v2-Test-a-specific-case-of-physical-slot-invalidation.patch

From ef8d9fb83d72b15f23d96e705122ad153dcb4fa5 Mon Sep 17 00:00:00 2001
From: Vitaly Davydov <v.davydov@postgrespro.ru>
Date: Sun, 26 Oct 2025 11:22:54 +0300
Subject: [PATCH] Test a specific case of physical slot invalidation

When ReplicationSlotReserveWal() succeeds to read old RedoRecPtr
right before the assignment of a new RedoRecPtr in a checkpointer
which runs in parallel, the created slot may be invalidated.

The core issue: redo rec ptr change during wal reservation by a slot.
The serialization of execution of redo rec ptr assignment and slot
reservation may fix the issue.
---
 src/backend/access/transam/xlog.c             |   3 +
 src/backend/replication/slot.c                |   4 +
 src/test/recovery/meson.build                 |   1 +
 ..._create_physical_slot_during_checkpoint.pl | 176 ++++++++++++++++++
 4 files changed, 184 insertions(+)
 create mode 100644 src/test/recovery/t/100_create_physical_slot_during_checkpoint.pl

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 22d0a2e8c3a..64b394383ac 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -7385,6 +7385,9 @@ CreateCheckPoint(int flags)
 	 */
 	XLByteToSeg(RedoRecPtr, _logSegNo, wal_segment_size);
 	KeepLogSeg(recptr, &_logSegNo);
+
+	INJECTION_POINT("checkpoint-before-old-wal-removal-2", NULL);
+
 	if (InvalidateObsoleteReplicationSlots(RS_INVAL_WAL_REMOVED | RS_INVAL_IDLE_TIMEOUT,
 										   _logSegNo, InvalidOid,
 										   InvalidTransactionId))
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index 1ec1e997b27..4b5b24d3759 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -1610,10 +1610,14 @@ ReplicationSlotReserveWal(void)
 		else
 			restart_lsn = GetXLogInsertRecPtr();
 
+		INJECTION_POINT("physical-slot-reserve-wal-get-redo", NULL);
+
 		SpinLockAcquire(&slot->mutex);
 		slot->data.restart_lsn = restart_lsn;
 		SpinLockRelease(&slot->mutex);
 
+		INJECTION_POINT("physical-slot-reserve-wal-before-compute-required-lsn", NULL);
+
 		/* prevent WAL removal as fast as possible */
 		ReplicationSlotsComputeRequiredLSN();
 
diff --git a/src/test/recovery/meson.build b/src/test/recovery/meson.build
index 523a5cd5b52..189c1710f28 100644
--- a/src/test/recovery/meson.build
+++ b/src/test/recovery/meson.build
@@ -58,6 +58,7 @@ tests += {
       't/047_checkpoint_physical_slot.pl',
       't/048_vacuum_horizon_floor.pl',
       't/049_wait_for_lsn.pl',
+      't/100_create_physical_slot_during_checkpoint.pl'
     ],
   },
 }
diff --git a/src/test/recovery/t/100_create_physical_slot_during_checkpoint.pl b/src/test/recovery/t/100_create_physical_slot_during_checkpoint.pl
new file mode 100644
index 00000000000..d12bc5f2d56
--- /dev/null
+++ b/src/test/recovery/t/100_create_physical_slot_during_checkpoint.pl
@@ -0,0 +1,176 @@
+# This test checks that the new slot maybe invalidated by checkpoint
+
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+if ($ENV{enable_injection_points} ne 'yes')
+{
+	plan skip_all => 'Injection points not supported by this build';
+}
+
+my $res;
+
+# Setup primary node
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init(allows_streaming => 1);
+
+$node->append_conf('postgresql.conf', q{
+	wal_level = logical
+	checkpoint_timeout = 30min
+	checkpoint_completion_target = 0.1
+});
+
+$node->start();
+$node->safe_psql('postgres', q{create extension injection_points;});
+
+my $createslot = $node->background_psql('postgres');
+my $checkpoint = $node->background_psql('postgres');
+
+sub physreplslot_start_create()
+{
+	$createslot->query_until(
+		qr/start-create-slot/,
+		q(\echo start-create-slot
+		select pg_create_physical_replication_slot('standby1', true);
+	));
+}
+
+sub checkpoint_start()
+{
+	$checkpoint->query_until(
+		qr/start-checkpoint/,
+		q(\echo start-checkpoint
+		checkpoint;
+	));
+}
+
+sub injection_point_attach($$)
+{
+	my ($injectpname, $event) = @_;
+
+	$node->safe_psql('postgres', "select injection_points_attach('$injectpname','$event')");
+}
+
+sub injection_point_detach($)
+{
+	my $injectpname = shift;
+
+	$node->safe_psql('postgres', "select injection_points_detach('$injectpname');");
+}
+
+sub injection_point_wait($$)
+{
+	my ($subsystem, $injectpname) = @_;
+
+	note("waiting for $injectpname injection point");
+	$node->wait_for_event($subsystem, $injectpname);
+	note("injection_point $injectpname is reached");
+}
+
+sub injection_point_wakeup($)
+{
+	my $injectpname = shift;
+
+	$node->safe_psql('postgres', "select injection_points_wakeup('$injectpname');");
+}
+
+sub get_slot_invalidation_state($)
+{
+	my $slotname = shift;
+
+	return $node->safe_psql('postgres',
+		"select invalidation_reason from pg_replication_slots where slot_name='$slotname'");
+}
+
+# Original case: injection point in the checkpointer right before the calculation
+# of WAL segments for removal.
+sub test1()
+{
+	injection_point_attach('physical-slot-reserve-wal-get-redo', 'wait');
+	injection_point_attach('checkpoint-before-old-wal-removal', 'wait');
+	injection_point_attach("physical-slot-reserve-wal-before-compute-required-lsn", 'wait');
+
+	# start create physical replication slot
+	physreplslot_start_create();
+
+	# reach the get-redo injection point and stop there
+	injection_point_wait('client backend', 'physical-slot-reserve-wal-get-redo');
+
+	$node->advance_wal(6);
+
+	# start checkpoint
+	checkpoint_start();
+
+	# reach the injection point before old WAL removal and stop there
+	injection_point_wait('checkpointer', 'checkpoint-before-old-wal-removal');
+
+	injection_point_wakeup('physical-slot-reserve-wal-get-redo');
+
+	injection_point_wakeup('checkpoint-before-old-wal-removal');
+
+	injection_point_wakeup('physical-slot-reserve-wal-before-compute-required-lsn');
+
+	# complete physical slot creation
+	eval { $createslot->quit(); };
+
+	# complete checkpoint
+	eval { $checkpoint->quit(); };
+
+	is(get_slot_invalidation_state('standby1'), "", "slot is not invalidated by checkpoint");
+
+	injection_point_detach('physical-slot-reserve-wal-get-redo');
+	injection_point_detach('checkpoint-before-old-wal-removal');
+	injection_point_detach("physical-slot-reserve-wal-before-compute-required-lsn");
+
+	$node->safe_psql('postgres', "select pg_drop_replication_slot('standby1')");
+}
+
+# Based on Hayato's case: injection point in the checkpointer between the
+# calculation of WAL segments for removal and slot invalidation.
+sub test2()
+{
+	injection_point_attach('physical-slot-reserve-wal-get-redo', 'wait');
+	injection_point_attach('checkpoint-before-old-wal-removal-2', 'wait');
+	injection_point_attach("physical-slot-reserve-wal-before-compute-required-lsn", 'wait');
+
+	# start create physical replication slot
+	physreplslot_start_create();
+
+	# reach the get-redo injection point and stop there
+	injection_point_wait('client backend', 'physical-slot-reserve-wal-get-redo');
+
+	$node->advance_wal(6);
+
+	# start checkpoint
+	checkpoint_start();
+
+	# reach the injection point before old WAL removal and stop there
+	injection_point_wait('checkpointer', 'checkpoint-before-old-wal-removal-2');
+
+	injection_point_wakeup('physical-slot-reserve-wal-get-redo');
+
+	injection_point_wakeup('checkpoint-before-old-wal-removal-2');
+
+	injection_point_wakeup('physical-slot-reserve-wal-before-compute-required-lsn');
+
+	# complete physical slot creation
+	eval { $createslot->quit(); };
+
+	# complete checkpoint
+	eval { $checkpoint->quit(); };
+
+	is(get_slot_invalidation_state('standby1'), "", "slot is not invalidated by checkpoint");
+
+	injection_point_detach('physical-slot-reserve-wal-get-redo');
+	injection_point_detach('checkpoint-before-old-wal-removal-2');
+	injection_point_detach("physical-slot-reserve-wal-before-compute-required-lsn");
+}
+
+test1();
+test2();
+
+done_testing();
-- 
2.43.0