Disable STARTUP_PROGRESS_TIMEOUT in standby mode.

In standby mode, we don't actually report progress of recovery,
but up until now, startup_progress_timeout_handler() nevertheless
got called every log_startup_progress_interval seconds. That's
an unnecessary expense, so avoid it.

Report by Thomas Munro. Patch by Bharath Rupireddy, reviewed by
Simon Riggs, Thomas Munro, and me. Back-patch to v15, where
the problem was introduced.

Discussion: https://www.postgresql.org/message-id/CA%2BhUKGKCHSffAj8zZJKJvNX7ygnQFxVD6wm1d-2j3fVw%2BMafPQ%40mail.gmail.com

src/backend/access/transam/xlogrecovery.c

@@ -385,6 +385,7 @@ static bool recoveryStopAfter;
 /* prototypes for local functions */
 static void ApplyWalRecord(XLogReaderState *xlogreader, XLogRecord *record, TimeLineID *replayTLI);
 
+static void EnableStandbyMode(void);
 static void readRecoverySignalFile(void);
 static void validateRecoveryParameters(void);
 static bool read_backup_label(XLogRecPtr *checkPointLoc,
@@ -469,6 +470,24 @@ XLogRecoveryShmemInit(void)
 	ConditionVariableInit(&XLogRecoveryCtl->recoveryNotPausedCV);
 }
 
+/*
+ * A thin wrapper to enable StandbyMode and do other preparatory work as
+ * needed.
+ */
+static void
+EnableStandbyMode(void)
+{
+	StandbyMode = true;
+
+	/*
+	 * To avoid server log bloat, we don't report recovery progress in a
+	 * standby as it will always be in recovery unless promoted. We disable
+	 * startup progress timeout in standby mode to avoid calling
+	 * startup_progress_timeout_handler() unnecessarily.
+	 */
+	disable_startup_progress_timeout();
+}
+
 /*
  * Prepare the system for WAL recovery, if needed.
  *
@@ -602,7 +621,7 @@ InitWalRecovery(ControlFileData *ControlFile, bool *wasShutdown_ptr,
 		 */
 		InArchiveRecovery = true;
 		if (StandbyModeRequested)
-			StandbyMode = true;
+			EnableStandbyMode();
 
 		/*
 		 * When a backup_label file is present, we want to roll forward from
@@ -739,7 +758,7 @@ InitWalRecovery(ControlFileData *ControlFile, bool *wasShutdown_ptr,
 		{
 			InArchiveRecovery = true;
 			if (StandbyModeRequested)
-				StandbyMode = true;
+				EnableStandbyMode();
 		}
 
 		/* Get the last valid checkpoint record. */
@@ -3117,7 +3136,7 @@ ReadRecord(XLogPrefetcher *xlogprefetcher, int emode,
 						(errmsg_internal("reached end of WAL in pg_wal, entering archive recovery")));
 				InArchiveRecovery = true;
 				if (StandbyModeRequested)
-					StandbyMode = true;
+					EnableStandbyMode();
 
 				SwitchIntoArchiveRecovery(xlogreader->EndRecPtr, replayTLI);
 				minRecoveryPoint = xlogreader->EndRecPtr;

src/backend/postmaster/startup.c

@@ -314,11 +314,22 @@ startup_progress_timeout_handler(void)
 	startup_progress_timer_expired = true;
 }
 
+void
+disable_startup_progress_timeout(void)
+{
+	/* Feature is disabled. */
+	if (log_startup_progress_interval == 0)
+		return;
+
+	disable_timeout(STARTUP_PROGRESS_TIMEOUT, false);
+	startup_progress_timer_expired = false;
+}
+
 /*
  * Set the start timestamp of the current operation and enable the timeout.
  */
 void
-begin_startup_progress_phase(void)
+enable_startup_progress_timeout(void)
 {
 	TimestampTz fin_time;
 
@@ -326,8 +337,6 @@ begin_startup_progress_phase(void)
 	if (log_startup_progress_interval == 0)
 		return;
 
-	disable_timeout(STARTUP_PROGRESS_TIMEOUT, false);
-	startup_progress_timer_expired = false;
 	startup_progress_phase_start_time = GetCurrentTimestamp();
 	fin_time = TimestampTzPlusMilliseconds(startup_progress_phase_start_time,
 										   log_startup_progress_interval);
@@ -335,6 +344,21 @@ begin_startup_progress_phase(void)
 						 log_startup_progress_interval);
 }
 
+/*
+ * A thin wrapper to first disable and then enable the startup progress
+ * timeout.
+ */
+void
+begin_startup_progress_phase(void)
+{
+	/* Feature is disabled. */
+	if (log_startup_progress_interval == 0)
+		return;
+
+	disable_startup_progress_timeout();
+	enable_startup_progress_timeout();
+}
+
 /*
  * Report whether startup progress timeout has occurred. Reset the timer flag
  * if it did, set the elapsed time to the out parameters and return true,

src/include/postmaster/startup.h

@@ -32,6 +32,8 @@ extern void PostRestoreCommand(void);
 extern bool IsPromoteSignaled(void);
 extern void ResetPromoteSignaled(void);
 
+extern void enable_startup_progress_timeout(void);
+extern void disable_startup_progress_timeout(void);
 extern void begin_startup_progress_phase(void);
 extern void startup_progress_timeout_handler(void);
 extern bool has_startup_progress_timeout_expired(long *secs, int *usecs);