I have spent a few days trying to work out why my Metron-REST module in Ambari claims to start successfuly but then shortly after returns to the stopped state. After a bit of digging, I have found there is an issue with my environment variables meaning that the Java executable was failing to start due to an invalid (well, nonexistent) zookeeper URL*
Putting aside my incompetence re. Java and Ambari's broken automatic configuration, it would probably be worth making it more obvious that something like this is happening than a successful start notification from systemctl.
*well, that and I didn't appear to have Java installed despite having it in a functional Ambari cluster ¯_(ツ)_/¯