DESTINATION_CSVLOG;
+		else if (pg_strcasecmp(tok, "jsonlog") == 0)
+			newlogdest |= LOG_DESTINATION_JSONLOG;
 #ifdef HAVE_SYSLOG
 		else if (pg_strcasecmp(tok, "syslog") == 0)
 			newlogdest |= LOG_DESTINATION_SYSLOG;
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index a1acd46b61..817d5f5324 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -432,14 +432,15 @@
 # - Where to Log -
 
 #log_destination = 'stderr'		# Valid values are combinations of
-					# stderr, csvlog, syslog, and eventlog,
-					# depending on platform.  csvlog
-					# requires logging_collector to be on.
+					# stderr, csvlog, jsonlog, syslog, and
+					# eventlog, depending on platform.
+					# csvlog and jsonlog require
+					# logging_collector to be on.
 
 # This is used when logging to stderr:
-#logging_collector = off		# Enable capturing of stderr and csvlog
-					# into log files. Required to be on for
-					# csvlogs.
+#logging_collector = off		# Enable capturing of stderr, jsonlog
+					# and csvlog into log files. Required
+					# to be on for csvlogs and jsonlogs.
 					# (change requires restart)
 
 # These are only used if logging_collector is on:
diff --git a/src/bin/pg_ctl/t/004_logrotate.pl b/src/bin/pg_ctl/t/004_logrotate.pl
index e04331bfef..c0194359b4 100644
--- a/src/bin/pg_ctl/t/004_logrotate.pl
+++ b/src/bin/pg_ctl/t/004_logrotate.pl
@@ -6,7 +6,7 @@ use warnings;
 
 use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
-use Test::More tests => 10;
+use Test::More tests => 14;
 use Time::HiRes qw(usleep);
 
 # Extract the file name of a $format from the contents of
@@ -39,7 +39,7 @@ sub check_log_pattern
 	my $node     = shift;
 	my $lfname   = fetch_file_name($logfiles, $format);
 
-	my $max_attempts = 180 * 10;
+	my $max_attempts = 360 * 10;
 
 	my $logcontents;
 	for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
@@ -65,7 +65,7 @@ $node->init();
 $node->append_conf(
 	'postgresql.conf', qq(
 logging_collector = on
-log_destination = 'stderr, csvlog'
+log_destination = 'stderr, csvlog, jsonlog'
 # these ensure stability of test results:
 log_rotation_age = 0
 lc_messages = 'C'
@@ -78,7 +78,7 @@ $node->start();
 $node->psql('postgres', 'SELECT 1/0');
 
 # might need to retry if logging collector process is slow...
-my $max_attempts = 180 * 10;
+my $max_attempts = 360 * 10;
 
 my $current_logfiles;
 for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
@@ -96,11 +96,13 @@ note "current_logfiles = $current_logfiles";
 like(
 	$current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'current_logfiles is sane');
 
 check_log_pattern('stderr', $current_logfiles, 'division by zero', $node);
 check_log_pattern('csvlog', $current_logfiles, 'division by zero', $node);
+check_log_pattern('jsonlog', $current_logfiles, 'division by zero', $node);
 
 # Sleep 2 seconds and ask for log rotation; this should result in
 # output into a different log file name.
@@ -122,7 +124,8 @@ note "now current_logfiles = $new_current_logfiles";
 like(
 	$new_current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'new current_logfiles is sane');
 
 # Verify that log output gets to this file, too
@@ -130,5 +133,6 @@ $node->psql('postgres', 'fee fi fo fum');
 
 check_log_pattern('stderr', $new_current_logfiles, 'syntax error', $node);
 check_log_pattern('csvlog', $new_current_logfiles, 'syntax error', $node);
+check_log_pattern('jsonlog', $new_current_logfiles, 'syntax error', $node);
 
 $node->stop();
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index afbb6c35e3..c29ced427c 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5931,7 +5931,8 @@ SELECT * FROM parent WHERE key = 2400;
        <para>
         <productname>PostgreSQL</productname> supports several methods
          for logging server messages, including
-         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem> and
+         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem>,
+         <systemitem>jsonlog</systemitem>, and
          <systemitem>syslog</systemitem>. On Windows,
          <systemitem>eventlog</systemitem> is also supported. Set this
          parameter to a list of desired log destinations separated by
@@ -5949,6 +5950,14 @@ SELECT * FROM parent WHERE key = 2400;
         <xref linkend="guc-logging-collector"/> must be enabled to generate
         CSV-format log output.
        </para>
+       <para>
+        If <systemitem>jsonlog</systemitem> is included in <varname>log_destination</varname>,
+        log entries are output in <acronym>JSON</acronym> format, which is convenient for
+        loading logs into programs.
+        See <xref linkend="runtime-config-logging-jsonlog"/> for details.
+        <xref linkend="guc-logging-collector"/> must be enabled to generate
+        JSON-format log output.
+       </para>
        <para>
         When either <systemitem>stderr</systemitem> or
         <systemitem>csvlog</systemitem> are included, the file
@@ -5960,13 +5969,14 @@ SELECT * FROM parent WHERE key = 2400;
 <programlisting>
 stderr log/postgresql.log
 csvlog log/postgresql.csv
+jsonlog log/postgresql.json
 </programlisting>
 
         <filename>current_logfiles</filename> is recreated when a new log file
         is created as an effect of rotation, and
         when <varname>log_destination</varname> is reloaded.  It is removed when
-        neither <systemitem>stderr</systemitem>
-        nor <systemitem>csvlog</systemitem> are included
+        none of <systemitem>stderr</systemitem>,
+        <systemitem>csvlog</systemitem>, <systemitem>jsonlog</systemitem> are included
         in <varname>log_destination</varname>, and when the logging collector is
         disabled.
        </para>
@@ -6106,6 +6116,13 @@ local0.*    /var/log/postgresql
         (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
         replaced instead.)
        </para>
+       <para>
+        If JSON-format output is enabled in <varname>log_destination</varname>,
+        <literal>.json</literal> will be appended to the timestamped
+        log file name to create the file name for JSON-format output.
+        (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
+        replaced instead.)
+       </para>
        <para>
         This parameter can only be set in the <filename>postgresql.conf</filename>
         file or on the server command line.
@@ -7467,6 +7484,186 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         </orderedlist>
       </para>
     </sect2>
+     <sect2 id="runtime-config-logging-jsonlog">
+     <title>Using JSON-Format Log Output</title>
+
+     <para>
+      Including <literal>jsonlog</literal> in the <varname>log_destination</varname> list
+      provides a convenient way to import log files into many different programs.
+      This option emits log lines in (<acronym>JSON</acronym>) format.
+     </para>
+
+     <para>
+      String fields with null values are excluded from output.
+      Additional fields may be added in the future. User applications that process jsonlog
+      output should ignore unknown fields.
+     </para>
+
+     <para>
+      Each log line is serialized as a JSON object as of the following
+      set of keys with their values.
+     </para>
+
+     <table>
+      <title>Keys and values of JSON log entries</title>
+      <tgroup cols="3">
+       <thead>
+        <row>
+         <entry>Key name</entry>
+         <entry>Type</entry>
+         <entry>Description</entry>
+        </row>
+       </thead>
+       <tbody>
+        <row>
+         <entry><literal>timestamp</literal></entry>
+         <entry>string</entry>
+         <entry>Time stamp with milliseconds</entry>
+        </row>
+        <row>
+         <entry><literal>user</literal></entry>
+         <entry>string</entry>
+         <entry>User name</entry>
+        </row>
+        <row>
+         <entry><literal>dbname</literal></entry>
+         <entry>string</entry>
+         <entry>Database name</entry>
+        </row>
+        <row>
+         <entry><literal>pid</literal></entry>
+         <entry>number</entry>
+         <entry>Process ID</entry>
+        </row>
+        <row>
+         <entry><literal>remote_host</literal></entry>
+         <entry>string</entry>
+         <entry>Client host</entry>
+        </row>
+        <row>
+         <entry><literal>remote_port</literal></entry>
+         <entry>number</entry>
+         <entry>Client port</entry>
+        </row>
+        <row>
+         <entry><literal>session_id</literal></entry>
+         <entry>string</entry>
+         <entry>Session ID</entry>
+        </row>
+        <row>
+         <entry><literal>line_num</literal></entry>
+         <entry>number</entry>
+         <entry>Per-session line number</entry>
+        </row>
+        <row>
+         <entry><literal>ps</literal></entry>
+         <entry>string</entry>
+         <entry>Current ps display</entry>
+        </row>
+        <row>
+         <entry><literal>session_start</literal></entry>
+         <entry>string</entry>
+         <entry>Session start time</entry>
+        </row>
+        <row>
+         <entry><literal>vxid</literal></entry>
+         <entry>string</entry>
+         <entry>Virtual transaction ID</entry>
+        </row>
+        <row>
+         <entry><literal>txid</literal></entry>
+         <entry>string</entry>
+         <entry>Regular transaction ID</entry>
+        </row>
+        <row>
+         <entry><literal>error_severity</literal></entry>
+         <entry>string</entry>
+         <entry>Error severity</entry>
+        </row>
+        <row>
+         <entry><literal>state_code</literal></entry>
+         <entry>string</entry>
+         <entry>SQLSTATE code</entry>
+        </row>
+        <row>
+         <entry><literal>message</literal></entry>
+         <entry>string</entry>
+         <entry>Error message</entry>
+        </row>
+        <row>
+         <entry><literal>detail</literal></entry>
+         <entry>string</entry>
+         <entry>Error message detail</entry>
+        </row>
+        <row>
+         <entry><literal>hint</literal></entry>
+         <entry>string</entry>
+         <entry>Error message hint</entry>
+        </row>
+        <row>
+         <entry><literal>internal_query</literal></entry>
+         <entry>string</entry>
+         <entry>Internal query that led to the error</entry>
+        </row>
+        <row>
+         <entry><literal>internal_position</literal></entry>
+         <entry>number</entry>
+         <entry>Cursor index into internal query</entry>
+        </row>
+        <row>
+         <entry><literal>context</literal></entry>
+         <entry>string</entry>
+         <entry>Error context</entry>
+        </row>
+        <row>
+         <entry><literal>statement</literal></entry>
+         <entry>string</entry>
+         <entry>Client-supplied query string</entry>
+        </row>
+        <row>
+         <entry><literal>cursor_position</literal></entry>
+         <entry>string</entry>
+         <entry>Cursor index into query string</entry>
+        </row>
+        <row>
+         <entry><literal>func_name</literal></entry>
+         <entry>string</entry>
+         <entry>Error location function name</entry>
+        </row>
+        <row>
+         <entry><literal>file_name</literal></entry>
+         <entry>string</entry>
+         <entry>File name of error location</entry>
+        </row>
+        <row>
+         <entry><literal>file_line_num</literal></entry>
+         <entry>number</entry>
+         <entry>File line number of the error location</entry>
+        </row>
+        <row>
+         <entry><literal>application_name</literal></entry>
+         <entry>string</entry>
+         <entry>Client application name</entry>
+        </row>
+        <row>
+         <entry><literal>backend_type</literal></entry>
+         <entry>string</entry>
+         <entry>Type of backend</entry>
+        </row>
+        <row>
+         <entry><literal>leader_pid</literal></entry>
+         <entry>number</entry>
+         <entry>Process ID of leader for active parallel workers</entry>
+        </row>
+        <row>
+         <entry><literal>query_id</literal></entry>
+         <entry>number</entry>
+         <entry>Query ID</entry>
+        </row>
+       </tbody>
+      </tgroup>
+     </table>
+    </sect2>
 
    <sect2>
     <title>Process Title</title>
-- 
2.34.1

From b5b0e35d66e491df0f75c874ff4dd73fb7607c68 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Wed, 12 Jan 2022 15:19:16 +0900
Subject: [PATCH v10] JSON logging

---
 src/include/postmaster/syslogger.h            |   1 +
 src/include/utils/elog.h                      |   2 +
 src/backend/postmaster/syslogger.c            | 105 ++++++-
 src/backend/utils/adt/misc.c                  |   5 +-
 src/backend/utils/error/Makefile              |   3 +-
 src/backend/utils/error/elog.c                |  18 ++
 src/backend/utils/error/jsonlog.c             | 294 ++++++++++++++++++
 src/backend/utils/misc/guc.c                  |   4 +-
 src/backend/utils/misc/postgresql.conf.sample |  13 +-
 src/bin/pg_ctl/t/004_logrotate.pl             |  20 +-
 doc/src/sgml/config.sgml                      | 203 +++++++++++-
 11 files changed, 632 insertions(+), 36 deletions(-)
 create mode 100644 src/backend/utils/error/jsonlog.c

diff --git a/src/include/postmaster/syslogger.h b/src/include/postmaster/syslogger.h
index 2df68a196e..1ca326e52e 100644
--- a/src/include/postmaster/syslogger.h
+++ b/src/include/postmaster/syslogger.h
@@ -64,6 +64,7 @@ typedef union
 /* log destinations */
 #define PIPE_PROTO_DEST_STDERR	0x10
 #define PIPE_PROTO_DEST_CSVLOG	0x20
+#define PIPE_PROTO_DEST_JSONLOG	0x40
 
 /* GUC options */
 extern bool Logging_collector;
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 5bc38663cb..3eb8de3966 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -436,6 +436,7 @@ extern bool syslog_split_messages;
 #define LOG_DESTINATION_SYSLOG	 2
 #define LOG_DESTINATION_EVENTLOG 4
 #define LOG_DESTINATION_CSVLOG	 8
+#define LOG_DESTINATION_JSONLOG	16
 
 /* Other exported functions */
 extern void DebugFileOpen(void);
@@ -453,6 +454,7 @@ extern void write_pipe_chunks(char *data, int len, int dest);
 
 /* Destination-specific functions */
 extern void write_csvlog(ErrorData *edata);
+extern void write_jsonlog(ErrorData *edata);
 
 #ifdef HAVE_SYSLOG
 extern void set_syslog_parameters(const char *ident, int facility);
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index 2256f072aa..8d26573817 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -86,9 +86,11 @@ static bool pipe_eof_seen = false;
 static bool rotation_disabled = false;
 static FILE *syslogFile = NULL;
 static FILE *csvlogFile = NULL;
+static FILE *jsonlogFile = NULL;
 NON_EXEC_STATIC pg_time_t first_syslogger_file_time = 0;
 static char *last_sys_file_name = NULL;
 static char *last_csv_file_name = NULL;
+static char *last_json_file_name = NULL;
 
 /*
  * Buffers for saving partial messages from different backends.
@@ -281,6 +283,8 @@ SysLoggerMain(int argc, char *argv[])
 	last_sys_file_name = logfile_getname(first_syslogger_file_time, NULL);
 	if (csvlogFile != NULL)
 		last_csv_file_name = logfile_getname(first_syslogger_file_time, ".csv");
+	if (jsonlogFile != NULL)
+		last_json_file_name = logfile_getname(first_syslogger_file_time, ".json");
 
 	/* remember active logfile parameters */
 	currentLogDir = pstrdup(Log_directory);
@@ -367,6 +371,14 @@ SysLoggerMain(int argc, char *argv[])
 				(csvlogFile != NULL))
 				rotation_requested = true;
 
+			/*
+			 * Force a rotation if JSONLOG output was just turned on or off
+			 * and we need to open or close jsonlogFile accordingly.
+			 */
+			if (((Log_destination & LOG_DESTINATION_JSONLOG) != 0) !=
+				(jsonlogFile != NULL))
+				rotation_requested = true;
+
 			/*
 			 * If rotation time parameter changed, reset next rotation time,
 			 * but don't immediately force a rotation.
@@ -417,6 +429,12 @@ SysLoggerMain(int argc, char *argv[])
 				rotation_requested = true;
 				size_rotation_for |= LOG_DESTINATION_CSVLOG;
 			}
+			if (jsonlogFile != NULL &&
+				ftell(jsonlogFile) >= Log_RotationSize * 1024L)
+			{
+				rotation_requested = true;
+				size_rotation_for |= LOG_DESTINATION_JSONLOG;
+			}
 		}
 
 		if (rotation_requested)
@@ -426,7 +444,7 @@ SysLoggerMain(int argc, char *argv[])
 			 * was sent by pg_rotate_logfile() or "pg_ctl logrotate".
 			 */
 			if (!time_based_rotation && size_rotation_for == 0)
-				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG;
+				size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG | LOG_DESTINATION_JSONLOG;
 			logfile_rotate(time_based_rotation, size_rotation_for);
 		}
 
@@ -632,6 +650,20 @@ SysLogger_Start(void)
 		pfree(filename);
 	}
 
+	/*
+	 * Likewise for the initial JSON log file, if that's enabled.  (Note that
+	 * we open syslogFile even when only JSON output is nominally enabled,
+	 * since some code paths will write to syslogFile anyway.)
+	 */
+	if (Log_destination & LOG_DESTINATION_JSONLOG)
+	{
+		filename = logfile_getname(first_syslogger_file_time, ".json");
+
+		jsonlogFile = logfile_open(filename, "a", false);
+
+		pfree(filename);
+	}
+
 #ifdef EXEC_BACKEND
 	switch ((sysloggerPid = syslogger_forkexec()))
 #else
@@ -729,6 +761,11 @@ SysLogger_Start(void)
 				fclose(csvlogFile);
 				csvlogFile = NULL;
 			}
+			if (jsonlogFile != NULL)
+			{
+				fclose(jsonlogFile);
+				jsonlogFile = NULL;
+			}
 			return (int) sysloggerPid;
 	}
 
@@ -805,6 +842,7 @@ syslogger_forkexec(void)
 	int			ac = 0;
 	char		filenobuf[32];
 	char		csvfilenobuf[32];
+	char		jsonfilenobuf[32];
 
 	av[ac++] = "postgres";
 	av[ac++] = "--forklog";
@@ -817,6 +855,9 @@ syslogger_forkexec(void)
 	snprintf(csvfilenobuf, sizeof(csvfilenobuf), "%d",
 			 syslogger_fdget(csvlogFile));
 	av[ac++] = csvfilenobuf;
+	snprintf(jsonfilenobuf, sizeof(jsonfilenobuf), "%d",
+			 syslogger_fdget(jsonlogFile));
+	av[ac++] = jsonfilenobuf;
 
 	av[ac] = NULL;
 	Assert(ac < lengthof(av));
@@ -834,7 +875,7 @@ syslogger_parseArgs(int argc, char *argv[])
 {
 	int			fd;
 
-	Assert(argc == 5);
+	Assert(argc == 6);
 	argv += 3;
 
 	/*
@@ -848,6 +889,8 @@ syslogger_parseArgs(int argc, char *argv[])
 	syslogFile = syslogger_fdopen(fd);
 	fd = atoi(*argv++);
 	csvlogFile = syslogger_fdopen(fd);
+	fd = atoi(*argv++);
+	jsonlogFile = syslogger_fdopen(fd);
 }
 #endif							/* EXEC_BACKEND */
 
@@ -896,7 +939,9 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 
 		/* Do we have a valid header? */
 		memcpy(&p, cursor, offsetof(PipeProtoHeader, data));
-		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR | PIPE_PROTO_DEST_CSVLOG);
+		dest_flags = p.flags & (PIPE_PROTO_DEST_STDERR |
+								PIPE_PROTO_DEST_CSVLOG |
+								PIPE_PROTO_DEST_JSONLOG);
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&
@@ -918,6 +963,8 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 				dest = LOG_DESTINATION_STDERR;
 			else if ((p.flags & PIPE_PROTO_DEST_CSVLOG) != 0)
 				dest = LOG_DESTINATION_CSVLOG;
+			else if ((p.flags & PIPE_PROTO_DEST_JSONLOG) != 0)
+				dest = LOG_DESTINATION_JSONLOG;
 			else
 			{
 				/* this should never happen as of the header validation */
@@ -1097,19 +1144,24 @@ write_syslogger_file(const char *buffer, int count, int destination)
 	FILE	   *logfile;
 
 	/*
-	 * If we're told to write to csvlogFile, but it's not open, dump the data
-	 * to syslogFile (which is always open) instead.  This can happen if CSV
-	 * output is enabled after postmaster start and we've been unable to open
-	 * csvlogFile.  There are also race conditions during a parameter change
-	 * whereby backends might send us CSV output before we open csvlogFile or
-	 * after we close it.  Writing CSV-formatted output to the regular log
-	 * file isn't great, but it beats dropping log output on the floor.
+	 * If we're told to write to a structured log file, but it's not open,
+	 * dump the data to syslogFile (which is always open) instead.  This can
+	 * happen if structured output is enabled after postmaster start and we've
+	 * been unable to open logFile.  There are also race conditions during a
+	 * parameter change whereby backends might send us structured output
+	 * before we open the logFile or after we close it.  Writing formatted
+	 * output to the regular log file isn't great, but it beats dropping log
+	 * output on the floor.
 	 *
-	 * Think not to improve this by trying to open csvlogFile on-the-fly.  Any
+	 * Think not to improve this by trying to open logFile on-the-fly.  Any
 	 * failure in that would lead to recursion.
 	 */
-	logfile = (destination == LOG_DESTINATION_CSVLOG &&
-			   csvlogFile != NULL) ? csvlogFile : syslogFile;
+	if ((destination & LOG_DESTINATION_CSVLOG) && csvlogFile != NULL)
+		logfile = csvlogFile;
+	else if ((destination & LOG_DESTINATION_JSONLOG) && jsonlogFile != NULL)
+		logfile = jsonlogFile;
+	else
+		logfile = syslogFile;
 
 	rc = fwrite(buffer, 1, count, logfile);
 
@@ -1180,7 +1232,8 @@ pipeThread(void *arg)
 		if (Log_RotationSize > 0)
 		{
 			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
-				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
+				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L) ||
+				(jsonlogFile != NULL && ftell(jsonlogFile) >= Log_RotationSize * 1024L))
 				SetLatch(MyLatch);
 		}
 		LeaveCriticalSection(&sysloggerSection);
@@ -1292,6 +1345,8 @@ logfile_rotate_dest(bool time_based_rotation, int size_rotation_for,
 		logFileExt = NULL;
 	else if (target_dest == LOG_DESTINATION_CSVLOG)
 		logFileExt = ".csv";
+	else if (target_dest == LOG_DESTINATION_JSONLOG)
+		logFileExt = ".json";
 	else
 	{
 		/* cannot happen */
@@ -1379,6 +1434,12 @@ logfile_rotate(bool time_based_rotation, int size_rotation_for)
 							 &csvlogFile))
 		return;
 
+	/* file rotation for jsonlog */
+	if (!logfile_rotate_dest(time_based_rotation, size_rotation_for, fntime,
+							 LOG_DESTINATION_JSONLOG, &last_json_file_name,
+							 &jsonlogFile))
+		return;
+
 	update_metainfo_datafile();
 
 	set_next_rotation_time();
@@ -1465,7 +1526,8 @@ update_metainfo_datafile(void)
 	mode_t		oumask;
 
 	if (!(Log_destination & LOG_DESTINATION_STDERR) &&
-		!(Log_destination & LOG_DESTINATION_CSVLOG))
+		!(Log_destination & LOG_DESTINATION_CSVLOG) &&
+		!(Log_destination & LOG_DESTINATION_JSONLOG))
 	{
 		if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
 			ereport(LOG,
@@ -1523,6 +1585,19 @@ update_metainfo_datafile(void)
 			return;
 		}
 	}
+
+	if (last_json_file_name && (Log_destination & LOG_DESTINATION_JSONLOG))
+	{
+		if (fprintf(fh, "jsonlog %s\n", last_json_file_name) < 0)
+		{
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not write file \"%s\": %m",
+							LOG_METAINFO_DATAFILE_TMP)));
+			fclose(fh);
+			return;
+		}
+	}
 	fclose(fh);
 
 	if (rename(LOG_METAINFO_DATAFILE_TMP, LOG_METAINFO_DATAFILE) != 0)
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index fe4f180b6f..936fec451f 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -843,11 +843,12 @@ pg_current_logfile(PG_FUNCTION_ARGS)
 	{
 		logfmt = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
-		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0)
+		if (strcmp(logfmt, "stderr") != 0 && strcmp(logfmt, "csvlog") != 0 &&
+			strcmp(logfmt, "jsonlog") != 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("log format \"%s\" is not supported", logfmt),
-					 errhint("The supported log formats are \"stderr\" and \"csvlog\".")));
+					 errhint("The supported log formats are \"stderr\", \"csvlog\", and \"jsonlog\".")));
 	}
 
 	fd = AllocateFile(LOG_METAINFO_DATAFILE, "r");
diff --git a/src/backend/utils/error/Makefile b/src/backend/utils/error/Makefile
index ef770dd2f2..65ba61fb3c 100644
--- a/src/backend/utils/error/Makefile
+++ b/src/backend/utils/error/Makefile
@@ -15,6 +15,7 @@ include $(top_builddir)/src/Makefile.global
 OBJS = \
 	assert.o \
 	csvlog.o \
-	elog.o
+	elog.o \
+	jsonlog.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 4db41ba564..650927109d 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2984,6 +2984,22 @@ send_message_to_server_log(ErrorData *edata)
 			fallback_to_stderr = true;
 	}
 
+	/* Write to JSON log, if enabled */
+	if ((Log_destination & LOG_DESTINATION_JSONLOG) != 0)
+	{
+		/*
+		 * Send JSON data if it's safe to do so (syslogger doesn't need the
+		 * pipe).  If this is not possible, fallback to an entry written to
+		 * stderr.
+		 */
+		if (redirection_done || MyBackendType == B_LOGGER)
+		{
+			write_jsonlog(edata);
+		}
+		else
+			fallback_to_stderr = true;
+	}
+
 	/*
 	 * Write to stderr, if enabled or if required because of a previous
 	 * limitation.
@@ -3059,6 +3075,8 @@ write_pipe_chunks(char *data, int len, int dest)
 		p.proto.flags |= PIPE_PROTO_DEST_STDERR;
 	else if (dest == LOG_DESTINATION_CSVLOG)
 		p.proto.flags |= PIPE_PROTO_DEST_CSVLOG;
+	else if (dest == LOG_DESTINATION_JSONLOG)
+		p.proto.flags |= PIPE_PROTO_DEST_JSONLOG;
 
 	/* write all but the last chunk */
 	while (len > PIPE_MAX_PAYLOAD)
diff --git a/src/backend/utils/error/jsonlog.c b/src/backend/utils/error/jsonlog.c
new file mode 100644
index 0000000000..51b81fca23
--- /dev/null
+++ b/src/backend/utils/error/jsonlog.c
@@ -0,0 +1,294 @@
+/*-------------------------------------------------------------------------
+ *
+ * jsonlog.c
+ *	  JSON logging
+ *
+ * Copyright (c) 2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/error/jsonlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "libpq/libpq.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/syslogger.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/backend_status.h"
+#include "utils/elog.h"
+#include "utils/guc.h"
+#include "utils/json.h"
+#include "utils/ps_status.h"
+
+static void appendJSONKeyValueFmt(StringInfo buf, const char *key,
+								  bool escape_key,
+								  const char *fmt,...) pg_attribute_printf(4, 5);
+
+/*
+ * appendJSONKeyValue
+ * Append to a StringInfo a comma followed by a JSON key and value.
+ * The key is always escaped. The value can be escaped optionally.
+ */
+static void
+appendJSONKeyValue(StringInfo buf, const char *key, const char *value,
+				   bool escape_value)
+{
+	Assert(key != NULL);
+
+	if (value == NULL)
+		return;
+
+	appendStringInfoChar(buf, ',');
+	escape_json(buf, key);
+	appendStringInfoChar(buf, ':');
+
+	if (escape_value)
+		escape_json(buf, value);
+	else
+		appendStringInfoString(buf, value);
+}
+
+
+/*
+ * appendJSONKeyValueFmt
+ *
+ * Evaluate the fmt string and then invoke appendJSONKeyValue as the
+ * value of the JSON property. Both the key and value will be escaped by
+ * appendJSONKeyValue.
+ */
+static void
+appendJSONKeyValueFmt(StringInfo buf, const char *key,
+					  bool escape_key, const char *fmt,...)
+{
+	int			save_errno = errno;
+	size_t		len = 128;		/* initial assumption about buffer size */
+	char	   *value;
+
+	for (;;)
+	{
+		va_list		args;
+		size_t		newlen;
+
+		/* Allocate result buffer */
+		value = (char *) palloc(len);
+
+		/* Try to format the data. */
+		errno = save_errno;
+		va_start(args, fmt);
+		newlen = pvsnprintf(value, len, fmt, args);
+		va_end(args);
+
+		if (newlen < len)
+			break;				/* success */
+
+		/* Release buffer and loop around to try again with larger len. */
+		pfree(value);
+		len = newlen;
+	}
+
+	appendJSONKeyValue(buf, key, value, escape_key);
+
+	/* Clean up */
+	pfree(value);
+}
+
+/*
+ * Write logs in json format.
+ */
+void
+write_jsonlog(ErrorData *edata)
+{
+	StringInfoData buf;
+	char	   *start_time;
+	char	   *log_time;
+
+	/* static counter for line numbers */
+	static long log_line_number = 0;
+
+	/* Has the counter been reset in the current process? */
+	static int	log_my_pid = 0;
+
+	/*
+	 * This is one of the few places where we'd rather not inherit a static
+	 * variable's value from the postmaster.  But since we will, reset it when
+	 * MyProcPid changes.
+	 */
+	if (log_my_pid != MyProcPid)
+	{
+		log_line_number = 0;
+		log_my_pid = MyProcPid;
+		reset_formatted_start_time();
+	}
+	log_line_number++;
+
+	initStringInfo(&buf);
+
+	/* Initialize string */
+	appendStringInfoChar(&buf, '{');
+
+	/* timestamp with milliseconds */
+	log_time = get_formatted_log_time();
+
+	/*
+	 * First property does not use appendJSONKeyValue as it does not have
+	 * comma prefix.
+	 */
+	escape_json(&buf, "timestamp");
+	appendStringInfoChar(&buf, ':');
+	escape_json(&buf, log_time);
+
+	/* username */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "user", MyProcPort->user_name, true);
+
+	/* database name */
+	if (MyProcPort)
+		appendJSONKeyValue(&buf, "dbname", MyProcPort->database_name, true);
+
+	/* Process ID */
+	if (MyProcPid != 0)
+		appendJSONKeyValueFmt(&buf, "pid", false, "%d", MyProcPid);
+
+	/* Remote host and port */
+	if (MyProcPort && MyProcPort->remote_host)
+	{
+		appendJSONKeyValue(&buf, "remote_host", MyProcPort->remote_host, true);
+		if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+			appendJSONKeyValue(&buf, "remote_port", MyProcPort->remote_port, false);
+	}
+
+	/* Session id */
+	appendJSONKeyValueFmt(&buf, "session_id", true, "%lx.%x", (long) MyStartTime, MyProcPid);
+
+	/* Line number */
+	appendJSONKeyValueFmt(&buf, "line_num", false, "%ld", log_line_number);
+
+	/* PS display */
+	if (MyProcPort)
+	{
+		StringInfoData msgbuf;
+		const char *psdisp;
+		int			displen;
+
+		initStringInfo(&msgbuf);
+		psdisp = get_ps_display(&displen);
+		appendBinaryStringInfo(&msgbuf, psdisp, displen);
+		appendJSONKeyValue(&buf, "ps", msgbuf.data, true);
+
+		pfree(msgbuf.data);
+	}
+
+	/* session start timestamp */
+	start_time = get_formatted_start_time();
+	appendJSONKeyValue(&buf, "session_start", start_time, true);
+
+	/* Virtual transaction id */
+	/* keep VXID format in sync with lockfuncs.c */
+	if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
+		appendJSONKeyValueFmt(&buf, "vxid", true, "%d/%u", MyProc->backendId, MyProc->lxid);
+
+	/* Transaction id */
+	appendJSONKeyValueFmt(&buf, "txid", false, "%u", GetTopTransactionIdIfAny());
+
+	/* Error severity */
+	if (edata->elevel)
+		appendJSONKeyValue(&buf, "error_severity",
+						   (char *) error_severity(edata->elevel), true);
+
+	/* SQL state code */
+	if (edata->sqlerrcode)
+		appendJSONKeyValue(&buf, "state_code",
+						   unpack_sql_state(edata->sqlerrcode), true);
+
+	/* errmessage */
+	appendJSONKeyValue(&buf, "message", edata->message, true);
+
+	/* errdetail or error_detail log */
+	if (edata->detail_log)
+		appendJSONKeyValue(&buf, "detail", edata->detail_log, true);
+	else
+		appendJSONKeyValue(&buf, "detail", edata->detail, true);
+
+	/* errhint */
+	if (edata->hint)
+		appendJSONKeyValue(&buf, "hint", edata->hint, true);
+
+	/* internal query */
+	if (edata->internalquery)
+		appendJSONKeyValue(&buf, "internal_query", edata->internalquery, true);
+
+	/* if printed internal query, print internal pos too */
+	if (edata->internalpos > 0 && edata->internalquery != NULL)
+		appendJSONKeyValueFmt(&buf, "internal_position", false, "%u",
+							  edata->internalpos);
+
+	/* errcontext */
+	if (edata->context && !edata->hide_ctx)
+		appendJSONKeyValue(&buf, "context", edata->context, true);
+
+	/* user query --- only reported if not disabled by the caller */
+	if (check_log_of_query(edata))
+	{
+		appendJSONKeyValue(&buf, "statement", debug_query_string, true);
+		if (edata->cursorpos > 0)
+			appendJSONKeyValueFmt(&buf, "cursor_position", false, "%d",
+								  edata->cursorpos);
+	}
+
+	/* file error location */
+	if (Log_error_verbosity >= PGERROR_VERBOSE)
+	{
+		if (edata->funcname)
+			appendJSONKeyValue(&buf, "func_name", edata->funcname, true);
+		if (edata->filename)
+		{
+			appendJSONKeyValue(&buf, "file_name", edata->filename, true);
+			appendJSONKeyValueFmt(&buf, "file_line_num", false, "%d",
+								  edata->lineno);
+		}
+	}
+
+	/* Application name */
+	if (application_name && application_name[0] != '\0')
+		appendJSONKeyValue(&buf, "application_name", application_name, true);
+
+	/* backend type */
+	appendJSONKeyValue(&buf, "backend_type", get_backend_type_for_log(), true);
+
+	/* leader PID */
+	if (MyProc)
+	{
+		PGPROC	   *leader = MyProc->lockGroupLeader;
+
+		/*
+		 * Show the leader only for active parallel workers.  This leaves out
+		 * the leader of a parallel group.
+		 */
+		if (leader && leader->pid != MyProcPid)
+			appendJSONKeyValueFmt(&buf, "leader_pid", false, "%d", leader->pid);
+	}
+
+	/* query id */
+	appendJSONKeyValueFmt(&buf, "query_id", false, "%lld",
+						  (long long) pgstat_get_my_query_id());
+
+	/* Finish string */
+	appendStringInfoChar(&buf, '}');
+	appendStringInfoChar(&buf, '\n');
+
+	/* If in the syslogger process, try to write messages direct to file */
+	if (MyBackendType == B_LOGGER)
+		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+	else
+		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
+
+	pfree(buf.data);
+}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 6fc5cbc09a..b651429ed6 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4264,7 +4264,7 @@ static struct config_string ConfigureNamesString[] =
 		{"log_destination", PGC_SIGHUP, LOGGING_WHERE,
 			gettext_noop("Sets the destination for server log output."),
 			gettext_noop("Valid values are combinations of \"stderr\", "
-						 "\"syslog\", \"csvlog\", and \"eventlog\", "
+						 "\"syslog\", \"csvlog\", \"jsonlog\" and \"eventlog\", "
 						 "depending on the platform."),
 			GUC_LIST_INPUT
 		},
@@ -11740,6 +11740,8 @@ check_log_destination(char **newval, void **extra, GucSource source)
 			newlogdest |= LOG_DESTINATION_STDERR;
 		else if (pg_strcasecmp(tok, "csvlog") == 0)
 			newlogdest |= LOG_DESTINATION_CSVLOG;
+		else if (pg_strcasecmp(tok, "jsonlog") == 0)
+			newlogdest |= LOG_DESTINATION_JSONLOG;
 #ifdef HAVE_SYSLOG
 		else if (pg_strcasecmp(tok, "syslog") == 0)
 			newlogdest |= LOG_DESTINATION_SYSLOG;
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index a1acd46b61..817d5f5324 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -432,14 +432,15 @@
 # - Where to Log -
 
 #log_destination = 'stderr'		# Valid values are combinations of
-					# stderr, csvlog, syslog, and eventlog,
-					# depending on platform.  csvlog
-					# requires logging_collector to be on.
+					# stderr, csvlog, jsonlog, syslog, and
+					# eventlog, depending on platform.
+					# csvlog and jsonlog require
+					# logging_collector to be on.
 
 # This is used when logging to stderr:
-#logging_collector = off		# Enable capturing of stderr and csvlog
-					# into log files. Required to be on for
-					# csvlogs.
+#logging_collector = off		# Enable capturing of stderr, jsonlog
+					# and csvlog into log files. Required
+					# to be on for csvlogs and jsonlogs.
 					# (change requires restart)
 
 # These are only used if logging_collector is on:
diff --git a/src/bin/pg_ctl/t/004_logrotate.pl b/src/bin/pg_ctl/t/004_logrotate.pl
index e04331bfef..de6028760d 100644
--- a/src/bin/pg_ctl/t/004_logrotate.pl
+++ b/src/bin/pg_ctl/t/004_logrotate.pl
@@ -6,7 +6,7 @@ use warnings;
 
 use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
-use Test::More tests => 10;
+use Test::More tests => 14;
 use Time::HiRes qw(usleep);
 
 # Extract the file name of a $format from the contents of
@@ -65,7 +65,7 @@ $node->init();
 $node->append_conf(
 	'postgresql.conf', qq(
 logging_collector = on
-log_destination = 'stderr, csvlog'
+log_destination = 'stderr, csvlog, jsonlog'
 # these ensure stability of test results:
 log_rotation_age = 0
 lc_messages = 'C'
@@ -96,11 +96,13 @@ note "current_logfiles = $current_logfiles";
 like(
 	$current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'current_logfiles is sane');
 
-check_log_pattern('stderr', $current_logfiles, 'division by zero', $node);
-check_log_pattern('csvlog', $current_logfiles, 'division by zero', $node);
+check_log_pattern('stderr',  $current_logfiles, 'division by zero', $node);
+check_log_pattern('csvlog',  $current_logfiles, 'division by zero', $node);
+check_log_pattern('jsonlog', $current_logfiles, 'division by zero', $node);
 
 # Sleep 2 seconds and ask for log rotation; this should result in
 # output into a different log file name.
@@ -122,13 +124,15 @@ note "now current_logfiles = $new_current_logfiles";
 like(
 	$new_current_logfiles,
 	qr|^stderr log/postgresql-.*log
-csvlog log/postgresql-.*csv$|,
+csvlog log/postgresql-.*csv
+jsonlog log/postgresql-.*json$|,
 	'new current_logfiles is sane');
 
 # Verify that log output gets to this file, too
 $node->psql('postgres', 'fee fi fo fum');
 
-check_log_pattern('stderr', $new_current_logfiles, 'syntax error', $node);
-check_log_pattern('csvlog', $new_current_logfiles, 'syntax error', $node);
+check_log_pattern('stderr',  $new_current_logfiles, 'syntax error', $node);
+check_log_pattern('csvlog',  $new_current_logfiles, 'syntax error', $node);
+check_log_pattern('jsonlog', $new_current_logfiles, 'syntax error', $node);
 
 $node->stop();
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index afbb6c35e3..c29ced427c 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5931,7 +5931,8 @@ SELECT * FROM parent WHERE key = 2400;
        <para>
         <productname>PostgreSQL</productname> supports several methods
          for logging server messages, including
-         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem> and
+         <systemitem>stderr</systemitem>, <systemitem>csvlog</systemitem>,
+         <systemitem>jsonlog</systemitem>, and
          <systemitem>syslog</systemitem>. On Windows,
          <systemitem>eventlog</systemitem> is also supported. Set this
          parameter to a list of desired log destinations separated by
@@ -5949,6 +5950,14 @@ SELECT * FROM parent WHERE key = 2400;
         <xref linkend="guc-logging-collector"/> must be enabled to generate
         CSV-format log output.
        </para>
+       <para>
+        If <systemitem>jsonlog</systemitem> is included in <varname>log_destination</varname>,
+        log entries are output in <acronym>JSON</acronym> format, which is convenient for
+        loading logs into programs.
+        See <xref linkend="runtime-config-logging-jsonlog"/> for details.
+        <xref linkend="guc-logging-collector"/> must be enabled to generate
+        JSON-format log output.
+       </para>
        <para>
         When either <systemitem>stderr</systemitem> or
         <systemitem>csvlog</systemitem> are included, the file
@@ -5960,13 +5969,14 @@ SELECT * FROM parent WHERE key = 2400;
 <programlisting>
 stderr log/postgresql.log
 csvlog log/postgresql.csv
+jsonlog log/postgresql.json
 </programlisting>
 
         <filename>current_logfiles</filename> is recreated when a new log file
         is created as an effect of rotation, and
         when <varname>log_destination</varname> is reloaded.  It is removed when
-        neither <systemitem>stderr</systemitem>
-        nor <systemitem>csvlog</systemitem> are included
+        none of <systemitem>stderr</systemitem>,
+        <systemitem>csvlog</systemitem>, <systemitem>jsonlog</systemitem> are included
         in <varname>log_destination</varname>, and when the logging collector is
         disabled.
        </para>
@@ -6106,6 +6116,13 @@ local0.*    /var/log/postgresql
         (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
         replaced instead.)
        </para>
+       <para>
+        If JSON-format output is enabled in <varname>log_destination</varname>,
+        <literal>.json</literal> will be appended to the timestamped
+        log file name to create the file name for JSON-format output.
+        (If <varname>log_filename</varname> ends in <literal>.log</literal>, the suffix is
+        replaced instead.)
+       </para>
        <para>
         This parameter can only be set in the <filename>postgresql.conf</filename>
         file or on the server command line.
@@ -7467,6 +7484,186 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         </orderedlist>
       </para>
     </sect2>
+     <sect2 id="runtime-config-logging-jsonlog">
+     <title>Using JSON-Format Log Output</title>
+
+     <para>
+      Including <literal>jsonlog</literal> in the <varname>log_destination</varname> list
+      provides a convenient way to import log files into many different programs.
+      This option emits log lines in (<acronym>JSON</acronym>) format.
+     </para>
+
+     <para>
+      String fields with null values are excluded from output.
+      Additional fields may be added in the future. User applications that process jsonlog
+      output should ignore unknown fields.
+     </para>
+
+     <para>
+      Each log line is serialized as a JSON object as of the following
+      set of keys with their values.
+     </para>
+
+     <table>
+      <title>Keys and values of JSON log entries</title>
+      <tgroup cols="3">
+       <thead>
+        <row>
+         <entry>Key name</entry>
+         <entry>Type</entry>
+         <entry>Description</entry>
+        </row>
+       </thead>
+       <tbody>
+        <row>
+         <entry><literal>timestamp</literal></entry>
+         <entry>string</entry>
+         <entry>Time stamp with milliseconds</entry>
+        </row>
+        <row>
+         <entry><literal>user</literal></entry>
+         <entry>string</entry>
+         <entry>User name</entry>
+        </row>
+        <row>
+         <entry><literal>dbname</literal></entry>
+         <entry>string</entry>
+         <entry>Database name</entry>
+        </row>
+        <row>
+         <entry><literal>pid</literal></entry>
+         <entry>number</entry>
+         <entry>Process ID</entry>
+        </row>
+        <row>
+         <entry><literal>remote_host</literal></entry>
+         <entry>string</entry>
+         <entry>Client host</entry>
+        </row>
+        <row>
+         <entry><literal>remote_port</literal></entry>
+         <entry>number</entry>
+         <entry>Client port</entry>
+        </row>
+        <row>
+         <entry><literal>session_id</literal></entry>
+         <entry>string</entry>
+         <entry>Session ID</entry>
+        </row>
+        <row>
+         <entry><literal>line_num</literal></entry>
+         <entry>number</entry>
+         <entry>Per-session line number</entry>
+        </row>
+        <row>
+         <entry><literal>ps</literal></entry>
+         <entry>string</entry>
+         <entry>Current ps display</entry>
+        </row>
+        <row>
+         <entry><literal>session_start</literal></entry>
+         <entry>string</entry>
+         <entry>Session start time</entry>
+        </row>
+        <row>
+         <entry><literal>vxid</literal></entry>
+         <entry>string</entry>
+         <entry>Virtual transaction ID</entry>
+        </row>
+        <row>
+         <entry><literal>txid</literal></entry>
+         <entry>string</entry>
+         <entry>Regular transaction ID</entry>
+        </row>
+        <row>
+         <entry><literal>error_severity</literal></entry>
+         <entry>string</entry>
+         <entry>Error severity</entry>
+        </row>
+        <row>
+         <entry><literal>state_code</literal></entry>
+         <entry>string</entry>
+         <entry>SQLSTATE code</entry>
+        </row>
+        <row>
+         <entry><literal>message</literal></entry>
+         <entry>string</entry>
+         <entry>Error message</entry>
+        </row>
+        <row>
+         <entry><literal>detail</literal></entry>
+         <entry>string</entry>
+         <entry>Error message detail</entry>
+        </row>
+        <row>
+         <entry><literal>hint</literal></entry>
+         <entry>string</entry>
+         <entry>Error message hint</entry>
+        </row>
+        <row>
+         <entry><literal>internal_query</literal></entry>
+         <entry>string</entry>
+         <entry>Internal query that led to the error</entry>
+        </row>
+        <row>
+         <entry><literal>internal_position</literal></entry>
+         <entry>number</entry>
+         <entry>Cursor index into internal query</entry>
+        </row>
+        <row>
+         <entry><literal>context</literal></entry>
+         <entry>string</entry>
+         <entry>Error context</entry>
+        </row>
+        <row>
+         <entry><literal>statement</literal></entry>
+         <entry>string</entry>
+         <entry>Client-supplied query string</entry>
+        </row>
+        <row>
+         <entry><literal>cursor_position</literal></entry>
+         <entry>string</entry>
+         <entry>Cursor index into query string</entry>
+        </row>
+        <row>
+         <entry><literal>func_name</literal></entry>
+         <entry>string</entry>
+         <entry>Error location function name</entry>
+        </row>
+        <row>
+         <entry><literal>file_name</literal></entry>
+         <entry>string</entry>
+         <entry>File name of error location</entry>
+        </row>
+        <row>
+         <entry><literal>file_line_num</literal></entry>
+         <entry>number</entry>
+         <entry>File line number of the error location</entry>
+        </row>
+        <row>
+         <entry><literal>application_name</literal></entry>
+         <entry>string</entry>
+         <entry>Client application name</entry>
+        </row>
+        <row>
+         <entry><literal>backend_type</literal></entry>
+         <entry>string</entry>
+         <entry>Type of backend</entry>
+        </row>
+        <row>
+         <entry><literal>leader_pid</literal></entry>
+         <entry>number</entry>
+         <entry>Process ID of leader for active parallel workers</entry>
+        </row>
+        <row>
+         <entry><literal>query_id</literal></entry>
+         <entry>number</entry>
+         <entry>Query ID</entry>
+        </row>
+       </tbody>
+      </tgroup>
+     </table>
+    </sect2>
 
    <sect2>
     <title>Process Title</title>
-- 
2.34.1