Programming WCF Services, 2nd Edition

Queued Services

1. On the client, always verify that the queue (and a dead-letter queue, when applicable) is available before calling the queued service. Use QueuedServiceHelper.VerifyQueues( ) for this purpose.

2. Always verify that the queue is available when hosting a queued service (this is done automatically by ServiceHost<T>).

3. Except in isolated scenarios, avoid designing the same service to work both queued and non-queued.

4. The service should participate in the playback transaction.

5. When participating in the playback transaction, avoid lengthy processing in the queued service.

6. Avoid sessionful queued services.

7. When using a singleton queued service, use a volatile resource manager to manage the singleton state.

8. When using a per-call queued service, explicitly configure the contract and the service to be per-call and sessionless:

   [ServiceContract(SessionMode = SessionMode.NotAllowed)]
   interface IMyContract
   {...}
   
   [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
   class MyService : IMyContract
   {...}

9. Always explicitly set contracts on a queued singleton to disallow sessions:

   [ServiceContract(SessionMode = SessionMode.NotAllowed)]
   interface IMyContract
   {...}
   
   [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
   class MyService : IMyContract
   {...}

10. The client should call a queued service inside a transaction.

11. On the client side, do not store a queued service proxy in a member variable.

12. Avoid relatively short values of TimeToLive, as they negate the justification for a ...