Gracefully handling SIGTERM

signal_catcher.py

"""Gracefully handling SIGTERM

References:

- https://stackoverflow.com/questions/18499497/how-to-process-sigterm-signal-gracefully/31464349#31464349
- https://devcenter.heroku.com/articles/dynos#shutdown
"""

import logging
import signal
import time


logger = logging.getLogger(__name__)
logger.setLevel(logging.INFO)
stream_handler = logging.StreamHandler()
stream_handler.setLevel(logging.INFO)
logger.addHandler(stream_handler)


class SignalCatcher(object):
    caught_signal = False

    def __init__(self):
        """
        TODO: Should we catch anything else??
        """
        signal.signal(signal.SIGINT, self.handle_signal)
        signal.signal(signal.SIGTERM, self.handle_signal)

    def handle_signal(self, signum, frame):
        logger.warning("SignalCatcher caught signum `%s`", signum)
        self.caught_signal = True


catcher = SignalCatcher()


def do_stuff():
    logger.info("Doing stuff!")
    while True:
        logger.info("Doing some stuff in a loop!")
        time.sleep(3)
        if catcher.caught_signal:
            logger.info("I got killed gracefully! Finishing up some stuff ...")
            time.sleep(2)
            break
    logger.info("Done!")


def main():
    try:
        do_stuff()
    except Exception as e:
        logger.exception("Caught exception! %s", e)


main()