How can I cause a child process to exit when the parent does?

Question

I am launching a child process with ProcessBuilder, and need the child process to exit if the parent process does. Under normal circumstances, my code is stopping the child properly. However, if I cause the OS to kill the parent, the child will continue running.

Is there any way to "tie" the child process to the parent, such that it'll exit when the parent is killed?

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Answer 1

While you cannot protect against a hard abort (e.g. SIGKILL on Unix), you can protect against other signals that cause your parent process to shut down (e.g. SIGINT) and clean up your child process. You can accomplish this through use of shutdown hooks: see Runtime#addShutdownHook, as well as a related SO question here.

Your code might look something like this:

String[] command; final Process childProcess = new ProcessBuilder(command).start();  Thread closeChildThread = new Thread() {     public void run() {         childProcess.destroy();     } };  Runtime.getRuntime().addShutdownHook(closeChildThread);  

Answer 2

There is no tie between a child process and its parent. They may know each others process ID, but there's no hard connection between them. What you're talking about a orphan process. And it's an OS level concern. Meaning any solution is probably platform dependent.

About the only thing I can think of is to have the child check its parents status periodically, exiting if the parent's shutdown. I don't think this would be all that reliable though.