I have a small SharePoint farm with 2 internal WFE servers and one in DMZ. In the last couple of days I had a situation twice where the DMZ server returned a “HTTP Error 503. The service is unavailable”. I found the following error in the logs:
Log Name: System
Event ID: 5013
A process serving application pool 'app_pool_name' exceeded time limits during shut down. The process id was 'XXXX'.
Doing the iisreset fixed the problem in both situations. Any idea why this is happening and how to fix it? Is the server really performing a shutdown? Why?