[rabbitmq-discuss] RabbitMQ writes non stop to disk

[Raphael Simon]

Hi Matthias, so just to re-iterate: we see this behavior only on one broker,
other brokers with similar load don't exhibit the issue. We've never see
that much i/o apart from when we hit the issues Matthew fixed for 2.4.
Trying RabbitMQ 2.6 will take time as we have custom code and plugin we need
to migrate. This issue only appears on production so there is no way for us
to quickly try it.

Here is the CPU graph on the broker exhibiting the issue:

[image: cpu_overview.png]

And the load on a broker that does not:

[image: cpu_overview2.png]

The spikes every minute is because we run rabbitmqctl list_queues every
minute to monitor the queues. The spikes every 4 hours is due to a cleanup
daemon that cleans up stale queues every 4 hours.

--
Raphael.


On Wed, Oct 26, 2011 at 3:45 PM, Matthias Radestock
<matthias at rabbitmq.com>wrote:

> Raphael,
>
>
> On 25/10/11 17:23, Raphael Simon wrote:
>
>> All the messages are consumed pretty much immediately.
>>
>
> That is irrelevant. Persistent messages sent to durable queues *always* get
> written to disk unless they can be sent to an auto-ack'ing consumer
> immediately.
>
> The next rabbit release contains an optimisation s.t. when messages get
> ack'ed before they have been written to disk then they won't be written to
> disk.
>
> The only thing slightly strange about what you have reported is the high
> write count. Any chance you could give RabbitMQ 2.6.1 a try?
>
> Regards,
>
> Matthias.
>
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