90 lines
3.2 KiB
Python
90 lines
3.2 KiB
Python
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import pycares # type: ignore
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import socket
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from tornado.concurrent import Future
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from tornado import gen
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from tornado.ioloop import IOLoop
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from tornado.netutil import Resolver, is_valid_ip
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import typing
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if typing.TYPE_CHECKING:
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from typing import Generator, Any, List, Tuple, Dict # noqa: F401
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class CaresResolver(Resolver):
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"""Name resolver based on the c-ares library.
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This is a non-blocking and non-threaded resolver. It may not produce
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the same results as the system resolver, but can be used for non-blocking
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resolution when threads cannot be used.
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c-ares fails to resolve some names when ``family`` is ``AF_UNSPEC``,
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so it is only recommended for use in ``AF_INET`` (i.e. IPv4). This is
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the default for ``tornado.simple_httpclient``, but other libraries
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may default to ``AF_UNSPEC``.
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.. versionchanged:: 5.0
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The ``io_loop`` argument (deprecated since version 4.1) has been removed.
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"""
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def initialize(self) -> None:
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self.io_loop = IOLoop.current()
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self.channel = pycares.Channel(sock_state_cb=self._sock_state_cb)
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self.fds = {} # type: Dict[int, int]
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def _sock_state_cb(self, fd: int, readable: bool, writable: bool) -> None:
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state = (IOLoop.READ if readable else 0) | (IOLoop.WRITE if writable else 0)
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if not state:
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self.io_loop.remove_handler(fd)
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del self.fds[fd]
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elif fd in self.fds:
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self.io_loop.update_handler(fd, state)
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self.fds[fd] = state
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else:
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self.io_loop.add_handler(fd, self._handle_events, state)
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self.fds[fd] = state
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def _handle_events(self, fd: int, events: int) -> None:
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read_fd = pycares.ARES_SOCKET_BAD
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write_fd = pycares.ARES_SOCKET_BAD
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if events & IOLoop.READ:
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read_fd = fd
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if events & IOLoop.WRITE:
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write_fd = fd
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self.channel.process_fd(read_fd, write_fd)
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@gen.coroutine
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def resolve(
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self, host: str, port: int, family: int = 0
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) -> "Generator[Any, Any, List[Tuple[int, Any]]]":
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if is_valid_ip(host):
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addresses = [host]
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else:
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# gethostbyname doesn't take callback as a kwarg
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fut = Future() # type: Future[Tuple[Any, Any]]
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self.channel.gethostbyname(
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host, family, lambda result, error: fut.set_result((result, error))
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)
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result, error = yield fut
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if error:
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raise IOError(
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"C-Ares returned error %s: %s while resolving %s"
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% (error, pycares.errno.strerror(error), host)
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)
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addresses = result.addresses
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addrinfo = []
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for address in addresses:
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if "." in address:
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address_family = socket.AF_INET
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elif ":" in address:
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address_family = socket.AF_INET6
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else:
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address_family = socket.AF_UNSPEC
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if family != socket.AF_UNSPEC and family != address_family:
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raise IOError(
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"Requested socket family %d but got %d" % (family, address_family)
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)
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addrinfo.append((typing.cast(int, address_family), (address, port)))
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return addrinfo
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