Extract peer-disconnect detection into _is_peer_disconnect() helper

Author: dkropachev

cassandra/io/asyncioreactor.py

@@ -13,6 +13,23 @@
 
 log = logging.getLogger(__name__)
 
+# Errno values that indicate the remote peer has disconnected.
+_PEER_DISCONNECT_ERRNOS = frozenset((
+    errno.ENOTCONN, errno.ESHUTDOWN,
+    errno.ECONNRESET, errno.ECONNABORTED,
+))
+
+# Windows winerror codes for the same conditions:
+# 10053 = WSAECONNABORTED, 10054 = WSAECONNRESET
+_PEER_DISCONNECT_WINERRORS = frozenset((10053, 10054))
+
+
+def _is_peer_disconnect(err):
+    """Return True if *err* indicates the remote peer closed the connection."""
+    return (isinstance(err, ConnectionError)
+            or getattr(err, 'winerror', None) in _PEER_DISCONNECT_WINERRORS
+            or getattr(err, 'errno', None) in _PEER_DISCONNECT_ERRNOS)
+
 
 # This module uses ``yield from`` and ``@asyncio.coroutine`` over ``await`` and
 # ``async def`` for pre-Python-3.5 compatibility, so keep in mind that the
@@ -229,21 +246,7 @@ async def handle_write(self):
                 if next_msg:
                     await self._loop.sock_sendall(self._socket, next_msg)
             except socket.error as err:
-                # Peer disconnected — do a clean close instead of defunct.
-                # Use ConnectionError (parent of BrokenPipeError,
-                # ConnectionResetError, ConnectionAbortedError) plus a
-                # winerror check for Windows IOCP which may raise plain
-                # OSError with winerror=10054 (WSAECONNRESET) or
-                # 10053 (WSAECONNABORTED).
-                # Also check errno for ENOTCONN/ESHUTDOWN/ECONNRESET
-                # which macOS raises as plain OSError (not ConnectionError).
-                _peer_errnos = (
-                    errno.ENOTCONN, errno.ESHUTDOWN,
-                    errno.ECONNRESET, errno.ECONNABORTED,
-                )
-                if (isinstance(err, ConnectionError)
-                        or getattr(err, 'winerror', None) in (10053, 10054)
-                        or getattr(err, 'errno', None) in _peer_errnos):
+                if _is_peer_disconnect(err):
                     log.debug("Connection %s closed by peer during write: %s",
                               self, err)
                     self.close()