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From: Thom Brown <thom@linux.com>
Date: Wed, 20 Aug 2025 18:30:00 +0100
Message-ID: <CAA-aLv6Vh04awXunt8mbHp_1vtT0fFLJpaXvs38ToW8mxRB2WA@mail.gmail.com>
Subject: Re: Streaming replica hangs periodically for ~ 1 second - how to diagnose/debug
To: depesz@depesz.com
Cc: Adrian Klaver <adrian.klaver@aklaver.com>, 
	PostgreSQL General <pgsql-general@lists.postgresql.org>
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On Wed, 20 Aug 2025 at 17:08, hubert depesz lubaczewski
<depesz@depesz.com> wrote:
>
> On Wed, Aug 20, 2025 at 08:14:47AM -0700, Adrian Klaver wrote:
> > Hmm.
> >
> > From initial post:
> >
> > "For ~ 1 second there are no logs going to log (we usually have at 5-20
> > messages logged per second), no connection, nothing. And then we get
> > bunch (30+) messages with the same milisecond time."
> >
> > Are the 30+ messages all coming in on one connection or multiple
> > connections?
>
> Multiple connections.
>
> > Also to be clear these are statements that are being run on the replica
> > locally, correct?
>
> What do you mean locally?
>
> Application servers are *not* on the same server as the db. So no, they
> are not local.
>
> > Does the AWS monitoring indicate any issues?
>
> Nope. All looks "fine".
>
> Same for our monitoring  - CPU usage, iops, load.
>
> Best regards,
>
> depesz

Do you have THP enabled? Can you use mpstat and see what %steal shows as?

Thom