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help / color / mirror / Atom feedFrom: Michael Paquier <michael@paquier.xyz>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix race with timeline selection in logical decoding during prom
Date: Thu, 11 Jun 2026 08:30:01 +0000
Message-ID: <E1wXanZ-001ymD-1r@gemulon.postgresql.org> (raw)
Fix race with timeline selection in logical decoding during promotion
During promotion, there is a window where RecoveryInProgress() returns
true but the WAL segments of the old timeline have already been removed.
A logical decoding could pick up the old timeline in this window when
reading a page, failing with the following error:
ERROR: requested WAL segment ... has already been removed
This issue does not lead to any data correctness issue, as retrying to
decode the data works in follow-up decoding attempts. It impacts
availability, though. Other WAL page read callbacks have a similar
issue, this commit takes care of what should be the noisiest code path:
logical decoding with START_REPLICATION in a WAL sender.
A TAP test, based on an injection point waiting in the startup process
after the segments have been removed/recycled, is added. This part is
backpatched down to v17.
This issue has been causing sporadic failures in the buildfarm, and
was reproducible manually. This issue happens since logical decoding on
standbys exists, down to v16.
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Xuneng Zhou <xunengzhou@gmail.com>
Discussion: https://postgr.es/m/7daef094-abf3-4672-bc23-3df4763b16a3@gmail.com
Backpatch-through: 16
Branch
------
REL_16_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/8cd687c44b62cda3cc6dec88d414e8e2837dc56b
Modified Files
--------------
src/backend/replication/walsender.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
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To: pgsql-committers@postgresql.org
Cc: michael@paquier.xyz, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix race with timeline selection in logical decoding during prom
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