Don't switch to list_notifier unless necessary.

Some notification tests depend on a different, single notifier being
used. So, don't switch to the list notifier just because we loaded
this class; only switch if an actual plugin needs it.

Also: improved the test that makes sure all this notifier-switching
doesn't break the notifier that was present in the first place.

Change-Id: I170477bccb3ad9505fe6dbfbc214f77c09f6862f

2 files changed, 33 insertions, 17 deletions

diff --git a/openstack/common/plugin/pluginmanager.py b/openstack/common/plugin/pluginmanager.py
index 2e3d497..d9b6bc3 100644
--- a/openstack/common/plugin/pluginmanager.py
+++ b/openstack/common/plugin/pluginmanager.py
@@ -53,15 +53,16 @@ class PluginManager(object):
         self._service_name = service_name
         self.plugins = []
 
-        # Make sure we're using the list_notifier.
-        if not hasattr(CONF, "list_notifier_drivers"):
-            CONF.list_notifier_drivers = []
-        old_notifier = CONF.notification_driver
-        drvstring = 'openstack.common.notifier.list_notifier'
-        CONF.notification_driver = drvstring
-        if (old_notifier and
-            old_notifier != 'openstack.common.notifier.list_notifier'):
-            list_notifier.add_driver(old_notifier)
+    def _force_use_list_notifier(self):
+        if (CONF.notification_driver !=
+            'openstack.common.notifier.list_notifier'):
+            if not hasattr(CONF, "list_notifier_drivers"):
+                CONF.list_notifier_drivers = []
+            old_notifier = CONF.notification_driver
+            drvstring = 'openstack.common.notifier.list_notifier'
+            CONF.notification_driver = drvstring
+            if old_notifier:
+                list_notifier.add_driver(old_notifier)
 
     def load_plugins(self):
         self.plugins = []
@@ -76,6 +77,13 @@ class PluginManager(object):
                 LOG.error(_("Failed to load plugin %(plug)s: %(exc)s") %
                           {'plug': entrypoint, 'exc': exc})
 
+        # See if we need to turn on the list notifier
+        for plugin in self.plugins:
+            if plugin.notifiers:
+                self._force_use_list_notifier()
+                break
+
+        # Register individual notifiers.
         for plugin in self.plugins:
             for notifier in plugin.notifiers:
                 list_notifier.add_driver(notifier)
diff --git a/tests/unit/test_plugin.py b/tests/unit/test_plugin.py
index cfbbb23..01665ba 100644
--- a/tests/unit/test_plugin.py
+++ b/tests/unit/test_plugin.py
@@ -16,6 +16,7 @@
 import pkg_resources
 import unittest
 
+from openstack.common import cfg
 from openstack.common import notifier
 from openstack.common.notifier import api as notifier_api
 from openstack.common.notifier import no_op_notifier
@@ -33,6 +34,12 @@ class SimpleNotifier(object):
         self.message_list.append(message)
 
 
+class SimplerNotifier(object):
+    def notify(self, context, message):
+        global simpler_notify_called
+        simpler_notify_called = True
+
+
 class ManagerTestCase(test_utils.BaseTestCase):
     def tearDown(self):
         super(ManagerTestCase, self).tearDown()
@@ -49,13 +56,10 @@ class NotifyTestCase(test_utils.BaseTestCase):
 
         # Set up a 'normal' notifier to make sure the plugin logic
         #  doesn't mess anything up.
-        self.config(
-                notification_driver='openstack.common.notifier.no_op_notifier')
-
-        def mock_notify(cls, *args):
-            self.no_op_notify_called = True
-        self.stubs.Set(no_op_notifier, 'notify',
-                mock_notify)
+        self.stubs.Set(cfg.CONF, 'notification_driver',
+                SimplerNotifier())
+        global simpler_notify_called
+        simpler_notify_called = False
 
     def tearDown(self):
         super(NotifyTestCase, self).tearDown()
@@ -90,7 +94,11 @@ class NotifyTestCase(test_utils.BaseTestCase):
                             notifier_api.WARN, dict(a=3))
 
         self.assertEqual(len(notifier.message_list), 1)
-        self.assertTrue(self.no_op_notify_called)
+
+        # Verify that the original baseline notifier is still
+        # installed and working.
+        global simpler_notify_called
+        self.assertTrue(simpler_notify_called)
 
 
 class StubControllerExtension(object):