Date: Wed, 10 Apr 2024 10:00:34 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Kirill Reshke <reshkekirill@gmail.com>,
	"Leung, Anthony" <antholeu@amazon.com>,
	"Andrey M. Borodin" <x4mmm@yandex-team.ru>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: Allow non-superuser to cancel superuser tasks.
Message-ID: <20240410150034.GA1673069@nathanxps13>
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On Wed, Apr 10, 2024 at 07:58:39AM +0900, Michael Paquier wrote:
> On Wed, Apr 10, 2024 at 12:52:19AM +0300, Kirill Reshke wrote:
>> On Tue, 9 Apr 2024 at 08:53, Michael Paquier <michael@paquier.xyz> wrote:
>>> The thing is that you cannot rely on a lookup of the backend type for
>>> the error information, or you open yourself to letting the caller of
>>> pg_cancel_backend or pg_terminate_backend know if a backend is
>>> controlled by a superuser or if a backend is an autovacuum worker.
>> 
>> Good catch. Thanks.  I think we need to update the error message to not
>> leak backend type info.
> 
> Yep, that's necessary I am afraid.

Isn't it relatively easy to discover this same information today via
pg_stat_progress_vacuum?  That has the following code:

		/* Value available to all callers */
		values[0] = Int32GetDatum(beentry->st_procpid);
		values[1] = ObjectIdGetDatum(beentry->st_databaseid);

I guess I'm not quite following why we are worried about leaking whether a
backend is an autovacuum worker.

>>> The choice of pg_signal_autovacuum is a bit inconsistent, as well,
>>> because autovacuum workers operate like regular backends.  This name
>>> can also be confused with the autovacuum launcher.
>> 
>> Ok. What would be a good choice? Is `pg_signal_autovacuum_worker` good
>> enough?
> 
> Sounds fine to me.  Perhaps others have an opinion about that?

WFM

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com