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Detect early deadlock in Hot Standby when Startup is already waiting. First

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stage of required deadlock detection to allow re-enabling max_standby_delay
setting of -1, which is now essential in the absence of improved relation-
specific conflict resoluton. Requested by Greg Stark et al.
This commit is contained in:
Simon Riggs
2010-01-31 19:01:11 +00:00
parent 034fffbf31
commit c85c941470
3 changed files with 46 additions and 4 deletions
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38
src/backend/storage/ipc/standby.c
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@ -11,7 +11,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/ipc/standby.c,v 1.8 2010/01/29 17:10:05 sriggs Exp $
* $PostgreSQL: pgsql/src/backend/storage/ipc/standby.c,v 1.9 2010/01/31 19:01:11 sriggs Exp $
*
*-------------------------------------------------------------------------
*/
@ -22,6 +22,7 @@
#include "access/xlog.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "storage/proc.h"
#include "storage/procarray.h"
@ -384,7 +385,7 @@ ResolveRecoveryConflictWithBufferPin(void)
TimestampDifference(GetLatestXLogTime(), now,
&standby_delay_secs, &standby_delay_usecs);
if (standby_delay_secs >= (long) MaxStandbyDelay)
if (standby_delay_secs >= MaxStandbyDelay)
SendRecoveryConflictWithBufferPin();
else
{
@ -445,6 +446,39 @@ SendRecoveryConflictWithBufferPin(void)
CancelDBBackends(InvalidOid, PROCSIG_RECOVERY_CONFLICT_BUFFERPIN, false);
}
/*
* In Hot Standby perform early deadlock detection. We abort the lock
* wait if are about to sleep while holding the buffer pin that Startup
* process is waiting for. The deadlock occurs because we can only be
* waiting behind an AccessExclusiveLock, which can only clear when a
* transaction completion record is replayed, which can only occur when
* Startup process is not waiting. So if Startup process is waiting we
* never will clear that lock, so if we wait we cause deadlock. If we
* are the Startup process then no need to check for deadlocks.
*/
void
CheckRecoveryConflictDeadlock(LWLockId partitionLock)
{
Assert(!InRecovery);
if (!HoldingBufferPinThatDelaysRecovery())
return;
LWLockRelease(partitionLock);
/*
* Error message should match ProcessInterrupts() but we avoid calling
* that because we aren't handling an interrupt at this point. Note
* that we only cancel the current transaction here, so if we are in a
* subtransaction and the pin is held by a parent, then the Startup
* process will continue to wait even though we have avoided deadlock.
*/
ereport(ERROR,
(errcode(ERRCODE_QUERY_CANCELED),
errmsg("canceling statement due to conflict with recovery"),
errdetail("User transaction caused buffer deadlock with recovery.")));
}
/*
* -----------------------------------------------------
* Locking in Recovery Mode