[rabbitmq-discuss] Connection.createChannel() hangs using amqp-client 3.1.1

Fri Jun 7 16:47:57 BST 2013

Hey Tim,

Sounds good. Thanks for the info.

- jonathan

On Fri, Jun 7, 2013 at 1:57 AM, Tim Watson <tim at rabbitmq.com> wrote:

> Hi Jonathan,
>
> Ok, you can safely ignore what I've written below. What's actually going
> on (thanks to Matthias for pointing it out) is that the ShutdownListener
> callbacks run in the connection's thread, so the call to createChannel
> causes a deadlock since it blocks waiting for a response (whilst the
> connection's thread is stuck executing the listener). I'm going to add some
> notes to the API documentation explaining that, so future users don't get
> caught out in the same way.
>
> The canonical approach to dealing with this is to have the shutdown
> listener callback signal your own (application) thread, from which you can
> manage recovery without risking deadlock in this fashion.
>
> Cheers,
> Tim
>
> On 7 Jun 2013, at 09:38, Tim Watson wrote:
>
> > Hi Jonathan,
> >
> > On 6 Jun 2013, at 23:42, Jonathan Halterman wrote:
> >> I hit on a scenario where connection.createChannel() may hang forever.
> The scenario: obtain a channel and attempt to publish to a non-existent
> exchange. The channel will be shutdown. Attempt to establish a new
> (replacement) channel via Connection.createChannel(), which hangs forever.
> A simple version of this scenario:
> >>
> >
> > This should not be happening. Are you absolutely sure you're using
> version 3.1.1 of the java client library, since a similar bug (involving
> accidentally re-used channel ids) was fixed in a previous release:
> http://hg.rabbitmq.com/rabbitmq-java-client/rev/ea7d68c2154d
> >
> >> From Tracer:
> >>
> >> 1370554962786: <Tracer-0> ch#1 <-
> {#method<channel.close>(reply-code=404, reply-text=NOT_FOUND - no exchange
> 'foo' in vhost '/', class-id=60, method-id=40), null, ""}
> >> 1370554962788: <Tracer-0> ch#1 -> {#method<channel.close-ok>(), null,
> ""}
> >> 1370554974891: <Tracer-0> ch#1 -> {#method<channel.open>(out-of-band=),
> null, ""}
> >> 1370554974970: <Tracer-0> ch#1 <-
> {#method<channel.open-ok>(channel-id=), null, ""}
> >>
> >
> > That last line seems very odd - I would've expected to a see a channel
> id in there, though truth be told I'm not overly familiar with the Tracer
> tool in the java client.
> >
> >> Any ideas why things are hanging?
> >>
> >
> > According to the last line of the trace you've supplied, a new channel
> was opened successfully, though there's no channel id present which is
> worrying. Please confirm that you are definitely using the right version
> (i.e., where did you obtain the amqp-client binary from) and we'll take a
> closer look.
> >
> > Cheers,
> > Tim
> >
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