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effectively superseded by pg_ctl promote and pg_promote() a long time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 <simon.riggs@enterprisedb.com>
Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Ian Lawrence Barwick <barwick@gmail.com>
Discussion: https://postgr.es/m/CANbhV-FsjnzVOQGBpQ589%3DnWuL1Ex0Ykn74Nh1hEjp2usZSR5g%40mail.gmail.com

1 files changed, 16 insertions, 41 deletions

diff --git a/src/backend/access/transam/xlogrecovery.c b/src/backend/access/transam/xlogrecovery.c
index cb07694aea6..ffdb55fd394 100644
--- a/src/backend/access/transam/xlogrecovery.c
+++ b/src/backend/access/transam/xlogrecovery.c
@@ -95,7 +95,6 @@ int			recovery_min_apply_delay = 0;
 /* options formerly taken from recovery.conf for XLOG streaming */
 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;
 }