[3.7] bpo-35380: Enable TCP_NODELAY for proactor event loop (GH-10867) (GH-10872)

* bpo-35380: Enable TCP_NODELAY for proactor event loop (GH-10867)
(cherry picked from commit 3bc0ebab17)

Co-authored-by: Andrew Svetlov <andrew.svetlov@gmail.com>

Lib/asyncio/base_events.py

@@ -165,6 +165,17 @@ def _run_until_complete_cb(fut):
     futures._get_loop(fut).stop()
 
 
+if hasattr(socket, 'TCP_NODELAY'):
+    def _set_nodelay(sock):
+        if (sock.family in {socket.AF_INET, socket.AF_INET6} and
+                sock.type == socket.SOCK_STREAM and
+                sock.proto == socket.IPPROTO_TCP):
+            sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
+else:
+    def _set_nodelay(sock):
+        pass
+
+
 class _SendfileFallbackProtocol(protocols.Protocol):
     def __init__(self, transp):
         if not isinstance(transp, transports._FlowControlMixin):

Lib/asyncio/proactor_events.py

@@ -444,6 +444,11 @@ class _ProactorSocketTransport(_ProactorReadPipeTransport,
 
     _sendfile_compatible = constants._SendfileMode.TRY_NATIVE
 
+    def __init__(self, loop, sock, protocol, waiter=None,
+                 extra=None, server=None):
+        super().__init__(loop, sock, protocol, waiter, extra, server)
+        base_events._set_nodelay(sock)
+
     def _set_extra(self, sock):
         self._extra['socket'] = sock
 

Lib/asyncio/selector_events.py

@@ -39,17 +39,6 @@ def _test_selector_event(selector, fd, event):
         return bool(key.events & event)
 
 
-if hasattr(socket, 'TCP_NODELAY'):
-    def _set_nodelay(sock):
-        if (sock.family in {socket.AF_INET, socket.AF_INET6} and
-                sock.type == socket.SOCK_STREAM and
-                sock.proto == socket.IPPROTO_TCP):
-            sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
-else:
-    def _set_nodelay(sock):
-        pass
-
-
 class BaseSelectorEventLoop(base_events.BaseEventLoop):
     """Selector event loop.
 
@@ -733,7 +722,7 @@ class _SelectorSocketTransport(_SelectorTransport):
         # Disable the Nagle algorithm -- small writes will be
         # sent without waiting for the TCP ACK.  This generally
         # decreases the latency (in some cases significantly.)
-        _set_nodelay(self._sock)
+        base_events._set_nodelay(self._sock)
 
         self._loop.call_soon(self._protocol.connection_made, self)
         # only start reading when connection_made() has been called

Lib/test/test_asyncio/test_base_events.py

@@ -272,7 +272,7 @@ class BaseEventLoopTests(test_utils.TestCase):
         loop.set_debug(debug)
         if debug:
             msg = ("Non-thread-safe operation invoked on an event loop other "
-                  "than the current one")
+                   "than the current one")
             with self.assertRaisesRegex(RuntimeError, msg):
                 loop.call_soon(cb)
             with self.assertRaisesRegex(RuntimeError, msg):
@@ -2056,5 +2056,31 @@ class BaseLoopSockSendfileTests(test_utils.TestCase):
             self.run_loop(self.loop.sock_sendfile(sock, self.file, -1))
 
 
+class TestSelectorUtils(test_utils.TestCase):
+    def check_set_nodelay(self, sock):
+        opt = sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY)
+        self.assertFalse(opt)
+
+        base_events._set_nodelay(sock)
+
+        opt = sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY)
+        self.assertTrue(opt)
+
+    @unittest.skipUnless(hasattr(socket, 'TCP_NODELAY'),
+                         'need socket.TCP_NODELAY')
+    def test_set_nodelay(self):
+        sock = socket.socket(family=socket.AF_INET, type=socket.SOCK_STREAM,
+                             proto=socket.IPPROTO_TCP)
+        with sock:
+            self.check_set_nodelay(sock)
+
+        sock = socket.socket(family=socket.AF_INET, type=socket.SOCK_STREAM,
+                             proto=socket.IPPROTO_TCP)
+        with sock:
+            sock.setblocking(False)
+            self.check_set_nodelay(sock)
+
+
+
 if __name__ == '__main__':
     unittest.main()

Lib/test/test_asyncio/test_selector_events.py

@@ -15,7 +15,6 @@ from asyncio.selector_events import BaseSelectorEventLoop
 from asyncio.selector_events import _SelectorTransport
 from asyncio.selector_events import _SelectorSocketTransport
 from asyncio.selector_events import _SelectorDatagramTransport
-from asyncio.selector_events import _set_nodelay
 from test.test_asyncio import utils as test_utils
 
 
@@ -1746,30 +1745,5 @@ class SelectorDatagramTransportTests(test_utils.TestCase):
             exc_info=(ConnectionRefusedError, MOCK_ANY, MOCK_ANY))
 
 
-class TestSelectorUtils(test_utils.TestCase):
-    def check_set_nodelay(self, sock):
-        opt = sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY)
-        self.assertFalse(opt)
-
-        _set_nodelay(sock)
-
-        opt = sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY)
-        self.assertTrue(opt)
-
-    @unittest.skipUnless(hasattr(socket, 'TCP_NODELAY'),
-                         'need socket.TCP_NODELAY')
-    def test_set_nodelay(self):
-        sock = socket.socket(family=socket.AF_INET, type=socket.SOCK_STREAM,
-                             proto=socket.IPPROTO_TCP)
-        with sock:
-            self.check_set_nodelay(sock)
-
-        sock = socket.socket(family=socket.AF_INET, type=socket.SOCK_STREAM,
-                             proto=socket.IPPROTO_TCP)
-        with sock:
-            sock.setblocking(False)
-            self.check_set_nodelay(sock)
-
-
 if __name__ == '__main__':
     unittest.main()

Misc/NEWS.d/next/Library/2018-12-03-14-41-11.bpo-35380.SdRF9l.rst

@@ -0,0 +1 @@
+Enable TCP_NODELAY on Windows for proactor asyncio event loop.