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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 0bead9af48
commit c3fe108c02
12 changed files with 58 additions and 48 deletions
Download Patch File Download Diff File Expand all files Collapse all files

30
src/backend/access/transam/xlog.c
View File

@ -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;
@ -9525,7 +9525,7 @@ 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();
@ -9576,9 +9576,9 @@ 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
@ -9616,14 +9616,20 @@ 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 */
@ -11328,7 +11334,7 @@ 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.

13
src/backend/replication/slotfuncs.c
View File

@ -413,19 +413,20 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
else
{
XLogSegNo targetSeg;
XLogSegNo keepSegs;
uint64 slotKeepSegs;
uint64 keepSegs;
XLogSegNo failSeg;
XLogRecPtr failLSN;
XLByteToSeg(slot_contents.data.restart_lsn, targetSeg, wal_segment_size);
/* determine how many segments slots can be kept by slots ... */
keepSegs = XLogMBVarToSegs(max_slot_wal_keep_size_mb, wal_segment_size);
/* ... and override by wal_keep_segments as needed */
keepSegs = Max(keepSegs, wal_keep_segments);
/* determine how many segments slots can be kept by slots */
slotKeepSegs = XLogMBVarToSegs(max_slot_wal_keep_size_mb, wal_segment_size);
/* ditto for wal_keep_size */
keepSegs = XLogMBVarToSegs(wal_keep_size_mb, wal_segment_size);
/* if currpos reaches failLSN, we lose our segment */
failSeg = targetSeg + keepSegs + 1;
failSeg = targetSeg + Max(slotKeepSegs, keepSegs) + 1;
XLogSegNoOffsetToRecPtr(failSeg, 0, wal_segment_size, failLSN);
values[i++] = Int64GetDatum(failLSN - currlsn);

11
src/backend/utils/misc/guc.c
View File

@ -2636,12 +2636,13 @@ static struct config_int ConfigureNamesInt[] =
},
{
{"wal_keep_segments", PGC_SIGHUP, REPLICATION_SENDING,
gettext_noop("Sets the number of WAL files held for standby servers."),
NULL
{"wal_keep_size", PGC_SIGHUP, REPLICATION_SENDING,
gettext_noop("Sets the size of WAL files held for standby servers."),
NULL,
GUC_UNIT_MB
},
&wal_keep_segments,
0, 0, INT_MAX,
&wal_keep_size_mb,
0, 0, MAX_KILOBYTES,
NULL, NULL, NULL
},

2
src/backend/utils/misc/postgresql.conf.sample
View File

@ -290,7 +290,7 @@
#max_wal_senders = 10 # max number of walsender processes
# (change requires restart)
#wal_keep_segments = 0 # in logfile segments; 0 disables
#wal_keep_size = 0 # in megabytes; 0 disables
#max_slot_wal_keep_size = -1 # in megabytes; -1 disables
#wal_sender_timeout = 60s # in milliseconds; 0 disables

4
src/bin/pg_rewind/t/RewindTest.pm
View File

@ -135,11 +135,11 @@ sub setup_cluster
extra => $extra,
auth_extra => [ '--create-role', 'rewind_user' ]);
# Set wal_keep_segments to prevent WAL segment recycling after enforced
# Set wal_keep_size to prevent WAL segment recycling after enforced
# checkpoints in the tests.
$node_primary->append_conf(
'postgresql.conf', qq(
wal_keep_segments = 20
wal_keep_size = 320MB
));
return;
}

4
src/include/access/xlog.h
View File

@ -107,7 +107,7 @@ extern bool reachedConsistency;
extern int wal_segment_size;
extern int min_wal_size_mb;
extern int max_wal_size_mb;
extern int wal_keep_segments;
extern int wal_keep_size_mb;
extern int max_slot_wal_keep_size_mb;
extern int XLOGbuffers;
extern int XLogArchiveTimeout;
@ -273,7 +273,7 @@ typedef enum WALAvailability
WALAVAIL_INVALID_LSN, /* parameter error */
WALAVAIL_RESERVED, /* WAL segment is within max_wal_size */
WALAVAIL_EXTENDED, /* WAL segment is reserved by a slot or
* wal_keep_segments */
* wal_keep_size */
WALAVAIL_UNRESERVED, /* no longer reserved, but not removed yet */
WALAVAIL_REMOVED /* WAL segment has been removed */
} WALAvailability;

10
src/test/recovery/t/019_replslot_limit.pl
View File

@ -116,19 +116,19 @@ $start_lsn = $node_primary->lsn('write');
$node_primary->wait_for_catchup($node_standby, 'replay', $start_lsn);
$node_standby->stop;
# wal_keep_segments overrides max_slot_wal_keep_size
# wal_keep_size overrides max_slot_wal_keep_size
$result = $node_primary->safe_psql('postgres',
"ALTER SYSTEM SET wal_keep_segments to 8; SELECT pg_reload_conf();");
"ALTER SYSTEM SET wal_keep_size to '8MB'; SELECT pg_reload_conf();");
# Advance WAL again then checkpoint, reducing remain by 6 MB.
advance_wal($node_primary, 6);
$result = $node_primary->safe_psql('postgres',
"SELECT wal_status as remain FROM pg_replication_slots WHERE slot_name = 'rep1'"
);
is($result, "extended",
'check that wal_keep_segments overrides max_slot_wal_keep_size');
# restore wal_keep_segments
'check that wal_keep_size overrides max_slot_wal_keep_size');
# restore wal_keep_size
$result = $node_primary->safe_psql('postgres',
"ALTER SYSTEM SET wal_keep_segments to 0; SELECT pg_reload_conf();");
"ALTER SYSTEM SET wal_keep_size to 0; SELECT pg_reload_conf();");
# The standby can reconnect to primary
$node_standby->start;