[rabbitmq-discuss] Sematics of ACK/REQUEUE/DISCARD on a message

If you don't ack it, it will be retained by RabbitMQ and will be
redelivered to some other consumer eventually when your current
consumer cancels/dies.
Basic.reject is not implemented. Calling basic.recover{requeue=true}
will requeue all non-acknowledged messages outstanding on the current
*channel*. Note this is not queue specific.

The specification is silent as to where in the queues the messages
should be reentered and you should not rely on any particular behaviour.
Currently RabbitMQ requeues messages at the end of the queue (i.e. they
behave like new publishes), but that can change.

Matthew

Got it. Since the consumer is called through a call-back it will get the
same message again (after restarting and if it is the only consumer) if
the consumer dies without ack-ing the message.

Andreas

Careful here - cancelling a consumer with basic.cancel does *not* cause
unack'ed messages to be requeued/redelivered. For that to happen the
channel needs to be closed (explicitly, or implicitly via a connection
closure or termination).


Matthias.

Fair enough. Using Python you would ensure that the related code is
properly enclosed within a context manager. For the case the consumer
dies for whatever reasons: the channel would be closed and the action
taken by the queue as you described it.

Andreas