[rabbitmq-discuss] Lost messages after consumer crash

Simon MacMullen simon at rabbitmq.com
Mon Feb 14 13:55:42 GMT 2011

On 14/02/11 11:50, Fabio Margarido wrote:
> I've noticed that if I crash (Ctrl+C) the consumer in the middle if
> the message reception flow and then start it up again, there's a gap
> in the messages delivered, i.e., the sequential numbers after the
> restart don't pick up from where they stopped.
> Changing to transaction mode and manual ack didn't seem to help.
> Has anyone seen this behavior before? Am I missing something? How can
> I guarantee that all the messages are delivered?

Note: you must use manual acks. When you ack a message, you are saying 
you have taken responsibility for it (persisted it or whatever). 
RabbitMQ will never redeliver messages you have acked.

Note 2: when redelivering un-acked messages due to a client crash, the 
messages get reinserted at the *beginning* of the queue. Thus you will 
still see gaps in the message sequence, but those messages will be 
delivered later.

Cheers, Simon
Simon MacMullen
Staff Engineer, RabbitMQ
SpringSource, a division of VMware

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