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Don't allow walsender to send WAL data until it's been safely fsync'd on the

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master.  Otherwise a subsequent crash could cause the master to lose WAL that
has already been applied on the slave, resulting in the slave being out of
sync and soon corrupt.  Per recent discussion and an example from Robert Haas.

Fujii Masao
This commit is contained in:
Tom Lane
2010-06-17 16:41:25 +00:00
parent 8f4e121845
commit 07e8b6aabc
3 changed files with 20 additions and 17 deletions
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9
src/backend/access/transam/xlog.c
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@ -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/backend/access/transam/xlog.c,v 1.424 2010/06/14 06:04:21 heikki Exp $
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.425 2010/06/17 16:41:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -6803,17 +6803,18 @@ GetInsertRecPtr(void)
}
/*
* GetWriteRecPtr -- Returns the current write position.
* GetFlushRecPtr -- Returns the current flush position, ie, the last WAL
* position known to be fsync'd to disk.
*/
XLogRecPtr
GetWriteRecPtr(void)
GetFlushRecPtr(void)
{
/* use volatile pointer to prevent code rearrangement */
volatile XLogCtlData *xlogctl = XLogCtl;
XLogRecPtr recptr;
SpinLockAcquire(&xlogctl->info_lck);
recptr = xlogctl->LogwrtResult.Write;
recptr = xlogctl->LogwrtResult.Flush;
SpinLockRelease(&xlogctl->info_lck);
return recptr;