Prohibit max_slot_wal_keep_size to value other than -1 during upgrade.

Amit Kapila · Amit Kapila · commit 8bfb231b43d7 · 2023-11-10T08:45:01.000+05:30
We don't want existing slots in the old cluster to get invalidated during the upgrade. During an upgrade, we set this variable to -1 via the command line in an attempt to prevent such invalidations, but users have ways to override it. This patch ensures the value is not overridden by the user. Author: Kyotaro Horiguchi Reviewed-by: Peter Smith, Alvaro Herrera Discussion: http://postgr.es/m/20231027.115759.2206827438943188717.horikyota.ntt@gmail.com
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
@@ -2063,6 +2063,25 @@ check_wal_segment_size(int *newval, void **extra, GucSource source)
 	return true;
 }
 
+/*
+ * GUC check_hook for max_slot_wal_keep_size
+ *
+ * We don't allow the value of max_slot_wal_keep_size other than -1 during the
+ * binary upgrade. See start_postmaster() in pg_upgrade for more details.
+ */
+bool
+check_max_slot_wal_keep_size(int *newval, void **extra, GucSource source)
+{
+	if (IsBinaryUpgrade && *newval != -1)
+	{
+		GUC_check_errdetail("\"%s\" must be set to -1 during binary upgrade mode.",
+							"max_slot_wal_keep_size");
+		return false;
+	}
+
+	return true;
+}
+
 /*
  * At a checkpoint, how many WAL segments to recycle as preallocated future
  * XLOG segments? Returns the highest segment that should be preallocated.
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
@@ -1424,18 +1424,12 @@ InvalidatePossiblyObsoleteSlot(ReplicationSlotInvalidationCause cause,
 		SpinLockRelease(&s->mutex);
 
 		/*
-		 * The logical replication slots shouldn't be invalidated as
-		 * max_slot_wal_keep_size GUC is set to -1 during the upgrade.
-		 *
-		 * The following is just a sanity check.
+		 * The logical replication slots shouldn't be invalidated as GUC
+		 * max_slot_wal_keep_size is set to -1 during the binary upgrade. See
+		 * check_old_cluster_for_valid_slots() where we ensure that no
+		 * invalidated before the upgrade.
 		 */
-		if (*invalidated && SlotIsLogical(s) && IsBinaryUpgrade)
-		{
-			ereport(ERROR,
-					errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-					errmsg("replication slots must not be invalidated during the upgrade"),
-					errhint("\"max_slot_wal_keep_size\" must be set to -1 during the upgrade"));
-		}
+		Assert(!(*invalidated && SlotIsLogical(s) && IsBinaryUpgrade));
 
 		if (active_pid != 0)
 		{
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
@@ -2845,7 +2845,7 @@ struct config_int ConfigureNamesInt[] =
 		},
 		&max_slot_wal_keep_size_mb,
 		-1, -1, MAX_KILOBYTES,
-		NULL, NULL, NULL
+		check_max_slot_wal_keep_size, NULL, NULL
 	},
 
 	{
diff --git a/src/include/utils/guc_hooks.h b/src/include/utils/guc_hooks.h
@@ -84,6 +84,8 @@ extern bool check_maintenance_io_concurrency(int *newval, void **extra,
 extern void assign_maintenance_io_concurrency(int newval, void *extra);
 extern bool check_max_connections(int *newval, void **extra, GucSource source);
 extern bool check_max_wal_senders(int *newval, void **extra, GucSource source);
+extern bool check_max_slot_wal_keep_size(int *newval, void **extra,
+										 GucSource source);
 extern void assign_max_wal_size(int newval, void *extra);
 extern bool check_max_worker_processes(int *newval, void **extra,
 									   GucSource source);

Original file line number	Diff line number	Diff line change
`@@ -2845,7 +2845,7 @@ struct config_int ConfigureNamesInt[] =`
`2845`	`2845`	`},`
`2846`	`2846`	`&max_slot_wal_keep_size_mb,`
`2847`	`2847`	`-1, -1, MAX_KILOBYTES,`
`2848`		`- NULL, NULL, NULL`
	`2848`	`+ check_max_slot_wal_keep_size, NULL, NULL`
`2849`	`2849`	`},`
`2850`	`2850`
`2851`	`2851`	`{`