From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?UTF-8?Q?Court=C3=A8s?=)
Subject: bug#32234: Cuirass: The SQLite built in busy handler might block the
	Fibers scheduler
Date: Mon, 23 Jul 2018 16:57:49 +0200
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To: =?UTF-8?Q?Cl=C3=A9ment?= Lassieur <clement@lassieur.org>
Cc: 32234@debbugs.gnu.org

Cl=C3=A9ment Lassieur <clement@lassieur.org> skribis:

> Ludovic Court=C3=A8s <ludo@gnu.org> writes:

[...]

>> Perhaps instead we need to set the timeout to a small value and handle
>> SQLITE_BUSY at the call site in our code.  We could define a macro that
>> automatically retries upon SQLITE_BUSY.
>
> That would limit the issue to the first timeout span: for that short
> time the scheduler would be blocked.  I think a timeout of 0 would be
> better.

Yes, 0 is an acceptable =E2=80=9Csmall value.=E2=80=9D  ;-)  Perhaps 100ms =
would be
acceptable if the situation is rare enough, dunno.

> Another solution would be to serialize all the database accesses as we
> do already with the url handler, and stop using the SQLITE
> multithreading features.  It would probably make the code simpler
> because we would use the same paradigm everywhere, and we would avoid
> looping until SQLITE isn't busy at each request.

In essence we=E2=80=99d introduce a =E2=80=9Cdatabase server=E2=80=9D runni=
ng as a fiber, and
everyone would talk to that server.

I considered doing that before but then though sqlite would probably be
able to do better than this, but I don=E2=80=99t know.

What=E2=80=99s a bit annoying with switching to a database server model is =
that
we=E2=80=99d need to adapt every call site.

Thoughts?

Ludo=E2=80=99.