Why do IIS application pools need to be recycled?

Question

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 bu

Answer 1

From https://weblogs.asp.net/owscott/why-is-the-iis-default-app-pool-recycle-set-to-1740-minutes

You may ask whether a fixed recycle is even needed. A daily recycle is just a band-aid to freshen IIS in case there is a slight memory leak or anything else that slowly creeps into the worker process. In theory you don’t need a daily recycle unless you have a known problem. I used to recommend that you turn it off completely if you don’t need it. However, I’m leaning more today towards setting it to recycle once per day at an off-peak time as a proactive measure.

My reason is that, first, your site should be able to survive a recycle without too much impact, so recycling daily shouldn’t be a concern. Secondly, I’ve found that even well behaving app pools can eventually have something sneak in over time that impacts the app pool. I’ve seen issues from traffic patterns that cause excessive caching or something odd in the application, and I’ve seen the very rare IIS bug (rare indeed!) that isn’t a problem if recycled daily. Is it a band-aid? Possibly, but if a daily recycle keeps a non-critical issue from bubbling to the top then I believe that it’s a good proactive measure to save a lot of troubleshooting effort on something that probably isn’t important to troubleshoot. However, if you think you have a real issue that is being suppressed by recycling then, by all means, turn off the auto-recycling so that you can track down and resolve your issue. There’s no black and white answer. Only you can make the best decision for your environment.

There's a lot more useful/interesting info for someone relatively unlearned in the IIS world (like me), I recommend you read it.