我有一个协程如下:

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

DataManager.download() 方法如下所示:

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

这是一个好的做法吗？如果不是，我如何在 download() 中使用 asyncio.sleep？

或者这样的代码结构在概念上是错误的？

最佳答案

这是我的解决方案:

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's 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()

结果:

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

至于 sleep() 函数 - 不，您不应该使用它。它会阻塞整个 python 解释器 1 秒，这不是你想要的。

请记住，您没有并行性(线程等)，您有并发性。

即你有一个只有 1 个执行线程的 python 解释器，你的主循环和所有协程都在其中运行，相互抢占。您希望您的解释器将 99.999% 的工作时间花在由 asyncio 创建的主循环中，轮询套接字并等待超时。

你所有的协程都应该尽可能快地返回并且绝对不应该包含阻塞 sleep - 如果你调用它，它会阻塞整个解释器并阻止主循环从套接字或正在运行的协程中获取信息响应数据，到达那些套接字。

因此，您应该等待 asyncio.sleep()，它本质上等同于 Javascript 的 setTimeout() - 它只是告诉主循环在特定时间它应该唤醒这个协程并继续运行它。

推荐阅读:

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

关于python - 同步 sleep 进入asyncio协程，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/42279675/