Besides a proper monitoring tool, every application should have application developed health check to verify the environment is up and for troubleshooting.

Essential

Really should have these in order of importance.

Application Up - Basic test to ensure application is working not going through the web server.

Load Balancer Health Check - Note here the sample code (to be provided) which minimizes load to the system.

Code Version - Version of code deployed. Actually for trouble-shooting with End Users suggest PC Financial at one point put a unique code at bottom footer.

Java Version - Obfuscated.

Server Name - Obfuscated.

Recommended

Database Connectivity - Basic test to ensure connection works. Make sure to keep this very limited.

Key Services - Verifies key services are working.

Key Integration Points - Good example is verifying an external web service.