Processus Python multiprocessing.Queue +: terminer correctement les deux programmes

Question

Compte tenu de ce programme Python:

# commented out code are alternatives I tried that don't work. 

from multiprocessing import Process, Queue 
#from multiprocessing import Process, JoinableQueue as Queue 

def start_process(queue): 
    # queue.cancel_join_thread() 
    while True: 
     print queue.get() 

if __name__ == '__main__': 
    queue = Queue() 
    # queue.cancel_join_thread() 

    process = Process(target=start_process, args=(queue,)) 
    process.start() 

    queue.put(12) 
    process.join() 

Quand je tue ce programme avec CTRL-C, cela se produit:

$> python queuetest.py 
12 
^CTraceback (most recent call last): 
    File "queuetest.py", line 19, in <module> 
    process.join() 
    File ".../python2.7/multiprocessing/process.py", line 119, in join 
    res = self._popen.wait(timeout) 
Process Process-1: 
    File ".../python2.7/multiprocessing/forking.py", line 122, in wait 
Traceback (most recent call last): 
    return self.poll(0) 
    File ".../python2.7/multiprocessing/forking.py", line 107, in poll 
    pid, sts = os.waitpid(self.pid, flag) 
    File ".../python2.7/multiprocessing/process.py", line 232, in _bootstrap 
KeyboardInterrupt 
    self.run() 
    File ".../python2.7/multiprocessing/process.py", line 88, in run 
    self._target(*self._args, **self._kwargs) 
    File "queuetest.py", line 9, in start_process 
    print queue.get() 
    File ".../python2.7/multiprocessing/queues.py", line 91, in get 
    res = self._recv() 
KeyboardInterrupt 

.. comment puis-je bien terminer les deux processess sur le signal? Ce que je veux réaliser: Dans mon programme non-minimal, le second processus contient un SocketServer et nécessite une interface de ligne de commande interactive supplémentaire.

Answer 1

Une solution consiste à envoyer un message spécifique (par exemple, la chaîne 'exit' dans mon exemple) via la file d'attente, pour terminer le worker (processus enfant) normal. Comme le signal CTRL-C est envoyé à tous les enfants, nous devons l'ignorer. Voici un exemple de code:

from multiprocessing import Process, Queue 

def start_process(queue): 
    while True: 
    try: 
     m = queue.get() 
     if m == 'exit': 
      print 'cleaning up worker...' 
      # add here your cleaning up code 
      break 
     else: 
      print m 
    except KeyboardInterrupt: 
     print 'ignore CTRL-C from worker' 


if __name__ == '__main__': 
    queue = Queue() 

    process = Process(target=start_process, args=(queue,)) 
    process.start() 

    queue.put(12) 

    try: 
    process.join() 
    except KeyboardInterrupt: 
    print 'wait for worker to cleanup...' 
    queue.put('exit') 
    process.join() 

    ## or to kill anyway the worker if is not terminated after 5 seconds ... 
    ## process.join(5) 
    ## if process.is_alive(): 
    ##  process.terminate()