How to retract a message in RabbitMQ?

Question

I've got something like a job queue over RabbitMQ and, upon a request to cancel a job, I'd like to retract the tasks that have not yet started processing (their messages have not been ack'd), which corresponds to retracting these messages from the queues that they've been routed to.

I haven't found this functionality in AMQP or in the RabbitMQ API; perhaps I haven't searched well enough? Or will I have to use a workaround (it's not hard, but still)?

Answer 1

At least two ways to achieve your target:

• basic.reject will requeue message if requeue=true is set (otherwise it will reject message).
  (supported since RabbitMQ 2.0.0; see http://www.rabbitmq.com/blog/2010/08/03/well-ill-let-you-go-basicreject-in-rabbitmq/).

• basic.recover will ask broker to redeliver unacked messages on channel.