Friday, 24 February 2012

Wcf Service In Windows Azure WorkerRole

Worker roles are mainly used for backgroung processes in windows azure.We can host WCF services in worker role.
->Create new azure project and add new workerrole project.
->Open  ServiceDefinition.csdef file add new endpoint in workerrole tag.

      <InputEndpoint name="Rest" protocol="http" port="80" />

->Add new IService interface.
Service Interface:
    public interface IService
        string SayHello(string name);

->Add new Service class and implement IService interface.

Service Implementation:
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
    public class Service : IService
        public string SayHello(string name)
            return "Hello " + name;
->Open WorkerRole.cs class,create serviceHost varaible
 and add CreateServiceHost method to host our Wcf REST service.

//Srvice host varible.
private ServiceHost serviceHost;

private void CreateServiceHost()
   //Url of service.
   Uri httpUri = new Uri(String.Format("http://{0}/{1}", RoleEnvironment.CurrentRoleInstance.InstanceEndpoints["Rest"].IPEndpoint.ToString(), "Rest"));

   //Assign url to service host.
   serviceHost = new ServiceHost(typeof(Service), httpUri);

   //Adding endpoint for REST service.
   ServiceEndpoint ep = serviceHost.AddServiceEndpoint(typeof(IService), new WebHttpBinding(), "");

   //Adding behavior for REST service.
   ep.Behaviors.Add(new WebHttpBehavior() { HelpEnabled = true });

   //Open the service host  to start listening for messages.


->Call CreateServiceHost function in OnStart() method.

If you follow all these steps and upload it then you got error like below.
HTTP could not register URL http://+:80/Rest/. Your process does not have access rights to this namespace (see for details). Source:System.ServiceModel.
Solution to this problem is find out the port it needs to open and give the workerrole permission to open the appropriate port.
->Create new console project PortDetect and configure Target framework as 3.5.
->Open Program.cs file and add below code which is used to detect the port and assign permission to open the appropriate port.

class Program
   static void Main(string[] args)
            Process.Start("netsh", string.Format("http add urlacl url=http://+:{0}/Rest user=everyone listen=yes delegate=yes",

 ->Build the project and get the  executable into you workerrole project.

->Set the Copy to Output Directory property of  executable to Copy Always.

-> Open  ServiceDefinition.csdef file specify PortDetect.exe as a startup task.

    <Task commandLine="PortDetect.exe" executionContext="elevated" taskType="simple">

That’s it now you can access the RestService  which is hosted(at port 80) on workerrole.

Let me know, if you have any feedback. Mail me for source code. Enjoy reading my articles…

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