Change unit of idle_replication_slot_timeout to seconds.

Previously, the idle_replication_slot_timeout parameter used minutes
as its unit, based on the assumption that values would typically exceed
one minute in production environments. However, this caused unexpected
behavior: specifying a value below 30 seconds would round down to 0,
effectively disabling the timeout. This could be surprising to users.

To allow finer-grained control and avoid such confusion, this commit changes
the unit of idle_replication_slot_timeout to seconds. Larger values can
still be specified easily using standard time suffixes, for example,
'24h' for 24 hours.

Back-patch to v18 where idle_replication_slot_timeout was added.

Reported-by: Gunnar Morling <gunnar.morling@googlemail.com>
Author: Fujii Masao <masao.fujii@gmail.com>
Reviewed-by: Laurenz Albe <laurenz.albe@cybertec.at>
Reviewed-by: David G. Johnston <david.g.johnston@gmail.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CADGJaX_0+FTguWpNSpgVWYQP_7MhoO0D8=cp4XozSQgaZ40Odw@mail.gmail.com
Backpatch-through: 18

doc/src/sgml/config.sgml

@@ -4620,7 +4620,7 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
        <para>
         Invalidate replication slots that have remained idle longer than this
         duration. If this value is specified without units, it is taken as
-        minutes. A value of zero (the default) disables the idle timeout
+        seconds. A value of zero (the default) disables the idle timeout
         invalidation mechanism. This parameter can only be set in the
         <filename>postgresql.conf</filename> file or on the server command
         line.

src/backend/replication/slot.c

@@ -154,7 +154,7 @@ int			max_replication_slots = 10; /* the maximum number of replication
  * Invalidate replication slots that have remained idle longer than this
  * duration; '0' disables it.
  */
-int			idle_replication_slot_timeout_mins = 0;
+int			idle_replication_slot_timeout_secs = 0;
 
 /*
  * This GUC lists streaming replication standby server slot names that
@@ -1612,13 +1612,10 @@ ReportSlotInvalidation(ReplicationSlotInvalidationCause cause,
 
 		case RS_INVAL_IDLE_TIMEOUT:
 			{
-				int			minutes = slot_idle_seconds / SECS_PER_MINUTE;
-				int			secs = slot_idle_seconds % SECS_PER_MINUTE;
-
 				/* translator: %s is a GUC variable name */
-				appendStringInfo(&err_detail, _("The slot's idle time of %dmin %02ds exceeds the configured \"%s\" duration of %dmin."),
+				appendStringInfo(&err_detail, _("The slot's idle time of %lds exceeds the configured \"%s\" duration of %ds."),
-								 minutes, secs, "idle_replication_slot_timeout",
+								 slot_idle_seconds, "idle_replication_slot_timeout",
-								 idle_replication_slot_timeout_mins);
+								 idle_replication_slot_timeout_secs);
 				/* translator: %s is a GUC variable name */
 				appendStringInfo(&err_hint, _("You might need to increase \"%s\"."),
 								 "idle_replication_slot_timeout");
@@ -1656,7 +1653,7 @@ ReportSlotInvalidation(ReplicationSlotInvalidationCause cause,
 static inline bool
 CanInvalidateIdleSlot(ReplicationSlot *s)
 {
-	return (idle_replication_slot_timeout_mins != 0 &&
+	return (idle_replication_slot_timeout_secs != 0 &&
 			!XLogRecPtrIsInvalid(s->data.restart_lsn) &&
 			s->inactive_since > 0 &&
 			!(RecoveryInProgress() && s->data.synced));
@@ -1717,9 +1714,9 @@ DetermineSlotInvalidationCause(uint32 possible_causes, ReplicationSlot *s,
 		if (CanInvalidateIdleSlot(s))
 		{
 			/*
-			 * We simulate the invalidation due to idle_timeout as the minimum
+			 * Simulate the invalidation due to idle_timeout to test the
-			 * time idle time is one minute which makes tests take a long
+			 * timeout behavior promptly, without waiting for it to trigger
-			 * time.
+			 * naturally.
 			 */
 #ifdef USE_INJECTION_POINTS
 			if (IS_INJECTION_POINT_ATTACHED("slot-timeout-inval"))
@@ -1734,7 +1731,7 @@ DetermineSlotInvalidationCause(uint32 possible_causes, ReplicationSlot *s,
 			 * idle_replication_slot_timeout GUC.
 			 */
 			if (TimestampDifferenceExceedsSeconds(s->inactive_since, now,
-												  idle_replication_slot_timeout_mins * SECS_PER_MINUTE))
+												  idle_replication_slot_timeout_secs))
 			{
 				*inactive_since = s->inactive_since;
 				return RS_INVAL_IDLE_TIMEOUT;

src/backend/utils/misc/guc_tables.c

@@ -3100,10 +3100,10 @@ struct config_int ConfigureNamesInt[] =
 			gettext_noop("Sets the duration a replication slot can remain idle before "
 						 "it is invalidated."),
 			NULL,
-			GUC_UNIT_MIN
+			GUC_UNIT_S
 		},
-		&idle_replication_slot_timeout_mins,
+		&idle_replication_slot_timeout_secs,
-		0, 0, INT_MAX / SECS_PER_MINUTE,
+		0, 0, INT_MAX,
 		check_idle_replication_slot_timeout, NULL, NULL
 	},
 

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

@@ -342,7 +342,7 @@
 				# (change requires restart)
 #wal_keep_size = 0		# in megabytes; 0 disables
 #max_slot_wal_keep_size = -1	# in megabytes; -1 disables
-#idle_replication_slot_timeout = 0	# in minutes; 0 disables
+#idle_replication_slot_timeout = 0	# in seconds; 0 disables
 #wal_sender_timeout = 60s	# in milliseconds; 0 disables
 #track_commit_timestamp = off	# collect timestamp of transaction commit
 				# (change requires restart)

src/include/replication/slot.h

@@ -266,7 +266,7 @@ extern PGDLLIMPORT ReplicationSlot *MyReplicationSlot;
 /* GUCs */
 extern PGDLLIMPORT int max_replication_slots;
 extern PGDLLIMPORT char *synchronized_standby_slots;
-extern PGDLLIMPORT int idle_replication_slot_timeout_mins;
+extern PGDLLIMPORT int idle_replication_slot_timeout_secs;
 
 /* shmem initialization functions */
 extern Size ReplicationSlotsShmemSize(void);