A small number of our sites intermediately experience an error that is a mystery to us.

Our set up is:

  • Windows Server 2003
  • IIS6
  • .NET 3.5
  • We have about 35 Websites running on IIS
  • Each site has it's own App Pool
  • Each App Pool has the identity: Network Service

The symptom is: The Application Pool for a site stops, and when you browse to the site, you only see:


In the Event Logs, we have one Error, that looks like this:

Application pool 'AppPool1' is being automatically disabled due to a series of failures in the process(es) serving that application pool.

And we have several Warnings leading up to the error, that look like this (note: the warnings look the same, except for the process id):

A process serving application pool 'AppPool1' suffered a fatal communication error with the World Wide Web Publishing Service. The process id was '292'. The data field contains the error number.

What's causing this? As I said, it doeasn't happen very often....the last time was about 6 months ago...and it usually happens with the same site/App pool.

Any ideas?



The reason the app pool is being disabled is because Rapid Fail protection is on, so after a number of App Pool faults it will Stop the pool rather than restarting it.

You can disable Rapid Fail protection, but obviously that means you're still getting the error and you're just restarting the app pool every time; the best solution is to find out why it's crashing in the first place.

Unfortunately the error messages you get from IIS are not terribly useful, so to get a better idea of what is causing the crash you're going to need to run an IIS debug tool such as DebugDiag or IISState to get more information about the error.

It could be a problem with the particular code a site is running, or if its happening to multiple sites then maybe it's something more general. Running these tools should give you a better idea of what's causing it.

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