Reputation: 33
I want to read the payload, or messageId of unacknowledged messages in a RabbitMQ queue. Is this possible?
The reason I want to do so is I trying to use RabbitMQ dead letter feature to build a cycle to for auto-generating message periodically. Briefly, create two queues - work queue and delay queue.
I want to make sure there is no missing or duplicate messages in the cycle since I do not want missing job or double doing the job at the same time. However, there is tiny tiny chance duplicate messages can happen. Below show the consumer first write back the message to delay queue, and acknowledge the work queue. If the thread crashes right between below two lines, the message would be in the delay queue, and Rabbit republish the message again into work queue. The end up with duplicate messages in the cycle.
channel.basicPublish(DELAY_EXCHANGE, "", null, message.getBytes());
channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false);
To prevent above, I want to add a dog watch logic after above two line:
Check the total number of messages in the cycle (total messages in both queues) to see whether it is equal my expected number (I expected the number less 10);
If the number does not matches, I want to figure out which one is missing or which one is duplicate, then deal with it. I do not care about the sequence of those messages, or the frequency has been disturbed since this is a really really edge case to consider. I can easily retrieve those messages which are ready and requeue them. But the problem is how to deal with those unacknowledged messages?
Thank you very much in advance!
Roy
Upvotes: 3
Views: 8366
Reputation: 12869
It's not possible to read unacknowledged messages from other context the original messages was consumed and held as un-aked.
Upvotes: 2