Dead Letter Queue and Poison Queues

Question

I understand the difference between Dead Letter Queue and Poison Queue. I will be speaking in the context of transactions and durability.

DLQ: Client sends message. MSMQ is not able to deliver the message. Message remains in queue, waiting to be sent to the destination queue.

PQ: Message is successfully delivered. WCF service processes the message. Some error occured during the WCF operations. Message is placed in the poison queue.

(please correct me if I am wrong above)

Now, if the WCF Service encounters an error, and with the transaction scope in place (attribute), then how does it place the message in the poison queue or does this have to be developed? if it needs to be developed then how is it done? What about processing poison messages? Is there a way to place them back in the queue for processing again? How is it determined if the message is poison? For example, an operation in WCF may encounter an error but can recover from it.

Answer 1

You can read more about Poison Message Handling on MSDN More about the MSMQ on MSDN - How to: Exchange Messages with WCF Endpoints and Message Queuing Applications

"When the service reads messages from the target queue under a transaction, the service may fail to process the message for various reasons. The message is then put back into the queue to be read again. To deal with messages that fail repeatedly, a set of poison-message handling properties can be configured in the binding. There are four properties: ReceiveRetryCount, MaxRetryCycles, RetryCycleDelay, and ReceiveErrorHandling. "

Answer 2

Only Message Queuing places messages in dead-letter queues. Applications can only read and delete messages in dead-letter queues.