Simple steps to enable tracing in WCF

Tracing mechanism in Windows Communication Foundation is based on the classes that resides in System.Diagnostic namespace.Important classes are Trace, TraceSource and TraceListener.

Following are the steps to enable tracing in WCF:

1. Configuring WCF to emit tracing information/Define Trace Source, we have the following options:

• System.ServiceModel 
• System.ServiceModel.MessageLogging 
• System.ServiceModel.IdentityModel
• System.ServiceModel.Activation 
• System.Runtime.Serialization 
• System.IO.Log
• Cardspace

In configuration file, we will define a source to enable this configuration as follows:

       <source name="System.ServiceModel.MessageLogging">

2. Setting Tracing Level, we have the following available options, we need to set this tracing level to available options other than default "Off": 

• Off
• Critical
• Error
• Warning
• Information
• Verbose
• ActivityTracing
• All

In configuration file, we can choose above values for switchValue attribute as follows:

<source name="System.ServiceModel.MessageLogging"
                               switchValue="Information">

3. Configuring a trace listener

For configuring a trace listener, we will add following to config file.

      <listeners>
        <add name="messages"
                 type="System.Diagnostics.XmlWriterTraceListener"
                 initializeData="d:\logs\messages.svclog" />
      </listeners>

4. Enabling message logging.     

      <system.serviceModel>
         <diagnostics>
            <messageLogging 
                    logEntireMessage="true" 
                    logMalformedMessages="false"
                    logMessagesAtServiceLevel="true" 
                    logMessagesAtTransportLevel="false"
                    maxMessagesToLog="3000"
                    maxSizeOfMessageToLog="2000"/>
         </diagnostics>
       </system.serviceModel>

• logEntireMessage: By default, only the message header is logged but if we set it to true, entire message including message header as well as body will be logged.
• logMalformedMessages: this option log messages those are rejected by WCF stack at any stage are known as malformed messages.
• logMessagesAtServiceLevel: messages those are about to enter or leave user.
• logMessagesAtTransportLevel: messages those are about to encode or decode.
• maxMessagesToLog: maximum quota for messages. Default value is 10000.
• maxSizeOfMessageToLog: message size in bytes.

Finally, putting all this together, configuration file will appear like this. 

 <system.diagnostics> 
   <sources>
      <source name="System.ServiceModel.MessageLogging">
        <listeners>
          <add name="messagelistener"
               type="System.Diagnostics.XmlWriterTraceListener" 
                      initializeData="d:\logs\myMessages.svclog"></add>
        </listeners>
      </source>
    </sources>
  </system.diagnostics> 
  <system.serviceModel>       
      <diagnostics>
        <messageLogging logEntireMessage="true"
                        logMessagesAtServiceLevel="false"
                        logMessagesAtTransportLevel="false"
                        logMalformedMessages="true"
                        maxMessagesToLog="5000"
                        maxSizeOfMessageToLog="2000">         
        </messageLogging>
      </diagnostics>
  </system.serviceModel>

Note: In this case, information will be buffered and not published to file automatically, So, we can set the autoflush property of the trace under sources as follows:

<trace autoflush ="true" />

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