[rabbitmq-discuss] Read all, ack later?

[Simon MacMullen]

It's not an awful thing to do. The cost of an unacked message varies 
(depending on whether it's paged out etc) but is always somewhat higher 
than that of a "ready" message. And requeuing a ton of unacked messages 
can be expensive (particularly if a lot of them are paged out). Finally, 
the delivery tags of unacked messages are always held in memory and 
can't be paged out.

So it depends a bit. I would be wary of doing it (at least I would want 
to do my own performance tests) if the queue was not expected to fit in 
memory. Of course, doing your own performance tests is always a good 
idea :-)

Cheers, Simon

On 11/11/2013 10:52AM, RocknrollArmy wrote:
> Hello,
>
> is it a valid scenario for RabbitMQ to have a queue with persisted
> messages, where a consumer first wants to read all messages from the queue,
> but do the ack for all or none of them later on?
>
> It's about keeping messages in a queue until some consumer criteria
> decides that all messages needed are received. If the criteria fails,
> the connection just dies and the messages would remain in the queue
> until a new message arrives and a new consumer connects and does the
> check again.
>
> Not sure if this is generally a good/bad idea or a use case where a
> queue is the right tool.
>
> Any thoughts on this?
>
> Best regards,
>
> Daniel
>
>
>
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-- 
Simon MacMullen
RabbitMQ, Pivotal