Merge "notification listener: add allow_requeue param"

oslo/messaging/_drivers/base.py

@@ -67,6 +67,11 @@ class BaseDriver(object):
         self._default_exchange = default_exchange
         self._allowed_remote_exmods = allowed_remote_exmods
 
+    def require_features(self, requeue=False):
+        if requeue:
+            raise NotImplementedError('Message requeueing not supported by '
+                                      'this transport driver')
+
     @abc.abstractmethod
     def send(self, target, ctxt, message,
              wait_for_reply=None, timeout=None, envelope=False):

oslo/messaging/_drivers/impl_fake.py

@@ -122,6 +122,9 @@ class FakeDriver(base.BaseDriver):
 
         self._exchange_manager = FakeExchangeManager(default_exchange)
 
+    def require_features(self, requeue=True):
+        pass
+
     @staticmethod
     def _check_serialize(message):
         """Make sure a message intended for rpc can be serialized.

oslo/messaging/_drivers/impl_qpid.py

@@ -100,8 +100,7 @@ class QpidMessage(dict):
         self._session.acknowledge(self._raw_message)
 
     def requeue(self):
-        raise NotImplementedError('The QPID driver does not yet support '
-                                  'requeuing messages')
+        pass
 
 
 class ConsumerBase(object):

oslo/messaging/_drivers/impl_rabbit.py

@@ -744,3 +744,6 @@ class RabbitDriver(amqpdriver.AMQPDriverBase):
                                            connection_pool,
                                            default_exchange,
                                            allowed_remote_exmods)
+
+    def require_features(self, requeue=True):
+        pass

oslo/messaging/_drivers/impl_zmq.py

@@ -844,8 +844,7 @@ class ZmqIncomingMessage(base.IncomingMessage):
             self.condition.notify()
 
     def requeue(self):
-        raise NotImplementedError('The ZeroMQ driver does not yet support '
-                                  'requeuing messages')
+        pass
 
 
 class ZmqListener(base.Listener):

oslo/messaging/notify/dispatcher.py

@@ -44,10 +44,11 @@ class NotificationDispatcher(object):
     message to the endpoints
     """
 
-    def __init__(self, targets, endpoints, serializer):
+    def __init__(self, targets, endpoints, serializer, allow_requeue):
         self.targets = targets
         self.endpoints = endpoints
         self.serializer = serializer or msg_serializer.NoOpSerializer()
+        self.allow_requeue = allow_requeue
 
         self._callbacks_by_priority = {}
         for endpoint, prio in itertools.product(endpoints, PRIORITIES):
@@ -119,7 +120,7 @@ class NotificationDispatcher(object):
                 ret = callback(ctxt, publisher_id, event_type, payload,
                                metadata)
                 ret = NotificationResult.HANDLED if ret is None else ret
-                if ret != NotificationResult.HANDLED:
+                if self.allow_requeue and ret == NotificationResult.REQUEUE:
                     return ret
             finally:
                 localcontext.clear_local_context()

oslo/messaging/notify/listener.py

@@ -73,26 +73,20 @@ priority
 Parameters to endpoint methods are the request context supplied by the client,
 the publisher_id of the notification message, the event_type, the payload.
 
-An endpoint method can return explicitly messaging.NotificationResult.HANDLED
+By supplying a serializer object, a listener can deserialize a request context
+and arguments from - and serialize return values to - primitive types.
+
+An endpoint method can explicitly return messaging.NotificationResult.HANDLED
 to acknowledge a message or messaging.NotificationResult.REQUEUE to requeue the
 message.
 
-The message is acknowledge only if all endpoints return
-messaging.NotificationResult.HANDLED
+The message is acknowledged only if all endpoints either return
+messaging.NotificationResult.HANDLED or None.
 
-If nothing is returned by an endpoint, this is considered like
-messaging.NotificationResult.HANDLED
-
-messaging.NotificationResult values needs to be handled by drivers:
-
-* HANDLED: supported by all drivers
-* REQUEUE: supported by drivers: fake://, rabbit://
-
-In case of an unsupported driver nothing is done to the message and a
-NotImplementedError is raised and logged.
-
-By supplying a serializer object, a listener can deserialize a request context
-and arguments from - and serialize return values to - primitive types.
+Note that not all transport drivers implement support for requeueing. In order
+to use this feature, applications should assert that the feature is available
+by passing allow_requeue=True to get_notification_listener(). If the driver
+does not support requeueing, it will raise NotImplementedError at this point.
 """
 
 from oslo.messaging.notify import dispatcher as notify_dispatcher
@@ -100,7 +94,8 @@ from oslo.messaging import server as msg_server
 
 
 def get_notification_listener(transport, targets, endpoints,
-                              executor='blocking', serializer=None):
+                              executor='blocking', serializer=None,
+                              allow_requeue=False):
     """Construct a notification listener
 
     The executor parameter controls how incoming messages will be received and
@@ -117,7 +112,12 @@ def get_notification_listener(transport, targets, endpoints,
     :type executor: str
     :param serializer: an optional entity serializer
     :type serializer: Serializer
+    :param allow_requeue: whether NotificationResult.REQUEUE support is needed
+    :type allow_requeue: bool
+    :raises: NotImplementedError
     """
+    transport._require_driver_features(requeue=allow_requeue)
     dispatcher = notify_dispatcher.NotificationDispatcher(targets, endpoints,
-                                                          serializer)
+                                                          serializer,
+                                                          allow_requeue)
     return msg_server.MessageHandlingServer(transport, dispatcher, executor)

oslo/messaging/transport.py

@@ -78,6 +78,9 @@ class Transport(object):
         self.conf = driver.conf
         self._driver = driver
 
+    def _require_driver_features(self, requeue=False):
+        self._driver.require_features(requeue=requeue)
+
     def _send(self, target, ctxt, message, wait_for_reply=None, timeout=None):
         if not target.topic:
             raise exceptions.InvalidTarget('A topic is required to send',

tests/test_notify_dispatcher.py

@@ -97,9 +97,8 @@ class TestDispatcher(test_utils.BaseTestCase):
         msg['priority'] = self.priority
 
         targets = [messaging.Target(topic='notifications')]
-        dispatcher = notify_dispatcher.NotificationDispatcher(targets,
-                                                              endpoints,
-                                                              None)
+        dispatcher = notify_dispatcher.NotificationDispatcher(
+            targets, endpoints, None, allow_requeue=True)
 
         # check it listen on wanted topics
         self.assertEqual(sorted(dispatcher._targets_priorities),
@@ -141,9 +140,8 @@ class TestDispatcher(test_utils.BaseTestCase):
     def test_dispatcher_unknown_prio(self, mylog):
         msg = notification_msg.copy()
         msg['priority'] = 'what???'
-        dispatcher = notify_dispatcher.NotificationDispatcher([mock.Mock()],
-                                                              [mock.Mock()],
-                                                              None)
+        dispatcher = notify_dispatcher.NotificationDispatcher(
+            [mock.Mock()], [mock.Mock()], None, allow_requeue=True)
         with dispatcher(mock.Mock(ctxt={}, message=msg)) as callback:
             callback()
         mylog.warning.assert_called_once_with('Unknown priority "what???"')

tests/test_notify_listener.py

@@ -33,7 +33,7 @@ class ListenerSetupMixin(object):
             self._expect_messages = expect_messages
             self._received_msgs = 0
             self._listener = messaging.get_notification_listener(
-                transport, targets, endpoints + [self])
+                transport, targets, endpoints + [self], allow_requeue=True)
 
         def info(self, ctxt, publisher_id, event_type, payload):
             self._received_msgs += 1