python-3.x - 在 Python 中关闭异步事件循环会导致异常结束

Question

对于在 Windows 上的 Python 3.4 中使用 asyncio 和 aiohttp 的 https 请求，我需要使用 2 个事件循环。用于运行 shell 命令的 ProactorEventLoop，以及用于 HTTPS 请求的默认事件循环。不幸的是，ProactorEventLoop 不适用于 HTTPS 命令。

下面的代码显示了当我使用新创建的默认事件循环并尝试在 Windows 上结束时关闭它时发生的情况。如果我在最后调用 loop.close ，我会在最后得到异常，如下所示:

> Traceback (most recent call last):
>  File "C:\BuildUtilities\p3.4env0\lib\site-packages\aiohttp\connector.py", line 56, in __del__
>    self.close()
>  File "C:\BuildUtilities\p3.4env0\lib\site-packages\aiohttp\connector.py", line 97, in close
>    transport.close()
>  File "C:\Python34\Lib\asyncio\selector_events.py", line 375, in close
>    self._loop.remove_reader(self._sock_fd)
>  File "C:\Python34\Lib\asyncio\selector_events.py", line 155, in remove_reader
>    key = self._selector.get_key(fd)
> AttributeError: 'NoneType' object has no attribute 'get_key'

将其注释掉会删除异常，我不知道为什么。唯一的

import asyncio
import aiohttp

@asyncio.coroutine
def get_body(url):
    response = yield from aiohttp.request('GET', url)
    return (yield from response.read_and_close())

#loop = asyncio.ProactorEventLoop()
loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)

f = asyncio.async( get_body('https://www.google.com') )
try:
    loop.run_until_complete(f)
except Exception as e:
    print(e)

if f.result():
    print(f.result())

loop.close()

谢谢，格林杰

Answer 1

更新:看起来问题已在 github 版本 (0.7.2) 中修复。它不会产生错误。作为@danj.py said , 它由 "Get rid of __del__ in connector" commit 修复.

---

它不是 ProactorEventLoop 或 Windows 特定的。我可以使用默认事件循环在 Ubuntu 上重现错误:

#!/usr/bin/env python3
import asyncio
import aiohttp # $ pip install aiohttp

@asyncio.coroutine
def get_body(url):
    response = yield from aiohttp.request('GET', url)
    return (yield from response.read_and_close())

loop = asyncio.get_event_loop()
body = loop.run_until_complete(get_body('https://stackoverflow.com/q/23283502'))
print(len(body), type(body), body[:200])
loop.close()

这可能是 aiohttp 中的错误，因为用法似乎是正确的。

不加aiohttp请求不会报错:

#!/usr/bin/env python3
import asyncio
from contextlib import closing
from urllib.parse import urlsplit

@asyncio.coroutine
def get_body(url):
    # parse url
    url = urlsplit(url)
    path = '/' * (not url.path) + url.path + '?' * bool(url.query) + url.query
    # open connection
    reader, writer = yield from asyncio.open_connection(
        host=url.hostname,
        port=url.port or (443 if url.scheme == 'https' else 80),
        ssl=(url.scheme == 'https'))
    with closing(writer):
        # send request
        writer.write(b'GET ' + path.encode('ascii') + b' HTTP/1.1\r\n'
                     b'Host: ' + url.netloc.encode('ascii') + b'\r\n'
                     b'Connection: close\r\n\r\n')
        # read headers
        while True:
            line = yield from reader.readline()
            line = line.rstrip(b'\n\r')
            print(line.decode('latin-1'))
            if not line:
                break
        # read body
        body = yield from reader.read()
    return body

loop = asyncio.get_event_loop()
body = loop.run_until_complete(get_body('https://stackoverflow.com/q/23283502'))
print(len(body), type(body), body[:200])
loop.close()

注意:示例并不完全等同，例如，后者不遵循重定向。