File based watchdog timer.

watchdog.py

class FileWatchdog(threading.Thread):
  """Watchdog for a file (typically `sys.stdin`).

  When the file closes, terminate the process.
  (This typically occurs when the parent process is lost.)
  """
  def __init__(self, file_handle):
    threading.Thread.__init__(self, name='WatchdogThread')
    self.setDaemon(True)
    self.file_handle = file_handle
    # self.log = open('/tmp/watchdog.%d' % os.getpid(), 'w')

  def run(self):
    f = [self.file_handle]
    while 1:
      r, w, x = select.select(f, f, f, 1.0)
      # print >>self.log, 'Watchdog running: %s %s %s' % (r,w,x)
      # self.log.flush()
      if r:
        # print >>self.log, 'Watchdog: file closed.  Shutting down.'
        # self.log.flush()
        os._exit(1)
      time.sleep(1)