[How to] Reject a message for DLQ

[vitorpmoreira]

Hi,

I was looking into the Reject method that is available for the Consumers and noticed that it calls the Modify on the underlying ReceiverLink and was wondering why this is the behavior that is enforced for a Reject when you can effectively Reject message and it gets sent to the DLQ.

This is helpful for scenarios where you consumed a message and you know that can't/won't do anything with it and you want to reject it but leave it in the DLQ for later analysis.

Best Regards,
Vítor Moreira

[Havret]

Hi Vítor,

Thanks for your question.

You're absolutely right that in certain scenarios—where a message is known to be invalid or cannot be processed—it's desirable to reject it and have it sent directly to the DLQ for analysis.

In our implementation, the Reject method maps to the AMQP Modify outcome (with deliveryFailed = true and undeliverableHere = false), which results in the message being requeued for redelivery. This behavior is intended to support cases where the failure might be transient or retryable.

You can achieve the desired reject-to-DLQ behavior by configuring the address with the max-delivery-attempts option. When the delivery count for a message exceeds this threshold—after repeated rejections—the broker will automatically route it to the DLQ.

I hope that helps,
Krzysztof

[vitorpmoreira]

I got it, but it still needs to go through those max attempts when we know we won't/can't process it.
Would you be open for a new Reject implementation, or a new param, which actually Rejects the message instead of Modifying it?

[Havret]

Yes, I am open to changing the current behavior to better align with the AMQP specification. While it would be a breaking change, I think it would make the API clearer and more consistent.

I’d suggest something along these lines:

void Reject(Message message, string? errorCondition = null, string? errorDescription = null);

void Modify(Message message, bool deliveryFailed = true, bool undeliverableHere = false);

If you're happy with this design, feel free to submit a PR — I’d be glad to review it.