if the process is killed forcefully from the OS or if it's crashing due to resource issues (e.g., out of memory), shutdown hooks won't be invoked.
The process is requested to stop running; it should try to exit cleanly
The process will be killed by the kernel; this signal cannot be ignored.
So should we better use 'kill -15' ?
will never be called for supervisor:
will never be called for worker:
We'd better add something like :
(.addShutdownHook (Runtime/getRuntime) (Thread. (fn  (.shutdown mk-sv)))))) ?