Re: IPC/MultixactCreation on the Standby server

From: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
To: Dmitry <dsy(dot)075(at)yandex(dot)ru>
Cc: pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: IPC/MultixactCreation on the Standby server
Date: 2025-06-28 18:24:03
Message-ID: B367F878-4E6E-4F1A-8D76-3F8CF5676230@yandex-team.ru
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> On 28 Jun 2025, at 00:37, Andrey Borodin <x4mmm(at)yandex-team(dot)ru> wrote:
>
> Indeed.

After some experiments I could get unstable repro on my machine.
I've added some logging and that's what I've found:

2025-06-28 23:03:40.598 +05 [40887] 006_MultiXact_standby.pl WARNING: Timed out: nextMXact 415832 tmpMXact 415827 pageno 203 prev_pageno 203 entryno 83 offptr[1] 831655 offptr[0] 0 offptr[-1] 831651

We are reading 415827-1 Multi, while 415827 is not filled yet. But we are holding a buffer that prevents next Multi to be filled in.
This seems like a recovery conflict.
I'm somewhat surprized with 415827+1 is already filled in...

Can you please try your reproduction with applied patch? This seems to be fixing issue for me.

Best regards, Andrey Borodin.

Attachment Content-Type Size
v4-0001-Make-next-multixact-sleep-timed-with-a-recovery-c.patch application/octet-stream 6.3 KB

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