[rabbitmq-discuss] AMQP 0.9.1 Specification: Suport for Deliver API

Mon Feb 7 22:25:40 GMT 2011

Hi Emile

I tried second approach of yours , but the issue with the approach is
that republishing of message goes into recursive publishing.

A publish to Q where my consumer check if header has count and if not
=5 update and republish ( this republish , shoudl be rather
reject(requue = true ) ).

so that set me wondering whether we can alter header of a message and
requeue it back rather than republishing it ?

Regds
Prashant

On Feb 7, 10:10 am, Emile Joubert <em... at rabbitmq.com> wrote:
> Hi Prashant,
>
> On 06/02/11 21:00, Prashant wrote:
>
>
>
> > Helo,
>
> > I was stuck while trying to use deliver option in channel. Now , in my
> > experiment , I am trying to use basicRecover to republish all the
> > unack messages back to the channel. These messages gets again repub ,
> > so far so good. But i fear , it might go into a loop as ,when Consumer
> > cannot consume messages it will be returned back to channel.
>
> > I looked into Spec refrence and found out that channel has a deliver
> > mechanism , which basically checks for relivered bit .
> > Per specification-----
> > This method delivers a message to the client, via a consumer. In the
> > asynchronous message delivery model, the client starts a consumer
> > using the Consume method, then the server responds with Deliver
> > methods as and when messages arrive for that consumer.
>
> >      * The server SHOULD track the number of times a message has been
> > delivered to clients and when a message is redelivered a certain
> > number of times - e.g. 5 times - without being acknowledged, the
> > server SHOULD consider the message to be unprocessable (possibly
> > causing client applications to abort), and move the message to a dead
> > letter queue.
> > -------
> > Now , my question is how I can leverage this , i.e.  if messge is
> > redelivered 5 times to channel , I intend to publish a message about
> > the status of this message with specifics that it has been failed
> > after trying 5 times...
> > If , its pssible , where do I need to add the logic to check this,
> > certainly now publisher as the messages are in channel.Can you please
> > throw in some pointers.
>
> The specification does indeed suggest that a broker should track the
> number of redeliveries. You can get more details about conformance for
> this feature on the specification page:
>
>  http://www.rabbitmq.com/specification.html
>
> The feature that you describe has reference "basic / deliver / 01" and
> is mark as "planned", which means that it has not been implemented yet.
> It is possible to get similar functionality without broker support though.
>
> A possible way to deal with your scenario is to republish
> non-processable messages to a different queue instead of leaving them
> unacknowledged. You might even republish messages together with the
> cause of failure to aid the decision about their fate.
>
> Another option might be to publish messages initially with a processing
> count of 0. Each time a consumer fails to publish the message, republish
> the message to the same queue with an incremented processing count
> instead of leaving the message unacknowledged. When the processing count
> reaches 5 then you can take appropriate action.
>
> Regards
>
> Emile
>
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