asyncio: Skip getaddrinfo if host is already resolved.

getaddrinfo takes an exclusive lock on some platforms, causing clients to queue
up waiting for the lock if many names are being resolved concurrently. Users
may want to handle name resolution in their own code, for the sake of caching,
using an alternate resolver, or to measure DNS duration separately from
connection duration. Skip getaddrinfo if the "host" passed into
create_connection is already resolved.

See https://github.com/python/asyncio/pull/302 for details.

Patch by A. Jesse Jiryu Davis.

Lib/asyncio/base_events.py

@@ -16,8 +16,10 @@ to modify the meaning of the API call itself.
 
 import collections
 import concurrent.futures
+import functools
 import heapq
 import inspect
+import ipaddress
 import itertools
 import logging
 import os
@@ -70,49 +72,83 @@ def _format_pipe(fd):
         return repr(fd)
 
 
+# Linux's sock.type is a bitmask that can include extra info about socket.
+_SOCKET_TYPE_MASK = 0
+if hasattr(socket, 'SOCK_NONBLOCK'):
+    _SOCKET_TYPE_MASK |= socket.SOCK_NONBLOCK
+if hasattr(socket, 'SOCK_CLOEXEC'):
+    _SOCKET_TYPE_MASK |= socket.SOCK_CLOEXEC
+
+
+@functools.lru_cache(maxsize=1024)
+def _ipaddr_info(host, port, family, type, proto):
+    # Try to skip getaddrinfo if "host" is already an IP. Since getaddrinfo
+    # blocks on an exclusive lock on some platforms, users might handle name
+    # resolution in their own code and pass in resolved IPs.
+    if proto not in {0, socket.IPPROTO_TCP, socket.IPPROTO_UDP} or host is None:
+        return None
+
+    type &= ~_SOCKET_TYPE_MASK
+    if type == socket.SOCK_STREAM:
+        proto = socket.IPPROTO_TCP
+    elif type == socket.SOCK_DGRAM:
+        proto = socket.IPPROTO_UDP
+    else:
+        return None
+
+    if hasattr(socket, 'inet_pton'):
+        if family == socket.AF_UNSPEC:
+            afs = [socket.AF_INET, socket.AF_INET6]
+        else:
+            afs = [family]
+
+        for af in afs:
+            # Linux's inet_pton doesn't accept an IPv6 zone index after host,
+            # like '::1%lo0', so strip it. If we happen to make an invalid
+            # address look valid, we fail later in sock.connect or sock.bind.
+            try:
+                if af == socket.AF_INET6:
+                    socket.inet_pton(af, host.partition('%')[0])
+                else:
+                    socket.inet_pton(af, host)
+                return af, type, proto, '', (host, port)
+            except OSError:
+                pass
+
+        # "host" is not an IP address.
+        return None
+
+    # No inet_pton. (On Windows it's only available since Python 3.4.)
+    # Even though getaddrinfo with AI_NUMERICHOST would be non-blocking, it
+    # still requires a lock on some platforms, and waiting for that lock could
+    # block the event loop. Use ipaddress instead, it's just text parsing.
+    try:
+        addr = ipaddress.IPv4Address(host)
+    except ValueError:
+        try:
+            addr = ipaddress.IPv6Address(host.partition('%')[0])
+        except ValueError:
+            return None
+
+    af = socket.AF_INET if addr.version == 4 else socket.AF_INET6
+    if family not in (socket.AF_UNSPEC, af):
+        # "host" is wrong IP version for "family".
+        return None
+
+    return af, type, proto, '', (host, port)
+
+
 def _check_resolved_address(sock, address):
     # Ensure that the address is already resolved to avoid the trap of hanging
     # the entire event loop when the address requires doing a DNS lookup.
-    #
-    # getaddrinfo() is slow (around 10 us per call): this function should only
-    # be called in debug mode
-    family = sock.family
-
-    if family == socket.AF_INET:
-        host, port = address
-    elif family == socket.AF_INET6:
-        host, port = address[:2]
-    else:
+
+    if hasattr(socket, 'AF_UNIX') and sock.family == socket.AF_UNIX:
         return
 
-    # On Windows, socket.inet_pton() is only available since Python 3.4
-    if hasattr(socket, 'inet_pton'):
-        # getaddrinfo() is slow and has known issue: prefer inet_pton()
-        # if available
-        try:
-            socket.inet_pton(family, host)
-        except OSError as exc:
-            raise ValueError("address must be resolved (IP address), "
-                             "got host %r: %s"
-                             % (host, exc))
-    else:
-        # Use getaddrinfo(flags=AI_NUMERICHOST) to ensure that the address is
-        # already resolved.
-        type_mask = 0
-        if hasattr(socket, 'SOCK_NONBLOCK'):
-            type_mask |= socket.SOCK_NONBLOCK
-        if hasattr(socket, 'SOCK_CLOEXEC'):
-            type_mask |= socket.SOCK_CLOEXEC
-        try:
-            socket.getaddrinfo(host, port,
-                               family=family,
-                               type=(sock.type & ~type_mask),
-                               proto=sock.proto,
-                               flags=socket.AI_NUMERICHOST)
-        except socket.gaierror as err:
-            raise ValueError("address must be resolved (IP address), "
-                             "got host %r: %s"
-                             % (host, err))
+    host, port = address[:2]
+    if _ipaddr_info(host, port, sock.family, sock.type, sock.proto) is None:
+        raise ValueError("address must be resolved (IP address),"
+                         " got host %r" % host)
 
 
 def _run_until_complete_cb(fut):
@@ -535,7 +571,12 @@ class BaseEventLoop(events.AbstractEventLoop):
 
     def getaddrinfo(self, host, port, *,
                     family=0, type=0, proto=0, flags=0):
-        if self._debug:
+        info = _ipaddr_info(host, port, family, type, proto)
+        if info is not None:
+            fut = futures.Future(loop=self)
+            fut.set_result([info])
+            return fut
+        elif self._debug:
             return self.run_in_executor(None, self._getaddrinfo_debug,
                                         host, port, family, type, proto, flags)
         else:

Lib/asyncio/proactor_events.py

@@ -441,8 +441,7 @@ class BaseProactorEventLoop(base_events.BaseEventLoop):
 
     def sock_connect(self, sock, address):
         try:
-            if self._debug:
-                base_events._check_resolved_address(sock, address)
+            base_events._check_resolved_address(sock, address)
         except ValueError as err:
             fut = futures.Future(loop=self)
             fut.set_exception(err)

Lib/asyncio/selector_events.py

@@ -397,8 +397,7 @@ class BaseSelectorEventLoop(base_events.BaseEventLoop):
             raise ValueError("the socket must be non-blocking")
         fut = futures.Future(loop=self)
         try:
-            if self._debug:
-                base_events._check_resolved_address(sock, address)
+            base_events._check_resolved_address(sock, address)
         except ValueError as err:
             fut.set_exception(err)
         else:

Lib/asyncio/test_utils.py

@@ -446,9 +446,14 @@ def disable_logger():
     finally:
         logger.setLevel(old_level)
 
-def mock_nonblocking_socket():
+
+def mock_nonblocking_socket(proto=socket.IPPROTO_TCP, type=socket.SOCK_STREAM,
+                            family=socket.AF_INET):
     """Create a mock of a non-blocking socket."""
-    sock = mock.Mock(socket.socket)
+    sock = mock.MagicMock(socket.socket)
+    sock.proto = proto
+    sock.type = type
+    sock.family = family
     sock.gettimeout.return_value = 0.0
     return sock
 

Lib/test/test_asyncio/test_base_events.py

@@ -32,6 +32,120 @@ MOCK_ANY = mock.ANY
 PY34 = sys.version_info >= (3, 4)
 
 
+def mock_socket_module():
+    m_socket = mock.MagicMock(spec=socket)
+    for name in (
+        'AF_INET', 'AF_INET6', 'AF_UNSPEC', 'IPPROTO_TCP', 'IPPROTO_UDP',
+        'SOCK_STREAM', 'SOCK_DGRAM', 'SOL_SOCKET', 'SO_REUSEADDR', 'inet_pton'
+    ):
+        if hasattr(socket, name):
+            setattr(m_socket, name, getattr(socket, name))
+        else:
+            delattr(m_socket, name)
+
+    m_socket.socket = mock.MagicMock()
+    m_socket.socket.return_value = test_utils.mock_nonblocking_socket()
+
+    return m_socket
+
+
+def patch_socket(f):
+    return mock.patch('asyncio.base_events.socket',
+                      new_callable=mock_socket_module)(f)
+
+
+class BaseEventTests(test_utils.TestCase):
+
+    def setUp(self):
+        super().setUp()
+        base_events._ipaddr_info.cache_clear()
+
+    def tearDown(self):
+        base_events._ipaddr_info.cache_clear()
+        super().tearDown()
+
+    def test_ipaddr_info(self):
+        UNSPEC = socket.AF_UNSPEC
+        INET = socket.AF_INET
+        INET6 = socket.AF_INET6
+        STREAM = socket.SOCK_STREAM
+        DGRAM = socket.SOCK_DGRAM
+        TCP = socket.IPPROTO_TCP
+        UDP = socket.IPPROTO_UDP
+
+        self.assertEqual(
+            (INET, STREAM, TCP, '', ('1.2.3.4', 1)),
+            base_events._ipaddr_info('1.2.3.4', 1, INET, STREAM, TCP))
+
+        self.assertEqual(
+            (INET, STREAM, TCP, '', ('1.2.3.4', 1)),
+            base_events._ipaddr_info('1.2.3.4', 1, UNSPEC, STREAM, TCP))
+
+        self.assertEqual(
+            (INET, DGRAM, UDP, '', ('1.2.3.4', 1)),
+            base_events._ipaddr_info('1.2.3.4', 1, UNSPEC, DGRAM, UDP))
+
+        # Socket type STREAM implies TCP protocol.
+        self.assertEqual(
+            (INET, STREAM, TCP, '', ('1.2.3.4', 1)),
+            base_events._ipaddr_info('1.2.3.4', 1, UNSPEC, STREAM, 0))
+
+        # Socket type DGRAM implies UDP protocol.
+        self.assertEqual(
+            (INET, DGRAM, UDP, '', ('1.2.3.4', 1)),
+            base_events._ipaddr_info('1.2.3.4', 1, UNSPEC, DGRAM, 0))
+
+        # No socket type.
+        self.assertIsNone(
+            base_events._ipaddr_info('1.2.3.4', 1, UNSPEC, 0, 0))
+
+        # IPv4 address with family IPv6.
+        self.assertIsNone(
+            base_events._ipaddr_info('1.2.3.4', 1, INET6, STREAM, TCP))
+
+        self.assertEqual(
+            (INET6, STREAM, TCP, '', ('::3', 1)),
+            base_events._ipaddr_info('::3', 1, INET6, STREAM, TCP))
+
+        self.assertEqual(
+            (INET6, STREAM, TCP, '', ('::3', 1)),
+            base_events._ipaddr_info('::3', 1, UNSPEC, STREAM, TCP))
+
+        # IPv6 address with family IPv4.
+        self.assertIsNone(
+            base_events._ipaddr_info('::3', 1, INET, STREAM, TCP))
+
+        # IPv6 address with zone index.
+        self.assertEqual(
+            (INET6, STREAM, TCP, '', ('::3%lo0', 1)),
+            base_events._ipaddr_info('::3%lo0', 1, INET6, STREAM, TCP))
+
+    @patch_socket
+    def test_ipaddr_info_no_inet_pton(self, m_socket):
+        del m_socket.inet_pton
+        self.test_ipaddr_info()
+
+    def test_check_resolved_address(self):
+        sock = socket.socket(socket.AF_INET)
+        base_events._check_resolved_address(sock, ('1.2.3.4', 1))
+
+        sock = socket.socket(socket.AF_INET6)
+        base_events._check_resolved_address(sock, ('::3', 1))
+        base_events._check_resolved_address(sock, ('::3%lo0', 1))
+        self.assertRaises(ValueError,
+                          base_events._check_resolved_address, sock, ('foo', 1))
+
+    def test_check_resolved_sock_type(self):
+        # Ensure we ignore extra flags in sock.type.
+        if hasattr(socket, 'SOCK_NONBLOCK'):
+            sock = socket.socket(type=socket.SOCK_STREAM | socket.SOCK_NONBLOCK)
+            base_events._check_resolved_address(sock, ('1.2.3.4', 1))
+
+        if hasattr(socket, 'SOCK_CLOEXEC'):
+            sock = socket.socket(type=socket.SOCK_STREAM | socket.SOCK_CLOEXEC)
+            base_events._check_resolved_address(sock, ('1.2.3.4', 1))
+
+
 class BaseEventLoopTests(test_utils.TestCase):
 
     def setUp(self):
@@ -875,7 +989,12 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
         self.loop = asyncio.new_event_loop()
         self.set_event_loop(self.loop)
 
-    @mock.patch('asyncio.base_events.socket')
+    def tearDown(self):
+        # Clear mocked constants like AF_INET from the cache.
+        base_events._ipaddr_info.cache_clear()
+        super().tearDown()
+
+    @patch_socket
     def test_create_connection_multiple_errors(self, m_socket):
 
         class MyProto(asyncio.Protocol):
@@ -908,7 +1027,7 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
 
         self.assertEqual(str(cm.exception), 'Multiple exceptions: err1, err2')
 
-    @mock.patch('asyncio.base_events.socket')
+    @patch_socket
     def test_create_connection_timeout(self, m_socket):
         # Ensure that the socket is closed on timeout
         sock = mock.Mock()
@@ -986,7 +1105,7 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
         with self.assertRaises(OSError):
             self.loop.run_until_complete(coro)
 
-    @mock.patch('asyncio.base_events.socket')
+    @patch_socket
     def test_create_connection_multiple_errors_local_addr(self, m_socket):
 
         def bind(addr):
@@ -1018,6 +1137,46 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
         self.assertTrue(str(cm.exception).startswith('Multiple exceptions: '))
         self.assertTrue(m_socket.socket.return_value.close.called)
 
+    def _test_create_connection_ip_addr(self, m_socket, allow_inet_pton):
+        # Test the fallback code, even if this system has inet_pton.
+        if not allow_inet_pton:
+            del m_socket.inet_pton
+
+        def getaddrinfo(*args, **kw):
+            self.fail('should not have called getaddrinfo')
+
+        m_socket.getaddrinfo = getaddrinfo
+        sock = m_socket.socket.return_value
+
+        self.loop.add_reader = mock.Mock()
+        self.loop.add_reader._is_coroutine = False
+        self.loop.add_writer = mock.Mock()
+        self.loop.add_writer._is_coroutine = False
+
+        coro = self.loop.create_connection(MyProto, '1.2.3.4', 80)
+        self.loop.run_until_complete(coro)
+        sock.connect.assert_called_with(('1.2.3.4', 80))
+        m_socket.socket.assert_called_with(family=m_socket.AF_INET,
+                                           proto=m_socket.IPPROTO_TCP,
+                                           type=m_socket.SOCK_STREAM)
+
+        sock.family = socket.AF_INET6
+        coro = self.loop.create_connection(MyProto, '::2', 80)
+
+        self.loop.run_until_complete(coro)
+        sock.connect.assert_called_with(('::2', 80))
+        m_socket.socket.assert_called_with(family=m_socket.AF_INET6,
+                                           proto=m_socket.IPPROTO_TCP,
+                                           type=m_socket.SOCK_STREAM)
+
+    @patch_socket
+    def test_create_connection_ip_addr(self, m_socket):
+        self._test_create_connection_ip_addr(m_socket, True)
+
+    @patch_socket
+    def test_create_connection_no_inet_pton(self, m_socket):
+        self._test_create_connection_ip_addr(m_socket, False)
+
     def test_create_connection_no_local_addr(self):
         @asyncio.coroutine
         def getaddrinfo(host, *args, **kw):
@@ -1153,11 +1312,9 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
         f = self.loop.create_server(MyProto, '0.0.0.0', 0)
         self.assertRaises(OSError, self.loop.run_until_complete, f)
 
-    @mock.patch('asyncio.base_events.socket')
+    @patch_socket
     def test_create_server_nosoreuseport(self, m_socket):
         m_socket.getaddrinfo = socket.getaddrinfo
-        m_socket.SOCK_STREAM = socket.SOCK_STREAM
-        m_socket.SOL_SOCKET = socket.SOL_SOCKET
         del m_socket.SO_REUSEPORT
         m_socket.socket.return_value = mock.Mock()
 
@@ -1166,7 +1323,7 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
 
         self.assertRaises(ValueError, self.loop.run_until_complete, f)
 
-    @mock.patch('asyncio.base_events.socket')
+    @patch_socket
     def test_create_server_cant_bind(self, m_socket):
 
         class Err(OSError):
@@ -1182,7 +1339,7 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
         self.assertRaises(OSError, self.loop.run_until_complete, fut)
         self.assertTrue(m_sock.close.called)
 
-    @mock.patch('asyncio.base_events.socket')
+    @patch_socket
     def test_create_datagram_endpoint_no_addrinfo(self, m_socket):
         m_socket.getaddrinfo.return_value = []
         m_socket.getaddrinfo._is_coroutine = False
@@ -1211,7 +1368,7 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
         self.assertRaises(
             OSError, self.loop.run_until_complete, coro)
 
-    @mock.patch('asyncio.base_events.socket')
+    @patch_socket 
     def test_create_datagram_endpoint_socket_err(self, m_socket):
         m_socket.getaddrinfo = socket.getaddrinfo
         m_socket.socket.side_effect = OSError
@@ -1234,7 +1391,7 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
         self.assertRaises(
             ValueError, self.loop.run_until_complete, coro)
 
-    @mock.patch('asyncio.base_events.socket')
+    @patch_socket
     def test_create_datagram_endpoint_setblk_err(self, m_socket):
         m_socket.socket.return_value.setblocking.side_effect = OSError
 
@@ -1250,12 +1407,11 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
             asyncio.DatagramProtocol)
         self.assertRaises(ValueError, self.loop.run_until_complete, coro)
 
-    @mock.patch('asyncio.base_events.socket')
+    @patch_socket
     def test_create_datagram_endpoint_cant_bind(self, m_socket):
         class Err(OSError):
             pass
 
-        m_socket.AF_INET6 = socket.AF_INET6
         m_socket.getaddrinfo = socket.getaddrinfo
         m_sock = m_socket.socket.return_value = mock.Mock()
         m_sock.bind.side_effect = Err
@@ -1369,11 +1525,8 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
         self.loop.run_until_complete(protocol.done)
         self.assertEqual('CLOSED', protocol.state)
 
-    @mock.patch('asyncio.base_events.socket')
+    @patch_socket
     def test_create_datagram_endpoint_nosoreuseport(self, m_socket):
-        m_socket.getaddrinfo = socket.getaddrinfo
-        m_socket.SOCK_DGRAM = socket.SOCK_DGRAM
-        m_socket.SOL_SOCKET = socket.SOL_SOCKET
         del m_socket.SO_REUSEPORT
         m_socket.socket.return_value = mock.Mock()
 
@@ -1385,6 +1538,29 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
 
         self.assertRaises(ValueError, self.loop.run_until_complete, coro)
 
+    @patch_socket
+    def test_create_datagram_endpoint_ip_addr(self, m_socket):
+        def getaddrinfo(*args, **kw):
+            self.fail('should not have called getaddrinfo')
+
+        m_socket.getaddrinfo = getaddrinfo
+        m_socket.socket.return_value.bind = bind = mock.Mock()
+        self.loop.add_reader = mock.Mock()
+        self.loop.add_reader._is_coroutine = False
+
+        reuseport_supported = hasattr(socket, 'SO_REUSEPORT')
+        coro = self.loop.create_datagram_endpoint(
+            lambda: MyDatagramProto(loop=self.loop),
+            local_addr=('1.2.3.4', 0),
+            reuse_address=False,
+            reuse_port=reuseport_supported)
+
+        self.loop.run_until_complete(coro)
+        bind.assert_called_with(('1.2.3.4', 0))
+        m_socket.socket.assert_called_with(family=m_socket.AF_INET,
+                                           proto=m_socket.IPPROTO_UDP,
+                                           type=m_socket.SOCK_DGRAM)
+
     def test_accept_connection_retry(self):
         sock = mock.Mock()
         sock.accept.side_effect = BlockingIOError()

Lib/test/test_asyncio/test_events.py

@@ -1573,10 +1573,6 @@ class EventLoopTestsMixin:
              'selector': self.loop._selector.__class__.__name__})
 
     def test_sock_connect_address(self):
-        # In debug mode, sock_connect() must ensure that the address is already
-        # resolved (call _check_resolved_address())
-        self.loop.set_debug(True)
-
         addresses = [(socket.AF_INET, ('www.python.org', 80))]
         if support.IPV6_ENABLED:
             addresses.extend((

Lib/test/test_asyncio/test_proactor_events.py

@@ -436,7 +436,7 @@ class ProactorSocketTransportTests(test_utils.TestCase):
 class BaseProactorEventLoopTests(test_utils.TestCase):
 
     def setUp(self):
-        self.sock = mock.Mock(socket.socket)
+        self.sock = test_utils.mock_nonblocking_socket()
         self.proactor = mock.Mock()
 
         self.ssock, self.csock = mock.Mock(), mock.Mock()
@@ -491,8 +491,8 @@ class BaseProactorEventLoopTests(test_utils.TestCase):
         self.proactor.send.assert_called_with(self.sock, b'data')
 
     def test_sock_connect(self):
-        self.loop.sock_connect(self.sock, 123)
-        self.proactor.connect.assert_called_with(self.sock, 123)
+        self.loop.sock_connect(self.sock, ('1.2.3.4', 123))
+        self.proactor.connect.assert_called_with(self.sock, ('1.2.3.4', 123))
 
     def test_sock_accept(self):
         self.loop.sock_accept(self.sock)