IIS6: 503 errors and CPU spikes

Question

So, there is a horribly written site that I occasionally help out with that was originally written in classic ASP.

It was then "ported" to ASP.NET by moving the global variables to the code behind and leaving the rest of the code in the aspx...Its a huge mess.

On some pages, an occasional race condition seems to be triggered that causes IIS6 to die (returns 503 errors) and spikes the CPU to 100%.

We set up some monitoring tools and recycle the apppool when this happens to keep the site stable, but this is just a bandaid.

Does anyone know of any tools to get me pointed in the right direction for finding why this happens?

Memory usage remains flat, so its not a leaking reference issue.

Answer 1

Usually the best place to start is the Http.sys log:

HTTP.SYS error log - %windir%\System32\LogFiles\HTTPERR

You can also check the event log and IIS log to see if you have any additional information in there.

Answer 2

Hi, Check out thus guy's blog

http://blogs.msdn.com/tom/default.aspx ASP.NET debugging. You may find something there. I believe h'd mentioned something related to your issue sometime in June.