.NET Application receiving 503 Service Unavailable error when calling web service.

Question

This is a bit of unusual problem that I'm experiencing, but recently one of the users of a production application started reporting errors in the system. These were traced to a 503 Service Unavailable error when making a call to a web service used by the application.

Now here's the odd part, only the one user is affected by this issue. Other users of the application have not reported any errors. When the user logged on to a different machine that worked for another user, they still received the error.

Any ideas what might be going on here?

Answer 1

I don't know what's going on - but maybe your server does. Ask it, nicely.

Take a look in the event logs, and in fact at the IIS logs. There may have been more 503 errors than you think, and possibly from users who have not reported them. Attempt to correlate event log entries with the IIS entries.

You might also consider running a PerfMon log to collect performance counters for the server. Start small - pick just a few performance counters. If the problem happens and nothing is interesting in the performance counters, then add more.

Finally, consider the possibility that the server may be telling you the truth. Perhaps there are no available connections or threads for some period of time.