[rabbitmq-discuss] Occasional slow message on a local machine

[Jacques du Rand]

What are the avg sizes and the size of a msg that is slow?  Network?
Mtu,nagle?   Does your NIC have tcp offload?  As a black magic solution ser
your system to use deadline schedulerr to see if its worse or better?
jacques
On Jul 24, 2012 11:39 AM, "Francesco Mazzoli" <francesco at rabbitmq.com>
wrote:

> Hi Brennan,
> At Mon, 23 Jul 2012 15:57:24 -0400,
> Brennan Sellner wrote:
> > The rabbitmq server (v2.8.2) is running on the same machine, so there
> aren't
> > any external networks involved.  We're still running Fedora 11 (kernel
> 2.6.29,
> > Erlang R12B-5.8) for the moment, if that's relevant.
>
> Please upgrade both RabbitMQ and Erlang if you can (especially rabbit), or
> things will be hard to diagnose for us.
>
> > Time 0.90: The consumer receives and responds to an AMQP heartbeat from
> > the server, and acks the delivery of a prior message.  It again drops
> > into an amqp_simple_wait_frame.
>
> That does not sound right, heartbeats require no response.
>
> > My understanding is that when dealing solely with non-persistent
> > messages, Rabbit won't hit the disk until it runs out of RAM.  Is that
> > accurate?
>
> It is accurate, but your understanding of "runs out of RAM" might be
> misguided:
> rabbit will start swapping to disc when the RAM used exceeds `total_ram *
> vm_memory_high_watermark', where `vm_high_watermark' is a configurable
> application variable, with 0.4 as default:
> http://www.rabbitmq.com/configure.html .
>
> > Any ideas as to what else might cause this sort of delay, or suggestions
> on
> > how to get further useful information?
>
> I would say that the most likely thing to be happening is for rabbit to
> start
> paging to disc, so please check that first.  You can monitor your disc
> space
> usage with the rabbitmq management plugin.
>
> You might also be hitting flow control, but that is related to running out
> of
> RAM.  You can check that as well via the management plugin, the
> connections will
> be marked as "blocked".
>
> Another option could be that you are running out of file descriptors
> (maybe you
> have a large number of connections open?) and rabbit is blocking until
> some are
> available.
>
> --
> Francesco * Often in error, never in doubt
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