Reintroduces fake_rabbit config option

This change reintroduces the fake_rabbit only for backward compatibility,
but mark it as deprecated.

Now, to use the kombu in-memory driver (that is not thread safe) we must
set the transport_url config option to 'kombu+memory:////" or the
rpc_backend to kombu+memory.

Or we can use the fake driver of oslo.messaging by setting the
transport_url to 'fake:///' or the rpc_backend to 'fake'

This is effectively reverting commit bcb3b23b8f.

Closes-bug: #1399085

Change-Id: I7b6fb3811fc6f695f75ecd350e04e69afd26c428

oslo/messaging/_drivers/impl_rabbit.py

@@ -100,6 +100,12 @@ rabbit_opts = [
                 help='Use HA queues in RabbitMQ (x-ha-policy: all). '
                      'If you change this option, you must wipe the '
                      'RabbitMQ database.'),
+
+    # NOTE(sileht): deprecated option since oslo.messaging 1.5.0,
+    cfg.BoolOpt('fake_rabbit',
+                default=False,
+                help='Deprecated, use rpc_backend=kombu+memory or '
+                'rpc_backend=fake'),
 ]
 
 LOG = logging.getLogger(__name__)
@@ -441,7 +447,12 @@ class Connection(object):
             virtual_host = self.conf.rabbit_virtual_host
 
         self._url = ''
-        if url.hosts:
+        if self.conf.fake_rabbit:
+            LOG.warn("Deprecated: fake_rabbit option is deprecated, set "
+                     "rpc_backend to kombu+memory or use the fake "
+                     "driver instead.")
+            self._url = 'memory://%s/' % virtual_host
+        elif url.hosts:
             for host in url.hosts:
                 transport = url.transport.replace('kombu+', '')
                 transport = url.transport.replace('rabbit', 'amqp')

tests/drivers/test_impl_rabbit.py

@@ -24,6 +24,7 @@ import mock
 from oslotest import mockpatch
 import testscenarios
 
+from oslo.config import cfg
 from oslo import messaging
 from oslo.messaging._drivers import amqpdriver
 from oslo.messaging._drivers import common as driver_common
@@ -34,6 +35,24 @@ from tests import utils as test_utils
 load_tests = testscenarios.load_tests_apply_scenarios
 
 
+class TestDeprecatedRabbitDriverLoad(test_utils.BaseTestCase):
+
+    def setUp(self):
+        super(TestDeprecatedRabbitDriverLoad, self).setUp(
+            conf=cfg.ConfigOpts())
+        self.messaging_conf.transport_driver = 'rabbit'
+        self.config(fake_rabbit=True)
+
+    def test_driver_load(self):
+        transport = messaging.get_transport(self.conf)
+        self.addCleanup(transport.cleanup)
+        driver = transport._driver
+        url = driver._get_connection()._url
+
+        self.assertIsInstance(driver, rabbit_driver.RabbitDriver)
+        self.assertEqual('memory:////', url)
+
+
 class TestRabbitDriverLoad(test_utils.BaseTestCase):
 
     def setUp(self):