Supported Bindings

• Task Queues (Work Queues)

##Task Queues

Task queues use the RabbitMQTaskQueueBinding binding and is based of the Work Queues example but have the following difference(s).

• Messages are acknowledged as soon as they're deserialized to a System.ServiceModel.Channels.Message
• A load balancer/throttle can be used to prevent processing of messages on the RabbitMQ queues.

The RabbitMQTaskQueueBinding binding supports both session and sessionless services and callback contracts can be uses with sessions. Load balancing is performed by calling the IDequeueThrottler.Throttle method before dequeuing a message. The method doesn't need to return immediately and is given a cancellation token when the method need the call has timed out or the channel needs to be closed.

The bindings can be created either in configuration or in code. Below is a sample server and client config

    <?xml version="1.0" encoding="utf-8" ?>
    <configuration>
    <system.serviceModel>
    <extensions>
      <bindingExtensions>
        <add name="rabbitMQTaskQueue" type="HB.RabbitMQ.ServiceModel.TaskQueue.RabbitMQTaskQueueBindingElementCollection, HB.RabbitMQ.ServiceModel"/>
      </bindingExtensions>
    </extensions>
    <bindings>
      <rabbitMQTaskQueue>
        <binding/>
      </rabbitMQTaskQueue>
    </bindings>
    <services>
      <service name="ConsoleServer.SimpleService">
        <endpoint address="hb.rmqtq://localhost:5672/Contracts.ISimpleService/" binding="rabbitMQTaskQueue" contract="Contracts.ISimpleService"/>
      </service>
    </services>
</system.serviceModel></configurarion>

    <?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <system.serviceModel>
    <extensions>
      <bindingExtensions>
        <add name="rabbitMQTaskQueue" type="HB.RabbitMQ.ServiceModel.TaskQueue.RabbitMQTaskQueueBindingElementCollection, HB.RabbitMQ.ServiceModel"/>
      </bindingExtensions>
    </extensions>
    <bindings>
      <rabbitMQTaskQueue>
        <binding/>
      </rabbitMQTaskQueue>
    </bindings>
    <client>
      <endpoint name="SimpleService" address="hb.rmqtq://localhost:5672/Contracts.ISimpleService/" binding="rabbitMQTaskQueue" contract="Contracts.ISimpleService" />
    </client>
  </system.serviceModel>
</configuration>

The URI for the service is in the following format. hb.rmqtq://QUEUE_NAME where QUEUE_NAME is the name of the queue that the WCF services will read from. The following settings can be passed in query string entries.

• exchange: The name of the rabbit MQ exchange the queue will be created on.
• durable: Sets if the queue will be created as durable. The default value is true.
• deleteonclose: Set to true to delete the queue when the channel is closed. The default value is false.
• ttl: A timespan that sets the queue ttl. The default value is null which indicates a ttl will not be set on the queue.