cron.py

import asyncio as aio
import signal
import os

from datetime import datetime, timedelta

alerts = {
 1: datetime(2015, 12, 12, 11, 57, 4),
 2: datetime(2015, 8, 16, 11, 58, 5)
}

def sleep_calculator(id):
    while True:
        now = datetime.now()

        alert = alerts[id]
        next_send = now.replace(hour=alert.hour, minute=alert.minute, second=alert.second)

        if next_send <= now:
            next_send += timedelta(days=1)

        yield (next_send - now).total_seconds()


async def send_alert(id):
    print('I am sending alert', id)


async def wait_for_alert(id):
    print('Starting the wait for', id)
    for delay in sleep_calculator(id):
        print('Will wait', delay, 'for', id)
        try:
            # This is cancellable
            await aio.sleep(delay)
        except aio.CancelledError:
            print('Terminating coroutine for', id)
            return

        # This is not cancellable
        await aio.shield(send_alert(id))


def handle_terminate(tasks):
    print('Shutting down')
    for t in tasks:
        t.cancel()


def main():
    print('kill -TERM', os.getpid())
    loop = aio.get_event_loop()
    tasks = [aio.ensure_future(wait_for_alert(id)) for id in alerts]

    loop.add_signal_handler(signal.SIGTERM, handle_terminate, tasks)

    loop.run_until_complete(aio.gather(*tasks))

    loop.close()

if __name__ == '__main__':
    main()