IIS application pool failed to respond to ping

Solution 1:

"Ping" in IIS is nothing but a health check done by W3SVC to monitor the state of the worker process. When you see an event such as "A process serving application pool 'appPool' failed to respond to a ping." means the process is in dead state.

Rapid fail protection is the recycling option which takes care of such issue and recycles the appPool on it's own to such that it maintains good health of the worker process.

You will need to debug the process to get to the root of the issue.

Since you have .net application loaded in the workper process it's not a bad idea to check the Application Event log and see for any .net framework Warning or Error. You can attach Debug Diagnostics tool to the process and take a dump to check what is causing the issue. Follow the article How to use the Debug Diagnostics tool to troubleshoot a process that has stopped responding in IIS

Solution 2:

Have you looked in the global HTTP Error Log?

It's called httperr.log and is usually in the log file directory C:\windows\system32\LogFiles, under the main W3CSVC1 service.

Whenever I've had a problem with app pools that file has been quite helpful.