When multiple consumers are consuming from a single, logical, HA queue
mirrored across N nodes, is there any potential for duplicate messages
beyond the documented case when a slave is promoted to master?

I am thinking specifically about the case when consumer A is consuming
from slave queue on node X and consumer B is consuming from slave
queue on node Y. From very superficial testing with noAck=true, it
appears as though the master queue only delivers a single msg to
either A or B as desired, yet I'm assuming it must notify the other
queue of the msgs existence. Is this in fact correct, or must I be
concerned with the msg arriving at BOTH A and B. Does this behavior
change when noAck=false since master is no longer Acking the message?

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  • Simon MacMullen at Jan 12, 2012 at 4:15 pm

    On 12/01/12 16:12, Dave Stevens wrote:
    I am thinking specifically about the case when consumer A is consuming
    from slave queue on node X and consumer B is consuming from slave
    queue on node Y.
    This doesn't really happen.

    A can consume from node X, and B from node Y, *but* internally to the
    cluster both are connected to the master node. That's pretty much what
    makes it the master. The reason for this is exactly the concern you
    raise :-)

    So publishes go to all nodes, consumes just come from the master (which
    then informs the slaves so they drop the messages).

    Cheers, Simon

    --
    Simon MacMullen
    RabbitMQ, VMware

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postedJan 12, '12 at 4:12p
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