Hosting workflow services in Windows Azure

Since the latest release of the Windows Azure Development Kit (June), Azure provides support for .NET 4 applications, which is a real important step from the point of adoption, I believe.

The first thing we wanted to try was to host a XAMLX Workflow Service in a web role on Azure.

Example workflow service

I created a standard Workflow Service that accepted two parameters, on  one operation (Multiply) and returns the result of the multiplication to the client.  This service was called Calc.xamlx.

These are the steps I followed to make my service available.  I added the exceptions, because that’s typically what users will search for J

Enable visualization of errors

Standard behavior of web roles, is to hide the exception for the users, browsing to a web page.  Therefore, it is advised to add the following in the system.web section of the web.config:

<customErrors mode="Off"/>

Configure handler for Workflow Services

The typical error one would get, when just adding the Workflow Service to your web role and trying to browse it, is the following:

The requested url '/calc.xamlx' hosts a XAML document with root element type 'System.ServiceModel.Activities.WorkflowService'; but no http handler is configured for this root element type. Please check the configuration file and make sure that the 'system.xaml.hosting/httpHandlers' section exists and a http handler is configured for root element type 'System.ServiceModel.Activities.WorkflowService'.

We need to specify the correct HTTP handler that needs to be used for XAMLX files.  Therefore, we link the workflow services and activities to the correct Workflow Service ServiceModel handler.

To solve this, the following needs to be added to the web.config.

 

<configuration>
       <configSections>
             <sectionGroup name="system.xaml.hosting" type="System.Xaml.Hosting.Configuration.XamlHostingSectionGroup, System.Xaml.Hosting, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">
                   <section name="httpHandlers" type="System.Xaml.Hosting.Configuration.XamlHostingSection, System.Xaml.Hosting, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
             sectionGroup>
       configSections>
       <!-- Removed other sections for clarity -–>
       <system.xaml.hosting>
             <httpHandlers>
                    <add xamlRootElementType="System.ServiceModel.Activities.WorkflowService, System.ServiceModel.Activities, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" httpHandlerType="System.ServiceModel.Activities.Activation.ServiceModelActivitiesActivationHandlerAsync, System.ServiceModel.Activation, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
                    <add xamlRootElementType="System.Activities.Activity, System.Activities, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" httpHandlerType="System.ServiceModel.Activities.Activation.ServiceModelActivitiesActivationHandlerAsync, System.ServiceModel.Activation, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
             httpHandlers>
       system.xaml.hosting>
configuration>

Enabling metadata exposure of the workflow service

To enable consumers of our workflow service to generate their proxy classes, we want to expose the WSDL metadata of the service, by providing the following configuration section in the web.config.

Notice the simplicity of configuration, compared to WCF3.5.  Making use of the default behaviors, allows us to only specify what we want to override.

<system.serviceModel>
       <serviceHostingEnvironment multipleSiteBindingsEnabled="true" >
             <serviceActivations>
                    <add relativeAddress="~/Calc.xamlx" service="Calc.xamlx"  factory="System.ServiceModel.Activities.Activation.WorkflowServiceHostFactory"/>
             serviceActivations>
       serviceHostingEnvironment>
       <behaviors>
             <serviceBehaviors>
                    <behavior>
                           <serviceMetadata httpGetEnabled="true"/>
                    behavior>
             serviceBehaviors>
       behaviors>
system.serviceModel>

Testing and publishing

After successfully testing locally in the Azure Development Fabric, I uploaded and deployed the package, using the new Tools in Visual Studio to my Azure test account.

Author : Sam Vanhoutte, CODit

Taken from: http://www.codit.eu/Blog/post/2010/06/17/Hosting-workflow-services-in-Windows-Azure.aspx