Terminating process from Timer thread

Question

I would better start the question from the code.

from multiprocessing import Process, Event, Queue
from threading import Timer
from Queue import Empty

class MyServer(Process):
    def __init__(self, port, queue):
        Process.__init__(self)

        self.port = port
        self.queue = queue
        self.sd = None

    def run(self):
        try:
            self.start_serving()

        except KeyboardInterrupt:
            print("Shutting down..")

        finally:
            if self.sd is not None:
                self.sd.close()

    def start_serving(self):
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.sd = s
        try:
            s.bind(('', self.port))
            s.listen(1)
            while True:
                conn, addr = s.accept()
                while True:
                    # I dont want to bore you with excess code
                    # just recv data from clients
                    try:
                        msg = self.queue.get_nowait()
                        # here i start Timer with delay from message (I'll describe Message class below)
                        Timer(msg.delay, self.response_handler, args=(conn, msg)).start()
                    except Empty:
                        pass
                conn.close()

        finally:
            s.close()

    def response_handler(self, sd, msg):
        # doesn't matter
        # and now I want to terminate the MyServer instance
        if msg.terminate:
            # the problem is here. Lets call it 'problem line'
            sys.exit()

msg is instance of Message class which is:

class Message(object):
    def __init__(self, port, delay, values, terminate=False):
        self.port = port
        self.delay = delay
        self.values = values
        self.terminate = terminate

The logic is I get data from clients via TCP connection and check Queue for message. Messages are things to control the server. Sometimes I get a message like "wait 3 seconds and terminate the server". What I have done so far.

1. Call self.terminate() at the problem line. I get AttributeError: 'NoneType' object has no attribute 'terminate'
2. Raise an exception at the problem line. I assumed the exception was caught in run() function. I was wrong
3. Call sys.exit(). It doesn't work too.

Perhaps my question can be shorter. How to terminate the process from its thread in Python?

Answer 1

Why don't you use multiprocessing.Event (you are already importing it) and exit the process gracefully if you get an terminate message.

To do this add this to __init__:

self.exit = Event()

And change the two while loops:

while True:
    conn, addr = s.accept()
    while True:
    #...

to

while not self.exit.is_set():
    conn, addr = s.accept()
    while not self.exit.is_set()
    #...

then in your response handler:

if msg.terminate:
    self.exit.set()

this will allow the code to naturally exit the loops, ensuring that conn.close() is called.