Add GUC option to log lock acquisition failures.

This commit introduces a new GUC, log_lock_failure, which controls whether
a detailed log message is produced when a lock acquisition fails. Currently,
it only supports logging lock failures caused by SELECT ... NOWAIT.

The log message includes information about all processes holding or
waiting for the lock that couldn't be acquired, helping users analyze and
diagnose the causes of lock failures.

Currently, this option does not log failures from SELECT ... SKIP LOCKED,
as that could generate excessive log messages if many locks are skipped,
causing unnecessary noise.

This mechanism can be extended in the future to support for logging
lock failures from other commands, such as LOCK TABLE ... NOWAIT.

Author: Yuki Seino <seinoyu@oss.nttdata.com>
Co-authored-by: Fujii Masao <masao.fujii@gmail.com>
Reviewed-by: Jelte Fennema-Nio <postgres@jeltef.nl>
Discussion: https://postgr.es/m/411280a186cc26ef7034e0f2dfe54131@oss.nttdata.com

1 files changed, 18 insertions, 15 deletions

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index fa7935a0ed3..21575a8ffef 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -98,7 +98,8 @@ static void MultiXactIdWait(MultiXactId multi, MultiXactStatus status, uint16 in
 							Relation rel, ItemPointer ctid, XLTW_Oper oper,
 							int *remaining);
 static bool ConditionalMultiXactIdWait(MultiXactId multi, MultiXactStatus status,
-									   uint16 infomask, Relation rel, int *remaining);
+									   uint16 infomask, Relation rel, int *remaining,
+									   bool logLockFailure);
 static void index_delete_sort(TM_IndexDeleteOp *delstate);
 static int	bottomup_sort_and_shrink(TM_IndexDeleteOp *delstate);
 static XLogRecPtr log_heap_new_cid(Relation relation, HeapTuple tup);
@@ -162,8 +163,8 @@ static const struct
 	LockTuple((rel), (tup), tupleLockExtraInfo[mode].hwlock)
 #define UnlockTupleTuplock(rel, tup, mode) \
 	UnlockTuple((rel), (tup), tupleLockExtraInfo[mode].hwlock)
-#define ConditionalLockTupleTuplock(rel, tup, mode) \
-	ConditionalLockTuple((rel), (tup), tupleLockExtraInfo[mode].hwlock)
+#define ConditionalLockTupleTuplock(rel, tup, mode, log) \
+	ConditionalLockTuple((rel), (tup), tupleLockExtraInfo[mode].hwlock, (log))
 
 #ifdef USE_PREFETCH
 /*
@@ -4894,7 +4895,7 @@ l3:
 					case LockWaitSkip:
 						if (!ConditionalMultiXactIdWait((MultiXactId) xwait,
 														status, infomask, relation,
-														NULL))
+														NULL, false))
 						{
 							result = TM_WouldBlock;
 							/* recovery code expects to have buffer lock held */
@@ -4905,7 +4906,7 @@ l3:
 					case LockWaitError:
 						if (!ConditionalMultiXactIdWait((MultiXactId) xwait,
 														status, infomask, relation,
-														NULL))
+														NULL, log_lock_failure))
 							ereport(ERROR,
 									(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
 									 errmsg("could not obtain lock on row in relation \"%s\"",
@@ -4934,7 +4935,7 @@ l3:
 										  XLTW_Lock);
 						break;
 					case LockWaitSkip:
-						if (!ConditionalXactLockTableWait(xwait))
+						if (!ConditionalXactLockTableWait(xwait, false))
 						{
 							result = TM_WouldBlock;
 							/* recovery code expects to have buffer lock held */
@@ -4943,7 +4944,7 @@ l3:
 						}
 						break;
 					case LockWaitError:
-						if (!ConditionalXactLockTableWait(xwait))
+						if (!ConditionalXactLockTableWait(xwait, log_lock_failure))
 							ereport(ERROR,
 									(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
 									 errmsg("could not obtain lock on row in relation \"%s\"",
@@ -5203,12 +5204,12 @@ heap_acquire_tuplock(Relation relation, ItemPointer tid, LockTupleMode mode,
 			break;
 
 		case LockWaitSkip:
-			if (!ConditionalLockTupleTuplock(relation, tid, mode))
+			if (!ConditionalLockTupleTuplock(relation, tid, mode, false))
 				return false;
 			break;
 
 		case LockWaitError:
-			if (!ConditionalLockTupleTuplock(relation, tid, mode))
+			if (!ConditionalLockTupleTuplock(relation, tid, mode, log_lock_failure))
 				ereport(ERROR,
 						(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
 						 errmsg("could not obtain lock on row in relation \"%s\"",
@@ -7581,7 +7582,8 @@ DoesMultiXactIdConflict(MultiXactId multi, uint16 infomask,
  * fail if lock is unavailable.  'rel', 'ctid' and 'oper' are used to set up
  * context information for error messages.  'remaining', if not NULL, receives
  * the number of members that are still running, including any (non-aborted)
- * subtransactions of our own transaction.
+ * subtransactions of our own transaction.  'logLockFailure' indicates whether
+ * to log details when a lock acquisition fails with 'nowait' enabled.
  *
  * We do this by sleeping on each member using XactLockTableWait.  Any
  * members that belong to the current backend are *not* waited for, however;
@@ -7602,7 +7604,7 @@ static bool
 Do_MultiXactIdWait(MultiXactId multi, MultiXactStatus status,
 				   uint16 infomask, bool nowait,
 				   Relation rel, ItemPointer ctid, XLTW_Oper oper,
-				   int *remaining)
+				   int *remaining, bool logLockFailure)
 {
 	bool		result = true;
 	MultiXactMember *members;
@@ -7649,7 +7651,7 @@ Do_MultiXactIdWait(MultiXactId multi, MultiXactStatus status,
 			 */
 			if (nowait)
 			{
-				result = ConditionalXactLockTableWait(memxid);
+				result = ConditionalXactLockTableWait(memxid, logLockFailure);
 				if (!result)
 					break;
 			}
@@ -7682,7 +7684,7 @@ MultiXactIdWait(MultiXactId multi, MultiXactStatus status, uint16 infomask,
 				int *remaining)
 {
 	(void) Do_MultiXactIdWait(multi, status, infomask, false,
-							  rel, ctid, oper, remaining);
+							  rel, ctid, oper, remaining, false);
 }
 
 /*
@@ -7700,10 +7702,11 @@ MultiXactIdWait(MultiXactId multi, MultiXactStatus status, uint16 infomask,
  */
 static bool
 ConditionalMultiXactIdWait(MultiXactId multi, MultiXactStatus status,
-						   uint16 infomask, Relation rel, int *remaining)
+						   uint16 infomask, Relation rel, int *remaining,
+						   bool logLockFailure)
 {
 	return Do_MultiXactIdWait(multi, status, infomask, true,
-							  rel, NULL, XLTW_None, remaining);
+							  rel, NULL, XLTW_None, remaining, logLockFailure);
 }
 
 /*