prevent_lock_conflict_from_slowing_failover_v1.patch

*** a/doc/src/sgml/config.sgml
--- b/doc/src/sgml/config.sgml
***************
*** 1963,1968 **** SET ENABLE_SEQSCAN TO OFF;
--- 1963,1974 ----
         allow significantly less than <varname>max_standby_delay</> seconds
         before query cancellation is possible.
        </para>
+       <para>
+        In standby mode, ever since the failover is requested, this parameter
+        is treated as zero, and all the conflicting queries are canceled
+        immediately. This is for preventing the conflict from slowing a recovery
+        and increasing the failover time.
+       </para>
        </listitem>
       </varlistentry>
  
*** a/doc/src/sgml/high-availability.sgml
--- b/doc/src/sgml/high-availability.sgml
***************
*** 1527,1532 **** if (!triggered)
--- 1527,1539 ----
      heavy update load.
     </para>
  
+    <para>
+     Note that, in standby mode, ever since the failover is requested,
+     <varname>max_standby_delay</> is treated as zero, and all the
+     conflicting queries are canceled immediately. This is for preventing
+     the conflict from slowing a recovery and increasing the failover time.
+    </para>
+ 
     <caution>
      <para>
       Be sure that the primary and standby servers' clocks are kept in sync;
*** a/src/backend/access/transam/xlog.c
--- b/src/backend/access/transam/xlog.c
***************
*** 511,516 **** static bool InRedo = false;
--- 511,519 ----
  /* Have we launched bgwriter during recovery? */
  static bool bgwriterLaunched = false;
  
+ /* Have we found the trigger file? */
+ bool	standbyIsTriggered = false;
+ 
  /*
   * Information logged when we detect a change in one of the parameters
   * important for Hot Standby.
***************
*** 589,595 **** static void writeTimeLineHistory(TimeLineID newTLI, TimeLineID parentTLI,
  static void WriteControlFile(void);
  static void ReadControlFile(void);
  static char *str_time(pg_time_t tnow);
- static bool CheckForStandbyTrigger(void);
  
  #ifdef WAL_DEBUG
  static void xlog_outrec(StringInfo buf, XLogRecord *record);
--- 592,597 ----
***************
*** 9576,9582 **** emode_for_corrupt_record(int emode, XLogRecPtr RecPtr)
   * to shut down walreceiver, wait for it to exit, remove the trigger
   * file, and return true.
   */
! static bool
  CheckForStandbyTrigger(void)
  {
  	struct stat stat_buf;
--- 9578,9584 ----
   * to shut down walreceiver, wait for it to exit, remove the trigger
   * file, and return true.
   */
! bool
  CheckForStandbyTrigger(void)
  {
  	struct stat stat_buf;
***************
*** 9584,9595 **** CheckForStandbyTrigger(void)
--- 9586,9602 ----
  	if (TriggerFile == NULL)
  		return false;
  
+ 	/* Quick exit if already known triggered */
+ 	if (standbyIsTriggered)
+ 		return true;
+ 
  	if (stat(TriggerFile, &stat_buf) == 0)
  	{
  		ereport(LOG,
  				(errmsg("trigger file found: %s", TriggerFile)));
  		ShutdownWalRcv();
  		unlink(TriggerFile);
+ 		standbyIsTriggered = true;
  		return true;
  	}
  	return false;
*** a/src/backend/storage/ipc/standby.c
--- b/src/backend/storage/ipc/standby.c
***************
*** 124,133 **** static int	standbyWait_us = STANDBY_INITIAL_WAIT_US;
  static bool
  WaitExceedsMaxStandbyDelay(void)
  {
! 	/* Are we past max_standby_delay? */
! 	if (MaxStandbyDelay >= 0 &&
! 		TimestampDifferenceExceeds(GetLatestXLogTime(), GetCurrentTimestamp(),
! 								   MaxStandbyDelay))
  		return true;
  
  	/*
--- 124,141 ----
  static bool
  WaitExceedsMaxStandbyDelay(void)
  {
! 	/*
! 	 * Are we past max_standby_delay?
! 	 *
! 	 * If we've already been triggered, we cancel all the conflicting queries
! 	 * immediately to cause the recovery to end as soon as possible. Otherwise,
! 	 * the lock contention between a recovery and queries might increase the
! 	 * failover time significantly.
! 	 */
! 	if (standbyIsTriggered || MaxStandbyDelay == 0 ||
! 		(MaxStandbyDelay > 0 &&
! 		 TimestampDifferenceExceeds(GetLatestXLogTime(), GetCurrentTimestamp(),
! 									MaxStandbyDelay)))
  		return true;
  
  	/*
***************
*** 141,147 **** WaitExceedsMaxStandbyDelay(void)
--- 149,159 ----
  	 */
  	standbyWait_us *= 2;
  	if (standbyWait_us > 1000000)
+ 	{
  		standbyWait_us = 1000000;
+ 		if (CheckForStandbyTrigger())
+ 			return true;
+ 	}
  
  	return false;
  }
*** a/src/include/access/xlog.h
--- b/src/include/access/xlog.h
***************
*** 196,201 **** extern bool EnableHotStandby;
--- 196,203 ----
  extern int	MaxStandbyDelay;
  extern bool log_checkpoints;
  
+ extern bool	standbyIsTriggered;
+ 
  /* WAL levels */
  typedef enum WalLevel
  {
***************
*** 297,302 **** extern XLogRecPtr GetInsertRecPtr(void);
--- 299,305 ----
  extern XLogRecPtr GetWriteRecPtr(void);
  extern void GetNextXidAndEpoch(TransactionId *xid, uint32 *epoch);
  extern TimeLineID GetRecoveryTargetTLI(void);
+ extern bool CheckForStandbyTrigger(void);
  
  extern void HandleStartupProcInterrupts(void);
  extern void StartupProcessMain(void);