we have a set of application here that are aspnet running on IIS 8.5 - Win2012-R2. We have 4.6.2 version of .Net deployed.
On some of our servers, we see a strange behavior where IIS won't reply to some requests.
After investigation I noticed that the w3wp.exe process which is supposed to be running the application pool associated with handling these requests is not there (neither in IIS admin screen nor in process explorer view)
Stop/Start/Recycle of the application pool won't change anything the w3wp.exe will just not start.
There are no event in the event-viewer related to the AppPool in question and the htterr folder contains only logs of client aborted sessions (all those incoming query time-out of course)
IISReset will do not good either BUT if I restart the WAS service then all of a sudden the applications pools are spawned correctly.
Another 'fix' we found was to delete the application pool and create a new one under IIS which seems to do the trick too.
This fact leads me to believe that somehow the connection or meta-data between IIS and WAS get broken but I have no idea where it could be stored or why it gets damaged.
Once the problem is ongoing using procmon doesn't show anything out of the ordinary. Pools that are up are behaving, and pools that are down don't show anything.
Any idea on how to fix this for good?