Thursday, August 18, 2011

WCF: Get the operation name within a Message Inspector

For logging purposes I needed to get the operation name of the called WCF service and the content of the message.

How can you get this done?

Important to notice when you look at the code is that I created an attribute and implement both the IDispatchMessageInspector and IServiceBehavior interface. This allows me to register this message inspector by just adding the attribute on top of my WCF service class.

/// <summary>
/// When applying this attribute to a service contract,
/// the input and output messages will be logged.
/// </summary>
[AttributeUsage(AttributeTargets.Class)]
public class MessageLoggingBehaviorAttribute : Attribute, IDispatchMessageInspector, IServiceBehavior
{
#region IDispatchMessageInspector Members

/// <summary>
/// Will be executed after a request is received.
/// </summary>
/// <param name="request">The request.</param>
/// <param name="channel">The channel.</param>
/// <param name="instanceContext">The instance context.</param>
/// <returns></returns>
/// <exception cref="System.Configuration.ConfigurationErrorsException">Throws a configuration exception if the environments don't match.</exception>
public object AfterReceiveRequest(ref System.ServiceModel.Channels.Message request, System.ServiceModel.IClientChannel channel, System.ServiceModel.InstanceContext instanceContext)
{
LogMessage(ref request);
return null;
}

/// <summary>
/// Will be executed before the reply is send.
/// </summary>
/// <param name="reply">The reply.</param>
/// <param name="correlationState">State of the correlation.</param>
public void BeforeSendReply(ref System.ServiceModel.Channels.Message reply, object correlationState)
{
LogMessage(ref reply);
}

#endregion

#region IServiceBehavior Members

/// <summary>
/// Adds the binding parameters.
/// </summary>
/// <param name="serviceDescription">The service description.</param>
/// <param name="serviceHostBase">The service host base.</param>
/// <param name="endpoints">The endpoints.</param>
/// <param name="bindingParameters">The binding parameters.</param>
public void AddBindingParameters(ServiceDescription serviceDescription, System.ServiceModel.ServiceHostBase serviceHostBase, System.Collections.ObjectModel.Collection<ServiceEndpoint> endpoints, System.ServiceModel.Channels.BindingParameterCollection bindingParameters)
{
}

/// <summary>
/// Applies the dispatch behavior.
/// </summary>
/// <param name="serviceDescription">The service description.</param>
/// <param name="serviceHostBase">The service host base.</param>
public void ApplyDispatchBehavior(ServiceDescription serviceDescription, System.ServiceModel.ServiceHostBase serviceHostBase)
{
foreach (ChannelDispatcher chDisp in serviceHostBase.ChannelDispatchers)
{
foreach (EndpointDispatcher epDisp in chDisp.Endpoints)
{
epDisp.DispatchRuntime.MessageInspectors.Add(new MessageLoggingBehaviorAttribute());
}
}
}

/// <summary>
/// Validates the specified service description.
/// </summary>
/// <param name="serviceDescription">The service description.</param>
/// <param name="serviceHostBase">The service host base.</param>
public void Validate(ServiceDescription serviceDescription, System.ServiceModel.ServiceHostBase serviceHostBase)
{
}

#endregion
}

Inside the AfterReceiveRequest and BeforeSendReply methods I call the LogMessage method passing the message object as a reference. Inside the log message I extract the operation name from the incoming headers, do a little bit of service location to get an IMessageLogger instance and invoke the log method in a separate task.

private void LogMessage(ref Message message) 
{
var action = OperationContext.Current.IncomingMessageHeaders.Action;
var operationName = action.Substring(action.LastIndexOf("/")+1);

var messageLogger = IoC.Container.Resolve<IMessageLogger>();
var messageContent = message.ToString();
Task.Factory.StartNew(() => messageLogger.Log(operationName, new List<string> { messageContent })); 
}

And as a last step I add this attribute to my service class.

[MessageLoggingBehavior]
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
public class AanbiederService : IAanbiederService
{

2 comments:

Alberto said...

Very great article!

I'm testing this code but the LogMessage method must be inserted into MessageLoggingBehaviorAttribute class ?

Thanks in advice.

A.

Stephen Patten said...

I owe you beer or whiskey my friend, thank you.