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From: Alexander Kukushkin <cyberdemn@gmail.com>
Date: Thu, 26 Feb 2026 10:29:29 +0100
Message-ID: <CAFh8B=n0n5Zj0DDSQ9E5cznY85VgU1wwgfpAULaLZpOaNzvv4w@mail.gmail.com>
Subject: Re: synchronized_standby_slots behavior inconsistent with
 quorum-based synchronous replication
To: shveta malik <shveta.malik@gmail.com>
Cc: SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>, Ashutosh Sharma <ashu.coek88@gmail.com>, 
	Amit Kapila <amit.kapila16@gmail.com>, 
	PostgreSQL-development <pgsql-hackers@postgresql.org>, 
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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Hi,

On Thu, 26 Feb 2026 at 09:45, shveta malik <shveta.malik@gmail.com> wrote:

>
> As suggested in [1], IMO, it is a reasonably good idea for
> 'synchronized_standby_slots' to DEFAULT to the value of
> 'synchronous_standby_names'. That way, even if the user missed to
> configure 'synchronized_standby_slots' explicitly, we would still have
> reasonable protection in place.


Hmm.
synchronous_standby_names contains application_names,
while synchronized_standby_slots contains names of physical replication
slots.
These are two different things, and in fact sync replication doesn't even
require to use replication slots.
What is worse, even when all standbys use physical replication slots there
is no guarantee that values in synchronous_standby_names will match
physical slot names.

Regards,
--
Alexander Kukushkin

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<div dir=3D"ltr"><div>Hi,</div><br><div class=3D"gmail_quote gmail_quote_co=
ntainer"><div dir=3D"ltr" class=3D"gmail_attr">On Thu, 26 Feb 2026 at 09:45=
, shveta malik &lt;<a href=3D"mailto:shveta.malik@gmail.com">shveta.malik@g=
mail.com</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D=
"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-le=
ft:1ex"><br>
As suggested in [1], IMO, it is a reasonably good idea for<br>
&#39;synchronized_standby_slots&#39; to DEFAULT to the value of<br>
&#39;synchronous_standby_names&#39;. That way, even if the user missed to<b=
r>
configure &#39;synchronized_standby_slots&#39; explicitly, we would still h=
ave<br>
reasonable protection in place.</blockquote><div><br></div><div><div class=
=3D"gmail_quote gmail_quote_container">Hmm.</div><div class=3D"gmail_quote =
gmail_quote_container">synchronous_standby_names
 contains application_names, while=C2=A0synchronized_standby_slots contains=
=20
names of physical replication slots.</div><div class=3D"gmail_quote gmail_q=
uote_container">These are two different things, and in fact sync replicatio=
n doesn&#39;t even require to use replication slots.</div><div class=3D"gma=
il_quote gmail_quote_container">What is worse, even when all standbys use p=
hysical replication slots there is no guarantee that values in=C2=A0synchro=
nous_standby_names will match physical slot names.</div><br></div></div><di=
v dir=3D"ltr" class=3D"gmail_signature"><div dir=3D"ltr"><div>Regards,</div=
><div>--</div><div>Alexander Kukushkin<br></div></div></div></div>

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