1``tornado.platform.caresresolver`` --- Asynchronous DNS Resolver using C-Ares
2=============================================================================
3
4.. module:: tornado.platform.caresresolver
5
6This module contains a DNS resolver using the c-ares library (and its
7wrapper ``pycares``).
8
9.. py:class:: CaresResolver
10
11    Name resolver based on the c-ares library.
12
13    This is a non-blocking and non-threaded resolver.  It may not produce
14    the same results as the system resolver, but can be used for non-blocking
15    resolution when threads cannot be used.
16
17    c-ares fails to resolve some names when ``family`` is ``AF_UNSPEC``,
18    so it is only recommended for use in ``AF_INET`` (i.e. IPv4).  This is
19    the default for ``tornado.simple_httpclient``, but other libraries
20    may default to ``AF_UNSPEC``.
21