Friday, November 9, 2012

Load Testing & IIS Application pool

If you are doing a load testing to see if load is going to create a crash in your application pool, there is one setting worth checking.
In IIS 7 and 7.5

Go to Advanced settings for the app pool
In Rapid Fail Protection,Enable = true, set Maximum Failures=1

Right click on application pool->Properties
Click on Health tab
Enable Rapid fail protection should be checked and change Failures to 1

What this will help you is to catch application pool crash easliy. The default value for failures is 5.Which  means for the first 5 crashes the application pool will recover itself.So  if your goal of testing is to detect crash on load, you might need 5 times load to replicate the issue.


  1. Evey,

    This is good to know.

    Were you able to crash the app pool? What happens with requests, if the app pool recovers, is it a seamless recovery?

    If you made it crash, what did you need to do, overload the max connections?


  2. Yes Mike,I was able to crash app pool.. with a certain specific test cases.It was not with overload of max connections.One case was the vulnerability that was fixed in ColdFusion 10 update 5.
    If you have set max failures as 5 , the first five crashes will not stop the app pool... other requests will continue to get served. Windows Event viewer will have entries for crashes.