Different Retry policies for different messages in MSMQ

Question

We have a requirement for an API, which allows asynchronous updates via a MSMQ message queue, that I'm putting together which will allow the developer consuming the API to specify different retry policies per message. So a high priority client system, e.g. for sales will submit all messages with 5 delivery attempts (retries) and 15 minutes between each attempt, whereas a low priority client system, e.g. back-end mail shot system will allow users to update their marketing preferences, submitting messages with 3 retries and an hour between each attempt.

Is there a way in the System.Messaging MSMQ (version 3 or 4) implementation to specify number of retries, retry delay and things like whether messages are sent to a dead letter queue or just deleted? (and if so, how?)

I would be open to using other messaging frameworks if they fulfilled this requirement.

Answer 1

Is there a way in the System.Messaging MSMQ (version 3 or 4) implementation to specify number of retries

Depending on which operating system/msmq version you're using, specifying retry semantics is highly sophisticated in WCF. The following is for Windows 2008 and MSMQ4 using a transactional queue.

The main setting on the binding is called MaxRetryCycles. One retry cycle is an attempt to successfully read a message from a queue and process it inside the handling method. This "attempt" can actually be made up of multiple attempts, as defined by the msmq binding property ReceiveRetryCount. ReceiveRetryCount is the number of times an application will try to read the message and process it before rolling back the de-queue transaction. This marks the end of one retry cycle.

You can also introduce a delay in between cycles with the RetryCycleDelay property.

A more complicated consideration is what to do with the messages which fail even after multiple retry cycles.

allow the developer consuming the API to specify different retry policies per message

I am not sure how you could do this with MSMQ - as far as I'm aware it's only possible to set retry semantics on a per-endpoint basis. If you're using transactions then you can't even allow API users to set the priority of the messages being sent (transactional queues guarantee delivery in order).

The only thing you could do is host a another instance of your API as high-priority and one for low priority. These could be hosted on different environments, and this has the added benefit that low priority messages won't be competing for system resources with high priority messages.

Hope this helps.