Improve BlockDeviceMapping object cells awareness

This patch makes BlockDeviceMapping object methods that are creating and
updating the database more aware of the cells. There are 2 changes that
are good to distinguish between:

 - create() will _never_ work in the API cell and will raise an
   ObjectActionError.
 - save() and destroy() are now aware in which cell they are being
   called and do not attempt to propagate it upwards

This is currently a no-op change as we don not currently use objects in
any of the code that will run in the top cell. This is in fact
preparation for transiting the API code to using BlockDeviceMapping
objects.

Change-Id: Ic5806c844f2deab734011d68f5da316903000f67

nova/objects/block_device.py

@@ -13,6 +13,7 @@
 #    under the License.
 
 from nova import block_device
+from nova.cells import opts as cells_opts
 from nova.cells import rpcapi as cells_rpcapi
 from nova import db
 from nova import exception
@@ -81,6 +82,13 @@ def _from_db_object(context, block_device_obj,
 
     @base.remotable
     def create(self, context):
+        cell_type = cells_opts.get_cell_type()
+        if cell_type == 'api':
+            raise exception.ObjectActionError(
+                    action='create',
+                    reason='BlockDeviceMapping cannot be '
+                           'created in the API cell.')
+
         if self.obj_attr_is_set('id'):
             raise exception.ObjectActionError(action='create',
                                               reason='already created')
@@ -90,8 +98,9 @@ def create(self, context):
                                               reason='instance assigned')
 
         db_bdm = db.block_device_mapping_create(context, updates, legacy=False)
-        cells_api = cells_rpcapi.CellsAPI()
-        cells_api.bdm_update_or_create_at_top(context, db_bdm, create=True)
+        if cell_type == 'compute':
+            cells_api = cells_rpcapi.CellsAPI()
+            cells_api.bdm_update_or_create_at_top(context, db_bdm, create=True)
         self._from_db_object(context, self, db_bdm)
 
     @base.remotable
@@ -101,10 +110,13 @@ def destroy(self, context):
                                               reason='already destroyed')
         db.block_device_mapping_destroy(context, self.id)
         delattr(self, base.get_attrname('id'))
-        cells_api = cells_rpcapi.CellsAPI()
-        cells_api.bdm_destroy_at_top(context, self.instance_uuid,
-                                     device_name=self.device_name,
-                                     volume_id=self.volume_id)
+
+        cell_type = cells_opts.get_cell_type()
+        if cell_type == 'compute':
+            cells_api = cells_rpcapi.CellsAPI()
+            cells_api.bdm_destroy_at_top(context, self.instance_uuid,
+                                         device_name=self.device_name,
+                                         volume_id=self.volume_id)
 
     @base.remotable
     def save(self, context):
@@ -115,8 +127,10 @@ def save(self, context):
         updates.pop('id', None)
         updated = db.block_device_mapping_update(self._context, self.id,
                                                  updates, legacy=False)
-        cells_api = cells_rpcapi.CellsAPI()
-        cells_api.bdm_update_or_create_at_top(context, updated)
+        cell_type = cells_opts.get_cell_type()
+        if cell_type == 'compute':
+            cells_api = cells_rpcapi.CellsAPI()
+            cells_api.bdm_update_or_create_at_top(context, updated)
         self._from_db_object(context, self, updated)
 
     @base.remotable_classmethod

nova/tests/objects/test_block_device.py

@@ -43,7 +43,12 @@ def fake_bdm(self, instance=None):
             fake_bdm['instance'] = instance
         return fake_bdm
 
-    def test_save(self):
+    def _test_save(self, cell_type=None):
+        if cell_type:
+            self.flags(enable=True, cell_type=cell_type, group='cells')
+        else:
+            self.flags(enable=False, group='cells')
+
         fake_bdm = self.fake_bdm()
         with contextlib.nested(
             mock.patch.object(
@@ -59,7 +64,20 @@ def test_save(self):
             bdm_update_mock.assert_called_once_with(
                     self.context, 123, {'volume_id': 'fake_volume_id'},
                     legacy=False)
-            cells_update_mock.assert_called_once_with(self.context, fake_bdm)
+            if cell_type != 'compute':
+                self.assertFalse(cells_update_mock.called)
+            else:
+                cells_update_mock.assert_called_once_with(
+                        self.context, fake_bdm)
+
+    def test_save_nocells(self):
+        self._test_save()
+
+    def test_save_apicell(self):
+        self._test_save(cell_type='api')
+
+    def test_save_computecell(self):
+        self._test_save(cell_type='compute')
 
     def test_save_instance_changed(self):
         bdm_object = objects.BlockDeviceMapping()
@@ -108,7 +126,11 @@ def test_get_by_volume_id_with_expected(self, get_by_vol_id):
                                               ['instance'])
         self.assertRemotes()
 
-    def test_create_mocked(self):
+    def _test_create_mocked(self, cell_type=None):
+        if cell_type:
+            self.flags(enable=True, cell_type=cell_type, group='cells')
+        else:
+            self.flags(enable=False, group='cells')
         values = {'source_type': 'volume', 'volume_id': 'fake-vol-id',
                   'destination_type': 'volume',
                   'instance_uuid': 'fake-instance'}
@@ -121,11 +143,30 @@ def test_create_mocked(self):
                               'bdm_update_or_create_at_top')
         ) as (bdm_create_mock, cells_update_mock):
             bdm = objects.BlockDeviceMapping(**values)
-            bdm.create(self.context)
-            bdm_create_mock.assert_called_once_with(
+
+            if cell_type == 'api':
+                self.assertRaises(exception.ObjectActionError,
+                                  bdm.create, self.context)
+            elif cell_type == 'compute':
+                bdm.create(self.context)
+                bdm_create_mock.assert_called_once_with(
+                    self.context, values, legacy=False)
+                cells_update_mock.assert_called_once_with(
+                        self.context, fake_bdm, create=True)
+            else:
+                bdm.create(self.context)
+                self.assertFalse(cells_update_mock.called)
+                bdm_create_mock.assert_called_once_with(
                     self.context, values, legacy=False)
-            cells_update_mock.assert_called_once_with(
-                    self.context, fake_bdm, create=True)
+
+    def test_create_nocells(self):
+        self._test_create_mocked()
+
+    def test_create_apicell(self):
+        self._test_create_mocked(cell_type='api')
+
+    def test_create_computecell(self):
+        self._test_create_mocked(cell_type='compute')
 
     def test_create(self):
         values = {'source_type': 'volume', 'volume_id': 'fake-vol-id',
@@ -158,21 +199,37 @@ def test_create_fails_instance(self):
         self.assertRaises(exception.ObjectActionError,
                           bdm.create, self.context)
 
-    def test_destroy_mocked(self):
+    def _test_destroy_mocked(self, cell_type=None):
         values = {'source_type': 'volume', 'volume_id': 'fake-vol-id',
                   'destination_type': 'volume', 'id': 1,
                   'instance_uuid': 'fake-instance', 'device_name': 'fake'}
+        if cell_type:
+            self.flags(enable=True, cell_type=cell_type, group='cells')
+        else:
+            self.flags(enable=False, group='cells')
         with contextlib.nested(
             mock.patch.object(db, 'block_device_mapping_destroy'),
             mock.patch.object(cells_rpcapi.CellsAPI, 'bdm_destroy_at_top')
         ) as (bdm_del, cells_destroy):
             bdm = objects.BlockDeviceMapping(**values)
             bdm.destroy(self.context)
             bdm_del.assert_called_once_with(self.context, values['id'])
-            cells_destroy.assert_called_once_with(
-                self.context, values['instance_uuid'],
-                device_name=values['device_name'],
-                volume_id=values['volume_id'])
+            if cell_type != 'compute':
+                self.assertFalse(cells_destroy.called)
+            else:
+                cells_destroy.assert_called_once_with(
+                    self.context, values['instance_uuid'],
+                    device_name=values['device_name'],
+                    volume_id=values['volume_id'])
+
+    def test_destroy_nocells(self):
+        self._test_destroy_mocked()
+
+    def test_destroy_apicell(self):
+        self._test_destroy_mocked(cell_type='api')
+
+    def test_destroy_computecell(self):
+        self._test_destroy_mocked(cell_type='compute')
 
 
 class TestBlockDeviceMappingObject(test_objects._LocalTest,