Teach standby conflict resolution to use SIGUSR1

Conflict reason is passed through directly to the backend, so we can
take decisions about the effect of the conflict based upon the local
state. No specific changes, as yet, though this prepares for later work.
CancelVirtualTransaction() sends signals while holding ProcArrayLock.
Introduce errdetail_abort() to give message detail explaining that the
abort was caused by conflict processing. Remove CONFLICT_MODE states
in favour of using PROCSIG_RECOVERY_CONFLICT states directly, for clarity.

src/backend/access/transam/xact.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.280 2010/01/09 16:49:27 sriggs Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.281 2010/01/16 10:05:50 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -313,8 +313,7 @@ IsTransactionState(void)
 /*
  *	IsAbortedTransactionBlockState
  *
- *	This returns true if we are currently running a query
- *	within an aborted transaction block.
+ *	This returns true if we are within an aborted transaction block.
  */
 bool
 IsAbortedTransactionBlockState(void)

src/backend/storage/ipc/procarray.c

@@ -37,7 +37,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.55 2010/01/10 15:44:28 sriggs Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.56 2010/01/16 10:05:50 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -324,6 +324,7 @@ ProcArrayEndTransaction(PGPROC *proc, TransactionId latestXid)
 		/* must be cleared with xid/xmin: */
 		proc->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
 		proc->inCommit = false; /* be sure this is cleared in abort */
+		proc->recoveryConflictPending = false;
 
 		/* Clear the subtransaction-XID cache too while holding the lock */
 		proc->subxids.nxids = 0;
@@ -350,6 +351,7 @@ ProcArrayEndTransaction(PGPROC *proc, TransactionId latestXid)
 		/* must be cleared with xid/xmin: */
 		proc->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
 		proc->inCommit = false; /* be sure this is cleared in abort */
+		proc->recoveryConflictPending = false;
 
 		Assert(proc->subxids.nxids == 0);
 		Assert(proc->subxids.overflowed == false);
@@ -377,7 +379,7 @@ ProcArrayClearTransaction(PGPROC *proc)
 	proc->xid = InvalidTransactionId;
 	proc->lxid = InvalidLocalTransactionId;
 	proc->xmin = InvalidTransactionId;
-	proc->recoveryConflictMode = 0;
+	proc->recoveryConflictPending = false;
 
 	/* redundant, but just in case */
 	proc->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
@@ -1665,7 +1667,7 @@ GetConflictingVirtualXIDs(TransactionId limitXmin, Oid dbOid,
 		if (proc->pid == 0)
 			continue;
 
-		if (skipExistingConflicts && proc->recoveryConflictMode > 0)
+		if (skipExistingConflicts && proc->recoveryConflictPending)
 			continue;
 
 		if (!OidIsValid(dbOid) ||
@@ -1704,7 +1706,7 @@ GetConflictingVirtualXIDs(TransactionId limitXmin, Oid dbOid,
  * Returns pid of the process signaled, or 0 if not found.
  */
 pid_t
-CancelVirtualTransaction(VirtualTransactionId vxid, int cancel_mode)
+CancelVirtualTransaction(VirtualTransactionId vxid, ProcSignalReason sigmode)
 {
 	ProcArrayStruct *arrayP = procArray;
 	int			index;
@@ -1722,28 +1724,22 @@ CancelVirtualTransaction(VirtualTransactionId vxid, int cancel_mode)
 		if (procvxid.backendId == vxid.backendId &&
 			procvxid.localTransactionId == vxid.localTransactionId)
 		{
-			/*
-			 * Issue orders for the proc to read next time it receives SIGINT
-			 */
-			if (proc->recoveryConflictMode < cancel_mode)
-				proc->recoveryConflictMode = cancel_mode;
-
+			proc->recoveryConflictPending = true;
 			pid = proc->pid;
+			if (pid != 0)
+			{
+				/*
+				 * Kill the pid if it's still here. If not, that's what we wanted
+				 * so ignore any errors.
+				 */
+				(void) SendProcSignal(pid, sigmode, vxid.backendId);
+			}
 			break;
 		}
 	}
 
 	LWLockRelease(ProcArrayLock);
 
-	if (pid != 0)
-	{
-		/*
-		 * Kill the pid if it's still here. If not, that's what we wanted
-		 * so ignore any errors.
-		 */
-		kill(pid, SIGINT);
-	}
-
 	return pid;
 }
 
@@ -1834,6 +1830,7 @@ CancelDBBackends(Oid databaseid)
 {
 	ProcArrayStruct *arrayP = procArray;
 	int			index;
+	pid_t		pid = 0;
 
 	/* tell all backends to die */
 	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
@@ -1844,8 +1841,21 @@ CancelDBBackends(Oid databaseid)
 
 		if (proc->databaseId == databaseid)
 		{
-			proc->recoveryConflictMode = CONFLICT_MODE_FATAL;
-			kill(proc->pid, SIGINT);
+			VirtualTransactionId procvxid;
+
+			GET_VXID_FROM_PGPROC(procvxid, *proc);
+
+			proc->recoveryConflictPending = true;
+			pid = proc->pid;
+			if (pid != 0)
+			{
+				/*
+				 * Kill the pid if it's still here. If not, that's what we wanted
+				 * so ignore any errors.
+				 */
+				(void) SendProcSignal(pid, PROCSIG_RECOVERY_CONFLICT_DATABASE,
+										procvxid.backendId);
+			}
 		}
 	}
 

src/backend/storage/ipc/procsignal.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/procsignal.c,v 1.2 2010/01/02 16:57:51 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/procsignal.c,v 1.3 2010/01/16 10:05:50 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -24,6 +24,8 @@
 #include "storage/procsignal.h"
 #include "storage/shmem.h"
 #include "storage/sinval.h"
+#include "storage/standby.h"
+#include "tcop/tcopprot.h"
 
 
 /*
@@ -258,5 +260,17 @@ procsignal_sigusr1_handler(SIGNAL_ARGS)
 	if (CheckProcSignal(PROCSIG_NOTIFY_INTERRUPT))
 		HandleNotifyInterrupt();
 
+	if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_DATABASE))
+		RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_DATABASE);
+
+	if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_TABLESPACE))
+		RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_TABLESPACE);
+
+	if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_LOCK))
+		RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_LOCK);
+
+	if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_SNAPSHOT))
+		RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_SNAPSHOT);
+
 	errno = save_errno;
 }

src/backend/storage/ipc/standby.c

@@ -3,19 +3,15 @@
  * standby.c
  *	  Misc functions used in Hot Standby mode.
  *
- *	InitRecoveryTransactionEnvironment()
- *  ShutdownRecoveryTransactionEnvironment()
- *
- *  ResolveRecoveryConflictWithVirtualXIDs()
- *
  *  All functions for handling RM_STANDBY_ID, which relate to
  *  AccessExclusiveLocks and starting snapshots for Hot Standby mode.
+ *  Plus conflict recovery processing.
  *
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/standby.c,v 1.4 2010/01/14 11:08:02 sriggs Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/standby.c,v 1.5 2010/01/16 10:05:50 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -38,7 +34,7 @@ int		vacuum_defer_cleanup_age;
 static List *RecoveryLockList;
 
 static void ResolveRecoveryConflictWithVirtualXIDs(VirtualTransactionId *waitlist,
-									   char *reason, int cancel_mode);
+									   ProcSignalReason reason);
 static void ResolveRecoveryConflictWithLock(Oid dbOid, Oid relOid);
 static void LogCurrentRunningXacts(RunningTransactions CurrRunningXacts);
 static void LogAccessExclusiveLocks(int nlocks, xl_standby_lock *locks);
@@ -162,17 +158,13 @@ WaitExceedsMaxStandbyDelay(void)
  * recovery processing. Judgement has already been passed on it within
  * a specific rmgr. Here we just issue the orders to the procs. The procs
  * then throw the required error as instructed.
- *
- * We may ask for a specific cancel_mode, typically ERROR or FATAL.
  */
 static void
 ResolveRecoveryConflictWithVirtualXIDs(VirtualTransactionId *waitlist,
-									   char *reason, int cancel_mode)
+									   ProcSignalReason reason)
 {
 	char		waitactivitymsg[100];
 
-	Assert(cancel_mode > 0);
-
 	while (VirtualTransactionIdIsValid(*waitlist))
 	{
 		long wait_s;
@@ -206,12 +198,6 @@ ResolveRecoveryConflictWithVirtualXIDs(VirtualTransactionId *waitlist,
 					len = 100;
 				memcpy(waitactivitymsg, oldactivitymsg, len);
 
-				ereport(trace_recovery(DEBUG5),
-						(errmsg("virtual transaction %u/%u is blocking %s",
-								waitlist->backendId,
-								waitlist->localTransactionId,
-								reason)));
-
 				pgstat_report_waiting(true);
 
 				logged = true;
@@ -226,40 +212,14 @@ ResolveRecoveryConflictWithVirtualXIDs(VirtualTransactionId *waitlist,
 				 * Now find out who to throw out of the balloon.
 				 */
 				Assert(VirtualTransactionIdIsValid(*waitlist));
-				pid = CancelVirtualTransaction(*waitlist, cancel_mode);
+				pid = CancelVirtualTransaction(*waitlist, reason);
 
+				/*
+				 * Wait awhile for it to die so that we avoid flooding an
+				 * unresponsive backend when system is heavily loaded.
+				 */
 				if (pid != 0)
-				{
-					/*
-					 * Startup process debug messages
-					 */
-					switch (cancel_mode)
-					{
-						case CONFLICT_MODE_FATAL:
-							elog(trace_recovery(DEBUG1),
-								 "recovery disconnects session with pid %ld because of conflict with %s",
-								 (long) pid,
-								 reason);
-							break;
-						case CONFLICT_MODE_ERROR:
-							elog(trace_recovery(DEBUG1),
-								 "recovery cancels virtual transaction %u/%u pid %ld because of conflict with %s",
-								 waitlist->backendId,
-								 waitlist->localTransactionId,
-								 (long) pid,
-								 reason);
-							break;
-						default:
-							/* No conflict pending, so fall through */
-							break;
-					}
-
-					/*
-					 * Wait awhile for it to die so that we avoid flooding an
-					 * unresponsive backend when system is heavily loaded.
-					 */
 					pg_usleep(5000);
-				}
 			}
 		}
 
@@ -285,8 +245,7 @@ ResolveRecoveryConflictWithSnapshot(TransactionId latestRemovedXid)
 										 true);
 
 	ResolveRecoveryConflictWithVirtualXIDs(backends,
-										   "snapshot conflict",
-										   CONFLICT_MODE_ERROR);
+										   PROCSIG_RECOVERY_CONFLICT_SNAPSHOT);
 }
 
 void
@@ -317,8 +276,7 @@ ResolveRecoveryConflictWithTablespace(Oid tsid)
 												InvalidOid,
 												false);
 	ResolveRecoveryConflictWithVirtualXIDs(temp_file_users,
-										   "drop tablespace",
-										   CONFLICT_MODE_ERROR);
+										   PROCSIG_RECOVERY_CONFLICT_TABLESPACE);
 }
 
 void
@@ -379,8 +337,7 @@ ResolveRecoveryConflictWithLock(Oid dbOid, Oid relOid)
 		}
 
 		ResolveRecoveryConflictWithVirtualXIDs(backends,
-											   "exclusive lock",
-											   CONFLICT_MODE_ERROR);
+											   PROCSIG_RECOVERY_CONFLICT_LOCK);
 
 		if (LockAcquireExtended(&locktag, AccessExclusiveLock, true, true, false)
 											!= LOCKACQUIRE_NOT_AVAIL)

src/backend/storage/lmgr/proc.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.212 2010/01/15 09:19:03 heikki Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.213 2010/01/16 10:05:50 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -324,7 +324,7 @@ InitProcess(void)
 	MyProc->waitProcLock = NULL;
 	for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
 		SHMQueueInit(&(MyProc->myProcLocks[i]));
-	MyProc->recoveryConflictMode = 0;
+	MyProc->recoveryConflictPending = false;
 
 	/*
 	 * We might be reusing a semaphore that belonged to a failed process. So

src/include/storage/proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/proc.h,v 1.117 2010/01/15 09:19:09 heikki Exp $
+ * $PostgreSQL: pgsql/src/include/storage/proc.h,v 1.118 2010/01/16 10:05:50 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -96,11 +96,11 @@ struct PGPROC
 	uint8		vacuumFlags;	/* vacuum-related flags, see above */
 
 	/*
-	 * While in hot standby mode, setting recoveryConflictMode instructs
-	 * the backend to commit suicide. Possible values are the same as those
-	 * passed to ResolveRecoveryConflictWithVirtualXIDs().
+	 * While in hot standby mode, shows that a conflict signal has been sent
+	 * for the current transaction. Set/cleared while holding ProcArrayLock,
+	 * though not required. Accessed without lock, if needed.
 	 */
-	int			recoveryConflictMode;
+	bool		recoveryConflictPending;
 
 	/* Info about LWLock the process is currently waiting for, if any. */
 	bool		lwWaiting;		/* true if waiting for an LW lock */

src/include/storage/procarray.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.29 2010/01/10 15:44:28 sriggs Exp $
+ * $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.30 2010/01/16 10:05:56 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -15,6 +15,7 @@
 #define PROCARRAY_H
 
 #include "storage/lock.h"
+#include "storage/procsignal.h"
 #include "storage/standby.h"
 #include "utils/snapshot.h"
 
@@ -58,8 +59,7 @@ extern VirtualTransactionId *GetCurrentVirtualXIDs(TransactionId limitXmin,
 					  int *nvxids);
 extern VirtualTransactionId *GetConflictingVirtualXIDs(TransactionId limitXmin,
 					Oid dbOid, bool skipExistingConflicts);
-extern pid_t CancelVirtualTransaction(VirtualTransactionId vxid,
-						 int cancel_mode);
+extern pid_t CancelVirtualTransaction(VirtualTransactionId vxid, ProcSignalReason sigmode);
 
 extern int	CountActiveBackends(void);
 extern int	CountDBBackends(Oid databaseid);

src/include/storage/procsignal.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/procsignal.h,v 1.2 2010/01/02 16:58:08 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/storage/procsignal.h,v 1.3 2010/01/16 10:05:57 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -32,6 +32,12 @@ typedef enum
 	PROCSIG_CATCHUP_INTERRUPT,	/* sinval catchup interrupt */
 	PROCSIG_NOTIFY_INTERRUPT,	/* listen/notify interrupt */
 
+	/* Recovery conflict reasons */
+	PROCSIG_RECOVERY_CONFLICT_DATABASE,
+	PROCSIG_RECOVERY_CONFLICT_TABLESPACE,
+	PROCSIG_RECOVERY_CONFLICT_LOCK,
+	PROCSIG_RECOVERY_CONFLICT_SNAPSHOT,
+
 	NUM_PROCSIGNALS				/* Must be last! */
 } ProcSignalReason;
 

src/include/storage/standby.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/standby.h,v 1.3 2010/01/14 11:08:02 sriggs Exp $
+ * $PostgreSQL: pgsql/src/include/storage/standby.h,v 1.4 2010/01/16 10:05:57 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -19,11 +19,6 @@
 
 extern int	vacuum_defer_cleanup_age;
 
-/* cancel modes for ResolveRecoveryConflictWithVirtualXIDs */
-#define CONFLICT_MODE_NOT_SET		0
-#define CONFLICT_MODE_ERROR			1	/* Conflict can be resolved by canceling query */
-#define CONFLICT_MODE_FATAL			2	/* Conflict can only be resolved by disconnecting session */
-
 extern void ResolveRecoveryConflictWithSnapshot(TransactionId latestRemovedXid);
 extern void ResolveRecoveryConflictWithTablespace(Oid tsid);
 extern void ResolveRecoveryConflictWithDatabase(Oid dbid);

src/include/tcop/tcopprot.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/tcop/tcopprot.h,v 1.102 2010/01/02 16:58:09 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/tcop/tcopprot.h,v 1.103 2010/01/16 10:05:59 sriggs Exp $
  *
  * OLD COMMENTS
  *	  This file was created so that other c files could get the two
@@ -21,6 +21,7 @@
 
 #include "executor/execdesc.h"
 #include "nodes/parsenodes.h"
+#include "storage/procsignal.h"
 #include "utils/guc.h"
 
 
@@ -64,6 +65,7 @@ extern void die(SIGNAL_ARGS);
 extern void quickdie(SIGNAL_ARGS);
 extern void StatementCancelHandler(SIGNAL_ARGS);
 extern void FloatExceptionHandler(SIGNAL_ARGS);
+extern void RecoveryConflictInterrupt(ProcSignalReason reason); /* called from SIGUSR1 handler */
 extern void prepare_for_client_read(void);
 extern void client_read_ended(void);
 extern const char *process_postgres_switches(int argc, char *argv[],