Message-ID: <e25567b4-9893-48bf-ac17-0e884f1acef9@postgrespro.ru>
Date: Tue, 20 Jan 2026 20:03:55 +0300
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: Exit walsender before confirming remote flush in logical
 replication
To: Fujii Masao <masao.fujii@gmail.com>,
 Andrey Silitskiy <a.silitskiy@postgrespro.ru>
Cc: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>,
 "Takamichi Osumi (Fujitsu)" <osumi.takamichi@fujitsu.com>,
 "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>,
 "sawada.mshk@gmail.com" <sawada.mshk@gmail.com>,
 "michael@paquier.xyz" <michael@paquier.xyz>,
 "peter.eisentraut@enterprisedb.com" <peter.eisentraut@enterprisedb.com>,
 "dilipbalaut@gmail.com" <dilipbalaut@gmail.com>,
 "andres@anarazel.de" <andres@anarazel.de>,
 "amit.kapila16@gmail.com" <amit.kapila16@gmail.com>,
 Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
 Peter Smith <smithpb2250@gmail.com>, Greg Sabino Mullane
 <htamfids@gmail.com>, Alexander Korotkov <aekorotkov@gmail.com>
References: <TYAPR01MB58661D0EDEEDDA284226D401F5DB9@TYAPR01MB5866.jpnprd01.prod.outlook.com>
 <TYAPR01MB586649A34F241798B206FFF5F5D89@TYAPR01MB5866.jpnprd01.prod.outlook.com>
 <TYCPR01MB83733C978995A05389F51E3BEDD99@TYCPR01MB8373.jpnprd01.prod.outlook.com>
 <TYAPR01MB586683FC450662990E356A0EF5D99@TYAPR01MB5866.jpnprd01.prod.outlook.com>
 <CAHut+PtDhN6JBHJmmeU4U-0hWf106AV39bRjcS7UuqTBtdXQCg@mail.gmail.com>
 <TYAPR01MB5866BE7EA26E20A6D19B2297F5DE9@TYAPR01MB5866.jpnprd01.prod.outlook.com>
 <0fe5288d-5b4a-4aab-ae0e-c5a2fca0ee33@postgrespro.ru>
 <CAHGQGwEnb0-tZG8K2mVSbjzJ=Z_VFbjAypO+fYm0t1ZXaxbr0A@mail.gmail.com>
 <091704a7-dc44-45c2-874a-7eec7fba6071@postgrespro.ru>
 <CAHGQGwFHJ-80uwd8jgSsm9ZL_HBvi5SXa6O6nktXiOicxHKKxQ@mail.gmail.com>
 <dcf6a30c-ad28-4644-8523-58f9779156c2@postgrespro.ru>
 <CAHGQGwFk51nAFs20-dq2SLONdeyhYcvDQb_jZiPiJt5Rinb8Ug@mail.gmail.com>
 <3d024a19-1256-4177-942a-d7173dacba74@postgrespro.ru>
 <CAHGQGwHo6XgsS5NCiC9hwa3SqUBTHSLmcqNUVg=BSv76oDOFsw@mail.gmail.com>
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From: Vitaly Davydov <v.davydov@postgrespro.ru>
In-Reply-To: <CAHGQGwHo6XgsS5NCiC9hwa3SqUBTHSLmcqNUVg=BSv76oDOFsw@mail.gmail.com>
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Dear Hackers,

I think, I reproduced test fails. The test fails because walsender is in
waiting state in WalSndDoneImmediate -> ereport with the following stack (see
below). It seems, it tries to send the message to the replica and flush it, but
the replica is hung.

#0  0x00007a4b37f2a037 in epoll_wait
#1  0x000056855317a2e8 in WaitEventSetWaitBlock
#2  WaitEventSetWait
#3  0x0000568552feea8e in secure_write
#4  0x0000568552ff5666 in internal_flush_buffer
#5  0x0000568552ff5966 in internal_flush
#6  socket_flush ()
#7  socket_flush ()
#8  0x00005685532ff1b3 in send_message_to_frontend (edata=<optimized out>)
#9  EmitErrorReport ()
#10 0x00005685532ff6dd in errfinish
#11 0x000056855312cc9c in WalSndDoneImmediate () at walsender.c:3625

I would propose to remove the ereport call from WalSndDoneImmediate.

With best regards,
Vitaly

On 1/19/26 15:41, Fujii Masao wrote:
> On Sun, Jan 18, 2026 at 1:20 AM Andrey Silitskiy
> <a.silitskiy@postgrespro.ru> wrote:
>>
>> On Jan 9, 2026 at 10:04 AM Fujii Masao
>> <masao(dot)fujii(at)gmail(dot)com> wrote:
>>> Why do we need to send a "done" message to the receiver here?
>>> Since delivery isn't guaranteed in immediate mode, it seems of limited
>>> value.
>>
>> It seems to me that it is better to send a message in cases where it is
>> possible, so as not to raise errors on the subscriber during a clean shutdown.
>> And when this is not possible, exit the process without waiting.
>>
>>> For the immediate mode, would it make sense to log that the walsender is
>>> terminating in immediate mode and that WAL replication may be incomplete,
>>> so users can more easily understand what happened?
>>
>> Added to the latest patch.
> 
> Thanks for updating the patch!
> 
> cfbot is reporting a test failure. Could you please look into it and
> fix the issue?
> https://cirrus-ci.com/github/postgresql-cfbot/postgresql/cf%2F6234
> 
> Regards,
>