RabbitMQ: Pushing Messages to the Back of the Queue on NAck

Some useful discussion on the RabbitMQ mailing list looked at a way to push messages to the back of a queue upon negative acknowledgement.  Here was the scenario:

> Scenario:
> I'm processing messages from a queue with confirmation required.
> The number of messages relative to the consumption rate can be quite
> high at times. In excess of hundreds of thousands of messages, with
> consumption rate in the low hundreds per second range.
>> Sometimes we have to abandon processing a message for some transient
> reason (eg: external resource is locked/unavailable), and so we send a
> NAck.
> At the moment, RabbitMQ will immediately redeliver that message to any
> of the consumers. If the transient condition is still in place, we can
> potentially get into a tight loop where we're constantly consuming the
> same message(s) hundreds of times per second.
>> For our scenario, we *can* duplicate the message, send it to the
> exchange/queue, and Ack the original.

The advice on this email has some good suggestions for how to prevent getting into a tight loop.