Durable Duplex

This topic applies to Windows Workflow Foundation 4 (WF4).

This sample demonstrates how to set up and configure durable duplex message exchange using the messaging activities in Windows Workflow Foundation (WF). A durable duplex message exchange is a two-way message exchange that takes place over a long period of time. The lifetime of the message exchange may be longer than the lifetime of the communication channel and the in-memory lifetime of the service instances.

Sample Details

In this sample, two Windows Communication Foundation (WCF) services implemented using Windows Workflow Foundation are configured to have a durable duplex message exchange. The durable duplex message exchange is composed from two one-way messages sent over MSMQ and correlated using .NET Context Exchange. The messages are sent using the Send and Receive messaging activities. .NET Context Exchange is use to specify the callback address on the sent messages. Both services are hosted using Windows Process Activation Services (WAS) and are configured to enable persistence of the services instances.

The first service (Service1.xamlx) sends a request to the send service (Service2.xamlx) to do some work. Once the work is completed, Service2.xamlx sends a notification back to Service1.xamlx to indicate that the work has been completed. A workflow console application sets up the queues that the services are listening on and sends the initial Start message to activate Service1.xamlx. Once Service1.xamlx receives the notification from Service2.xamlx that the requested work has been completed, Service1.xamlx saves the result to an XML file. While waiting for the callback message, Service1.xamlx persists its instance state using the default WorkflowIdleBehavior. Service2.xamlx persists its instance state as part of completing the work requested by Service1.xamlx.

To configure the services to use .NET Context Exchange over MSMQ, both services are configured to use a custom binding that consists of the ContextBindingElement and the MsmqTransportBindingElement. A callback address is specified with the ContextBindingElement and is included in a callback context header with all messages sent using a custom binding. The following code example defines the custom binding.

<configuration>
     <system.serviceModel>
          …
          <bindings>
               <customBinding>
                    <binding name="netMsmqContextBinding">
                         <context clientCallbackAddress="net.msmq://localhost/private/DurableDuplex/Service1.xamlx"/>
                         <msmqTransport exactlyOnce="False">
                              <msmqTransportSecurity msmqAuthenticationMode="None" msmqProtectionLevel="None"/>
                         </msmqTransport>
                    </binding>
               </customBinding>
          </bindings>
          …
     </system.serviceModel>
</configuration>

The message sent by Service1.xamlx to Service2.xamlx is sent using a client endpoint configured with the address of Service2.xamlx and the custom binding defined previously. The callback from Service2.xamlx to Service1.xamlx is sent using a client endpoint with no explicitly configured address because the address is taken from the callback context sent by Service1.xamlx. The following code example defines the client endpoints.

<?xml version="1.0"?>
<configuration>
     <system.serviceModel>
          …
          <client>
               <endpoint address="net.msmq://localhost/private/DurableDuplex/Service2.xamlx" binding="customBinding" bindingConfiguration="netMsmqContextBinding" contract="IDoWork"/>
               <endpoint binding="customBinding" bindingConfiguration="netMsmqContextBinding" contract="INotify"/>
          </client>
          …
     </system.serviceModel>
</configuration>

The following code example exposes endpoints using this custom binding by changing the default protocol mapping for net.msmq base addresses to use this custom binding.

<configuration>
     <system.serviceModel>
          <protocolMapping>
               <add scheme="net.msmq" binding="customBinding" bindingConfiguration="netMsmqContextBinding"/>
          </protocolMapping>
          …
     </system.serviceModel>
</configuration>

The following code example enables persistence for both services by adding the SqlWorkflowInstanceStoreBehavior behavior to both services and specifying the connection string for the persistence database.

<?xml version="1.0"?>
<configuration>
    <system.serviceModel>
          …
          <behaviors>
               <serviceBehaviors>
                    <behavior>
                         <serviceDebug includeExceptionDetailInFaults="True"/>
                         <serviceMetadata httpGetEnabled="True"/>
                         <sqlWorkflowInstanceStore connectionString="Data Source=.\SQLEXPRESS;Initial Catalog=DefaultSampleStore;Integrated Security=True"/>
                    </behavior>
               </serviceBehaviors>
          </behaviors>
     </system.serviceModel>
</configuration>

System Requirements

This sample requires the following components.

1. Internet Information Services.

2. Internet Information Services -> IIS 6.0 Management Compatibility -> IIS Metabase and IIS 6.0 configuration compatibility.

3. World Wide Web Services -> Application Development Features -> ASP.NET.

4. Microsoft Message Queues (MSMQ) Server.

To use this sample

1. Set up the persistence database and the results directory.

   1. Open a Visual Studio 2010 command prompt.

   2. Navigate to the folder for this sample and run Setup.cmd.

2. Set up the virtual application.

   1. From a Visual Studio 2010 command prompt, register ASP.NET by running the following command.

      aspnet_regiis -i
      

   2. Run Visual Studio 2010 with administrator permissions by right-clicking Visual Studio 2010 and selecting Run as administrator.

   3. Using Visual Studio 2010, open the DurableDuplex.sln file.

3. Set up the service queues.

   1. To run the DurableDuplex client, press F5.

   2. Open the Computer Management console by running Compmgmt.msc from a command prompt.

   3. Expand Service and Applications, Message Queuing. Private Queues.

   4. Right-click the durableduplex/service1.xamlx and durableduplex/service2.xamlx queues and select Properties.

   5. Select the Security tab and allow Everyone Receive Message, Peek Message and Send Message permissions for both queues.

   6. Open Internet Information Services (IIS) Manager.

   7. Browse to Server, Sites, Default Web site, private, Durable Duplex and select Advanced Options.

   8. Change the Enabled Protocols to http,net.msmq.

4. Run the sample.

   1. Browse to https://localhost/private/durableduplex/service1.xamlx and https://localhost/private/durableduplex/service2.xamlx to ensure that both services are running.

   2. Press F5 to run DurableDuplexClient.

      When the durable duplex message exchange completes a result.xml file is saved to the C:\Inbox folder and contains the result of the message exchange.

To cleanup (Optional)

1. Run Cleanup.cmd.

   1. Open a Visual Studio 2010 command prompt.

   2. Navigate to the folder for this sample and run Cleanup.cmd.

2. Remove the virtual application for the services.

   1. Open the Internet Information Services (IIS) Manager by running Inetmgr.exe from a command prompt.

   2. Browse to the default Web site and remove the private virtual directory.

3. Remove the queues set up for this sample.

   1. Open the Computer Management console by running Compmgmt.msc from a command prompt.

   2. Expand Service and Applications, Message Queuing, Private Queues.

   3. Delete the durableduplex/service1.xamlx and durableduplex/service2.xamlx queues.

4. Remove the C:\Inbox directory.

Note:

The samples may already be installed on your machine. Check for the following (default) directory before continuing. <InstallDrive>:\WF_WCF_Samples If this directory does not exist, go to Windows Communication Foundation (WCF) and Windows Workflow Foundation (WF) Samples for .NET Framework 4 to download all Windows Communication Foundation (WCF) and WF samples. This sample is located in the following directory. <InstallDrive>:\WF_WCF_Samples\WF\Basic\Services\DurableDuplex