def wait_for_work(self):
"""
Periodically check if there is more work. After having waited for more
work to appear for a while, stop waiting.
"""
start_time = time.time()
while not TaskRunner.has_work():
# sleep and stop waiting if we get interrupted by user
try:
time.sleep(self.WAIT_FOR_WORK_SLEEP_SEC)
except KeyboardInterrupt:
return False
# determine total waiting time so far and stop waiting once
# we waited long enought...
time_ellapsed_sec = time.time() - start_time
if time_ellapsed_sec > self.MAX_WAIT_FOR_WORK_SEC:
return False
return True
def handle(self, *args, **options):
"""
Run command.
"""
# sleep for a random amount of time in case we are trying to
# start the task runner multiple times.
time.sleep(random.uniform(0.0, 3.0))
# immediatly exit if another instance of the task runner is
# already running...
if TaskRunner.is_running():
return
# mark ourselves as running
TaskRunner.signal_running()
# setup cleanup handler that is executed whenever we terminate
signal.signal(signal.SIGTERM, self.kill_handler)
# whenever we have a fresh re-start, notify yourself, so that we might
# pick up any work that is left to do for us, we might have missed
# a previous notification...
TaskRunner.notify()
# continiously execute background work unless we do not have any more
# work
while True:
if TaskRunner.has_work():
# indicate that there is no more work, since we are about to run
TaskRunner.signal_no_work()
# execute background tasks
runner = self.create_task_runner()
runner.run()
# wait for further work to appear...
if not self.wait_for_work():
break
# terminate
self.cleanup()