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help / color / mirror / Atom feedFrom: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Subject: [PATCH v2 2/4] Add injection-point test for logical decoding timeline race during promotion
Date: Tue, 9 Jun 2026 09:54:28 +0000
Add an injection point "promotion-after-wal-segment-cleanup" in StartupXLOG(),
right after CleanupAfterArchiveRecovery() removes old timeline WAL segments but
before SharedRecoveryState is set to RECOVERY_STATE_DONE.
Add a test in 035_standby_logical_decoding.pl that uses this injection point to
deterministically reproduce the race condition where a walsender doing logical
decoding would pick the old timeline after segment removal, resulting in:
ERROR: requested WAL segment ... has already been removed
The test pauses the startup process at the injection point, starts pg_recvlogical
(whose walsender must read WAL from the removed segment), verifies decoding
succeeds while startup is still paused, then resumes promotion.
Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: Xuneng Zhou <xunengzhou@gmail.com>
Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Discussion: https://postgr.es/m/7daef094-abf3-4672-bc23-3df4763b16a3%40gmail.com
---
src/backend/access/transam/xlog.c | 2 +
.../t/035_standby_logical_decoding.pl | 74 +++++++++++++++++++
2 files changed, 76 insertions(+)
97.8% src/test/recovery/t/
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index d69d03b2ef3..6c2304fef33 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6571,6 +6571,8 @@ StartupXLOG(void)
if (ArchiveRecoveryRequested)
CleanupAfterArchiveRecovery(EndOfLogTLI, EndOfLog, newTLI);
+ INJECTION_POINT("promotion-after-wal-segment-cleanup", NULL);
+
/*
* Local WAL inserts enabled, so it's time to finish initialization of
* commit timestamp.
diff --git a/src/test/recovery/t/035_standby_logical_decoding.pl b/src/test/recovery/t/035_standby_logical_decoding.pl
index 4421059f100..9b45c819241 100644
--- a/src/test/recovery/t/035_standby_logical_decoding.pl
+++ b/src/test/recovery/t/035_standby_logical_decoding.pl
@@ -1060,4 +1060,78 @@ is($cascading_stdout, $expected,
'got same expected output from pg_recvlogical decoding session on cascading standby'
);
+##################################################
+# Test that logical decoding on standby correctly handles the timeline
+# change during promotion. There is a window during promotion where
+# RecoveryInProgress() still returns true but old timeline WAL segments
+# have already been removed. Verify the walsender uses the correct
+# timeline in this window.
+##################################################
+
+# Create a logical slot on the cascading standby for this test.
+$node_cascading_standby->create_logical_slot_on_standby($node_standby,
+ 'race_slot', 'testdb');
+
+# Insert data so the slot has WAL to decode.
+$node_standby->safe_psql('testdb',
+ qq[INSERT INTO decoding_test(x,y) SELECT s, s::text FROM generate_series(10,13) s;]
+);
+$node_standby->wait_for_replay_catchup($node_cascading_standby);
+
+$expected = q{BEGIN
+table public.decoding_test: INSERT: x[integer]:10 y[text]:'10'
+table public.decoding_test: INSERT: x[integer]:11 y[text]:'11'
+table public.decoding_test: INSERT: x[integer]:12 y[text]:'12'
+table public.decoding_test: INSERT: x[integer]:13 y[text]:'13'
+COMMIT};
+
+# Create the injection_points extension on the cascading standby.
+$node_standby->safe_psql('testdb', 'CREATE EXTENSION injection_points;');
+$node_standby->wait_for_replay_catchup($node_cascading_standby);
+
+# Attach injection point to pause startup after WAL segment cleanup
+# but before RecoveryInProgress() flips to false.
+$node_cascading_standby->safe_psql('testdb',
+ "SELECT injection_points_attach('promotion-after-wal-segment-cleanup', 'wait');"
+);
+
+# Promote with no-wait so we can synchronize with the injection point.
+$node_cascading_standby->safe_psql('testdb', "SELECT pg_promote(false)");
+
+# Wait for startup to pause after removing old timeline WAL segments.
+$node_cascading_standby->wait_for_event('startup',
+ 'promotion-after-wal-segment-cleanup');
+
+# Start pg_recvlogical.
+my ($stdout2, $stderr2);
+my $handle2 = IPC::Run::start(
+ [
+ 'pg_recvlogical',
+ '--dbname' => $node_cascading_standby->connstr('testdb'),
+ '--slot' => 'race_slot',
+ '--option' => 'include-xids=0',
+ '--option' => 'skip-empty-xacts=1',
+ '--file' => '-',
+ '--no-loop',
+ '--start',
+ ],
+ '>' => \$stdout2,
+ '2>' => \$stderr2,
+ IPC::Run::timeout($default_timeout));
+
+# Verify pg_recvlogical successfully decodes the data while startup is still
+# paused. This proves the walsender went through logical_read_xlog_page()
+# and selected the correct timeline in the race window.
+$pump_timeout = IPC::Run::timer($default_timeout);
+ok( pump_until($handle2, $pump_timeout, \$stdout2, qr/COMMIT/s),
+ 'pg_recvlogical works during promotion timeline switch');
+chomp($stdout2);
+is($stdout2, $expected,
+ 'got expected output from pg_recvlogical during promotion timeline switch'
+);
+
+# Resume promotion.
+$node_cascading_standby->safe_psql('testdb',
+ "SELECT injection_points_wakeup('promotion-after-wal-segment-cleanup');");
+
done_testing();
--
2.34.1
--Wctt8FE9hhxDGrBZ
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
filename="v2-0003-Fix-race-condition-in-read_local_xlog_page_guts-t.patch"
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Subject: Re: [PATCH v2 2/4] Add injection-point test for logical decoding timeline race during promotion
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