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Logging running transactions every 15 seconds.

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Previously, we did this just once per checkpoint, but that could make
Hot Standby take a long time to initialize.  To avoid busying an
otherwise-idle system, we don't do this if no WAL has been written
since we did it last.

Andres Freund
This commit is contained in:
Robert Haas
2014-01-15 12:41:20 -05:00
parent d02c0ddb15
commit ed46758381
3 changed files with 86 additions and 5 deletions
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27
src/backend/storage/ipc/standby.c
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@@ -42,7 +42,7 @@ static void ResolveRecoveryConflictWithVirtualXIDs(VirtualTransactionId *waitlis
ProcSignalReason reason);
static void ResolveRecoveryConflictWithLock(Oid dbOid, Oid relOid);
static void SendRecoveryConflictWithBufferPin(ProcSignalReason reason);
static void LogCurrentRunningXacts(RunningTransactions CurrRunningXacts);
static XLogRecPtr LogCurrentRunningXacts(RunningTransactions CurrRunningXacts);
static void LogAccessExclusiveLocks(int nlocks, xl_standby_lock *locks);
@@ -853,10 +853,13 @@ standby_redo(XLogRecPtr lsn, XLogRecord *record)
* currently running xids, performed by StandbyReleaseOldLocks().
* Zero xids should no longer be possible, but we may be replaying WAL
* from a time when they were possible.
*
* Returns the RecPtr of the last inserted record.
*/
void
XLogRecPtr
LogStandbySnapshot(void)
{
XLogRecPtr recptr;
RunningTransactions running;
xl_standby_lock *locks;
int nlocks;
@@ -876,9 +879,12 @@ LogStandbySnapshot(void)
* record we write, because standby will open up when it sees this.
*/
running = GetRunningTransactionData();
LogCurrentRunningXacts(running);
recptr = LogCurrentRunningXacts(running);
/* GetRunningTransactionData() acquired XidGenLock, we must release it */
LWLockRelease(XidGenLock);
return recptr;
}
/*
@@ -889,7 +895,7 @@ LogStandbySnapshot(void)
* is a contiguous chunk of memory and never exists fully until it is
* assembled in WAL.
*/
static void
static XLogRecPtr
LogCurrentRunningXacts(RunningTransactions CurrRunningXacts)
{
xl_running_xacts xlrec;
@@ -939,6 +945,19 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts)
CurrRunningXacts->oldestRunningXid,
CurrRunningXacts->latestCompletedXid,
CurrRunningXacts->nextXid);
/*
* Ensure running_xacts information is synced to disk not too far in the
* future. We don't want to stall anything though (i.e. use XLogFlush()),
* so we let the wal writer do it during normal
* operation. XLogSetAsyncXactLSN() conveniently will mark the LSN as
* to-be-synced and nudge the WALWriter into action if sleeping. Check
* XLogBackgroundFlush() for details why a record might not be flushed
* without it.
*/
XLogSetAsyncXactLSN(recptr);
return recptr;
}
/*