Don't raise Timeout on no-matchmaker results

This patch was proposed by this review:
https://review.openstack.org/#/c/31231

The unit test is added.

Change-Id: Ie124dc22f4ef3bbaeed76186cf08924a39b52812
Co-Authored-By: Eric Windisch <ewindisch@docker.com>
Closes-Bug: #1186310
(cherry picked from commit f033fc9436)

oslo_messaging/_drivers/impl_zmq.py

@@ -35,7 +35,7 @@ from six import moves
 from oslo_messaging._drivers import base
 from oslo_messaging._drivers import common as rpc_common
 from oslo_messaging._executors import base as executor_base  # FIXME(markmc)
-from oslo_messaging._i18n import _, _LE
+from oslo_messaging._i18n import _, _LE, _LW
 
 
 zmq = importutils.try_import('eventlet.green.zmq')
@@ -770,10 +770,15 @@ def _multi_send(method, context, topic, msg, timeout=None,
 
     # Don't stack if we have no matchmaker results
     if not queues:
-        LOG.warn(_("No matchmaker results. Not casting."))
+        warn_log = _LW("No matchmaker results. Not sending.")
+
+        if method.__name__ == '_cast':
+            LOG.warn(warn_log)
+            return
+
         # While not strictly a timeout, callers know how to handle
         # this exception and a timeout isn't too big a lie.
-        raise rpc_common.Timeout(_("No match from matchmaker."))
+        raise rpc_common.Timeout(warn_log)
 
     # This supports brokerless fanout (addresses > 1)
     return_val = None

oslo_messaging/tests/drivers/test_impl_zmq.py

@@ -27,6 +27,7 @@ except ImportError:
     zmq = None
 
 import oslo_messaging
+from oslo_messaging._drivers import common as rpc_common
 from oslo_messaging.tests import utils as test_utils
 
 # eventlet is not yet py3 compatible, so skip if not installed
@@ -384,6 +385,38 @@ class TestZmqListener(ZmqBaseTestCase):
 
 class TestZmqDriver(ZmqBaseTestCase):
 
+    @mock.patch('oslo_messaging._drivers.impl_zmq._cast', autospec=True)
+    @mock.patch('oslo_messaging._drivers.matchmaker.MatchMakerBase.queues',
+                autospec=True)
+    def test_zmqdriver_multi_send_cast_with_no_queues(self,
+                                                      mock_queues,
+                                                      mock_cast):
+        context = mock.Mock(autospec=impl_zmq.RpcContext)
+        topic = 'testtopic'
+        msg = 'jeronimo'
+
+        with mock.patch.object(impl_zmq.LOG, 'warn') as flog:
+            mock_queues.return_value = None
+            impl_zmq._multi_send(mock_cast, context, topic, msg)
+            self.assertEqual(1, flog.call_count)
+            args, kwargs = flog.call_args
+            self.assertIn('No matchmaker results', args[0])
+
+    @mock.patch('oslo_messaging._drivers.impl_zmq._call', autospec=True)
+    @mock.patch('oslo_messaging._drivers.matchmaker.MatchMakerBase.queues',
+                autospec=True)
+    def test_zmqdriver_multi_send_call_with_no_queues(self,
+                                                      mock_queues,
+                                                      mock_call):
+        context = mock.Mock(autospec=impl_zmq.RpcContext)
+        topic = 'testtopic'
+        msg = 'jeronimo'
+
+        mock_queues.return_value = None
+        self.assertRaises(rpc_common.Timeout,
+                          impl_zmq._multi_send,
+                          mock_call, context, topic, msg)
+
     @mock.patch('oslo_messaging._drivers.impl_zmq._cast', autospec=True)
     @mock.patch('oslo_messaging._drivers.impl_zmq._multi_send', autospec=True)
     def test_zmqdriver_send(self, mock_multi_send, mock_cast):