Make quotas respect instance_list_per_project_cells

This option was introduced in order to limit queries to cells which only
belong to the project we're interacting with.  However, The nova quota
code was not respecting it and therefore it was always trying to get the
cells assigned to a project even with that option disabled.

This patch makes the quota code respect that option and adds testing to
ensure that enabling the option does make sure it doesn't search all
cells but only the ones for this project.

Closes-Bug: #1878979
Change-Id: I2e0d48e799e70d550f912ad8a424c86df3ade3a2
(cherry picked from commit ab16946885)

nova/quota.py

@@ -1191,8 +1191,12 @@ def _instances_cores_ram_count_legacy(context, project_id, user_id=None):
     # this filtering if there is more than one non-cell0 cell.
     # TODO(tssurya): Consider adding a scatter_gather_cells_for_project
     # variant that makes this native to nova.context.
-    cell_mappings = objects.CellMappingList.get_by_project_id(
+    if CONF.api.instance_list_per_project_cells:
-        context, project_id)
+        cell_mappings = objects.CellMappingList.get_by_project_id(
+            context, project_id)
+    else:
+        nova_context.load_cells()
+        cell_mappings = nova_context.CELLS
     results = nova_context.scatter_gather_cells(
         context, cell_mappings, nova_context.CELL_TIMEOUT,
         objects.InstanceList.get_counts, project_id, user_id=user_id)

nova/tests/functional/db/test_quota.py

@@ -139,7 +139,9 @@ class QuotaTestCase(test.NoDBTestCase):
             ctxt, group, instance.user_id)
         self.assertEqual(2, count['user']['server_group_members'])
 
-    def test_instances_cores_ram_count(self):
+    @mock.patch('nova.objects.CellMappingList.get_by_project_id',
+        wraps=objects.CellMappingList.get_by_project_id)
+    def test_instances_cores_ram_count(self, mock_get_project_cell_mappings):
         ctxt = context.RequestContext('fake-user', 'fake-project')
         mapping1 = objects.CellMapping(context=ctxt,
                                        uuid=uuidutils.generate_uuid(),
@@ -197,10 +199,22 @@ class QuotaTestCase(test.NoDBTestCase):
                                          project_id='fake-project')
             im.create()
 
-        # Count instances, cores, and ram across cells
+        # Count instances, cores, and ram across cells (all cells)
         count = quota._instances_cores_ram_count(ctxt, 'fake-project',
                                                  user_id='fake-user')
+        mock_get_project_cell_mappings.assert_not_called()
+        self.assertEqual(3, count['project']['instances'])
+        self.assertEqual(10, count['project']['cores'])
+        self.assertEqual(2560, count['project']['ram'])
+        self.assertEqual(2, count['user']['instances'])
+        self.assertEqual(6, count['user']['cores'])
+        self.assertEqual(1536, count['user']['ram'])
 
+        # Count instances, cores, and ram across cells (query cell subset)
+        self.flags(instance_list_per_project_cells=True, group='api')
+        count = quota._instances_cores_ram_count(ctxt, 'fake-project',
+                                                 user_id='fake-user')
+        mock_get_project_cell_mappings.assert_called_with(ctxt, 'fake-project')
         self.assertEqual(3, count['project']['instances'])
         self.assertEqual(10, count['project']['cores'])
         self.assertEqual(2560, count['project']['ram'])