import asyncio

SCHEDULE_PERIOD = 60*60*6
EMAILS = []


async def fetch_from_db():
    result_file = None
    await asyncio.sleep(15)  # emulate some work
    return result_file


async def create_pdf(input_file):
    pdf_file = None
    await asyncio.sleep(15)  # emulate some work
    return pdf_file


async def send_to(email, pdf_file):
    await asyncio.sleep(2)  # emulate some work


async def email_users(pdf_file):
    coros = [send_to(e, pdf_file) for e in EMAILS]
    _ = await asyncio.gather(*coros)


async def periodic():
    while True:
        print('Start periodic fetch from db')
        result_file = await fetch_from_db()
        pdf_file = await create_pdf(result_file)
        await email_users(pdf_file)
        await asyncio.sleep(SCHEDULE_PERIOD)


def stop():
    task.cancel()


if __name__ == "__main__":
    task = asyncio.Task(periodic())
    loop = asyncio.get_event_loop()
    loop.call_later(5, stop)
    try:
        loop.run_until_complete(task)
    except asyncio.CancelledError:
        pass