[rabbitmq-discuss] Unexpected blocking in channel.basicGet()

Fri May 3 18:06:53 BST 2013

Thanks for the informative response; I appreciate the insight.

Dave

On Fri, May 3, 2013 at 12:19 PM, Tim Watson <tim at rabbitmq.com> wrote:

> On 3 May 2013, at 16:53, Dave Goldstein wrote:
>
> > So if the call blocks indefinitely without erroring out, what does that
> suggest
> >
>
> The usual suspect is a network connectivity problem, either due to an
> interruption in service, broker failure/crash/restart or intermediate
> network kit (such as firewalls). A typical TCP/IP stack can take quite a
> long time to "notice" the peer socket has "disappeared", while the client
> is sat waiting for a reply.
>
> > and is there any way for me to recover from this beyond detecting and
> killing the thread?
>
> Unfortunately there aren't any silver bullet solutions to this kind of
> problem. Detecting an idle worker (based on whatever your definition of
> "idle" happens to be) and killing it is certinaly the must common approach.
> Bear in mind that the OS networking stack is already trying to 'detect' the
> problem, and it's unlikely you'll be able to improve on what it is doing.
>
> It might help if you enable AMQP heartbeats in your client, which would at
> least detect an unresponsive network connection in a timely fashion. These
> will do the job of killing the connection and any channels for you, so at
> least you don't have to home bake a solution based on killing threads. The
> other thing that might help is to consider turning on TCP keep-alives in
> your OS networking configuration. These perform a similar function, but at
> a much lower level, however they come with overheads and caveats that they
> might affect your application (and/or other network interactions taking
> place on the machine) in a wide variety of ways.
>
> > BTW, I was running client 3.0.1 and have just moved to 3.0.4 to see if
> the behavior changes.
> >
>
> This won't have changed between releases, if I've diagnosed it correctly
> at least.
>
> Cheers,
> Tim
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