Fix bug with multiple threaded usage of stream sockets by guaranteeing the "size" and "message" packets are always sent one after another.

Author: ddrthall

datadog/dogstatsd/base.py

@@ -1317,8 +1317,9 @@ def _xmit_packet(self, packet, is_telemetry):
 
             encoded_packet = packet.encode(self.encoding)
             if socket_kind == socket.SOCK_STREAM:
-                mysocket.sendall(struct.pack('<I', len(encoded_packet)))
-                mysocket.sendall(encoded_packet)
+                with self._socket_lock:
+                    mysocket.sendall(struct.pack('<I', len(encoded_packet)))
+                    mysocket.sendall(encoded_packet)
             else:
                 mysocket.send(encoded_packet)