Add ipv6 support for dogstatsd (#791)

* Add ipv6 support

* Fix comment

* Use positional arguments for getaddrinfo

Keyword arguments not supported on py2.7

* Restore order of timeout and connect

This makes no difference with udp sockets, but do it anyway for
symmetry and ease of maintenace.

datadog/dogstatsd/base.py

@@ -625,12 +625,31 @@ def _get_uds_socket(cls, socket_path, timeout):
 
     @classmethod
     def _get_udp_socket(cls, host, port, timeout):
-        sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
-        sock.settimeout(timeout)
-        cls._ensure_min_send_buffer_size(sock)
-        sock.connect((host, port))
-
-        return sock
+        log.debug("Connecting to %s:%s", host, port)
+        addrinfo = socket.getaddrinfo(host, port, 0, socket.SOCK_DGRAM)
+        # Override gai.conf order for backwrads compatibility: prefer
+        # v4, so that a v4-only service on hosts with both addresses
+        # still works.
+        addrinfo.sort(key=lambda v: v[0] == socket.AF_INET, reverse=True)
+        lastaddr = len(addrinfo) - 1
+        for i, (af, ty, proto, _, addr) in enumerate(addrinfo):
+            sock = None
+            try:
+                sock = socket.socket(af, ty, proto)
+                sock.settimeout(timeout)
+                cls._ensure_min_send_buffer_size(sock)
+                sock.connect(addr)
+                log.debug("Connected to: %s", addr)
+                return sock
+            except Exception as e:
+                if sock is not None:
+                    sock.close()
+                log.debug("Failed to connect to %s: %s", addr, e)
+                if i < lastaddr:
+                    continue
+                raise e
+        else:
+            raise ValueError("getaddrinfo returned no addresses to connect to")
 
     def open_buffer(self, max_buffer_size=None):
         """

tests/unit/dogstatsd/test_statsd.py

@@ -697,7 +697,7 @@ def test_udp_socket_ensures_min_receive_buffer(self, mock_socket_create):
         datadog.flush()
 
         # Sanity check
-        mock_socket_create.assert_called_once_with(socket.AF_INET, socket.SOCK_DGRAM)
+        mock_socket_create.assert_called_once_with(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
 
         mock_socket.setsockopt.assert_called_once_with(
             socket.SOL_SOCKET,
@@ -1399,6 +1399,35 @@ def wait_for_data():
             expected_telemetry = telemetry_metrics(metrics=1, packets_sent=1, bytes_sent=8)
             self.assertEqual(udp_thread_telemetry_data, expected_telemetry)
 
+    def test_dedicated_udp6_telemetry_dest(self):
+        listener_sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
+        listener_sock.bind(('localhost', 0))
+
+        def wait_for_data():
+            global udp_thread_telemetry_data
+            udp_thread_telemetry_data = listener_sock.recvfrom(UDP_OPTIMAL_PAYLOAD_LENGTH)[0].decode('utf-8')
+
+        with closing(listener_sock):
+            port = listener_sock.getsockname()[1]
+
+            dogstatsd = DogStatsd(
+                host="localhost",
+                port=12345,
+                telemetry_min_flush_interval=0,
+                telemetry_host="::1", # use explicit address, localhost may resolve to v4.
+                telemetry_port=port,
+            )
+
+            server = threading.Thread(target=wait_for_data)
+            server.start()
+
+            dogstatsd.increment('abc')
+
+            server.join(3)
+
+            expected_telemetry = telemetry_metrics(metrics=1, packets_sent=1, bytes_sent=8)
+            self.assertEqual(udp_thread_telemetry_data, expected_telemetry)
+
     def test_dedicated_uds_telemetry_dest(self):
         tempdir = tempfile.mkdtemp()
         socket_path = os.path.join(tempdir, 'socket.sock')