deprecate usage of transport aliases

This change starts the deprecation process for the transport aliases.

The first step is deprecate this one cycle. To ensure deployer have
updated they configuration during Newton Then in Octacia we will deprecate
'aliases' kwargs of transportURL() and get_transport() for consuming
application.

Related-bug: #1424728

Change-Id: I314cefa5fb1803fa7e21e3e34300e5ced31bba89

oslo_messaging/tests/test_transport.py

@@ -14,6 +14,7 @@
 #    under the License.
 
 import fixtures
+import mock
 from mox3 import mox
 from oslo_config import cfg
 import six
@@ -112,7 +113,8 @@ class GetTransportTestCase(test_utils.BaseTestCase):
                           allowed=[]))),
     ]
 
-    def test_get_transport(self):
+    @mock.patch('oslo_messaging.transport.LOG')
+    def test_get_transport(self, fake_logger):
         self.config(rpc_backend=self.rpc_backend,
                     control_exchange=self.control_exchange,
                     transport_url=self.transport_url)
@@ -142,6 +144,12 @@ class GetTransportTestCase(test_utils.BaseTestCase):
             kwargs['aliases'] = self.aliases
         transport_ = oslo_messaging.get_transport(self.conf, **kwargs)
 
+        if self.aliases is not None:
+            self.assertEqual(fake_logger.warning.mock_calls,
+                             [mock.call('legacy "rpc_backend" is deprecated, '
+                                        '"testfoo" must be replaced by '
+                                        '"%s"' % self.aliases.get('testfoo'))])
+
         self.assertIsNotNone(transport_)
         self.assertIs(transport_.conf, self.conf)
         self.assertIs(transport_._driver, drvr)

oslo_messaging/transport.py

@@ -27,6 +27,8 @@ __all__ = [
     'set_transport_defaults',
 ]
 
+import logging
+
 from oslo_config import cfg
 import six
 from six.moves.urllib import parse
@@ -34,6 +36,7 @@ from stevedore import driver
 
 from oslo_messaging import exceptions
 
+LOG = logging.getLogger(__name__)
 
 _transport_opts = [
     cfg.StrOpt('transport_url',
@@ -240,7 +243,7 @@ class TransportURL(object):
     :type virtual_host: str
     :param hosts: a list of TransportHost objects
     :type hosts: list
-    :param aliases: A map of transport alias to transport name
+    :param aliases: DEPRECATED: A map of transport alias to transport name
     :type aliases: dict
     """
 
@@ -259,13 +262,28 @@ class TransportURL(object):
         else:
             self.aliases = aliases
 
+        self._deprecation_logged = False
+
     @property
     def transport(self):
         if self._transport is None:
             transport = self.conf.rpc_backend
         else:
             transport = self._transport
-        return self.aliases.get(transport, transport)
+        final_transport = self.aliases.get(transport, transport)
+        if not self._deprecation_logged and final_transport != transport:
+            # NOTE(sileht): The first step is deprecate this one cycle.
+            # To ensure deployer have updated they configuration during Octavia
+            # Then in P we will deprecate aliases kwargs of TransportURL() and
+            # get_transport() for consuming application
+            LOG.warning('legacy "rpc_backend" is deprecated, '
+                        '"%(legacy_transport)s" must be replaced by '
+                        '"%(final_transport)s"' % {
+                            'legacy_transport': transport,
+                            'final_transport': final_transport})
+            self._deprecation_logged = True
+
+        return final_transport
 
     @transport.setter
     def transport(self, value):