idle in txn query cancellation

From 2171feda1a91b0e77c1c0788abb3fc3183503b79 Mon Sep 17 00:00:00 2001
From: Andres Freund <andres@anarazel.de>
Date: Sat, 13 Feb 2010 22:30:41 +0100
Subject: [PATCH 2/2] Dont FATAL a IDLE IN TRANSACTIOn backend during conflict
 resolution. Instead avoid sending the error (and a later "read for
 query") to the client to avoid confusing the client state.

---
 src/backend/tcop/postgres.c |   41 ++++++++++++++++++++++++++++++++---------
 1 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 13734f0..e9c622e 100644
*** a/src/backend/tcop/postgres.c
--- b/src/backend/tcop/postgres.c
*************** static int	UseNewLine = 0;		/* Use EOF a
*** 176,181 ****
--- 176,187 ----
  static bool RecoveryConflictPending = false;
  static ProcSignalReason	RecoveryConflictReason;
  
+ /*
+  * Are we disallowed from sending a "ready for query" message right
+  * now because it would confuse the frontend?
+  */
+ bool silent_error_while_idle = false;
+ 
  /* ----------------------------------------------------------------
   *		decls for routines only used in this file
   * ----------------------------------------------------------------
*************** ProcessInterrupts(void)
*** 2917,2934 ****
  			RecoveryConflictPending = false;
  			DisableNotifyInterrupt();
  			DisableCatchupInterrupt();
! 			if (DoingCommandRead)
! 				ereport(FATAL,
! 						(errcode(ERRCODE_ADMIN_SHUTDOWN),
! 						 errmsg("terminating connection due to conflict with recovery"),
! 						 errdetail_recovery_conflict(),
! 						 errhint("In a moment you should be able to reconnect to the"
! 								 " database and repeat your command.")));
! 			else
  				ereport(ERROR,
  						(errcode(ERRCODE_QUERY_CANCELED),
  						 errmsg("canceling statement due to conflict with recovery"),
  						 errdetail_recovery_conflict()));
  		}
  
  		/*
--- 2923,2948 ----
  			RecoveryConflictPending = false;
  			DisableNotifyInterrupt();
  			DisableCatchupInterrupt();
! 			if (DoingCommandRead){
! 				/*
! 				 * We cant issue a normal ERROR here because the
! 				 * client doesnt expect the server to send an error at
! 				 * that point.
! 				 * We also may not send a "ready for query"/Z message
! 				 * because that would be unexpected as well.
! 				 */
! 				silent_error_while_idle = true;
! 				ereport(ERROR | LOG_NO_CLIENT,
! 						(errcode(ERRCODE_QUERY_CANCELED),
! 						 errmsg("canceling statement due to conflict with recovery"),
! 						 errdetail_recovery_conflict()));
! 			}
! 			else{
  				ereport(ERROR,
  						(errcode(ERRCODE_QUERY_CANCELED),
  						 errmsg("canceling statement due to conflict with recovery"),
  						 errdetail_recovery_conflict()));
+ 			}
  		}
  
  		/*
*************** PostgresMain(int argc, char *argv[], con
*** 3767,3773 ****
  		 * processing of batched messages, and because we don't want to report
  		 * uncommitted updates (that confuses autovacuum).
  		 */
! 		if (send_ready_for_query)
  		{
  			if (IsAbortedTransactionBlockState())
  			{
--- 3781,3787 ----
  		 * processing of batched messages, and because we don't want to report
  		 * uncommitted updates (that confuses autovacuum).
  		 */
! 		if (send_ready_for_query && !silent_error_while_idle)
  		{
  			if (IsAbortedTransactionBlockState())
  			{
*************** PostgresMain(int argc, char *argv[], con
*** 3792,3797 ****
--- 3806,3820 ----
  		}
  
  		/*
+ 		 * After ReadCommand continued we are sure that the frontend
+ 		 * sent a message and can handle a 'Z' message.  We cant set
+ 		 * that after ReadCommand because that will error out when in
+ 		 * an aborted transaction - which we are when
+ 		 * silent_error_while_idle was set.
+ 		 */
+ 		silent_error_while_idle = false;
+ 
+ 		/*
  		 * (2) Allow asynchronous signals to be executed immediately if they
  		 * come in while we are waiting for client input. (This must be
  		 * conditional since we don't want, say, reads on behalf of COPY FROM
-- 
1.6.5.12.gd65df24

From 04d726519fbc85ea13bb7919d65400c89e0df031 Mon Sep 17 00:00:00 2001
From: Andres Freund <andres@anarazel.de>
Date: Sat, 13 Feb 2010 22:21:15 +0100
Subject: [PATCH 1/2] Support transporting flags in the 'elevel' argument of ereport(). The
 reason is the wish to support avoiding the error to the client which
 was only possible using the COMERROR level - which is not a error but
 just a log message.
 The only supported flag till now is LOG_NO_CLIENT which does what
 COMERROR did for all error levels

---
 src/backend/utils/error/elog.c |    6 ++++--
 src/include/utils/elog.h       |   25 ++++++++++++++++---------
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index daa88a3..3ef07ad 100644
*** a/src/backend/utils/error/elog.c
--- b/src/backend/utils/error/elog.c
*************** errstart(int elevel, const char *filenam
*** 213,219 ****
  	bool		output_to_server;
  	bool		output_to_client = false;
  	int			i;
! 
  	/*
  	 * Check some cases in which we want to promote an error into a more
  	 * severe error.  None of this logic applies for non-error messages.
--- 213,220 ----
  	bool		output_to_server;
  	bool		output_to_client = false;
  	int			i;
! 	int			eflags = elevel & LOG_FLAG_MASK;
! 	elevel = elevel & ~LOG_FLAG_MASK;
  	/*
  	 * Check some cases in which we want to promote an error into a more
  	 * severe error.  None of this logic applies for non-error messages.
*************** errstart(int elevel, const char *filenam
*** 273,279 ****
  		output_to_server = (elevel >= log_min_messages);
  
  	/* Determine whether message is enabled for client output */
! 	if (whereToSendOutput == DestRemote && elevel != COMMERROR)
  	{
  		/*
  		 * client_min_messages is honored only after we complete the
--- 274,280 ----
  		output_to_server = (elevel >= log_min_messages);
  
  	/* Determine whether message is enabled for client output */
! 	if (whereToSendOutput == DestRemote && !(eflags & LOG_NO_CLIENT))
  	{
  		/*
  		 * client_min_messages is honored only after we complete the
*************** errstart(int elevel, const char *filenam
*** 332,337 ****
--- 333,339 ----
  	edata = &errordata[errordata_stack_depth];
  	MemSet(edata, 0, sizeof(ErrorData));
  	edata->elevel = elevel;
+ 	edata->eflags = eflags;
  	edata->output_to_server = output_to_server;
  	edata->output_to_client = output_to_client;
  	edata->filename = filename;
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 2ec3dd3..f3b4439 100644
*** a/src/include/utils/elog.h
--- b/src/include/utils/elog.h
***************
*** 16,21 ****
--- 16,24 ----
  
  #include <setjmp.h>
  
+ #define LOG_FLAG_MASK ((~0)<<20)
+ #define LOG_NO_CLIENT (2<<30)
+ 
  /* Error level codes */
  #define DEBUG5		10			/* Debugging messages, in categories of
  								 * decreasing detail. */
***************
*** 25,54 ****
  #define DEBUG1		14			/* used by GUC debug_* variables */
  #define LOG			15			/* Server operational messages; sent only to
  								 * server log by default. */
! #define COMMERROR	16			/* Client communication problems; same as LOG
  								 * for server reporting, but never sent to
! 								 * client. */
! #define INFO		17			/* Messages specifically requested by user (eg
  								 * VACUUM VERBOSE output); always sent to
  								 * client regardless of client_min_messages,
  								 * but by default not sent to server log. */
! #define NOTICE		18			/* Helpful messages to users about query
  								 * operation; sent to client and server log by
  								 * default. */
! #define WARNING		19			/* Warnings.  NOTICE is for expected messages
  								 * like implicit sequence creation by SERIAL.
  								 * WARNING is for unexpected messages. */
! #define ERROR		20			/* user error - abort transaction; return to
  								 * known state */
  /* Save ERROR value in PGERROR so it can be restored when Win32 includes
   * modify it.  We have to use a constant rather than ERROR because macros
   * are expanded only when referenced outside macros.
   */
  #ifdef WIN32
! #define PGERROR		20
  #endif
! #define FATAL		21			/* fatal error - abort process */
! #define PANIC		22			/* take down the other backends with me */
  
   /* #define DEBUG DEBUG1 */	/* Backward compatibility with pre-7.3 */
  
--- 28,60 ----
  #define DEBUG1		14			/* used by GUC debug_* variables */
  #define LOG			15			/* Server operational messages; sent only to
  								 * server log by default. */
! #define COMMERROR	(LOG|LOG_NO_CLIENT)/* Client communication problems; same as LOG
  								 * for server reporting, but never sent to
! 								 * client. For backward compatibility this is
! 								 * is available without explicitly specifying
! 								 * LOG_NO_CLIENT.*/
! #define INFO		16			/* Messages specifically requested by user (eg
  								 * VACUUM VERBOSE output); always sent to
  								 * client regardless of client_min_messages,
  								 * but by default not sent to server log. */
! #define NOTICE		17			/* Helpful messages to users about query
  								 * operation; sent to client and server log by
  								 * default. */
! #define WARNING		18			/* Warnings.  NOTICE is for expected messages
  								 * like implicit sequence creation by SERIAL.
  								 * WARNING is for unexpected messages. */
! #define ERROR		19			/* user error - abort transaction; return to
  								 * known state */
  /* Save ERROR value in PGERROR so it can be restored when Win32 includes
   * modify it.  We have to use a constant rather than ERROR because macros
   * are expanded only when referenced outside macros.
   */
  #ifdef WIN32
! #define PGERROR		19
  #endif
! #define FATAL		20			/* fatal error - abort process */
! #define PANIC		21			/* take down the other backends with me */
! 
  
   /* #define DEBUG DEBUG1 */	/* Backward compatibility with pre-7.3 */
  
*************** extern PGDLLIMPORT sigjmp_buf *PG_except
*** 291,296 ****
--- 297,303 ----
  typedef struct ErrorData
  {
  	int			elevel;			/* error level */
+ 	int			eflags;			/* error flags */
  	bool		output_to_server;		/* will report to server log? */
  	bool		output_to_client;		/* will report to client? */
  	bool		show_funcname;	/* true to force funcname inclusion */
-- 
1.6.5.12.gd65df24