龙卷风 Python 阻塞 _socket.getaddrinfo

Question

Python3.4

龙卷风 4.3

当使用 AsyncHttpClient 并捕获任何大于 1s 的阻塞调用时，我偶尔会得到这个堆栈跟踪。

_socket.getaddrinfo 正在阻塞。

怎么会这样？ DNS 没有缓存吗？域解析缓慢或网络故障？

IOLoop blocked for more than 1 seconds in
...
  response = yield client.fetch(request, raise_error=True)
File "/usr/local/lib/python3.4/dist-packages/tornado/httpclient.py", line 255, in fetch
  self.fetch_impl(request, handle_response)
File "/usr/local/lib/python3.4/dist-packages/tornado/simple_httpclient.py", line 133, in fetch_impl
  self._process_queue()
File "/usr/local/lib/python3.4/dist-packages/tornado/simple_httpclient.py", line 148, in _process_queue
  self._handle_request(request, release_callback, callback)
File "/usr/local/lib/python3.4/dist-packages/tornado/simple_httpclient.py", line 157, in _handle_request
  self.max_header_size, self.max_body_size)
File "/usr/local/lib/python3.4/dist-packages/tornado/simple_httpclient.py", line 236, in __init__
  callback=self._on_connect)
File "/usr/local/lib/python3.4/dist-packages/tornado/gen.py", line 230, in wrapper
  yielded = next(result)
File "/usr/local/lib/python3.4/dist-packages/tornado/tcpclient.py", line 164, in connect
  addrinfo = yield self.resolver.resolve(host, port, af)
File "/usr/local/lib/python3.4/dist-packages/tornado/concurrent.py", line 371, in wrapper
  future = getattr(self, executor).submit(fn, self, *args, **kwargs)
File "/usr/local/lib/python3.4/dist-packages/tornado/concurrent.py", line 337, in submit
  future.set_result(fn(*args, **kwargs))
File "/usr/local/lib/python3.4/dist-packages/tornado/netutil.py", line 374, in resolve
  addrinfo = socket.getaddrinfo(host, port, family, socket.SOCK_STREAM)
File "/usr/lib/python3.4/socket.py", line 530, in getaddrinfo
  for res in _socket.getaddrinfo(host, port, family, type, proto, flags):

Answer 1

根据操作系统的配置，DNS 查找可能会也可能不会被缓存。 Mac OS X 系统会缓存一分钟左右，Linux 系统通常不会在其默认配置中缓存 DNS。

默认情况下，Tornado 直接调用 getaddrinfo 并将其留给您的系统实现来缓存结果。您可以使用缓存配置您的系统，或者接受偶尔的 getaddrinfo 调用会很慢，或者为 Tornado 安装一个非阻塞解析器，如 PyCARES 或 Twisted。有关详细信息，请参阅 Tornado's documentation on configuring alternate resolvers。

龙卷风 Python 阻塞 _socket.getaddrinfo

Tornado Python blocking on _socket.getaddrinfo

python

networking

tornado