Application pools in IIS are recycled very frequently and I can't figure out why. I remember reading about a possible issue in IIS6 that meant you were forced to recycle but a quick search now turns up empty. On IIS6 or 7 you can turn off the idle time, duration and specific time recycle options so no problems there.
So why does every .net site recycle the application pool? If a site didn't have any memory leaks could you set up a site that never needed to recycle?
Also failing this, what would be the best way to ensure background tasks are called, is there any auto restart modules for IIS or should an external service be used to make those calls?
It sounds like it is possible to do if you really wanted/needed to?
Best Answer
Websites are intended to keep running (albeit in a stateless nature). There are a myriad of reasons why app pool recycling can be beneficial to the hosting platform to ensure both the website and the server run at optimum. These include (but not limited to) dynamically compiled assemblies remaining in the appdomain, use of session caching (with no guarantee of cleanup), other websites running amok and resources getting consumed over time etc. An app pool can typically serve more than one website, so app pool recycling can be beneficial to ensure everything runs smoothly.
Besides the initial boot when the app fires up again, the effect should be minimal. Http.sys holds onto requests while a new worker process is started so no requests should be dropped.