Message-ID: <fff6e3ab84fdc0861701469d78f5d8a099ddf22e.camel@cybertec.at>
Subject: Re: Query Spins
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Murthy Nunna <mnunna@fnal.gov>, "pgsql-admin@lists.postgresql.org"
	 <pgsql-admin@lists.postgresql.org>
Date: Mon, 01 Sep 2025 09:52:26 +0200
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On Mon, 2025-09-01 at 03:52 +0000, Murthy Nunna wrote:
> Pg16.10
> =C2=A0
> I have a query which runs fine most of the time. When it runs fine, it sp=
awns
> parallel workers. In pg_stat_activity, wait_event is blank, state is acti=
ve and
> backend_type =3D "client backend" for the main query. For parallel worker=
s of
> this query I see wait_event =3D MessageQueueSend, state is active and
> backend_type =3D "parallel worker"
> =C2=A0
> But some times, it has no parallel workers. wait_event is blank, state is=
 active
> and backend_type =3Dclient backend. And it never ends. It takes up lot of=
 CPU.
> The socket on both server and client server are in ESTABLISHED state
> (netstat -tulpa | grep <client_port>).

Perhaps no workers are spawned because "max_parallel_workers" has already
been exhausted by other backends.  Check for the number of concurrent paral=
lel
workers next time you get the error.

I cannot know the source of your performance problems, but perhaps it is
a combination of system overload and lack of available parallel worker
processes, which might well go together.

Yours,
Laurenz Albe