WCF Queued Dual HTTP Request Response Router

There are a lot of examples available for how to make WCF-based publish/subscribe messaging solutions, but not very many thay provides a simple queued dual HTTP request-response router. IDesign provides the queued Response Service from Juval Löwy's book Programming WCF Services, which provides a feature rich set of WCF goodies. Recommended. I've used it in combination with Sasha Goldshtein's Generic Forwarding Router to create a dual channel queued router.

The router container uses HTTP endpoints externally to interact with consumers, and MSMQ queues internally to talk to the service providers. This gives fewer queues to manage and monitor, and the consumers need not know anything about MSMQ.

The message forwarding ChannelFactory is cached for best performance. Read more about Channel and ChannelFactory caching in Wenlong Dong's post Performance Improvement for WCF Client Proxy Creation in .NET 3.5 and Best Practices.

Some useful resources related to making this router work:

• MSDN mag articles "Building a WCF router" part 1 and part 2
• Article series "MSMQ, WCF and IIS: Getting them to play nice" part 1, part 2 and part 3
• MSMQ activation of WAS
• Poison message handling in MSMQ 4.0 (and in MSMQ 3.0)
• NetMsmqBinding dead letter queues
• Correctly disposing WCF channels: Dispose extension method
• Really disabling the Visual Studio WCF Service Host, look for the <FlavorProperties/AutoStart> element

Note the poorly documented requirement that the WAS activated service endpoint path must be reflected in the MSMQ queue name:

<add key="targetQueueName" value=".\private$\ServiceModelSamples/service.svc" />

<endpoint address=
"net.msmq://localhost/private/servicemodelsamples/service.svc"

Failure to adhere to this convention will prevent messages added to the queue from automatically activating the WAS-hosted WCF service. Also ensure that the WAS app-pool identity has access rights on the queues.

Download the router example code here. The code is provided 'as-is' with no warranties and confers no rights. This example requires Windows Process Activation Service (Vista/WinServer2008), MSMQ 4.0 and .NET 3.0 WCF Non-HTTP Activation to be installed.