process_monitor.py

import multiprocessing
import time
import os


class PMonitor(multiprocessing.Process):
    def __init__(self, process_id):
        super(PMonitor, self).__init__()
        self.process_id = str(process_id)
        self.semaphore = multiprocessing.Event()

    def red_light(self):
        self.semaphore.set()

    def run(self):
        try:
            procdir = os.path.join('/proc', self.process_id)
            while not self.semaphore.is_set() and os.path.exists(procdir):
                print '[{0}] Working in child'.format(self.process_id)
                time.sleep(2)
        except KeyboardInterrupt, CalledProcessError:
            pass
        finally:
            print '[{0}] Cleanup'.format(self.process_id)


if __name__ == '__main__':
    monitors = {}
    try:
        while True:
            print "[Master] Scanning what I need to scan and span a new subprocess when necessary"
            # Get the pid of interresting process
            pid = 1
            if not pid in monitors:
                monitor = PMonitor(pid)
                monitors[pid] = monitor
                monitor.start()
            time.sleep(2)
    except KeyboardInterrupt:
        # Don't die immediatelly. Signalize to subprocesses and wait until they all finnish their work
        print "[Master] Finishing children"
        for monitor in monitors:
            monitors[monitor].red_light()
            # Join subprocess. This will block until subprocess dies
            monitors[monitor].join()
        print "[Master] All children terminated, exiting."