From: Tom Lane <tgl@sss.pgh.pa.us>
To: Konstantin Osipov <kostja.osipov@gmail.com>
cc: Greg Sabino Mullane <htamfids@gmail.com>,
        Nikolay Samokhvalov <nik@postgres.ai>,
        pgsql-hackers@lists.postgresql.org
Subject: Re: Built-in Raft replication
In-reply-to: <CAM527d9+eGvdih1GxoPDJ2WYs6eitf39oNTxGxnCK1PgF=A8wg@mail.gmail.com>
References: <Z_1Cq7JvabsFYjQo@ark> <CAKAnmmJxGHcQmzXqEQ-nppZjXyH7i5W_7Cz8JNMb2+6c5+D+og@mail.gmail.com> <CAM527d9+eGvdih1GxoPDJ2WYs6eitf39oNTxGxnCK1PgF=A8wg@mail.gmail.com>
Comments: In-reply-to Nikolay Samokhvalov <nik@postgres.ai>
	message dated "Tue, 15 Apr 2025 15:27:56 -0700"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <1798837.1744759182.1@sss.pgh.pa.us>
Date: Tue, 15 Apr 2025 19:19:42 -0400
Message-ID: <1798838.1744759182@sss.pgh.pa.us>
Archived-At: <https://www.postgresql.org/message-id/1798838.1744759182%40sss.pgh.pa.us>
Precedence: bulk

Nikolay Samokhvalov <nik@postgres.ai> writes:
> This is exactly what I wanted to write as well. The idea is great. At the
> same time, I think, consensus on many decisions will be extremely hard to
> reach, so this project has a high risk of being very long. Unless it's an
> extension, at least in the beginning.

Yeah.  The two questions you'd have to get past to get this into PG
core are:

1. Why can't it be an extension?  (You claimed it would work more
seamlessly in core, but I don't think you've made a proven case.)

2. Why depend on Raft rather than some other project?

Longtime PG developers are going to be particularly hard on point 2,
because we have a track record now of outliving outside projects
that we thought we could rely on.  One example here is the Snowball
stemmer; while its upstream isn't quite dead, it's twitching only
feebly, and seems to have a bus factor of 1.  Another example is the
Spencer regex engine; we thought we could depend on Tcl to be the
upstream for that, but for a decade or more they've acted as though
*we* are the upstream.  And then there's libxml2.  And uuid-ossp.
And autoconf.  And various documentation toolchains.  Need I go on?

The great advantage of implementing an outside dependency in an
extension is that if the depended-on project dies, we can say a few
words of mourning and move on.  It's a lot harder to walk away from
in-core features.

			regards, tom lane