[Koha-bugs] [Bug 32481] Rabbit times out when too many jobs are queued and the response takes too long

[bugzilla-daemon at bugs.koha-community.org]

https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=32481

--- Comment #13 from David Cook <dcook at prosentient.com.au> ---
(In reply to Nick Clemens from comment #12)
> > > It seems that koha receives all of the jobs immediately, but only
> > > acknowledges when complete - so the final job was waiting over 30 minutes
> > > for acknowledgement and this caused issues

Thanks for clarifying, Nick. Your comment also made me re-read the description,
and it made me realize that I've had this same problem before on a different
project, although it was with AMQP rather than STOMP. Let me see the STOMP way
of doing it...

The problem is that we're not defining a prefetch size. You can see the problem
here in ./misc/background_jobs_worker.pl:

$conn->subscribe({ destination => sprintf("/queue/%s-%s", $namespace, $queue),
ack => 'client' });

As per the docs, we need to set "'activemq.prefetchSize' => 1" in that
subscribe hashref argument:
https://metacpan.org/pod/Net::Stomp#activemq.prefetchSize

If you/we set that, I would bet that your problem goes away.

--

I have a RabbitMQ AMQP worker on another project that consumes many thousands
of messages a day, and I was noticing timeouts even though it was blazing
through the messages. I changed the prefetch size to 1 and ever since there's
been no more timeouts. It's just worked like a beast!

--

(Katrin, the above is what I mean about us all being beginning with this
stuff.)

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