On 2020/07/02 2:18, David Steele wrote:
On 7/1/20 10:54 AM, Alvaro Herrera wrote:
On 2020-Jul-01, Fujii Masao wrote:
On 2020/07/01 12:26, Alvaro Herrera wrote:
On 2020-Jun-30, Fujii Masao wrote:
When I talked about max_slot_wal_keep_size as new feature in v13
at the conference, I received the question like "Why are the units of
setting values in max_slot_wal_keep_size and wal_keep_segments different?"
from audience. That difference looks confusing for users and
IMO it's better to use the same unit for them. Thought?
Do we still need wal_keep_segments for anything?
Yeah, personally I like wal_keep_segments because its setting is very
simple and no extra operations on replication slots are necessary.
Okay. In that case I +1 the idea of renaming to wal_keep_size.
+1 for renaming to wal_keep_size.
I attached the patch that renames wal_keep_segments to wal_keep_size.
Regards,
--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index e9cdff4864..3d973a5c8e 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -11249,7 +11249,7 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts
ppx
<para><literal>extended</literal> means
that <varname>max_wal_size</varname> is exceeded but the files are
still retained, either by the replication slot or
- by <varname>wal_keep_segments</varname>.
+ by <varname>wal_keep_size</varname>.
</para>
</listitem>
<listitem>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 02909b1e66..33c3ccb923 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3124,7 +3124,7 @@ include_dir 'conf.d'
checkpoints. This is a soft limit; WAL size can exceed
<varname>max_wal_size</varname> under special circumstances, such as
heavy load, a failing <varname>archive_command</varname>, or a high
- <varname>wal_keep_segments</varname> setting.
+ <varname>wal_keep_size</varname> setting.
If this value is specified without units, it is taken as megabytes.
The default is 1 GB.
Increasing this parameter can increase the amount of time needed for
@@ -3751,21 +3751,21 @@ restore_command = 'copy "C:\\server\\archivedir\\%f"
"%p"' # Windows
</listitem>
</varlistentry>
- <varlistentry id="guc-wal-keep-segments" xreflabel="wal_keep_segments">
- <term><varname>wal_keep_segments</varname> (<type>integer</type>)
+ <varlistentry id="guc-wal-keep-size" xreflabel="wal_keep_size">
+ <term><varname>wal_keep_size</varname> (<type>integer</type>)
<indexterm>
- <primary><varname>wal_keep_segments</varname> configuration
parameter</primary>
+ <primary><varname>wal_keep_size</varname> configuration
parameter</primary>
</indexterm>
</term>
<listitem>
<para>
- Specifies the minimum number of past log file segments kept in the
+ Specifies the minimum size of past log file segments kept in the
<filename>pg_wal</filename>
directory, in case a standby server needs to fetch them for streaming
- replication. Each segment is normally 16 megabytes. If a standby
+ replication. If a standby
server connected to the sending server falls behind by more than
- <varname>wal_keep_segments</varname> segments, the sending server
might remove
- a WAL segment still needed by the standby, in which case the
+ <varname>wal_keep_size</varname> megabytes, the sending server might
+ remove a WAL segment still needed by the standby, in which case the
replication connection will be terminated. Downstream connections
will also eventually fail as a result. (However, the standby
server can recover by fetching the segment from archive, if WAL
@@ -3773,14 +3773,15 @@ restore_command = 'copy "C:\\server\\archivedir\\%f"
"%p"' # Windows
</para>
<para>
- This sets only the minimum number of segments retained in
+ This sets only the minimum size of segments retained in
<filename>pg_wal</filename>; the system might need to retain more
segments
for WAL archival or to recover from a checkpoint. If
- <varname>wal_keep_segments</varname> is zero (the default), the system
+ <varname>wal_keep_size</varname> is zero (the default), the system
doesn't keep any extra segments for standby purposes, so the number
of old WAL segments available to standby servers is a function of
the location of the previous checkpoint and status of WAL
archiving.
+ If this value is specified without units, it is taken as megabytes.
This parameter can only be set in the
<filename>postgresql.conf</filename> file or on the server command
line.
</para>
diff --git a/doc/src/sgml/high-availability.sgml
b/doc/src/sgml/high-availability.sgml
index 65c3fc62a9..2d4f9f03c7 100644
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -785,7 +785,7 @@ archive_cleanup_command = 'pg_archivecleanup
/path/to/archive %r'
archiving, the server might recycle old WAL segments before the standby
has received them. If this occurs, the standby will need to be
reinitialized from a new base backup. You can avoid this by setting
- <varname>wal_keep_segments</varname> to a value large enough to ensure that
+ <varname>wal_keep_size</varname> to a value large enough to ensure that
WAL segments are not recycled too early, or by configuring a replication
slot for the standby. If you set up a WAL archive that's accessible from
the standby, these solutions are not required, since the standby can
@@ -929,7 +929,7 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo
password=foopass'
</para>
<para>
In lieu of using replication slots, it is possible to prevent the removal
- of old WAL segments using <xref linkend="guc-wal-keep-segments"/>, or by
+ of old WAL segments using <xref linkend="guc-wal-keep-size"/>, or by
storing the segments in an archive using
<xref linkend="guc-archive-command"/>.
However, these methods often result in retaining more WAL segments than
diff --git a/doc/src/sgml/ref/pg_basebackup.sgml
b/doc/src/sgml/ref/pg_basebackup.sgml
index db480be674..91cfd92ab2 100644
--- a/doc/src/sgml/ref/pg_basebackup.sgml
+++ b/doc/src/sgml/ref/pg_basebackup.sgml
@@ -305,7 +305,7 @@ PostgreSQL documentation
<para>
The write-ahead log files are collected at the end of the backup.
Therefore, it is necessary for the
- <xref linkend="guc-wal-keep-segments"/> parameter to be set high
+ <xref linkend="guc-wal-keep-size"/> parameter to be set high
enough that the log is not removed before the end of the backup.
If the log has been rotated when it's time to transfer it, the
backup will fail and be unusable.
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index bd9fae544c..34af9961b4 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -578,7 +578,8 @@
<para>
Independently of <varname>max_wal_size</varname>,
- <xref linkend="guc-wal-keep-segments"/> + 1 most recent WAL files are
+ most recent <xref linkend="guc-wal-keep-size"/> megabytes
+ WAL files plus one WAL file are
kept at all times. Also, if WAL archiving is used, old segments can not be
removed or recycled until they are archived. If WAL archiving cannot keep up
with the pace that WAL is generated, or if
<varname>archive_command</varname>
diff --git a/src/backend/access/transam/xlog.c
b/src/backend/access/transam/xlog.c
index 91d99c113c..f1dfeeb765 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -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
+ * considering wal_keep_size and max_slot_wal_keep_size
*/
XLByteToSeg(targetLSN, targetSeg, wal_segment_size);
KeepLogSeg(currpos, &oldestSlotSeg);
@@ -9571,9 +9571,9 @@ 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
@@ -9611,14 +9611,20 @@ 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 */
@@ -11323,7 +11329,7 @@ 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.
diff --git a/src/backend/replication/slotfuncs.c
b/src/backend/replication/slotfuncs.c
index 9fe147bf44..03525eda35 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -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);
+ slotKeepSegs =
XLogMBVarToSegs(max_slot_wal_keep_size_mb, wal_segment_size);
+ /* ... and override by wal_keep_size as needed */
+ 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);
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 3a802d8627..498d0d991c 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2631,12 +2631,13 @@ 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
},
diff --git a/src/backend/utils/misc/postgresql.conf.sample
b/src/backend/utils/misc/postgresql.conf.sample
index 0d98e546a6..3558ba3eff 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -288,7 +288,7 @@
#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
diff --git a/src/bin/pg_rewind/t/RewindTest.pm
b/src/bin/pg_rewind/t/RewindTest.pm
index 7dabf395e1..9b01f60cbb 100644
--- a/src/bin/pg_rewind/t/RewindTest.pm
+++ b/src/bin/pg_rewind/t/RewindTest.pm
@@ -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_master->append_conf(
'postgresql.conf', qq(
-wal_keep_segments = 20
+wal_keep_size = 320MB
));
return;
}
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 77ac4e785f..bb4c6d1d71 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -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;
@@ -272,7 +272,7 @@ 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;
diff --git a/src/test/recovery/t/019_replslot_limit.pl
b/src/test/recovery/t/019_replslot_limit.pl
index af656c6902..5ddb3d6c3f 100644
--- a/src/test/recovery/t/019_replslot_limit.pl
+++ b/src/test/recovery/t/019_replslot_limit.pl
@@ -116,19 +116,19 @@ $start_lsn = $node_master->lsn('write');
$node_master->wait_for_catchup($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 = $node_master->safe_psql('postgres',
- "ALTER SYSTEM SET wal_keep_segments to 8; SELECT pg_reload_conf();");
+ "ALTER SYSTEM SET wal_keep_size to '128MB'; SELECT pg_reload_conf();");
# Advance WAL again then checkpoint, reducing remain by 6 MB.
advance_wal($node_master, 6);
$result = $node_master->safe_psql('postgres',
"SELECT wal_status as remain FROM pg_replication_slots WHERE slot_name
= 'rep1'"
);
is($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_master->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 master
$node_standby->start;
