[rabbitmq-discuss] Acknowledged Messages Requeued

[Ben Lewis]

Hi Emile,

Thanks for the response. Here's the output with from the rabbitmqctl
command at different stages:

First, with me ack'ing the messages:

Prior to starting consumer
------------------------
Listing queues ...
Test.ItemProcess    67645    0
...done.

As consumer is consuming, just reboot rebooting broker
------------------------
Listing queues ...
Test.ItemProcess    42936    1
...done.

After broker rebooted and RabbitMQ started
------------------------
Listing queues ...
Test.ItemProcess    67645    0
...done.

With noack=true the messages are delivered to the client quicker than I can
reboot the broker, but when it comes back up the queue is empty with 0
unacknowledged messages.

I'm not using transactions (I put a seperate console app together to test
this) and I do want to persist and acknowledge the message. I've stepped
through my code in debug and its hitting the BasicAck method.

Kind Regards,

Ben

On Fri, Nov 11, 2011 at 4:10 PM, Emile Joubert <emile at rabbitmq.com> wrote:

> Hi Ben,
>
> On 11/11/11 15:12, Ben Lewis wrote:
> > I have got a direct exchange feeding a durable queue, if I load say
> > 50,000 messages onto the queue and then start a consumer to work through
> > those item's.
> >
> > My consumer creates the connection, then creates the model (I'm using
> > .NET) and sets the Qos prefetch count to 1, then calls BasicGet,
> > processes the message, sends an ack (BasicAck), then enumerates until
> > BasicGet returns null. Finally disposing the model and closing the
> > connection.
>
> You don't need to set QoS if you retrieve messages synchronously
> (BasicGet). QoS makes sense with BasicConsume. That is not the cause of
> your trouble though.
>
> > If I restart the host I have the RabbitMQ broker running on (Windows)
> > after processing and ack'ing 40,000 messages while my consumer is
> > working through the remaining items, when the RabbitMQ broker comes back
> > online the 40,000 messages are redelivered (even though they were
> > acknowledged).
> >
> > Is this supposed to happen?
>
> No. Acknowledged messages are forgotten about by the broker, so you
> should not be seeing them again. What is the output of
>
> rabbitmqctl list_queues name messages_ready messages_unacknowledged
>
> before and after the restart? Is it possible that you are somehow not
> acknowledging the messages? Do you get the same result if you use the
> noAck flag of BasicGet?
>
> If you are using transactions and failing to commit the transaction then
> you could see apparently acknowledged message reappearing - is that a
> possibility?
>
> > If this is by design, any suggestions or advice on how I can minimise
> > the number of redelivered messages if the broker dies/restarts?
>
> If you don't care about persisting messages then you can publish the
> messages in non-persistent mode (set the delivery mode in the basic
> properties to 1).
>
>
> -Emile
>
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