[rabbitmq-discuss] 1 Fanout Exchange, 2 queues, 1 slow, 1 fast

Kenneth Loafman kenneth at loafman.com
Tue May 8 14:44:43 BST 2012

Thanks for the reply.

By intermittent, I mean burst, pause, burst, pause, ...

The problem has been 'solved' for now.  We were using basic_get and 96
consumers was too much even with a 1 second delay on no-data-received
(we're swapping over to callbacks ASAP).  I reduced the number of consumers
to 32 and got much better throughput, so the queue is keeping up now.


On Tue, May 8, 2012 at 5:47 AM, Emile Joubert <emile at rabbitmq.com> wrote:

> Hi Kenneth,
> On 07/05/12 20:10, Kenneth Loafman wrote:
> > I've got a fanout exchange running two queues.  One queue is responding
> > very quickly like normal, the other is intermittent.  What would cause
> > this?  The fast queue has 3 consumers, the slow queue has 64 consumers.
> >  Is there a limit to how many consumers can be attached to a queue?
> If you say the queue is responding intermittently, what do you mean
> exactly? Are you measuring latency between publish and deliver, or
> something else?
> The broker does not impose a fixed limit on the number of subscribers to
> a queue, but the server capacity may be a limit.
> It is possible that the problem is caused by some behaviour of the
> clients, or a difference in pre-fetch count. Do you get more comparable
> performance if you set the pre-fetch count to 3 on the "intermittent"
> queue?
> Depending on what you are measuring you may wish to enable the firehose
> tracer for debugging:
> http://www.rabbitmq.com/firehose.html
> -Emile
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