Re: background sessions

2017-03-09 14:52 GMT+01:00 Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)
com>:

> On 3/8/17 14:22, Pavel Stehule wrote:
> > 1. will be background session process closed automatically when parent
> > process is closed?
>
> If the communications queue goes away the process will eventually die.
> This is similar to how a backend process will eventually die if the
> client goes away. Some more testing would be good here.
>

what means "eventually die"?

I called pg_sleep() in called subprocess.

Cancel, terminating parent process has not any effect. It is maybe
artificial test.

Little bit more realistic - waiting on table lock in background worker was
successful - and when parent was cancelled, then worker process was
destroyed too.

But when parent was terminated, then background worker process continued.

What is worse - the background worker had 100% CPU and I had to restart
notebook.

CREATE OR REPLACE FUNCTION public.foo()
RETURNS void
LANGUAGE plpythonu
AS $function$
with plpy.BackgroundSession() as a:
a.execute('update foo2 set a = 30')
a.execute('insert into foo2 values(10)')
$function$
postgres=#

I blocked foo2 in another session.

Regards

Pavel

>
> > 2. what timeouts are valid for this process - statement timeout, idle in
> > transaction timeout
>
> Those should work the same way. It's the same code that runs the
> queries, starts/stops transactions, etc.
>
> > I see significant risk on leaking sessions.
>
> Yeah, that's a valid concern. But I think it works ok.
>
> > There can be more doc and examples in plpython doc. It will be main
> > interface for this feature. Mainly about session processing.
>
> OK, I'll look into that again.
>
> --
> Peter Eisentraut http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>