[rabbitmq-discuss] Drawbacks and advantages of "autoack" mode?

Matthias Radestock matthias at rabbitmq.com
Mon Apr 18 13:48:00 BST 2011


Alfonso Pantoja wrote:
> So the question is if a queue consumed by a consumer using auto_ack
> can contain messages with Delivered flag set to true?

Yes, it can. Specifically, when rabbit recovers from a non-clean 
shutdown it may mark all messages as delivered since it has no way of 
knowing for certain whether a message has been delivered. That way a 
consumer can be sure that if the flag is not set then the message 
definitely will not have been delivered before, which is the safer way 
to deal with this uncertainty.



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