Restart mDNSResponder if it's not responsible (just for MacOS)

check_mDNSResponder.py

#!/usr/bin/env python

""" Restart mDNSResponder if it's not responsible (just for MacOS)

Run this script as root via cron.

* * * * * /Users/xupeng/bin/check_mDNSResponder.py
"""

import os
import sys
import threading
import socket
import Queue

def check_dns(hostname, timeout):
    """ Do DNS resolving with given timeout

    return IP address if success before timeout, raise socket.timeout if timeout.
    """

    def proc():
        try:
            queue.put(socket.gethostbyname(hostname))
        except Exception, e:
            raise e

    queue = Queue.Queue()
    t = threading.Thread(target=proc)
    t.daemon = True
    t.start()

    try:
        return queue.get(timeout=timeout)
    except Queue.Empty:
        raise socket.timeout

def main():
    try:
        check_dns('www.douban.com', 1)
        return 0
    except socket.timeout:
        os.system('/usr/bin/killall -9 mDNSResponder')
        return 1

if __name__ == '__main__':
    sys.exit(main())