[rabbitmq-discuss] Almost all statistics drop to 0 every hour

[Simon MacMullen]

On 06/11/12 08:48, Irmo Manie wrote:
> As you can see, the delivery (no-ack) rate drops to 0 every hour for a
> couple of minutes. Other statistics on message processing indicate that
> actual delivery/consuming is continuing, so it looks like it's really
> only the statistics that are wrong.
>
> If I look at the json output during such a 'downtime' I can see that the
> publish rate is always available, but the rest of the rates
> (acknowledge, delivery, etc) are mostly 0.

Just the rates in /api/overview or the ones in /api/queues as well?

> I understand a bit from the sources that in this /api/overview call from
> the management api, these statistics are gathered from different places,
> both memory and database (with additional calculations executed on them
> while fetching), correct?

Yes. We get basic queue information from the Mnesia database, and then 
augment it with statistics information (including rates) from the 
(in-memory) management database.

> Could it be that some of these values are 0 because of certain time-outs
> while getting the data?

No, the requests for stats don't time out.

> In other words: do I have to start searching for
> the problem at the database disk/IO level?

No.

> I couldn't see any IO waits on the machine indicating something else is
> happening at the time. Also CPU load is normal.
> Still the weird thing is that this also happens on a test machine at
> roughly the same times.
> Since both machines are VM's, this might indicate that it could be an
> infrastructural problem, but I'd like to be sure before accusing 'others'.

If /api/overview and /api/queues contradict each other I'd like to know 
about it.

But if the rates drop to 0 in /api/queues as well, Occam's Razor 
suggests that maybe your consumers are pausing for some reason :)

Cheers, Simon

-- 
Simon MacMullen
RabbitMQ, VMware