Mark message as failed when fail to process

[jairhenrique]

Mark message as failed when actor raises an Exception.

On self.consumers[message.queue_name].post_process_message(message) the method nack will be called.

This change will enable refactor on dramatiq_sqs to skip message delete and redrive message to dlq. Bogdanp/dramatiq_sqs#10 (comment)

[spumer]

Without that fix we have incorrect behaviour in Retries middleware, when enqueue to DELAY queue failed we silently ACK message and lose it

@Bogdanp

[Bogdanp]

I don't think nacking here is the right solution, since that would cause the same message to be redelivered later by the Redis and RMQ backends.

[spumer]

It's would not be redelivered since it's acked.

Steps:

• processing in actor failed
• retry middleware try to delay (in after_process_message hook)
• delay failed (in after_process_message hook)
• message acked as processed

As result we have error but no have message in dead letter queue or delay queue.

I mean if exception raised in this line, when Retries middleware try to enqueue message:

dramatiq/dramatiq/worker.py

Line 517 in 5ed539c

self.broker.emit_after("process_message", message, exception=e)

Above fix does not help, it's right. But problem is real. We have workaround where we catch exception in retry middleware and mark message as failed.

We can open new issue for that