[rabbitmq-discuss] Lack of Ack, Failure and Re-delivery

[Bell, Paul M.]

Hi,

Suppose I have a producer on NodeP, a broker on NodeB, and a consumer on NodeC. Suppose further that explicit acks are required (i.e., if I've understood the docs, that "noack" is not in effect) and that after consuming a message from the queue, NodeC.consumer dispatches some other work in order to process that message. IOW: NodeC.consumer doesn't respond immediately with an ack.

So, from NodeB.broker's point of view, the message has been moved from the exchange to the queue, consumed, but not yet ack-ed.

What will happen under these two scenarios:

1. NodeB.broker bounces - when broker restarts what will he do with un-acked messages that have been delivered to queue and haven't been ack-ed; e.g., will these be again delivered to the queue?


2. NodeC.consumer bounces - when consumer restarts is there any way he can again consume the un-acked message, and begin again the work that this message represents? (I suppose that NodeB.broker might be implicated here because it might detect the loss of connection to the NodeC.consumer....).


When I say "bounces," I mean at a minimum that the application (broker, consumer) crashed and restarted. But I am also interested in the case where the node's OS is for whatever reason rebooted. Perhaps it looks no different.

Thanks for your help.

-Paul



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