I have an ASP.NET 4.0 Web Service running on IIS 6.0. I am trying to locate the appropriate Performance Counter to track 503 responses. I have limited "Web site connections" to 1 for testing purposes and have verified in my client that I am receiving a 503 - Server Unavailable.

According to Microsoft's documentation the ASP.NET\Requests Rejected counter specifically tracks 503 responses. I am not seeing this at all.

I have tried the following counters (all with scale set to 1 in the Performance graph) and none of them show any activity:

  • ASP.NET\Requests Rejected
  • ASP.NET v4.0.30319\Requests Rejected
  • ASP.NET Apps v4.0.30319\Requests Rejected
  • Active Server Pages\Requests Rejected
  • ASP.NET Applications\Requests Rejected

I have verified that other counters are tracking my web service activity properly (Web Service\Bytes Total/sec, ASP.NET Applications\Request Execution Time, etc)


Is it a new app pool with a custom identity? If so, make sure that your app pool identity is added to the IIS_WPG group. Otherwise it will throw the error you mentioned. It fails before it can log too, so that's consistent with your summary.

If it's not that, then test a test.html page to find out if it's .net related to app pool related.

  • The identity being used is in the IIS_WPG group. Could you elaborate on how i would test using a static page? – Jeff Swensen Apr 15 '11 at 16:55
  • If you create a simple page called test.html and in the body just put "This is a test". Does that work? Whether or not that works will help determine if the issue is with the app pool as a whole, or just asp.net. – Scott Forsyth - MVP Apr 15 '11 at 17:17

Limiting the "Web site connections" in IIS Manager keeps the requests from ever getting to ASP.NET and getting logged. I had to edit maxWorkerThreads and requestQueueLimit within the machine.config file for the 503 errors to show up under the counter ASP.NET\Requests Rejected.

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