Bad request, zero length response: where is the WCF log, where to investigate?

Question

I have a WCF self hosted service, which is called by an AJAX JavaScript. In some cases the response is Bad Request and the response length is 0.

What I've done so far:

• Inspecting req/resp with fiddler: Request seems to be OK, and response is http 400 'Bad Request' length is 0, so no info, no stack trace etc.
• Trying to set breakpoint in my service implementation: The service method does not even called

• Trying to set all exceptions in VS menu Debug/Exceptions: No exceptions fired.

• Now how to investigate toward?

• Is there any log what self hosted service is writing?
• Any other idea?

Answer 1

You can enable WCF tracing to track that error down. Just add the following snippet to your application configuration file:

<configuration>

  <system.diagnostics>

    <sources>

      <source name="System.ServiceModel"
              switchValue="Verbose, ActivityTracing"
              propagateActivity="true">
        <listeners>
          <add name="traceListener"
              type="System.Diagnostics.XmlWriterTraceListener"
              initializeData= "c:\Traces.svclog" />
        </listeners>
      </source>

    </sources>

  </system.diagnostics>

</configuration>

This will create a log file containing additional information for every request. You can open the log file with the Service Trace Viewer Tool which provides a nice GUI.