Horton

Re: t/035_standby_logical_decoding.pl might fail on attempt to read wrong timeline

Bertrand Drouvot <bertranddrouvot.pg@gmail.com>

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From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
To: Xuneng Zhou <xunengzhou@gmail.com>
Cc: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Alexander Lakhin <exclusion@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2026-06-08T14:21:59Z
Lists: pgsql-hackers 
Hi,

On Mon, Jun 08, 2026 at 09:00:17PM +0800, Xuneng Zhou wrote:
> I tweaked the reproducer based on the theory outlined above. The main
> changes from the original reproducer are:
> 
> 1) blocks at logical-walsender-after-slot-acquire in walsender.c,
> before the decoding context is created and before the reader starts
> from restart_lsn, matching the delay set by Alexander

> 2) Forces the first read to occur during promotion. It inserts rows
> 1..4, waits for replay, starts promotion with pg_promote(false), holds
> startup at startup-logical-decoding-status-change-end-of-recovery,
> then wakes the walsender.

Yeah, so this existing startup-logical-decoding-status-change-end-of-recovery
injection point already exists in the code tree and is also called after 
CleanupAfterArchiveRecovery() and before RECOVERY_STATE_DONE change in
StartupXLOG().

So this is the same window as the new injection point that was added in the new
tests in v1-0002 shared up-thread [1].

That said, I think I prefer the v1-0002 shared up-thread [1] approach for the
tests as:

- the injection point name clearly describes the tested condition
- no new injection point is added in walsender.c (it pauses startup mid-promotion
and lets the walsender connect)
- the test relies on one injection point (not two)

[1]: https://postgr.es/m/aiaBtENl7tTf2MM8%40bdtpg

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

Commits

  1. Fix second race with timeline selection during promotion

  2. Remove TAP test for timeline lookup race with logical decoding on standbys

  3. Fix race with timeline selection in logical decoding during promotion

  4. Backport GetWALInsertionTimeLineIfSet()

  5. TAP test for logical decoding on standby