Re: [PATCH] libpq: try all addresses for a host before moving to next on target_session_attrs mismatch

From: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Evgeny Kuzin <evgeny(dot)kuzin(at)outlook(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: [PATCH] libpq: try all addresses for a host before moving to next on target_session_attrs mismatch
Date: 2026-03-05 15:16:03
Message-ID: 8ED71201-8317-46F9-9D82-56C3D9A0E6C4@yandex-team.ru
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> On 5 Mar 2026, at 19:55, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> TBH, I'd say that your DNS setup is broken and you should fix it.
> It makes no sense to have the same DNS entry pointing to both
> read-write and read-only hosts. The proposed patch will mainly
> result in useless connection attempts in more-sanely-constructed
> setups.

This is very desired feature by cloud providers.

We sell PGaaS clusters which are just a bunch of hosts. Each of
these hosts can became primary any time.
Currently, when user adds more hosts they have to redeploy\reconfigure
their app.

Unless user uses pgx that already works this way, then we can just give
them one FQDN for whole cluster and update DNS records.

This was proposed before [0] and I think Andrew and Evgeny could join
efforts. Certainly, this can be implemented without affecting those
who do not need it.

Best regards, Andrey Borodin.

[0] https://commitfest.postgresql.org/patch/5396/

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