Windows7下Anaconda Python3.6.3异步请求遇ClientConnectorError求助

我在Windows 7 64位系统的Anaconda Python 3.6.3环境中，尝试用以下代码发起异步请求获取URL（代码来自某文章）：

import asyncio
from aiohttp import ClientSession
async def hello(url):
    async with ClientSession() as session:
        async with session.get(url) as response:
            response = await response.read()
            print(response)
loop = asyncio.get_event_loop()
loop.run_until_complete(hello("http://httpbin.org/headers"))

但运行后遇到了这个错误：

ClientConnectorError: Cannot connect to host httpbin.org:80 ssl:False [getaddrinfo failed]
Traceback (most recent call last):
File "<ipython-...

排查与解决方法 #

我之前也踩过类似的坑，给你几个实用的解决方向：

• 先确认网络基础连通性：getaddrinfo failed本质是DNS解析失败，先打开浏览器访问http://httpbin.org/headers，如果浏览器也打不开，那问题出在网络本身——可能是防火墙拦截了请求、网络需要代理，或者DNS服务器挂了。先把基础网络问题搞定。

• 配置代理（如果你的网络需要）：aiohttp默认不会自动读取系统代理设置，如果你的网络必须走代理，得手动给ClientSession加代理参数：

  import asyncio
  from aiohttp import ClientSession, TCPConnector
  
  async def hello(url):
      # 替换成你的代理地址和端口
      connector = TCPConnector(proxy="http://your-proxy-address:port")
      async with ClientSession(connector=connector) as session:
          async with session.get(url) as response:
              response = await response.read()
              print(response)
  
  loop = asyncio.get_event_loop()
  loop.run_until_complete(hello("http://httpbin.org/headers"))
  

• 升级aiohttp版本：Python 3.6.3属于比较老的版本，对应的aiohttp初始版本可能存在Windows 7下的DNS解析bug。试试用conda升级到兼容py3.6的稳定版本：

  conda install aiohttp==3.8.6
  

  这个版本对Python 3.6的兼容性很好，能解决不少老版本的兼容性问题。

• 手动指定DNS服务器：如果是DNS解析的问题，可以强制aiohttp用指定的DNS服务器（比如国内的114.114.114.114）：

  import asyncio
  from aiohttp import ClientSession, TCPConnector, AsyncResolver
  
  async def hello(url):
      resolver = AsyncResolver(nameservers=["114.114.114.114"])
      connector = TCPConnector(resolver=resolver)
      async with ClientSession(connector=connector) as session:
          async with session.get(url) as response:
              response = await response.read()
              print(response)
  
  loop = asyncio.get_event_loop()
  loop.run_until_complete(hello("http://httpbin.org/headers"))
  

• 禁用IPv6：Windows 7的IPv6配置有时候会出问题，导致解析优先尝试IPv6失败。可以强制aiohttp只用IPv4：

  import asyncio
  import socket
  from aiohttp import ClientSession, TCPConnector
  
  async def hello(url):
      connector = TCPConnector(family=socket.AF_INET)
      async with ClientSession(connector=connector) as session:
          async with session.get(url) as response:
              response = await response.read()
              print(response)
  
  loop = asyncio.get_event_loop()
  loop.run_until_complete(hello("http://httpbin.org/headers"))
  

内容的提问来源于stack exchange，提问作者BioGeek