同步睡眠进入asyncio协程

Question

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

这是一个好习惯吗？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？

Answer 1

这很可能是一种不好的做法，因为 time.sleep() 会阻止所有内容，而您只想阻止特定的协程（我猜）。

您正在异步世界中进行同步操作。

下面的模式呢？

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

Answer 2

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() 功能 - 不，您不应该使用它。它会阻塞整个 python 解释器 1 秒，这不是您想要的。

记住，你没有并行（线程等），你有并发。

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return尽可能快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获取信息或运行ning 协程响应数据，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ning 它。

同步睡眠进入asyncio协程

Synchronous sleep into asyncio coroutine

python

asynchronous

python-3.x

python-asyncio