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Rename wal_keep_segments to wal_keep_size.

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max_slot_wal_keep_size that was added in v13 and wal_keep_segments are
the GUC parameters to specify how much WAL files to retain for
the standby servers. While max_slot_wal_keep_size accepts the number of
bytes of WAL files, wal_keep_segments accepts the number of WAL files.
This difference of setting units between those similar parameters could
be confusing to users.

To alleviate this situation, this commit renames wal_keep_segments to
wal_keep_size, and make users specify the WAL size in it instead of
the number of WAL files.

There was also the idea to rename max_slot_wal_keep_size to
max_slot_wal_keep_segments, in the discussion. But we have been moving
away from measuring in segments, for example, checkpoint_segments was
replaced by max_wal_size. So we concluded to rename wal_keep_segments
to wal_keep_size.

Back-patch to v13 where max_slot_wal_keep_size was added.

Author: Fujii Masao
Reviewed-by: Álvaro Herrera, Kyotaro Horiguchi, David Steele
Discussion: https://postgr.es/m/574b4ea3-e0f9-b175-ead2-ebea7faea855@oss.nttdata.com
This commit is contained in:
Fujii Masao
2020-07-20 13:30:18 +09:00
parent 4a1ae21750
commit f5dff45962
12 changed files with 58 additions and 48 deletions
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30
src/backend/access/transam/xlog.c
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@ -88,7 +88,7 @@ extern uint32 bootstrap_data_checksum_version;
/* User-settable parameters */
int max_wal_size_mb = 1024; /* 1 GB */
int min_wal_size_mb = 80; /* 80 MB */
int wal_keep_segments = 0;
int wal_keep_size_mb = 0;
int XLOGbuffers = -1;
int XLogArchiveTimeout = 0;
int XLogArchiveMode = ARCHIVE_MODE_OFF;
@ -9523,7 +9523,7 @@ GetWALAvailability(XLogRecPtr targetLSN)
/*
* Calculate the oldest segment currently reserved by all slots,
* considering wal_keep_segments and max_slot_wal_keep_size. Initialize
* considering wal_keep_size and max_slot_wal_keep_size. Initialize
* oldestSlotSeg to the current segment.
*/
currpos = GetXLogWriteRecPtr();
@ -9574,9 +9574,9 @@ GetWALAvailability(XLogRecPtr targetLSN)
/*
* Retreat *logSegNo to the last segment that we need to retain because of
* either wal_keep_segments or replication slots.
* either wal_keep_size or replication slots.
*
* This is calculated by subtracting wal_keep_segments from the given xlog
* This is calculated by subtracting wal_keep_size from the given xlog
* location, recptr and by making sure that that result is below the
* requirement of replication slots. For the latter criterion we do consider
* the effects of max_slot_wal_keep_size: reserve at most that much space back
@ -9614,14 +9614,20 @@ KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo)
}
}
/* but, keep at least wal_keep_segments if that's set */
if (wal_keep_segments > 0 && currSegNo - segno < wal_keep_segments)
/* but, keep at least wal_keep_size if that's set */
if (wal_keep_size_mb > 0)
{
/* avoid underflow, don't go below 1 */
if (currSegNo <= wal_keep_segments)
segno = 1;
else
segno = currSegNo - wal_keep_segments;
uint64 keep_segs;
keep_segs = ConvertToXSegs(wal_keep_size_mb, wal_segment_size);
if (currSegNo - segno < keep_segs)
{
/* avoid underflow, don't go below 1 */
if (currSegNo <= keep_segs)
segno = 1;
else
segno = currSegNo - keep_segs;
}
}
/* don't delete WAL segments newer than the calculated segment */
@ -11336,7 +11342,7 @@ do_pg_stop_backup(char *labelfile, bool waitforarchive, TimeLineID *stoptli_p)
* If archiving is enabled, wait for all the required WAL files to be
* archived before returning. If archiving isn't enabled, the required WAL
* needs to be transported via streaming replication (hopefully with
* wal_keep_segments set high enough), or some more exotic mechanism like
* wal_keep_size set high enough), or some more exotic mechanism like
* polling and copying files from pg_wal with script. We have no knowledge
* of those mechanisms, so it's up to the user to ensure that he gets all
* the required WAL.