Date: Wed, 18 Aug 2021 13:04:11 -0400
From: "alvherre@alvh.no-ip.org" <alvherre@alvh.no-ip.org>
To: "Bossart, Nathan" <bossartn@amazon.com>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
	"x4mmm@yandex-team.ru" <x4mmm@yandex-team.ru>,
	"a.lubennikova@postgrespro.ru" <a.lubennikova@postgrespro.ru>,
	"hlinnaka@iki.fi" <hlinnaka@iki.fi>,
	"matsumura.ryo@fujitsu.com" <matsumura.ryo@fujitsu.com>,
	"masao.fujii@gmail.com" <masao.fujii@gmail.com>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: archive status ".ready" files may be created too early
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On 2021-Aug-17, alvherre@alvh.no-ip.org wrote:

> However, why do it in a WAL-producing client-connected backend?  It
> strikes me as a bad thing to do, because you are possibly causing delays
> for client-connected backends.  I suggest that we should give this task
> to the WAL writer process -- say, have XLogBackgroundFlush do it.

Reading the comments on walwriter.c I am hesitant of having walwriter do
it:

>  * Because the walwriter's cycle is directly linked to the maximum delay
>  * before async-commit transactions are guaranteed committed, it's probably
>  * unwise to load additional functionality onto it.  For instance, if you've
>  * got a yen to create xlog segments further in advance, that'd be better done
>  * in bgwriter than in walwriter.

So that comment suggests that we should give the responsibility to bgwriter.
This seems good enough to me.  I suppose if bgwriter has a long run of
buffers to write it could take a little bit of time (a few hundred
milliseconds?) but I think that should be okay.

-- 
Álvaro Herrera           39°49'30"S 73°17'W  —  https://www.EnterpriseDB.com/
"No renuncies a nada. No te aferres a nada."