Based on my understanding, there is a mechanism for the failover server to listen for a heartbeat signal from the main recording server to determine if it is still alive.
I was wondering if there exists a similar way for the VMS to listen for a signal that will allow it to know if an external Video Analytics Engine is still alive?
The failover recording server can only watch another recording server and then take over its configuration if it stops responding.
If you want to raise an event in the VMS when an external service stops responding, you will probably need to build or find an application that can monitor health and send a TCP message out to an external system on a failure. You would then catch that message as a generic event and do something with it in the rules or alarms.
One of my personal favorites for ad-hoc system health monitoring is PulseWay. It’s a watchdog type application with support for mobile clients and it’s extensible via .NET plugins as well.