Re: [HACKERS] [PATCH] pg_reload_backend to signal SIGHUP to aspecific backend

On Wed, 28 Jun 2017 13:59:51 +0200
Remi Colinet <remi.colinet@gmail.com> wrote:

> Hi Yugo,
> 
> The patch looks fine. Installed and tested.

Thank you for your interest.

> 
> But a similar function already exists for the Postmaster process.
> 
> Datum
> pg_reload_conf(PG_FUNCTION_ARGS)
> {
>         if (kill(PostmasterPid, SIGHUP))
>         {
>                 ereport(WARNING,
>                                 (errmsg("failed to send signal to
> postmaster: %m")));
>                 PG_RETURN_BOOL(false);
>         }
> 
>         PG_RETURN_BOOL(true);
> }
> 
> I would suggest to merge your patch with above function which is close to
> yours.
> Btw, your patch looks better that above function code.
> 
> You may for instance retain pg_reload_conf() without argument for the same
> purpose as currently (Postmaster signaling).
> And provide a pid argument to signal a given backend.

Actually, I proposed that version patch in the previous thread[1], but there
as a suggestion to use other function name, so I attached fixed version
in this thread. 

[1] https://www.postgresql.org/message-id/20170624000156.74ca9485.nagata%40sraoss.co.jp

> 
> Regards
> Remi
> 
> 
> 2017-06-28 12:17 GMT+02:00 Yugo Nagata <nagata@sraoss.co.jp>:
> 
> > Hi,
> >
> > Attached is a patch of pg_reload_backend that is a function signaling
> > SIGHUP to a specific backend. The original idea is from Michael Paquier[1].
> > The documatation isn't included in this patch yet.
> >
> > We can change some parameters of other backend using the function
> > as bellow.
> >
> > postgres=# alter system set log_min_messages to debug2;
> > ALTER SYSTEM
> > postgres=# select pg_reload_backend(18375);
> >  pg_reload_backend
> > -------------------
> >  t
> > (1 row)
> >
> > There are some usecases. For example:
> >
> > - changing log configuration in other backends temporally.
> > - changing cost parameters for planner in other backends.
> > - changing autovacuum parameters of an already running autovacuum worker.
> >
> >
> > Hoever, this function need the superuser previlige to execute as well as
> > pg_reload_conf(). Although we can grant the execution to public, it is
> > useless for normal users bacause only superuser can change postgresql.conf.
> >
> > To allow normal users to change parameters in ohter backends, instead
> > we might want another feature, for example, a function like set_config()
> > than can change other backend's parameters using shared memory and SIGUSR1.
> >
> > Any comments would be appreciated.
> >
> > Regards,
> >
> > [1]
> > https://www.postgresql.org/message-id/CAB7nPqT4y8-
> > QoGKEugk99_tFuEOtAshcs5kxOeZ_0w27UtdGyA%40mail.gmail.com
> >
> > --
> > Yugo Nagata <nagata@sraoss.co.jp>
> >
> >
> > --
> > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
> > To make changes to your subscription:
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> >
> >


-- 
Yugo Nagata <nagata@sraoss.co.jp>