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Change the logic to decide when to delete old WAL segments, so that it

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doesn't take into account how far the WAL senders are. This way a hung
WAL sender doesn't prevent old WAL segments from being recycled/removed
in the primary, ultimately causing the disk to fill up. Instead add
standby_keep_segments setting to control how many old WAL segments are
kept in the primary. This also makes it more reliable to use streaming
replication without WAL archiving, assuming that you set
standby_keep_segments high enough.
This commit is contained in:
Heikki Linnakangas
2010-04-12 09:52:29 +00:00
parent 93f35f0955
commit e57cd7f0a1
7 changed files with 174 additions and 33 deletions
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62
src/backend/replication/walsender.c
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@@ -30,7 +30,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/replication/walsender.c,v 1.14 2010/04/01 00:43:29 rhaas Exp $
* $PostgreSQL: pgsql/src/backend/replication/walsender.c,v 1.15 2010/04/12 09:52:29 heikki Exp $
*
*-------------------------------------------------------------------------
*/
@@ -508,6 +508,10 @@ XLogRead(char *buf, XLogRecPtr recptr, Size nbytes)
{
char path[MAXPGPATH];
uint32 startoff;
uint32 lastRemovedLog;
uint32 lastRemovedSeg;
uint32 log;
uint32 seg;
while (nbytes > 0)
{
@@ -527,10 +531,27 @@ XLogRead(char *buf, XLogRecPtr recptr, Size nbytes)
sendFile = BasicOpenFile(path, O_RDONLY | PG_BINARY, 0);
if (sendFile < 0)
ereport(FATAL, /* XXX: Why FATAL? */
(errcode_for_file_access(),
errmsg("could not open file \"%s\" (log file %u, segment %u): %m",
path, sendId, sendSeg)));
{
/*
* If the file is not found, assume it's because the
* standby asked for a too old WAL segment that has already
* been removed or recycled.
*/
if (errno == ENOENT)
{
char filename[MAXFNAMELEN];
XLogFileName(filename, ThisTimeLineID, sendId, sendSeg);
ereport(ERROR,
(errcode_for_file_access(),
errmsg("requested WAL segment %s has already been removed",
filename)));
}
else
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open file \"%s\" (log file %u, segment %u): %m",
path, sendId, sendSeg)));
}
sendOff = 0;
}
@@ -538,7 +559,7 @@ XLogRead(char *buf, XLogRecPtr recptr, Size nbytes)
if (sendOff != startoff)
{
if (lseek(sendFile, (off_t) startoff, SEEK_SET) < 0)
ereport(FATAL,
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not seek in log file %u, segment %u to offset %u: %m",
sendId, sendSeg, startoff)));
@@ -553,7 +574,7 @@ XLogRead(char *buf, XLogRecPtr recptr, Size nbytes)
readbytes = read(sendFile, buf, segbytes);
if (readbytes <= 0)
ereport(FATAL,
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from log file %u, segment %u, offset %u, "
"length %lu: %m",
@@ -566,6 +587,26 @@ XLogRead(char *buf, XLogRecPtr recptr, Size nbytes)
nbytes -= readbytes;
buf += readbytes;
}
/*
* After reading into the buffer, check that what we read was valid.
* We do this after reading, because even though the segment was present
* when we opened it, it might get recycled or removed while we read it.
* The read() succeeds in that case, but the data we tried to read might
* already have been overwritten with new WAL records.
*/
XLogGetLastRemoved(&lastRemovedLog, &lastRemovedSeg);
XLByteToPrevSeg(recptr, log, seg);
if (log < lastRemovedLog ||
(log == lastRemovedLog && seg <= lastRemovedSeg))
{
char filename[MAXFNAMELEN];
XLogFileName(filename, ThisTimeLineID, log, seg);
ereport(ERROR,
(errcode_for_file_access(),
errmsg("requested WAL segment %s has already been removed",
filename)));
}
}
/*
@@ -801,6 +842,12 @@ WalSndShmemInit(void)
}
}
/*
* This isn't currently used for anything. Monitoring tools might be
* interested in the future, and we'll need something like this in the
* future for synchronous replication.
*/
#ifdef NOT_USED
/*
* Returns the oldest Send position among walsenders. Or InvalidXLogRecPtr
* if none.
@@ -834,3 +881,4 @@ GetOldestWALSendPointer(void)
}
return oldest;
}
#endif