同步睡眠进入 asyncio 协程

我有一个协程如下：

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

DataManager.download()方法如下：

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？如果没有，我该如何使用asyncio.sleep in download()?

或者也许这样的代码结构在概念上是错误的？

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()

结果是：

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，你不应该使用它。它会阻塞整个 python 解释器 1 秒，这不是你想要的。

请记住，你没有并行性（线程等），你有并发性.

IE。你有一个只有 1 个执行线程的 python 解释器，主循环和所有协程都在其中运行，相互抢占。您希望解释器将 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。

所有协程都应该尽快返回并且绝对不应该包含阻塞sleep- 如果您调用它，它会阻止整个解释器并阻止主循环从套接字获取信息或运行协程以响应数据到达这些套接字。

所以，你应该等待asyncio.sleep()这本质上相当于 Javascript 的setTimeout()- 它只是告诉主循环，在特定的时间它应该唤醒这个协程并继续运行它。

建议阅读：

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