Category: WCF/WF

Yesterday I showed how to deploy the new WCF 4.0 Routing Service within IIS 7.  Today, I’m looking at how to take one of those underlying services we built and consume it from a WCF Workflow Service hosted in AppFabric.

In the previous post, I created a simple WCF service called “HelloServiceMan” which takes a name and spits back a greeting.  In this post, I will use this service completely illogically and only to prove a point.  Yes, I’m too lazy right now to create a new service which creates a more realistic scenario.  What I DO want is to call into my workflow, immediately send a response back, and then go about calling my existing web service.  I’m doing this to show that if my downstream service was down, my workflow (hosted with AppFabric) can be suspended, and then resume once my downstream service comes back online.  Got it?  Cool.

First, we need a WCF Workflow Service app.  In VS 2010, I pick this from the “Workflow” section.

I then added a single class file to this project which holds data contracts for the input and output message of the workflow service.

[DataContract(Namespace="https://seroter.com/Contracts")]
   public class NewOrderRequest
   {
       [DataMember]
       public string ProductId { get; set; }
       [DataMember]
       public string CustomerName { get; set; }
   }

   [DataContract(Namespace = "https://seroter.com/Contracts")]
   public class OrderAckResponse
   {
       [DataMember]
       public string OrderId { get; set; }
   }

Next I added a Service Reference to my existing WCF service.  This is the one that I plan to call from within the workflow service.  Once I have my reference defined, and build my project, a custom Workflow Activity should get added to my Toolbox.

If you’re familiar with building BizTalk orchestrations, then working with the Windows Workflow design interface is fairly intuitive.  Much like an orchestration, the first thing I do here is define my variables.  This includes the default “correlation handle” object which was already there, and then variables representing the input/output of my workflow service, and the request/response messages of my service reference.

Notice that for variables which aren’t explicitly instantiated by receiving messages into the workflow (i.e. initial received message, response from service call) have explicit instantiation in the “Default” column.

Next I sketched out the first part of the workflow which receives the inbound “order request” (defined in the above data contract), sets a tracking number and returns that value to the caller.  Think of when you order a package from an online merchant and they immediately ship you a tracking code while starting their order processing behind the scenes.

Next I call my referenced service by first setting the input variable attribute value, and then using the custom Workflow Activity shape which encapsulates the service request and response (once again, realize that this content of this solution makes no sense, but the principles do).

After building the solution successfully, we can get this deployed to IIS 7 and running in the AppFabric.  After creating an IIS web application which points to this solution, we can right click our new application and choose .NET 4 WCF and WF and then Configure.

On the Workflow Persistence tab, I clicked the Advanced button and made sure that on unhandled errors that I abandon and suspended.

If you are particularly astute, you may notice at the top of the previous image that there’s an error complaining about the net.pipe protocol missing from my Enabled Protocols.  HOWEVER, there is a bug/feature in this current release where you should ignore this and ONLY add net.pipe to the Enabled Protocols at the root web site.  If you put it down at the application level, you get bad things.

So, now I can browse to my workflow service and see a valid service endpoint.

I can call this service from the WCF Test Client, and hopefully I not only get back the immediate response, but also see a successfully completed workflow in the AppFabric console. Note that if you don’t see things showing up in your AppFabric console, check your list of Windows Services and make the sure the Application Server Event Collector is started.

Now, let’s turn off the WCF service application so that our workflow service can’t complete successfully.  After calling the service again, I should still get an immediate response back from my workflow since the response to the caller happens BEFORE the call to the downstream service.  If I check the AppFabric console now, I see this:

What the what??  The workflow didn’t suspend, and it’s in a non-recoverable state.  That’s not good for anybody.  What’s missing is that I never injected a persistence point into my workflow, so it doesn’t have a place to pick up and resume.  The quickest way to fix this is to go back to my workflow, and on the response to the initial request, set the PersistBeforeSend flag so that the workflow forces a persistence point.

After rebuilding the service, and once again shutting down the downstream service, I called my workflow service and got this in my AppFabric console:

Score!  I now have a suspended instance.  After starting my downstream service back up, I can select my suspended instance and resume it.

After resuming the instance, it disappears and goes under the “Completed Instances” bucket.

There you go.  For some reason, I just couldn’t find many examples at all of someone building/hosting/suspending WF 4.0 workflow services.  I know it’s new stuff, but I would have thought there was more out there.  Either way, I learned a few things and now that I’ve done it, it seems simple.  A few days ago, not so much.

I recently had occasion to explore the new WCF 4.0 Routing Service and thought I’d share how I set up a simple solution that demonstrated its capabilities and highlights how to host it within IIS.

[UPDATE: I’ve got a simpler way to do this in a later post that you can find here.]

This new built-in service allows us to put a simple broker in front of our services and route inbound messages based on content, headers, and more.  Problem for me was that every demo I’ve seen of this thing (from PDC, and other places) show simple console hosts for the service and not a more realistic web server host.  This is where I come in.

First off, I need to construct the services that will be fronted by the Routing Service.  In this simple case, I have two services that implement the same contract.  In essence, these services take a name and gender, and spit back the appropriate “hello.”  The service and data contracts look like this:

[ServiceContract]
    public interface IHelloService
    {
        [OperationContract]
        string SayHello(Person p);
    }

    [DataContract]
    public class Person
    {
        private string name;
        private string gender;

        [DataMember]
        public string Name
        {
            get { return name; }
            set { name = value; }
        }

        [DataMember]
        public string Gender
        {
            get { return gender; }
            set { gender = value; }
        }
    }

I then have a “HelloServiceMan” service and “HelloServiceWoman” service which implement this contract.

public class HelloServiceMan : IHelloService
    {

        public string SayHello(Person p)
        {
            return "Hey Mr. " + p.Name;
        }
    }

I’ve leveraged the new default binding capabilities in WCF 4.0 and left my web.config file virtually empty.  After deploying these services to IIS 7.0, I can use the WCF Test Client to prove that the service performs as expected.

Nice.  So now I can add the Routing Service.  Now, what initially perplexed me is that since the Routing Service is self contained, you don’t really have a *.svc file, but then I didn’t know how to build a web project that could host the service.  Thanks to Stephen Thomas (who got code from the great Christian Weyer) I got things working.

You need three total components to get this going.  First, I created a new, Empty ASP.NET Web Application project and added a .NET class file.  This class defines a new ServiceHostFactory class that the Routing Service will use.  That class looks like this:

class CustomServiceHostFactory : ServiceHostFactory
{
    protected override System.ServiceModel.ServiceHost CreateServiceHost(System.Type serviceType, System.Uri[] baseAddresses)
    {
        var host = base.CreateServiceHost(serviceType, baseAddresses);

        var aspnet = host.Description.Behaviors.Find<AspNetCompatibilityRequirementsAttribute>();

        if (aspnet == null)
        {
            aspnet = new AspNetCompatibilityRequirementsAttribute();
            host.Description.Behaviors.Add(aspnet);
        }

        aspnet.RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed;

        return host;
    }
}

Here comes the tricky, but totally logical part.  How do you get the WCF Routing Service instantiated?  Add a global.asax file to the project and add the following code to the Application_Start method:

using System.ServiceModel.Activation;
using System.ServiceModel.Routing;
using System.Web.Routing;

namespace WebRoutingService
{
    public class Global : System.Web.HttpApplication
    {

        protected void Application_Start(object sender, EventArgs e)
        {
            RouteTable.Routes.Add(
               new ServiceRoute("router", new CustomServiceHostFactory(),
                   typeof(RoutingService)));
        }

Here we stand up the Routing Service with a “router” URL extension.  Nice.  The final piece is the web.config file.  Here is where you actually define the Routing Service relationships and filters.  Within the system.serviceModel tags, I defined my client endpoints that the router can call.

<client>
      <endpoint address="http://localhost/FirstWcfService/HelloServiceMan.svc"
          binding="basicHttpBinding" bindingConfiguration="" contract="*"
          name="HelloMan" />
      <endpoint address="http://localhost/FirstWcfService/HelloServiceWoman.svc"
          binding="basicHttpBinding" bindingConfiguration="" contract="*"
          name="HelloWoman" />
    </client>

The Routing Service ASP.NET project does NOT have any references to the actual endpoint services, and you can see here that I ignore the implementation contract.  The router knows as little as possible about the actual endpoints besides the binding and address.

Next we have the brand new “routing” configuration type which identifies the filters used to route the service messages.

<routing>
      <namespaceTable>
        <add prefix="custom" namespace="http://schemas.datacontract.org/2004/07/FirstWcfService"/>
      </namespaceTable>
      <filters>
        <filter name="ManFilter" filterType="XPath" filterData="//custom:Gender = 'Male'"/>
        <filter name="WomanFilter" filterType="XPath" filterData="//custom:Gender = 'Female'"/>
      </filters>
      <filterTables>
        <filterTable name="filterTable1">
          <add filterName="ManFilter" endpointName="HelloMan" priority="0"/>
          <add filterName="WomanFilter" endpointName="HelloWoman" priority="0"/>
        </filterTable>
      </filterTables>
    </routing>

I first added a namespace prefix table, then have a filter collection which, in this case, uses XPath against the inbound message to determine the gender value within the request.  Note that if you want to use a comparison operation such as “<” or “>”, you’ll have to escape it in this string to “&gt;” or “&lt;”.  Finally, I have a filter table which maps a particular filter to which endpoint should be applied.

Finally, I have the service definition and behavior definition.  These both leverage objects and configuration items new to WCF 4.0.  Notice that I’m using the “IRequestReplyRouter” contract since I have a request/reply service being fronted by the Routing Service.

<services>
      <service behaviorConfiguration="RoutingBehavior" name="System.ServiceModel.Routing.RoutingService">
        <endpoint address="" binding="basicHttpBinding" bindingConfiguration=""
          name="RouterEndpoint1" contract="System.ServiceModel.Routing.IRequestReplyRouter" />
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="RoutingBehavior">
          <routing routeOnHeadersOnly="false" filterTableName="filterTable1" />
          <serviceDebug includeExceptionDetailInFaults="true"/>
          <serviceMetadata httpGetEnabled="true" />
        </behavior>
      </serviceBehaviors>
    </behaviors>

Once we build and deploy the service to IIS 7, we can browse it.  Recall that in our global.asax file we defined a URL suffix named “router.”  So, to hit the service, we load our web application and append “router.”

As you’d expect, this WSDL tells us virtually nothing about what data this service accepts.  What you can do from this point is build a service client which points at one of the actual services (e.g. “HelloServiceMan”), but then switch the URL address in the application’s configuration file.  This way, you can still import all the necessary contract definitions, while then switching to leverage the content-based routing service.

So, the Routing Service is pretty cool.  It does a light-weight version of what BizTalk does for routing.  I haven’t played with composite filters and don’t even know if it’s possible to have multiple filter criteria (like you can with a BizTalk Server subscription).  Either way, it’s good to know how to actually deploy this new capability in an enterprise web server instead of a console host.

Anyone else have lessons learned with the Routing Service?