python asyncio: pattern for async tasks function

Question

I have a program that needs to run multiple independent tasks. I need a way to start them and then stop them when an event occur

I've defined a base class like this

class InterruptibleTask:
    def __init__(self, stop_evt=None):
        self.stop_evt = stop_evt or asyncio.Event()

    async def init(self):
        pass

    async def cleanup(self):
        pass

    async def run(self):
        await self.init()
        await self.stop_evt.wait()
        await self.cleanup()

    async def stop(self):
        self.stop_evt.set()


class MyFirstTask(InterruptibleTask):
    async def do_work(self):
        while not self.stop_evt.is_set:
            print("Do Work")
            asyncio.sleep(1)

    async def init(self):
        await asyncio.create_task(self.do_work())

class MysecondTask(InterruptibleTask):
    async def do_work(self):
        while not self.stop_evt.is_set:
            print("Do 2nd Work")
            asyncio.sleep(3)

    async def init(self):
        await asyncio.create_task(self.do_work())


STOP = asyncio.Event()
tasks = [MyFirstTask(STOP), MysecondTask(STOP)]


async def run_tasks():
    await asyncio.gather(*tasks)


def stop_tasks():
    for task in tasks:
        task.stop()

try
    asyncio.run(run_tasks())
except KeyboardInterrupt:
    pass
finally:
    stop_tasks()

It this the right approach? Do you have any example? How can I stop all taks and subtask on exit?

creolo · Accepted Answer · 2019-12-10 07:41:08Z

1

What I do when I have several coroutines and want to stop my loop:

try:
    loop.run_until_complete(main())
except KeyboardInterrupt:
    pending = asyncio.Task.all_tasks()
    for c in pending:
        asyncio.wait_for(c, timeout=5)
finally:
    loop.stop()

So I don't have to have any bookkeeping of my coroutines and can still make sure that every coroutine is stopped. And since there can be coroutines that can take quite a long time to finish I add a timeout, so I don't have to wait for years for my programm to shut down.

edited Dec 10, 2019 at 7:41

answered Dec 9, 2019 at 16:37

creolo

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