RabbitMQ basic.get and acknowledgement

Question

I\'m invoking:

GetResponse response = channel.basicGet(\"some.queue\", false); // no auto-ack
....
channel.basicAck(deliveryTag, ...);

Howe

Answer 1

I'm doing the following to mimic Delaying the ack:

At consumption time

1. Get(consume) the message form the initial Queue.
2. Create a "PendingAck_123456" Queue.
   123456 is a unique id of the message.
   Set the following properties
   • x-message-ttl (to requeue after timeout)
   • x-expires (to make sure the temp queue will be deleted)
   • x-dead-letter-exchange and x-deal-letter-routing-key to requeue to the initial Queue upon TTL expiration.
3. Publish the message Pending ack to this "PendingAck_123456" Queue
4. Ack the message to delete it from the initial queue

At Acknowledge time

1. Calculate Queue Name from Message Id and Get from the "PendingAck_123456" Queue
2. Acknowledge it (no need to call .getBody() ).
   That'll delete it from this pending queue, preventing the TTL to requeue it

Remarks

• A Queue for only 1 message.. Is that an issue if there are a lot of such Queues ?
• A requeued message will be sent at the queue input side.. not at the queue output (as would do a real ack).. There is an impact on the messages order.
• Message is copied by the application to the Pending Queue.. This is an additional step that may have impacts on the overall performance.
• To mimic a Nack/Reject, you you may want to Copy the message to the Initial Queue, and Ack it from the PendingAck queue. By default, the TTL would do it (later).