public inbox for [email protected]  

help / color / mirror / Atom feed

From: Tom Lane <[email protected]>
To: [email protected]
Cc: Adrian Klaver <[email protected]>
Cc: PostgreSQL General <[email protected]>
Cc: Chris Wilson <[email protected]>
Subject: Re: Streaming replica hangs periodically for ~ 1 second - how to diagnose/debug
Date: Fri, 22 Aug 2025 11:55:18 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>

hubert depesz lubaczewski <[email protected]> writes:
> On Fri, Aug 22, 2025 at 11:21:22AM -0400, Tom Lane wrote:
>> 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.

Nonetheless, I'm suspecting an interaction with the startup process,
because there just isn't that much else that this process could be
needing to deal with.  Can you try strace'ing both the process doing
the test query and the startup process, to see what the startup
process is doing at the times the futex calls happen?

			regards, tom lane

view thread (27+ messages)  latest in thread

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected], [email protected], [email protected], [email protected]
  Subject: Re: Streaming replica hangs periodically for ~ 1 second - how to diagnose/debug
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox