Detach a subprocess started using python multiprocessing module

Question

I would like to create a process using the mutliprocessing module in python but ensure it continues running after the process that created the subprocess exits.

I can get the required functionality using the subprocess module and Popen, but I want to run my code as a function, not as a script. The reason I want to do this is to simplify creating pyro (python remote objects) objects. I want to start the pyro object request handler in a separate process using multiprocessing, but then I want the main process to exit while the process supporting the pyro object continues to run.

Volta

here is another way to detach a process that is started using multiprocessing #49123939 – Spandrel

Answer 1

I finally got what I wanted. I appreciate any suggestions to improve the code.

def start_server():
    pyrodaemon = Pyro.core.Daemon()
    #setup daemon and nameserver
    #Don't want to close the pyro socket
    #Need to remove SIGTERM map so Processing doesn't kill the subprocess
    #Need to explicitly detach for some reason I don't understand
    with daemon.DaemonContext(files_preserve=[pyrodaemon.sock],signal_map={signal.SIGTERM:None},detach_process=True):
        while running:
            pyrodaemon.handleRequests(timeout=1.0)
    #when finished, clean up
    pyrodaemon.shutdown()

def main():
    p = Process(target=start_server)
    p.daemon=True # Need to inform Process that this should run as a daemon
    p.start()
    time.sleep(3.0) # Important when running this program stand alone: Must wait long enough for start_server to get into the daemon context before the main program exits or Process will take down the subprocess before it detaches
    do_other_stuff_not_in_the_daemon()

Volta

The daemon word is getting abused here ;) Don't set Process.daemon to True. That tells multiprocessing to attempt to kill the child at exit (confusing huh?). I think this is why you're needing to catch SIGTERM and set detach_process in the above code. - docs.python.org/library/… – Deathful