I would imagine you have a watchdog of some sort (perhaps a special URL) and have something probe that every 15-60 seconds etc to see if it is up, if it does no

I would imagine you have a watchdog of some sort (perhaps a special URL) and have something probe that every 15-60 seconds etc to see if it is up, if it does not respond then spin up a new instance and kill the failed instance. Cattle not pets!