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Date: Fri, 22 Aug 2025 08:39:21 -0700
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Subject: Re: Streaming replica hangs periodically for ~ 1 second - how to
 diagnose/debug
To: depesz@depesz.com, Tom Lane <tgl@sss.pgh.pa.us>
Cc: PostgreSQL General <pgsql-general@lists.postgresql.org>,
 Chris Wilson <chris+google@qwirx.com>
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From: Adrian Klaver <adrian.klaver@aklaver.com>
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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?

> 
> depesz
> 


-- 
Adrian Klaver
adrian.klaver@aklaver.com