CountableResource: try count/get functions for all plugins

It's of no guarantee that core plugin implements counter/getter function
for a CountableResource. Instead of just trying core plugin, try every
plugin registered in the directory.

To retain backwards compatibility, we also make sure that core plugin is
checked first.

Change-Id: I5245e217e1f44281f85febbdfaf873321253dc5d
Closes-Bug: #1714769
(cherry picked from commit 07bfe6adb9)

neutron/db/quota/driver.py

@@ -93,6 +93,8 @@ class DbQuotaDriver(object):
                 used = resource.count_used(context, tenant_id,
                                            resync_usage=False)
             else:
+                # NOTE(ihrachys) .count won't use the plugin we pass, but we
+                # pass it regardless to keep the quota driver API intact
                 plugins = directory.get_plugins()
                 plugin = plugins.get(key, plugins[constants.CORE])
                 used = resource.count(context, plugin, tenant_id)

neutron/quota/resource.py

@@ -12,6 +12,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+from neutron_lib.plugins import constants
+from neutron_lib.plugins import directory
 from oslo_config import cfg
 from oslo_log import log
 from oslo_utils import excutils
@@ -24,20 +26,32 @@ from neutron.db.quota import api as quota_api
 LOG = log.getLogger(__name__)
 
 
-def _count_resource(context, plugin, collection_name, tenant_id):
+def _count_resource(context, collection_name, tenant_id):
     count_getter_name = "get_%s_count" % collection_name
+    getter_name = "get_%s" % collection_name
 
-    # Some plugins support a count method for particular resources,
-    # using a DB's optimized counting features. We try to use that one
-    # if present. Otherwise just use regular getter to retrieve all objects
-    # and count in python, allowing older plugins to still be supported
-    try:
-        obj_count_getter = getattr(plugin, count_getter_name)
-        return obj_count_getter(context, filters={'tenant_id': [tenant_id]})
-    except (NotImplementedError, AttributeError):
-        obj_getter = getattr(plugin, "get_%s" % collection_name)
-        obj_list = obj_getter(context, filters={'tenant_id': [tenant_id]})
-        return len(obj_list) if obj_list else 0
+    plugins = directory.get_plugins()
+    for pname in sorted(plugins,
+                        # inspect core plugin first
+                        key=lambda n: n != constants.CORE):
+        # Some plugins support a count method for particular resources, using a
+        # DB's optimized counting features. We try to use that one if present.
+        # Otherwise just use regular getter to retrieve all objects and count
+        # in python, allowing older plugins to still be supported
+        try:
+            obj_count_getter = getattr(plugins[pname], count_getter_name)
+            return obj_count_getter(
+                context, filters={'tenant_id': [tenant_id]})
+        except (NotImplementedError, AttributeError):
+            try:
+                obj_getter = getattr(plugins[pname], getter_name)
+                obj_list = obj_getter(
+                    context, filters={'tenant_id': [tenant_id]})
+                return len(obj_list) if obj_list else 0
+            except (NotImplementedError, AttributeError):
+                pass
+    raise NotImplementedError(
+        'No plugins that support counting %s found.' % collection_name)
 
 
 class BaseResource(object):
@@ -129,7 +143,8 @@ class CountableResource(BaseResource):
         self._count_func = count
 
     def count(self, context, plugin, tenant_id, **kwargs):
-        return self._count_func(context, plugin, self.plural_name, tenant_id)
+        # NOTE(ihrachys) _count_resource doesn't receive plugin
+        return self._count_func(context, self.plural_name, tenant_id)
 
 
 class TrackedResource(BaseResource):

neutron/tests/unit/db/quota/test_driver.py

@@ -29,7 +29,7 @@ from neutron.tests.unit import testlib_api
 DB_PLUGIN_KLASS = 'neutron.db.db_base_plugin_v2.NeutronDbPluginV2'
 
 
-def _count_resource(context, plugin, resource, tenant_id):
+def _count_resource(context, resource, tenant_id):
     """A fake counting function to determine current used counts"""
     if resource[-1] == 's':
         resource = resource[:-1]

neutron/tests/unit/quota/test_resource.py

@@ -14,6 +14,8 @@
 
 import mock
 from neutron_lib import context
+from neutron_lib.plugins import constants
+from neutron_lib.plugins import directory
 from oslo_config import cfg
 from oslo_utils import uuidutils
 import testtools
@@ -325,3 +327,45 @@ class TestTrackedResource(testlib_api.SqlTestCase):
             self.assertNotIn(self.tenant_id, res._out_of_sync_tenants)
             mock_set_quota_usage.assert_called_once_with(
                 self.context, self.resource, self.tenant_id, in_use=2)
+
+
+class Test_CountResource(base.BaseTestCase):
+
+    def test_all_plugins_checked(self):
+        plugin1 = mock.Mock()
+        plugin2 = mock.Mock()
+        plugins = {'plugin1': plugin1, 'plugin2': plugin2}
+
+        for name, plugin in plugins.items():
+            plugin.get_floatingips_count.side_effect = NotImplementedError
+            plugin.get_floatingips.side_effect = NotImplementedError
+            directory.add_plugin(name, plugin)
+
+        context = mock.Mock()
+        collection_name = 'floatingips'
+        tenant_id = 'fakeid'
+        self.assertRaises(
+            NotImplementedError,
+            resource._count_resource, context, collection_name, tenant_id)
+
+        for plugin in plugins.values():
+            for func in (plugin.get_floatingips_count, plugin.get_floatingips):
+                func.assert_called_with(
+                    context, filters={'tenant_id': [tenant_id]})
+
+    def test_core_plugin_checked_first(self):
+        plugin1 = mock.Mock()
+        plugin2 = mock.Mock()
+
+        plugin1.get_floatingips_count.side_effect = NotImplementedError
+        plugin1.get_floatingips.side_effect = NotImplementedError
+        directory.add_plugin('plugin1', plugin1)
+
+        plugin2.get_floatingips_count.return_value = 10
+        directory.add_plugin(constants.CORE, plugin2)
+
+        context = mock.Mock()
+        collection_name = 'floatingips'
+        tenant_id = 'fakeid'
+        self.assertEqual(
+            10, resource._count_resource(context, collection_name, tenant_id))