The use of x-delivery-count, x-acquired-count and delivery limit

[Gary]

Using Version 4.3.2 I've configured a quorum queue with a consumer timeout,  delivery limit and a delayed retry. Errors are handled as I expect with messages being re-queued with a delay.

A problem arises for me with trying to dead-letter messages should X number of attempts (attempts in my context is processing of the message) be made. According to the docs when is delivery count incremented? not all failures will increment the 'delivery-count', specifically consumer timeouts.

This is important for my application because I can only configure dead-lettering based on the 'delivery-count' (unless I am mistaken), but I want to be able to dead letter a message following any failure.

Is there a way around this and I'm not sure why/what the ultimate difference is between x-delivery-count and x-acquired-count is and why I cannot dead-letter based on the acquired-count.?

Gary

[Karl Nilsson]

Hi Gary,

We've discussed it internally and we can't recall what the reasoning was for not updating the delivery-count when a consumer timeout triggers. Intuitively I feel it should. We will look at changing this for RabbitMQ 4.4.

delivery-count is meant to track any failed deliveries - what can be reliably observed by the broker as a failure isn't always 100% clear. Acquired-count just tracks any message acquisition, i.e. assignment to a consumer irrespective of whether it was returned deliberately or as part of a potential processing failure.

Cheers

Karl Nilsson

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[Gary]

Thanks for your response Karl and I appreciate this being looked at.

Given that effort was spent documenting that a consumer-timeout won't increment the delivery count I would hazard a guess there was a good reason for it (obviously I'm no expert nor am I trying to tell you how to do your job of course!). It could  also be that other users rely on the current behaviour. What if dead-lettering could be also based on the acquired count, would that be a 'safer' change?

Regards

Gary