[rabbitmq-discuss] AutoAck issue
tim at rabbitmq.com
Thu May 30 13:57:05 BST 2013
On 30 May 2013, at 13:38, Adam Morgan wrote:
> I am trying to implement guaranteed delivery in my system but am having issues around acknowledgements being sent automagically.
> I have turned on channel.confirmSelect() on publishing channel.
> I have added my publisher as a ConfirmListener to the publishing channel.
> I very clearly have autoAck=false in my basicConsume() call.
> Despite this, my publisher/ConfirmListener is receiving an ack as soon as my consumer receives the message. Repeat, my consumer client has NOT yet called basicAck(), but my publisher/ConfirmListener callback is made.
> Is there something else I should be doing? Is there other configuration I might be doing that would interfere with this?
I think you're getting confused between confirms and ACKs. Confirms sent from the broker to a producer are orthogonal to ACKs sent from a consumer to the broker. When the broker has accepted responsibility for a message, it will send a confirm _in the form of an ACK_ to the publisher. Now "accepted responsibility" means various things depending on you configuration - see https://www.rabbitmq.com/reliability.html for details - but in general, if the broker is able to immediately deliver a message to an active consumer, then it has certainly discharged it's responsibility "to the producer" for handling that message, therefore it sends a confirm (i.e., an ACK) to the producer. This is completely independent of what the consumer does with the message - it might NACK/REJECT it but that's "the broker's problem to handle" and not the producer's. Once the broker sends a confirm, *it* is responsible for the message.
What you appear to be looking for is a kind of RPC (in terms of synchronicity) between producer and consumer, and /that/ is not what messaging systems typically deliver, opting instead for a de-coupled view of the interaction via an intermediary (i.e., the broker). Notably, even JMS transactions do *not* coordinate over both the producer and consumer, but handle only one perspective or the other.
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