I have a .Net based IIS Website that appears to be going down and coming back up without logging it. The only way I'm able to tell this is happening is from our CMS logging the time that it needs to re-initialize, and our Application Dynamics agents logging the time that they need to come back online. We thought this was the App Pool restarting at first, but we have all logging for the App Pool turned on and there are no entries when these events occur. After the event there's a period of slowness on the website that I've been attributing to a recompile time, but again no logs to indicate this.
Metrics on the server during these events appear to be standard and do not deviate from their norms. None of the normal suspects are higher than usual (CPU < 20%, Memory < 15%).
We've tried turning off all services on the server, increasing the worker process count from 1 to various amounts up to 10. Morning restarts of the app pools involved. Daily restarts of the server. Added various logging to Event Viewer.
This is happening during the middle of the day under normal load. There's around 1000 transactions per minute hitting the App Pool.
I would suggest a look at the Reliability Monitor for any crashes, errors, or other events on the server. Click Start, type Reliability and the search should produce the 'View Reliability History' in Control Panel.
To clarify, does the w3svc continue running the entire time the site is up/down?