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Subject: Re: Built-in Raft replication
From: Andrey Borodin <x4mmm@yandex-team.ru>
In-Reply-To: <1832513.1744777613@sss.pgh.pa.us>
Date: Wed, 16 Apr 2025 10:24:48 +0500
Cc: Konstantin Osipov <kostja.osipov@gmail.com>,
 Greg Sabino Mullane <htamfids@gmail.com>,
 Nikolay Samokhvalov <nik@postgres.ai>,
 PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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To: Tom Lane <tgl@sss.pgh.pa.us>
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> On 16 Apr 2025, at 09:26, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>=20
> Andrey Borodin <x4mmm@yandex-team.ru> writes:
>> I think it's what Konstantin is proposing. To have our own Raft =
implementation, without dependencies.
>=20
> Hmm, OK.  I thought that the proposal involved relying on some =
existing
> code, but re-reading the thread that was said nowhere.  Still, that
> moves it from a large project to a really large project :-(
>=20
> I continue to think that it'd be best to try to implement it as
> an extension, at least up till the point of finding show-stopping
> reasons why it cannot be that.

I think I can provide some reasons why it cannot be neither extension, =
nor any part running within postmaster reign.

1. When joining cluster, there=E2=80=99s not PGDATA to run postmaster on =
top of it.

2. After failover, old Primary node must rejoin cluster by running =
pg_rewind and following timeline switch.

The system in hand must be able to manipulate with PGDATA without =
starting Postgres.

My question to Konstantin is Why wouldn=E2=80=99t you just add Raft to =
Patroni? Is there a reason why something like Patroni is not in core and =
noone rushes to get it in?
Everyone is using it, or system like it.


Best regards, Andrey Borodin.=