Synchronous sleep in asyncio coroutine

Question

I have a coroutine as follows:

async def download():
    downloader = DataManager()
    downloader.download()

DataManager.download() the method is as follows:

def download(self):
    start_multiple_docker_containers()
    while True:
        check_containers_statuses()
        sleep(N)  # synchronous sleep from time module

Is this a good practice? If not, how can I use asyncio.sleepin download()?

Or maybe such a code structure is conceptually incorrect?

Answer 1

Here is my solution:

import asyncio
import time


# Mocks of domain-specific functions
# ----------------------------------

def get_container_status(container_id, initial_time):
    """This mocks container status to change to 'exited' in 10 seconds"""
    if time.time() - initial_time < 10:
        print("%s: container %s still running" % (time.time(), container_id))
        return 'running'
    else:
        print("%s: container %s exited" % (time.time(), container_id))
        return 'exited'

def is_download_complete(container_id, initial_time):
    """This mocks download finished in 20 seconds after program start"""
    if time.time() - initial_time < 20:
        print("%s: download from %s in progress" % (time.time(), container_id))
        return False
    else:
        print("%s: download from %s done" % (time.time(), container_id))
        return True

def get_downloaded_data(container_id):
    return "foo"


# Coroutines
# ----------

async def container_exited(container_id, initial_time):
    while True:
        await asyncio.sleep(1) # == setTimeout(1000), != sleep(1000)
        if get_container_status(container_id, initial_time) == 'exited':
            return container_id

async def download_data_by_container_id(container_id, initial_time):
    container_id = await container_exited(container_id, initial_time)
    while True:
        await asyncio.sleep(1)
        if is_download_complete(container_id, initial_time):
            return get_downloaded_data(container_id)


# Main loop
# ---------

if __name__ == "__main__":

    initial_time = time.time()

    loop = asyncio.get_event_loop()

    tasks = [
        asyncio.ensure_future(download_data_by_container_id("A", initial_time)),
        asyncio.ensure_future(download_data_by_container_id("B", initial_time))
    ]

    loop.run_until_complete(asyncio.wait(tasks))

    loop.close()

Results in:

1487334722.321165: container A still running
1487334722.321412: container B still running
1487334723.325897: container A still running
1487334723.3259578: container B still running
1487334724.3285959: container A still running
1487334724.328662: container B still running
1487334725.3312798: container A still running
1487334725.331337: container B still running
1487334726.3340318: container A still running
1487334726.33409: container B still running
1487334727.336779: container A still running
1487334727.336842: container B still running
1487334728.339425: container A still running
1487334728.339506: container B still running
1487334729.34211: container A still running
1487334729.342168: container B still running
1487334730.3448708: container A still running
1487334730.34493: container B still running
1487334731.34754: container A exited
1487334731.347598: container B exited
1487334732.350253: download from A in progress
1487334732.3503108: download from B in progress
1487334733.354369: download from A in progress
1487334733.354424: download from B in progress
1487334734.354686: download from A in progress
1487334734.3548028: download from B in progress
1487334735.358371: download from A in progress
1487334735.358461: download from B in progress
1487334736.3610592: download from A in progress
1487334736.361115: download from B in progress
1487334737.363115: download from A in progress
1487334737.363211: download from B in progress
1487334738.3664992: download from A in progress
1487334738.36656: download from B in progress
1487334739.369131: download from A in progress
1487334739.36919: download from B in progress
1487334740.371079: download from A in progress
1487334740.37119: download from B in progress
1487334741.374521: download from A done
1487334741.3745651: download from B done

As for the function sleep()- no, you should not use it. It blocks the entire Python interpreter for 1 second, which is not what you need.

Remember, you do not have concurrency (threads, etc.), you have concurrency.

.. Python , , . , 99,999% , asyncio, -.

sleep - , , .

, asyncio.sleep() Javascript setTimeout() - , .

---

:

• https://snarky.ca/how-the-heck-does-async-await-work-in-python-3-5/
• https://docs.python.org/3/library/asyncio.html

Answer 2

, , time.sleep() , ( ).

async.

?

async def download():
    downloader = DataManager()
    downloader.start_multiple_docker_containers()
    while True:
        downloader.check_containers_statuses()
        await syncio.sleep(N)

Answer 3

asyncio, , , f = app.loop.run_in_executor(None, your_sync_function, app,param1,param2,...)

then your_sync_functionexecuted in a separate thread, and you can execute time.sleep()without breaking the asyncio loop. It blocks the loop execution thread, but not the asyncio thread. At least that's the way it is.

If you want to send messages from your_sync_functionback to the asyncio loop, check out the libraryjanus

Additional tips on this subject:

https://carlosmaniero.imtqy.com/asyncio-handle-blocking-functions.html