I've come across situations on MapR 5.2 / 6.0 where Drill 1.10 / 1.13 is up and running but there are flexjson jar classpath errors meaning that Drill is not usable so queries fail even though the API gives the impression that Drill is available. This is bad for load balancers.
This API needs to be much more robust and terms of checking if Drill is fully working. I suggest internally doing a health check real query and if that executes successfully and returns the expected result, only then updating the status to OK / Running.
This internal health check query should be periodically re-executed (eg. every 30 secs) and the status set to ERROR or something if if fails.