Question

I have a MVC-app that has a controller with an action that is supposed to expose data from the latest message in a queue (msmq). I have added a private queue on my local machine. I want the application to automatically receive a message from the queue when one is added. For this i am using msmqIntegrationBinding on a WCF-service that has been added to the application. The method that takes the message in the contract i then supposed to save the message in the application cache so that it can be accessed when a client asks for the latest data.

The challenge I now face is that when I add a message to the queue, it’s not being picked up by the WCF-service. I need guidance at what I might be doing wrong or feedback on my approach. Please help.

The following is the endpoint-config for the WCF-service:

<bindings>
<msmqIntegrationBinding>
  <binding name="MsmqBinding">
    <security mode="None" />
  </binding>
</msmqIntegrationBinding>
</bindings>

<services>
  <service name="TestApp.Web.Service.QueueMessageReceiver">
    <endpoint address="msmq.formatname:DIRECT=OS:.\private$\testsmessagequeue"
                      binding="msmqIntegrationBinding"
                      bindingConfiguration="MsmqBinding"
                      contract="TestApp.Web.Service.IQueueMessageReceiver" />
  </service>
</services>

And the following code is from the QueueMessageReceiver.cs WCF-service:

public class QueueMessageReceiver : IQueueMessageReceiver
{
    private static readonly XmlSerializer Serializer = new XmlSerializer(typeof(ScrewInfoModel));

    [OperationBehavior(TransactionScopeRequired = true, TransactionAutoComplete = true)]
    public void PutScrewInfoMessage(System.ServiceModel.MsmqIntegration.MsmqMessage<System.Xml.XmlDocument> msg)
    {
        CacheScrewInfoModelFromScrewInfoXmlDoc(msg.Body);
    }

    private static void CacheScrewInfoModelFromScrewInfoXmlDoc(XmlNode screwInfoXmlDoc)
    {
        var reader = new StringReader(screwInfoXmlDoc.InnerXml);
        var screwInfoModel = (ScrewInfoModel)Serializer.Deserialize(reader);
        Common.Utils.CacheScrewInfo(screwInfoModel);
    }
}

And here is the Interface for the WCF:

[ServiceContract]
public interface IQueueMessageReceiver
{
    [OperationContract(IsOneWay = true, Action = "*")]
    void PutScrewInfoMessage(MsmqMessage<XmlDocument> msg);
}

Answer 1

Try changing your operation contract to

void PutScrewInfoMessage(MsmqMessage<string> msg);

It’s possible that the WCF stack is having difficulty with the deserialization to XmlDocument.

UPDATE

Things to try:

1. Make suer your queue “testsmessagequeue” have the correct permissions set. In this case the service account running the app pool hosting your controller needs to have the “Receive Message” permissions set.

2. Enable MSMQ logging (if you’re on windows 2008 server or windows 7 and above) which can be found in Event Viewer under: Applications and Services Logs -> Microsoft -> Windows -> MSMQ -> End2End. This will capture everything that happens in MSMQ including any errors.

3. Try making the queue transactional (if it not already). This will ensure that an error condition will exist on message non-delivery.

4. Enable WCF tracing on your service endpoint to see any specific WCF errors happening with the dequeuing of the message.

UPDATE 2

I think the problem is queue permissions. Your app pool is running under the user ApplicationPoolIdentity (if it’s running under the .net 4.0 app pool). The user which corresponds to this identity is called DefaultAppPool. You need to give this user receive message permissions on the queue. To select this user search for a local account called IIS AppPool\DefaultAppPool in the Select Users dialogue.

UPDATE 3

It just struck me that IIS is not an appropriate hosting container for a queue listener. The reason for this is that the app pool unloads after a period of inactivity. This is controlled by IIS and is not configurable. (see here)

I think you should create a new hosting container in a windows service (you can use a console host to spike this) to host the queue endpoint. The windows service will run under an actual service account so granting permissions will be less complicated.

This service can write either write directly into the cache, or if this is not possible, should write to a DB where the website controller can refresh the cache from.

Does this make sense?

UPDATE 4

Poison message means that the message cannot be dequeued because of some problem with it. Check the system queue called Transactional Dead Letter Queue and see if your message is in there.