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Commitac0e331

Browse files
author
Amit Kapila
committed
Invalidate inactive replication slots.
This commit introduces idle_replication_slot_timeout GUC that allowsinactive slots to be invalidated at the time of checkpoint. Becausecheckpoints happen checkpoint_timeout intervals, there can be some lagbetween when the idle_replication_slot_timeout was exceeded and when theslot invalidation is triggered at the next checkpoint. To avoid such lags,users can force a checkpoint to promptly invalidate inactive slots.Note that the idle timeout invalidation mechanism is not applicable forslots that do not reserve WAL or for slots on the standby server that aresynced from the primary server (i.e., standby slots having 'synced' field'true'). Synced slots are always considered to be inactive because theydon't perform logical decoding to produce changes.The slots can become inactive for a long period if a subscriber is downdue to a system error or inaccessible because of network issues. If such asituation persists, it might be more practical to recreate the subscriberrather than attempt to recover the node and wait for it to catch up whichcould be time-consuming.Then, external tools could create replication slots (e.g., for migrationsor upgrades) that may fail to remove them if an error occurs, leavingbehind unused slots that take up space and resources. Manually cleaningthem up can be tedious and error-prone, and without intervention, theselingering slots can cause unnecessary WAL retention and system bloat.As the duration of idle_replication_slot_timeout is in minutes, any testusing that would be time-consuming. We are planning to commit a follow uppatch for tests by using the injection point framework.Author: Nisha Moond <nisha.moond412@gmail.com>Author: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>Reviewed-by: Peter Smith <smithpb2250@gmail.com>Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>Reviewed-by: Vignesh C <vignesh21@gmail.com>Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>Reviewed-by: Hou Zhijie <houzj.fnst@fujitsu.com>Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>Discussion:https://postgr.es/m/CALj2ACW4aUe-_uFQOjdWCEN-xXoLGhmvRFnL8SNw_TZ5nJe+aw@mail.gmail.comDiscussion:https://postgr.es/m/OS0PR01MB5716C131A7D80DAE8CB9E88794FC2@OS0PR01MB5716.jpnprd01.prod.outlook.com
1 parentb464e51 commitac0e331

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15 files changed

+367
-86
lines changed

15 files changed

+367
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lines changed

‎doc/src/sgml/config.sgml

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@@ -4429,6 +4429,46 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
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</listitem>
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</varlistentry>
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<varlistentry id="guc-idle-replication-slot-timeout" xreflabel="idle_replication_slot_timeout">
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<term><varname>idle_replication_slot_timeout</varname> (<type>integer</type>)
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<indexterm>
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<primary><varname>idle_replication_slot_timeout</varname> configuration parameter</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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Invalidate replication slots that have remained idle longer than this
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duration. If this value is specified without units, it is taken as
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minutes. A value of zero (the default) disables the idle timeout
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invalidation mechanism. This parameter can only be set in the
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<filename>postgresql.conf</filename> file or on the server command
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line.
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</para>
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<para>
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Slot invalidation due to idle timeout occurs during checkpoint.
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Because checkpoints happen at <varname>checkpoint_timeout</varname>
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intervals, there can be some lag between when the
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<varname>idle_replication_slot_timeout</varname> was exceeded and when
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the slot invalidation is triggered at the next checkpoint.
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To avoid such lags, users can force a checkpoint to promptly invalidate
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inactive slots. The duration of slot inactivity is calculated using the
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slot's <link linkend="view-pg-replication-slots">pg_replication_slots</link>.<structfield>inactive_since</structfield>
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value.
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</para>
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<para>
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Note that the idle timeout invalidation mechanism is not applicable
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for slots that do not reserve WAL or for slots on the standby server
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that are being synced from the primary server (i.e., standby slots
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having <link linkend="view-pg-replication-slots">pg_replication_slots</link>.<structfield>synced</structfield>
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value <literal>true</literal>). Synced slots are always considered to
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be inactive because they don't perform logical decoding to produce
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changes.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-wal-sender-timeout" xreflabel="wal_sender_timeout">
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<term><varname>wal_sender_timeout</varname> (<type>integer</type>)
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<indexterm>

‎doc/src/sgml/logical-replication.sgml

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@@ -2390,6 +2390,11 @@ CONTEXT: processing remote data for replication origin "pg_16395" during "INSER
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plus some reserve for table synchronization.
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</para>
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<para>
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Logical replication slots are also affected by
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<link linkend="guc-idle-replication-slot-timeout"><varname>idle_replication_slot_timeout</varname></link>.
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</para>
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<para>
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<link linkend="guc-max-wal-senders"><varname>max_wal_senders</varname></link>
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should be set to at least the same as

‎doc/src/sgml/system-views.sgml

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Original file line numberDiff line numberDiff line change
@@ -2619,6 +2619,13 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
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perform logical decoding. It is set only for logical slots.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>idle_timeout</literal> means that the slot has remained
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idle longer than the configured
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<xref linkend="guc-idle-replication-slot-timeout"/> duration.
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</para>
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</listitem>
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</itemizedlist>
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</para></entry>
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</row>

‎src/backend/access/transam/xlog.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7337,7 +7337,7 @@ CreateCheckPoint(int flags)
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*/
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XLByteToSeg(RedoRecPtr,_logSegNo,wal_segment_size);
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KeepLogSeg(recptr,&_logSegNo);
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if (InvalidateObsoleteReplicationSlots(RS_INVAL_WAL_REMOVED,
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if (InvalidateObsoleteReplicationSlots(RS_INVAL_WAL_REMOVED |RS_INVAL_IDLE_TIMEOUT,
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_logSegNo,InvalidOid,
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InvalidTransactionId))
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{
@@ -7792,7 +7792,7 @@ CreateRestartPoint(int flags)
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replayPtr=GetXLogReplayRecPtr(&replayTLI);
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endptr= (receivePtr<replayPtr) ?replayPtr :receivePtr;
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KeepLogSeg(endptr,&_logSegNo);
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if (InvalidateObsoleteReplicationSlots(RS_INVAL_WAL_REMOVED,
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if (InvalidateObsoleteReplicationSlots(RS_INVAL_WAL_REMOVED |RS_INVAL_IDLE_TIMEOUT,
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_logSegNo,InvalidOid,
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InvalidTransactionId))
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{

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