In part one, we documented to pass correlationid to the asp.net MVC and OWIN applications. In this post, we will see how to accomplish it in WCF services.
Theory
As previously stated, correlation Id is a useful way to reconstruct the call graph. When the first call is made, a Unique Identifier, GUID, is generated, this GUID is then passed along to subsequent requests, which is put into logs in a structured way via the logging framework provided to a centralized log storage. You then can take advantage of the capabilities, the log management tool (Splunk) to trace the event all the way through your call graph.
Client:
When a client initiates a request to WCF service, we will examine if it is an initiating call. If so, a GUID will be generated and add an outgoing header to it. Otherwise, it will reuse the GUID coming from the upstream call.
Server:
Whenever the server receives a request, it will exam the incoming header for the existence of correlation Id. If it finds it, then it will be pass along with downstream call and used for any log in the current context.
Implementation
How can we generate such GUID implicitly without requiring a lot of efforts on application developers to add it to an existing application or brand new app? The solution we chose is to have a custom header for each WCF calls. The messageInspector, which will inspect the outgoing messages (Client) or incoming messages (Server), can help us to fulfill the requirement.
Client
On the client side, we implement the IClientMessageInspector to add a header to every outgoing request with GUID. An IEndpointBehavior implementation will inject this inspector into the client endpoint and a System.ServiceModel.Configuration.BehaviorExtensionElement is to facilitate it through the configuration files.
internal class ClientMessageInspector : IClientMessageInspector
{
public object BeforeSendRequest(ref Message request, IClientChannel channel)
{
if (request.Headers.Where(h => h.Name == "correlationId").Count() == 0)
{
object correlationId = CallContext.LogicalGetData("correlationId");
MessageHeader<string> messageHeader;
if (correlationId == null)
{
messageHeader = new MessageHeader<string>(Guid.NewGuid().ToString());
}
else
{
messageHeader = new MessageHeader<string>(correlationId.ToString());
}
var untypedMessageHeader = messageHeader.GetUntypedHeader("correlationId", string.Empty);
request.Headers.Add(untypedMessageHeader);
}
return null;
}
}
public class ClientEndPointBehavior : IEndpointBehavior
{
public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
{
#if NET35
clientRuntime.MessageInspectors.Add(new ClientMessageInspector());
#else
clientRuntime.ClientMessageInspectors.Add(new ClientMessageInspector());
#endif
}
}
public class ClientMessageHeaderBehaviorExtension : BehaviorExtensionElement
{
public override Type BehaviorType
{
get
{
return typeof(ClientEndPointBehavior);
}
}
protected override object CreateBehavior()
{
return new ClientEndPointBehavior();
}
}
Server
On the server side, We implement the IDispatchMessageInspector to inspect the received requests. A ServiceMessageHeaderInspectorAttribute is created to help decorate the service class that every request is checked before the operations are performed
public class ServiceMessageHeaderInspector : IDispatchMessageInspector
{
public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
{
if (request.Headers.FindHeader("ssicorrelationId", string.Empty) == -1)
{
//http://forums.asp.net/t/1986677.aspx?How+to+extract+header+info+in+WCF+service
//check if this is request from http request and then check the httpheader
var httpRequest = (HttpRequestMessageProperty) request.Properties[HttpRequestMessageProperty.Name];
if (httpRequest != null)
{
string colId = httpRequest.Headers["X-CorrelationId"];
if (!string.IsNullOrEmpty(colId))
{
CallContext.LogicalSetData("CorrelationId", colId);
}
}
else
{
//no correlationid using new id
CallContext.LogicalSetData("CorrelationId", Guid.NewGuid().ToString());
}
}
else
{
var id = request.Headers.GetHeader<string>("CorrelationId", string.Empty);
if (string.IsNullOrEmpty(id))
{
CallContext.LogicalSetData("CorrelationId", Guid.NewGuid().ToString());
}
else
{
CallContext.LogicalSetData("CorrelationId", id);
}
}
return instanceContext;
}
}
public class ServiceMessageHeaderInspectorAttribute : Attribute, IServiceBehavior
{
public void ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
{
foreach (ChannelDispatcher channelDispatcher in serviceHostBase.ChannelDispatchers)
{
foreach (var endpointDispatcher in channelDispatcher.Endpoints)
{
endpointDispatcher.DispatchRuntime.MessageInspectors.Add(new ServiceMessageHeaderInspector());
}
}
}
}
Usage
Server
On the server side, it is pretty straightforward, you will add the Common.dll as a reference and then add ServiceMessageHeaderInspectorAttribute on your service class implementation.
[ServiceMessageHeaderInspector]
public class WCFService : IWCFService
....
Client
On the client side, there are two options.
Using Configuration File not support .net35
- You will make the configuration aware of
MessageHeadeInspectorby adding behaviorExtension
<extensions>
<behaviorExtensions>
<add name="MessageHeaderInspector" type="Common.Logging.WCF.ClientMessageHeaderBehaviorExtension,Common"/>
</behaviorExtensions>
</extensions>
- Add endpointbehavior configuration to use it
<endpointBehaviors>
<behavior name="correlationEndpointBehavior">
<MessageHeaderInspector/>
</behavior>
</endpointBehaviors>
- Make sure the endpoint to use this behaviorConfiguration
<client>
<endpoint address="http://localhost:8733/WCFService/"
binding="basicHttpBinding" bindingConfiguration="BasicHttpBinding_IService1"
contract="Logging.Test.WCF.IWCFService" name="BasicHttpBinding_WCFService" behaviorConfiguration="correlationEndpointBehavior" />
</client>
Pragmatically
You will need explicitly add the Common.Logging.WCF.ClientEndPointBehavior to your WCF channel
.net 452 and .net 46
var endpoint = new EndpointAddress(url);
var channelFactory = new ChannelFactory<IWCFService>(binding, endpoint );
var correlationBehavior = new ClientEndPointBehavior();
channelFactory.Endpoint.EndpointBehaviors.Add(correlationBehavior);
IWCFService client = null;
...
.net 35
var endpoint = new EndpointAddress(url);
var channelFactory = new ChannelFactory<IWCFService>(binding, endpoint );
var correlationBehavior = new ClientEndPointBehavior();
channelFactory.Endpoint.Behaviors.Add(correlationBehavior);
IWCFService client = null;
...
Instead of the previous example that will use the correlation id stored in callcontext if it is presented, you can specify correlation id specifically for your WCF request
var id = Guid.NewGuid().ToString();
client = channelFactory.CreateChannel();
IClientChannel channel = client as IClientChannel;
using(new OperationContextScope(channel))
{
System.ServiceModel.Channels.MessageHeader aMessageHeader = System.ServiceModel.Channels.MessageHeader.CreateHeader("correlationid", "", id);
OperationContext.Current.OutgoingMessageHeaders.Add(aMessageHeader);
var message = client.GetData(1);
Assert.AreEqual(id, message);
}
Note: the header name has to be "correlationid" and namespace is an empty string.
in next post, we will explore the same idea to the Azure Service Fabric