Dead-letterred messages not getting requeue to original queue after ttl

Question

I have planned to delay the processing of messages in queue by following these two links link1 link2. So, as suggested in the link. I have declared the original queue with the x-dead-letter-exchange and x-dead-letter-routing-key args. Which published the messages to the so called dead-letter-queue when message either failed to get processed by consumer or ttl happen or queue length exceed. Now in the dead-letter-queue similar args have been set along with the ttl parameter. Which is suppose to republish the messages to the original queue after ttl exceed. But the problem is it is dropping all the messages.

Moreover, there is a catch here. If i explicitly publish the failed messages from original queue to dead-letter-queue. Then after ttl it republish the messages to the original queue. Why is it so and how do i make it work. So that dead-letter-queue republishes the messages to the original queue instead of dropping. I am using RabbitMQ 3.0.0.

FYI, I have created both the exchanges of direct type along with the routing key

Answer 1

When a queue has a TTL setup that means that messages in that queue will be sent to the dead-letter-exchange (DLX) associated with that queue after the TTL has expired. If the queue has no DLX assigned then the messages go into the bit bucket.

If you want to send messages back into the queue from which they came to be re-processed then you need to have the setup that I described in this post.

Dead-lettering dead-lettered messages in RabbitMQ

Hopefully that is helpful for you.

Answer 2

Suppose your original exchange is x.notification and is bind to the queue q.A with routing queue A. And your dead-letter-exchange namae is dlx.notification. Now in the queue q.A set ttl the time interval you want to wait and dead-lleter-exchange as dlx.notification. Now create another queue dlq.A to route the expired message from dlx.notification into dlq.A with routing key "A". I think thats all you need to do to achive your goal.