Date: Fri, 22 Aug 2025 17:42:08 +0200
From: hubert depesz lubaczewski <depesz@depesz.com>
Sender: depesz@depesz.com
To: Adrian Klaver <adrian.klaver@aklaver.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>,
	PostgreSQL General <pgsql-general@lists.postgresql.org>,
	Chris Wilson <chris+google@qwirx.com>
Subject: Re: Streaming replica hangs periodically for ~ 1 second - how to
 diagnose/debug
Message-ID: <aKiP0IJoJjEtkLbk@depesz.com>
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On Fri, Aug 22, 2025 at 08:39:21AM -0700, Adrian Klaver wrote:
> On 8/22/25 08:30, hubert depesz lubaczewski wrote:
> > On Fri, Aug 22, 2025 at 11:21:22AM -0400, Tom Lane wrote:
> > > hubert depesz lubaczewski <depesz@depesz.com> writes:
> > > > I got repeatable case today. Is is breaking on its own everyy
> > > > ~ 5 minutes.
> > > 
> > > Interesting.  That futex call is presumably caused by interaction
> > > with some other process within the standby server, and the only
> > > plausible candidate really is the startup process (which is replaying
> > > WAL received from the primary).  There are cases where WAL replay
> > > will take locks that can block queries on the standby.  Can you
> > > correlate the delays on the standby server with any DDL events
> > > occurring on the primary?
> > 
> > Nope. Plus there is certain repetition of these cases, so even if I'd
> > miss *some* create table/alter, it just isn't going to be happening
> > every 4-5 minutes.
> > 
> 
> > So, while there are outliers, I'd say that most of the problems happens every
> > 3-5 minutes.
> 
> Are you using the Postgres community version or the AWS variant?

Community. From pgdg repo.

Best regards,

depesz