Remove promote_trigger_file.

Previously, an idle startup (recovery) process would wake up every 5 seconds to have a chance to poll for promote_trigger_file, even if that GUC was not configured. That promotion triggering mechanism was effectively superseded by pg_ctl promote and pg_promote() a long time ago. There probably aren't many users left and it's very easy to change to the modern mechanisms, so we agreed to remove the feature. This is part of a campaign to reduce wakeups on idle systems. Author: Simon Riggs <[email protected]> Reviewed-by: Bharath Rupireddy <[email protected]> Reviewed-by: Robert Haas <[email protected]> Reviewed-by: Thomas Munro <[email protected]> Reviewed-by: Tom Lane <[email protected]> Reviewed-by: Ian Lawrence Barwick <[email protected]> Discussion: https://postgr.es/m/CANbhV-FsjnzVOQGBpQ589%3DnWuL1Ex0Ykn74Nh1hEjp2usZSR5g%40mail.gmail.com

Author: macdice

doc/src/sgml/appendix-obsolete-recovery-config.sgml

@@ -34,14 +34,11 @@
 </para>
 
 <para>
-The
-<literal>trigger_file</literal>
-<indexterm>
-<primary>trigger_file</primary>
-<see>promote_trigger_file</see>
-</indexterm>
-setting has been renamed to
-<xref linkend="guc-promote-trigger-file"/>.
+PostgreSQL 15 and below had a setting
+<literal>promote_trigger_file</literal>, or
+<literal>trigger_file</literal> before 12.
+Use <command>pg_ctl promote</command> or call
+<function>pg_promote()</function> to promote a standby instead.
 </para>
 
 <para>

doc/src/sgml/config.sgml

@@ -4610,24 +4610,6 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
 </listitem>
 </varlistentry>
 
-<varlistentry id="guc-promote-trigger-file" xreflabel="promote_trigger_file">
-<term><varname>promote_trigger_file</varname> (<type>string</type>)
-<indexterm>
-<primary><varname>promote_trigger_file</varname> configuration parameter</primary>
-</indexterm>
-</term>
-<listitem>
-<para>
-Specifies a trigger file whose presence ends recovery in the
-standby. Even if this value is not set, you can still promote
-the standby using <command>pg_ctl promote</command> or calling
-<function>pg_promote()</function>.
-This parameter can only be set in the <filename>postgresql.conf</filename>
-file or on the server command line.
-</para>
-</listitem>
-</varlistentry>
-
 <varlistentry id="guc-hot-standby" xreflabel="hot_standby">
 <term><varname>hot_standby</varname> (<type>boolean</type>)
 <indexterm>

doc/src/sgml/high-availability.sgml

@@ -653,11 +653,10 @@ protocol to make nodes agree on a serializable transactional order.
 
 <para>
 Standby mode is exited and the server switches to normal operation
-when <command>pg_ctl promote</command> is run,
-<function>pg_promote()</function> is called, or a trigger file is found
-(<varname>promote_trigger_file</varname>). Before failover,
-any WAL immediately available in the archive or in <filename>pg_wal</filename> will be
-restored, but no attempt is made to connect to the primary.
+when <command>pg_ctl promote</command> is run, or
+<function>pg_promote()</function> is called. Before failover,
+any WAL immediately available in the archive or in <filename>pg_wal</filename>
+will be restored, but no attempt is made to connect to the primary.
 </para>
 </sect2>
 
@@ -1483,15 +1482,10 @@ synchronous_standby_names = 'ANY 2 (s1, s2, s3)'
 
 <para>
 To trigger failover of a log-shipping standby server, run
-<command>pg_ctl promote</command>, call <function>pg_promote()</function>,
-or create a trigger file with the file name and path specified by the
-<varname>promote_trigger_file</varname>. If you're planning to use
-<command>pg_ctl promote</command> or to call
-<function>pg_promote()</function> to fail over,
-<varname>promote_trigger_file</varname> is not required. If you're
-setting up the reporting servers that are only used to offload read-only
-queries from the primary, not for high availability purposes, you don't
-need to promote it.
+<command>pg_ctl promote</command> or call <function>pg_promote()</function>.
+If you're setting up reporting servers that are only used to offload
+read-only queries from the primary, not for high availability purposes,
+you don't need to promote.
 </para>
 </sect1>
 

src/backend/access/transam/xlogrecovery.c

@@ -95,7 +95,6 @@ int recovery_min_apply_delay = 0;
 /* options formerly taken from recovery.conf for XLOG */
 char *PrimaryConnInfo = NULL;
 char *PrimarySlotName = NULL;
-char *PromoteTriggerFile = NULL;
 bool wal_receiver_create_temp_slot = false;
 
 /*
@@ -318,8 +317,8 @@ typedef struct XLogRecoveryCtlData
 
 /*
 * recoveryWakeupLatch is used to wake up the startup process to continue
-* WAL replay, if it is waiting for WAL to arrive or failover trigger file
-* to appear.
+* WAL replay, if it is waiting for WAL to arrive or promotion to be
+* requested.
 *
 * Note that the startup process also uses another latch, its procLatch,
 * to wait for recovery conflict. If we get rid of recoveryWakeupLatch for
@@ -2906,10 +2905,7 @@ recoveryApplyDelay(XLogReaderState *record)
 {
 ResetLatch(&XLogRecoveryCtl->recoveryWakeupLatch);
 
-/*
-* This might change recovery_min_apply_delay or the trigger file's
-* location.
-*/
+/* This might change recovery_min_apply_delay. */
 HandleStartupProcInterrupts();
 
 if (CheckForStandbyTrigger())
@@ -3155,8 +3151,8 @@ ReadRecord(XLogPrefetcher *xlogprefetcher, int emode,
 * as for waiting for the requested WAL record to arrive in standby mode.
 *
 * 'emode' specifies the log level used for reporting "file not found" or
-* "end of WAL" situations in archive recovery, or in standby mode when a
-* trigger file is found. If set to WARNING or below, XLogPageRead() returns
+* "end of WAL" situations in archive recovery, or in standby mode when
+* promotion is triggered. If set to WARNING or below, XLogPageRead() returns
 * XLREAD_FAIL in those situations, on higher log levels the ereport() won't
 * return.
 *
@@ -3424,7 +3420,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 *
 * 1. Read from either archive or pg_wal (XLOG_FROM_ARCHIVE), or just
 * pg_wal (XLOG_FROM_PG_WAL)
-* 2. Check trigger file
+* 2. Check for promotion trigger request
 * 3. Read from primary server via walreceiver (XLOG_FROM_STREAM)
 * 4. Rescan timelines
 * 5. Sleep wal_retrieve_retry_interval milliseconds, and loop back to 1.
@@ -3481,10 +3477,10 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 case XLOG_FROM_PG_WAL:
 
 /*
-* Check to see if the trigger file exists. Note that we
-* do this only after failure, so when you create the
-* trigger file, we still finish replaying as much as we
-* can from archive and pg_wal before failover.
+* Check to see if promotion is requested. Note that we do
+* this only after failure, so when you promote, we still
+* finish replaying as much as we can from archive and
+* pg_wal before failover.
 */
 if (StandbyMode && CheckForStandbyTrigger())
 {
@@ -3840,14 +3836,13 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 XLogPrefetcherComputeStats(xlogprefetcher);
 
 /*
-* Wait for more WAL to arrive. Time out after 5 seconds
-* to react to a trigger file promptly and to check if the
-* WAL receiver is still active.
+* Wait for more WAL to arrive, when we will be woken
+* immediately by the WAL receiver.
 */
 (void) WaitLatch(&XLogRecoveryCtl->recoveryWakeupLatch,
-WL_LATCH_SET | WL_TIMEOUT |
-WL_EXIT_ON_PM_DEATH,
-5000L, WAIT_EVENT_RECOVERY_WAL_STREAM);
+WL_LATCH_SET | WL_EXIT_ON_PM_DEATH,
+-1L,
+WAIT_EVENT_RECOVERY_WAL_STREAM);
 ResetLatch(&XLogRecoveryCtl->recoveryWakeupLatch);
 break;
 }
@@ -4294,14 +4289,11 @@ SetPromoteIsTriggered(void)
 }
 
 /*
-* Check to see whether the user-specified trigger file exists and whether a
-* promote request has arrived. If either condition holds, return true.
+* Check whether a promote request has arrived.
 */
 static bool
 CheckForStandbyTrigger(void)
 {
-struct stat stat_buf;
-
 if (LocalPromoteIsTriggered)
 return true;
 
@@ -4314,23 +4306,6 @@ CheckForStandbyTrigger(void)
 return true;
 }
 
-if (PromoteTriggerFile == NULL || strcmp(PromoteTriggerFile, "") == 0)
-return false;
-
-if (stat(PromoteTriggerFile, &stat_buf) == 0)
-{
-ereport(LOG,
-(errmsg("promote trigger file found: %s", PromoteTriggerFile)));
-unlink(PromoteTriggerFile);
-SetPromoteIsTriggered();
-return true;
-}
-else if (errno != ENOENT)
-ereport(ERROR,
-(errcode_for_file_access(),
-errmsg("could not stat promote trigger file \"%s\": %m",
-PromoteTriggerFile)));
-
 return false;
 }
 

src/backend/utils/misc/guc_tables.c

@@ -3819,16 +3819,6 @@ struct config_string ConfigureNamesString[] =
 check_recovery_target_lsn, assign_recovery_target_lsn, NULL
 },
 
-{
-{"promote_trigger_file", PGC_SIGHUP, REPLICATION_STANDBY,
-gettext_noop("Specifies a file name whose presence ends recovery in the standby."),
-NULL
-},
-&PromoteTriggerFile,
-"",
-NULL, NULL, NULL
-},
-
 {
 {"primary_conninfo", PGC_SIGHUP, REPLICATION_STANDBY,
 gettext_noop("Sets the connection string to be used to connect to the sending server."),

src/backend/utils/misc/postgresql.conf.sample

@@ -331,7 +331,6 @@
 
 #primary_conninfo = '' # connection string to sending server
 #primary_slot_name = '' # replication slot on sending server
-#promote_trigger_file = '' # file name whose presence ends recovery
 #hot_standby = on # "off" disallows queries during recovery
 # (change requires restart)
 #max_standby_archive_delay = 30s	# max delay before canceling queries

src/include/access/xlogrecovery.h

@@ -65,7 +65,6 @@ extern PGDLLIMPORT TimestampTz recoveryTargetTime;
 extern PGDLLIMPORT const char *recoveryTargetName;
 extern PGDLLIMPORT XLogRecPtr recoveryTargetLSN;
 extern PGDLLIMPORT RecoveryTargetType recoveryTarget;
-extern PGDLLIMPORT char *PromoteTriggerFile;
 extern PGDLLIMPORT bool wal_receiver_create_temp_slot;
 extern PGDLLIMPORT RecoveryTargetTimeLineGoal recoveryTargetTimeLineGoal;
 extern PGDLLIMPORT TimeLineID recoveryTargetTLIRequested;