Re: Two pg_rewind patches (auto generate recovery conf and ensure clean shutdown)

From: Alvaro Herrera from 2ndQuadrant <alvherre(at)alvh(dot)no-ip(dot)org>
To: Paul Guo <pguo(at)pivotal(dot)io>
Cc: Michael Paquier <michael(at)paquier(dot)xyz>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Jimmy Yih <jyih(at)pivotal(dot)io>, Ashwin Agrawal <aagrawal(at)pivotal(dot)io>
Subject: Re: Two pg_rewind patches (auto generate recovery conf and ensure clean shutdown)
Date: 2019-09-10 17:52:19
Message-ID: 20190910175219.GA8826@alvherre.pgsql
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On 2019-Sep-09, Paul Guo wrote:

> >
> > Thank for rebasing.
> >
> > I didn't like 0001 very much.
> >
> > * It seems now would be the time to stop pretending we're using a file
> > called recovery.conf; I know we still support older server versions that
> > use that file, but it sounds like we should take the opportunity to
> > rename the function to be less misleading once those versions vanish out
> > of existance.
>
> How about renaming the function names to
> GenerateRecoveryConf -> GenerateRecoveryConfContents
> WriteRecoveryConf -> WriteRecoveryConfInfo <- it writes standby.signal
> on pg12+, so function name WriteRecoveryConfContents is not accurate.

GenerateRecoveryConfig / WriteRecoveryConfig ?

> > I wonder about putting this new file in src/fe_utils instead of keeping
> > it in pg_basebackup and symlinking to pg_rewind. Maybe if we make it a
> > true module (recovery_config_gen.c) it makes more sense there.
> >
> I thought some about where to put the common code also. It seems pg_rewind
> and pg_basebackup are the only consumers of the small common code. I doubt
> it deserves a separate file under src/fe_utils.

Hmm, but other things there are also used by only two programs, say
psqlscan.l and conditional.c are just for psql and pgbench.

> > 0003:
> >
> > I still don't understand why we need a command-line option to do this.
> > Why should it not be the default behavior?
>
> This was discussed but frankly speaking I do not know how other postgres
> users or enterprise providers handle this (probably some have own scripts?).
> I could easily remove the option code if more and more people agree on that
> or at least we could turn it on by default?

Well, I've seen no contrary votes, and frankly I see no use for the
opposite (current) behavior.

--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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