Re: when the startup process doesn't - Mailing list pgsql-hackers

> > > +               {"log_min_duration_startup_process", PGC_SUSET, LOGGING_WHEN,
> > >
> > > I think it should be PGC_SIGHUP, to allow changing it during runtime.
> > > Obviously it has no effect except during startup, but the change will be
> > > effective if the current process crashes.
> > > See also: https://www.postgresql.org/message-id/20210526001359.GE3676@telsasoft.com
> >
> > I did not get exactly how it will change behaviour. In my
> > understanding, when the server restarts after a crash, it fetches the
> > value from the config file. So if there is any change that gets
> > affected. Kindly correct me if I am wrong.

Sorry my understanding was wrong. But I'm not completely convinced
with the above description saying that the change will be effective if
the current process crashes.
AFAIK, whenever we set the GucContext less than PGC_SIGHUP (that is
either PGC_POSTMASTER or PGC_INTERNAL) then any change in the config
file will not get affected during restart after crash. If the
GucContext is greater than or equal to PGC_SIGHUP, then any change in
the config file will be changed once it receives the SIGHUP signal. So
it gets affected by a restart after a crash. So since the GucContext
set here is PGC_SUSET which is greater than PGC_SIGHUP, there is no
change in the behaviour wrt this point.

> I've triple checked the behavior using a patch I submitted for Thomas' syncfs
> feature.  ALTER SYSTEM recovery_init_sync_method=syncfs was not picked up when
> I sent SIGABRT.  But with my patch, if I also do SELECT pg_reload_conf(), then
> a future crash uses syncfs.
> https://www.postgresql.org/message-id/20210526001359.GE3676@telsasoft.com

The difference is since the behaviour is compared between
PGC_POSTMASTER and PGC_SIGHUP.

> The GUC definitely isn't SUSET, since it's not useful to write in a (super)
> user session SET log_min_duration_startup_process=123.
I agree with this. I may have to change this value as setting in a
user session is not at all useful. But I am confused between
PGC_POSTMASTER and PGC_SIGHUP. We should use PGC_SIGHUP if we would
like to allow the change during restart after a crash. Otherwise
PGC_POSTMASTER would be sufficient. Kindly share your thoughts.

Thanks & Regards,
Nitin Jadhav

On Wed, Jun 9, 2021 at 9:49 PM Justin Pryzby <pryzby@telsasoft.com> wrote:
>
> On Wed, Jun 09, 2021 at 05:09:54PM +0530, Nitin Jadhav wrote:
> > > +               {"log_min_duration_startup_process", PGC_SUSET, LOGGING_WHEN,
> > >
> > > I think it should be PGC_SIGHUP, to allow changing it during runtime.
> > > Obviously it has no effect except during startup, but the change will be
> > > effective if the current process crashes.
> > > See also: https://www.postgresql.org/message-id/20210526001359.GE3676@telsasoft.com
> >
> > I did not get exactly how it will change behaviour. In my
> > understanding, when the server restarts after a crash, it fetches the
> > value from the config file. So if there is any change that gets
> > affected. Kindly correct me if I am wrong.
>
> I don't think so.  I checked and SelectConfigFiles is called only once to read
> config files and cmdline args.  And not called on restart_after_crash.
>
> The GUC definitely isn't SUSET, since it's not useful to write in a (super)
> user session SET log_min_duration_startup_process=123.
>
> I've triple checked the behavior using a patch I submitted for Thomas' syncfs
> feature.  ALTER SYSTEM recovery_init_sync_method=syncfs was not picked up when
> I sent SIGABRT.  But with my patch, if I also do SELECT pg_reload_conf(), then
> a future crash uses syncfs.
> https://www.postgresql.org/message-id/20210526001359.GE3676@telsasoft.com
>
> --
> Justin