zimingd/shutdownhook

testing shutdown hooks in Java +Docker

shutdownhook

testing Java shutdown hooks in Docker.

##Moral of the story: The last line of the Dockefile should be CMD exec <command> instead of CMD <command> because Docker only sends the termination signal to the process with pid=1, the latter command runs /bin/sh and forks the <command> to a child process. /bin/sh does not forward the termination signal to its children so the process running <command> will be unable to terminate gracefully. exec() is a system call that replaces the current process image with that of <command> so, in this context, the process running <command> will have pid=1 and be able to recieve the termination signal.