ops

lib/tornado/platform/caresresolver.py

@@ -0,0 +1,79 @@
+from __future__ import absolute_import, division, print_function
+import pycares  # type: ignore
+import socket
+
+from tornado.concurrent import Future
+from tornado import gen
+from tornado.ioloop import IOLoop
+from tornado.netutil import Resolver, is_valid_ip
+
+
+class CaresResolver(Resolver):
+    """Name resolver based on the c-ares library.
+
+    This is a non-blocking and non-threaded resolver.  It may not produce
+    the same results as the system resolver, but can be used for non-blocking
+    resolution when threads cannot be used.
+
+    c-ares fails to resolve some names when ``family`` is ``AF_UNSPEC``,
+    so it is only recommended for use in ``AF_INET`` (i.e. IPv4).  This is
+    the default for ``tornado.simple_httpclient``, but other libraries
+    may default to ``AF_UNSPEC``.
+
+    .. versionchanged:: 5.0
+       The ``io_loop`` argument (deprecated since version 4.1) has been removed.
+    """
+    def initialize(self):
+        self.io_loop = IOLoop.current()
+        self.channel = pycares.Channel(sock_state_cb=self._sock_state_cb)
+        self.fds = {}
+
+    def _sock_state_cb(self, fd, readable, writable):
+        state = ((IOLoop.READ if readable else 0) |
+                 (IOLoop.WRITE if writable else 0))
+        if not state:
+            self.io_loop.remove_handler(fd)
+            del self.fds[fd]
+        elif fd in self.fds:
+            self.io_loop.update_handler(fd, state)
+            self.fds[fd] = state
+        else:
+            self.io_loop.add_handler(fd, self._handle_events, state)
+            self.fds[fd] = state
+
+    def _handle_events(self, fd, events):
+        read_fd = pycares.ARES_SOCKET_BAD
+        write_fd = pycares.ARES_SOCKET_BAD
+        if events & IOLoop.READ:
+            read_fd = fd
+        if events & IOLoop.WRITE:
+            write_fd = fd
+        self.channel.process_fd(read_fd, write_fd)
+
+    @gen.coroutine
+    def resolve(self, host, port, family=0):
+        if is_valid_ip(host):
+            addresses = [host]
+        else:
+            # gethostbyname doesn't take callback as a kwarg
+            fut = Future()
+            self.channel.gethostbyname(host, family,
+                                       lambda result, error: fut.set_result((result, error)))
+            result, error = yield fut
+            if error:
+                raise IOError('C-Ares returned error %s: %s while resolving %s' %
+                              (error, pycares.errno.strerror(error), host))
+            addresses = result.addresses
+        addrinfo = []
+        for address in addresses:
+            if '.' in address:
+                address_family = socket.AF_INET
+            elif ':' in address:
+                address_family = socket.AF_INET6
+            else:
+                address_family = socket.AF_UNSPEC
+            if family != socket.AF_UNSPEC and family != address_family:
+                raise IOError('Requested socket family %d but got %d' %
+                              (family, address_family))
+            addrinfo.append((address_family, (address, port)))
+        raise gen.Return(addrinfo)