syslog configurable line splitting behavior

From 70bacecba46eb38c02c43957c2f1812faf5684df Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter_e@gmx.net>
Date: Fri, 26 Feb 2016 22:34:30 -0500
Subject: [PATCH 1/2] Add syslog_sequence_numbers parameter

---
 doc/src/sgml/config.sgml                      | 28 +++++++++++++++++++++++++++
 src/backend/utils/error/elog.c                | 12 ++++++++++--
 src/backend/utils/misc/guc.c                  | 10 ++++++++++
 src/backend/utils/misc/postgresql.conf.sample |  1 +
 src/include/utils/elog.h                      |  1 +
 5 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 6c73fb4..bbe87ce 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4305,6 +4305,34 @@ <title>Where To Log</title>
        </listitem>
       </varlistentry>
 
+      <varlistentry id="guc-syslog-sequence-numbers" xreflabel="syslog_sequence_numbers">
+       <term><varname>syslog_sequence_numbers</varname> (<type>boolean</type>)
+        <indexterm>
+         <primary><varname>syslog_sequence_numbers</> configuration parameter</primary>
+        </indexterm>
+       </term>
+
+       <listitem>
+        <para>
+         When logging to <application>syslog</application> and this is on (the
+         default), then each message will be prefixed by an increasing
+         sequence number (such as <literal>[2]</literal>).  This circumvents
+         the <quote>--- last message repeated N times ---</quote> suppression
+         that many syslog implementations perform by default.  In more modern
+         syslog implementations, repeat message suppression can be configured
+         (for example, <literal>$RepeatedMsgReduction</literal>
+         in <productname>rsyslog</productname>), so this might not be
+         necessary.  Also, you could turn this off if you actually want to
+         suppress repeated messages.
+        </para>
+
+        <para>
+         This parameter can only be set in the <filename>postgresql.conf</>
+         file or on the server command line.
+        </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-event-source" xreflabel="event_source">
       <term><varname>event_source</varname> (<type>string</type>)
       <indexterm>
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 5b7554b..88421c7 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -106,6 +106,7 @@ int			Log_error_verbosity = PGERROR_VERBOSE;
 char	   *Log_line_prefix = NULL;		/* format for extra log line info */
 int			Log_destination = LOG_DESTINATION_STDERR;
 char	   *Log_destination_string = NULL;
+bool		syslog_sequence_numbers = true;
 
 #ifdef HAVE_SYSLOG
 
@@ -2018,7 +2019,11 @@ write_syslog(int level, const char *line)
 
 			chunk_nr++;
 
-			syslog(level, "[%lu-%d] %s", seq, chunk_nr, buf);
+			if (syslog_sequence_numbers)
+				syslog(level, "[%lu-%d] %s", seq, chunk_nr, buf);
+			else
+				syslog(level, "[%d] %s", chunk_nr, buf);
+
 			line += buflen;
 			len -= buflen;
 		}
@@ -2026,7 +2031,10 @@ write_syslog(int level, const char *line)
 	else
 	{
 		/* message short enough */
-		syslog(level, "[%lu] %s", seq, line);
+		if (syslog_sequence_numbers)
+			syslog(level, "[%lu] %s", seq, line);
+		else
+			syslog(level, "%s", line);
 	}
 }
 #endif   /* HAVE_SYSLOG */
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index f0d4ec1..3ef432a 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1632,6 +1632,16 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"syslog_sequence_numbers", PGC_SIGHUP, LOGGING_WHERE,
+			gettext_noop("Add sequence number to syslog messags to avoid duplicate suppression."),
+			NULL
+		},
+		&syslog_sequence_numbers,
+		true,
+		NULL, NULL, NULL
+	},
+
 	/* End-of-list marker */
 	{
 		{NULL, 0, 0, NULL, NULL}, NULL, false, NULL, NULL, NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index ee3d378..b72ea6d 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -358,6 +358,7 @@
 # These are relevant when logging to syslog:
 #syslog_facility = 'LOCAL0'
 #syslog_ident = 'postgres'
+#syslog_sequence_numbers = on
 
 # This is only relevant when logging to eventlog (win32):
 #event_source = 'PostgreSQL'
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 7d338dd..e245b2e 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -397,6 +397,7 @@ extern int	Log_error_verbosity;
 extern char *Log_line_prefix;
 extern int	Log_destination;
 extern char *Log_destination_string;
+extern bool syslog_sequence_numbers;
 
 /* Log destination bitmap */
 #define LOG_DESTINATION_STDERR	 1
-- 
2.7.3

From 66f367f37d3e3d67977ccace5aa3bb9bb8f947f6 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter_e@gmx.net>
Date: Tue, 15 Mar 2016 22:48:53 -0400
Subject: [PATCH 2/2] Add syslog_split_messages parameter

---
 doc/src/sgml/config.sgml                      | 33 +++++++++++++++++++++++++++
 src/backend/utils/error/elog.c                |  3 ++-
 src/backend/utils/misc/guc.c                  | 10 ++++++++
 src/backend/utils/misc/postgresql.conf.sample |  1 +
 src/include/utils/elog.h                      |  1 +
 5 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index bbe87ce..a5c2746 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4333,6 +4333,39 @@ <title>Where To Log</title>
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-syslog-split-messages" xreflabel="syslog_split_messages">
+      <term><varname>syslog_split_messages</varname> (<type>boolean</type>)
+      <indexterm>
+       <primary><varname>syslog_split_messages</> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        When logging to <application>syslog</> is enabled, this parameter
+        determines how messages are delivered to syslog.  When on (the
+        default), messages are split by lines, and long lines are split so
+        that they will fit into 1024 bytes, which is a typical size limit for
+        traditional syslog implementations.  When off, PostgreSQL server log
+        messages are delivered to the syslog service as is, and it is up to
+        the syslog service to cope with the potentially bulky messages.
+       </para>
+
+       <para>
+        If syslog is ultimately logging to a text file, then the effect will
+        be the same either way, and it is best to leave the setting on, since
+        most syslog implementations either cannot handle large messages or
+        would need to be specially configured to handle them.  But if syslog
+        is ultimately writing into some other medium, it might be necessary or
+        more useful to keep messages logically together.
+       </para>
+
+       <para>
+        This parameter can only be set in the <filename>postgresql.conf</>
+        file or on the server command line.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-event-source" xreflabel="event_source">
       <term><varname>event_source</varname> (<type>string</type>)
       <indexterm>
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 88421c7..458f3aa 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -107,6 +107,7 @@ char	   *Log_line_prefix = NULL;		/* format for extra log line info */
 int			Log_destination = LOG_DESTINATION_STDERR;
 char	   *Log_destination_string = NULL;
 bool		syslog_sequence_numbers = true;
+bool		syslog_split_messages = true;
 
 #ifdef HAVE_SYSLOG
 
@@ -1966,7 +1967,7 @@ write_syslog(int level, const char *line)
 	 */
 	len = strlen(line);
 	nlpos = strchr(line, '\n');
-	if (len > PG_SYSLOG_LIMIT || nlpos != NULL)
+	if (syslog_split_messages && (len > PG_SYSLOG_LIMIT || nlpos != NULL))
 	{
 		int			chunk_nr = 0;
 
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 3ef432a..b6c8246 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1642,6 +1642,16 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"syslog_split_messages", PGC_SIGHUP, LOGGING_WHERE,
+			gettext_noop("Split messages sent to syslog by lines and to fit into 1024 bytes."),
+			NULL
+		},
+		&syslog_split_messages,
+		true,
+		NULL, NULL, NULL
+	},
+
 	/* End-of-list marker */
 	{
 		{NULL, 0, 0, NULL, NULL}, NULL, false, NULL, NULL, NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index b72ea6d..1a12765 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -359,6 +359,7 @@
 #syslog_facility = 'LOCAL0'
 #syslog_ident = 'postgres'
 #syslog_sequence_numbers = on
+#syslog_split_messages = on
 
 # This is only relevant when logging to eventlog (win32):
 #event_source = 'PostgreSQL'
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index e245b2e..901651f 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -398,6 +398,7 @@ extern char *Log_line_prefix;
 extern int	Log_destination;
 extern char *Log_destination_string;
 extern bool syslog_sequence_numbers;
+extern bool syslog_split_messages;
 
 /* Log destination bitmap */
 #define LOG_DESTINATION_STDERR	 1
-- 
2.7.3