Add function "has_table_columns" to OVSDB implementation API

Change-Id: Ide8ffcc99a05edf15ce511b1bd4a9b1552dad5d1
Closes-Bug: #1814577

vif_plug_ovs/ovsdb/api.py

@@ -10,7 +10,10 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import abc
+
 from oslo_utils import importutils
+import six
 
 
 interface_map = {
@@ -25,3 +28,15 @@ def get_instance(context, iface_name=None):
     iface = importutils.import_module(
         interface_map[iface_name or context.interface])
     return iface.api_factory(context)
+
+
+@six.add_metaclass(abc.ABCMeta)
+class ImplAPI(object):
+    @abc.abstractmethod
+    def has_table_column(self, table, column):
+        """Check if a column exists in a database table
+
+        :param table: (string) table name
+        :param column: (string) column name
+        :return: True if the column exists, False if not.
+        """

vif_plug_ovs/ovsdb/impl_vsctl.py

@@ -24,6 +24,7 @@ from oslo_utils import uuidutils
 from ovsdbapp import api as ovsdb_api
 import six
 
+from vif_plug_ovs.ovsdb import api
 from vif_plug_ovs import privsep
 
 
@@ -214,7 +215,7 @@ class BrExistsCommand(DbCommand):
                                                     log_errors=False)
 
 
-class OvsdbVsctl(ovsdb_api.API):
+class OvsdbVsctl(ovsdb_api.API, api.ImplAPI):
     def __init__(self, context):
         super(OvsdbVsctl, self).__init__()
         self.context = context
@@ -353,6 +354,17 @@ class OvsdbVsctl(ovsdb_api.API):
     def db_remove(self, table, record, column, *values, **keyvalues):
         raise NotImplementedError()
 
+    def has_table_column(self, table, column):
+        try:
+            self.db_list(table, columns=[column]).execute(check_error=True)
+            return True
+        except processutils.ProcessExecutionError as e:
+            msg = ('ovs-vsctl: %s does not contain a column whose name '
+                   'matches "%s"' % (table, column))
+            if msg in e.stderr:
+                return False
+            raise e
+
 
 def _set_colval_args(*col_values):
     args = []

vif_plug_ovs/ovsdb/ovsdb_lib.py

@@ -31,9 +31,7 @@ class BaseOVS(object):
         self.ovsdb = ovsdb_api.get_instance(self)
 
     def _ovs_supports_mtu_requests(self):
-        return bool(self.ovsdb.db_list(
-            'Interface', columns=['mtu_request']).execute(check_error=True,
-                                                          log_errors=True))
+        return self.ovsdb.has_table_column('Interface', 'mtu_request')
 
     def _set_mtu_request(self, dev, mtu):
         self.ovsdb.db_set('Interface', dev, ('mtu_request', mtu)).execute()

vif_plug_ovs/tests/unit/ovsdb/test_ovsdb_lib.py

@@ -13,6 +13,7 @@
 import mock
 import testtools
 
+from oslo_concurrency import processutils
 from oslo_config import cfg
 from oslo_utils import uuidutils
 
@@ -142,3 +143,27 @@ class BaseOVSTest(testtools.TestCase):
         self.br.ensure_ovs_bridge('bridge', constants.OVS_DATAPATH_SYSTEM)
         self.mock_add_br('bridge', may_exist=True,
                          datapath_type=constants.OVS_DATAPATH_SYSTEM)
+
+    def test__ovs_supports_mtu_requests(self):
+        with mock.patch.object(self.br.ovsdb, 'db_list') as mock_db_list:
+            self.assertTrue(self.br._ovs_supports_mtu_requests())
+            mock_db_list.assert_called_once_with('Interface',
+                                                 columns=['mtu_request'])
+
+    def test__ovs_supports_mtu_requests_not_supported(self):
+        with mock.patch.object(self.br.ovsdb, 'db_list') as mock_db_list:
+            mock_db_list.side_effect = processutils.ProcessExecutionError(
+                stderr='ovs-vsctl: Interface does not contain a column whose '
+                       'name matches "mtu_request"')
+            self.assertFalse(self.br._ovs_supports_mtu_requests())
+            mock_db_list.assert_called_once_with('Interface',
+                                                 columns=['mtu_request'])
+
+    def test__ovs_supports_mtu_requests_other_error(self):
+        with mock.patch.object(self.br.ovsdb, 'db_list') as mock_db_list:
+            mock_db_list.side_effect = processutils.ProcessExecutionError(
+                stderr='other error')
+            self.assertRaises(processutils.ProcessExecutionError,
+                              self.br._ovs_supports_mtu_requests)
+            mock_db_list.assert_called_once_with('Interface',
+                                                 columns=['mtu_request'])