Fix TypeError in native of_interface _get_dpid

If no bridge datapath_id was returned for some
reason (like broken deployment), _get_dpid()
would process further and raise TypeError while
trying to use int conversion on an empty list.
This patch addresses the problem by raising a
RuntimeError if no datapath was found for a
bridge.

Conflicts:
	neutron/agent/common/ovs_lib.py

Closes-Bug: #1615690

Change-Id: Ie97540793e5d2b14120d3f1bafbf659427c44117
(cherry picked from commit 59d29f7cda)

neutron/agent/common/ovs_lib.py

@@ -58,17 +58,13 @@ OVS_DEFAULT_CAPS = {
 _SENTINEL = object()
 
 
-def _ofport_result_pending(result):
+def _ovsdb_result_pending(result):
     """Return True if ovs-vsctl indicates the result is still pending."""
     # ovs-vsctl can return '[]' for an ofport that has not yet been assigned
-    try:
-        int(result)
-        return False
-    except (ValueError, TypeError):
-        return True
+    return result == []
 
 
-def _ofport_retry(fn):
+def _ovsdb_retry(fn):
     """Decorator for retrying when OVS has yet to assign an ofport.
 
     The instance's vsctl_timeout is used as the max waiting time. This relies
@@ -79,7 +75,7 @@ def _ofport_retry(fn):
         self = args[0]
         new_fn = tenacity.retry(
             reraise=True,
-            retry=tenacity.retry_if_result(_ofport_result_pending),
+            retry=tenacity.retry_if_result(_ovsdb_result_pending),
             wait=tenacity.wait_exponential(multiplier=0.01, max=1),
             stop=tenacity.stop_after_delay(
                 self.vsctl_timeout))(fn)
@@ -307,7 +303,7 @@ class OVSBridge(BaseOVS):
     def remove_all_flows(self):
         self.run_ofctl("del-flows", [])
 
-    @_ofport_retry
+    @_ovsdb_retry
     def _get_port_ofport(self, port_name):
         return self.db_get_val("Interface", port_name, "ofport")
 
@@ -321,9 +317,19 @@ class OVSBridge(BaseOVS):
                           port_name)
         return ofport
 
+    @_ovsdb_retry
+    def _get_datapath_id(self):
+        return self.db_get_val('Bridge', self.br_name, 'datapath_id')
+
     def get_datapath_id(self):
-        return self.db_get_val('Bridge',
-                               self.br_name, 'datapath_id')
+        try:
+            return self._get_datapath_id()
+        except tenacity.RetryError:
+            # if ovs fails to find datapath_id then something is likely to be
+            # broken here
+            LOG.exception(_LE("Timed out retrieving datapath_id on bridge "
+                              "%s."), self.br_name)
+            raise RuntimeError('No datapath_id on bridge %s' % self.br_name)
 
     def do_action_flows(self, action, kwargs_list):
         if action != 'del':

neutron/tests/unit/plugins/ml2/drivers/openvswitch/agent/openflow/native/test_ovs_bridge.py

@@ -33,3 +33,16 @@ class OVSAgentBridgeTestCase(ovs_test_base.OVSRyuTestBase):
         # make sure it correctly raises RuntimeError, not UnboundLocalError as
         # in LP https://bugs.launchpad.net/neutron/+bug/1588042
         self.assertRaises(RuntimeError, br._get_dp)
+
+    def test_get_datapath_no_data_returned(self):
+
+        def _mock_db_get_val(tb, rec, col):
+            if tb == 'Bridge':
+                return []
+
+        mock.patch('neutron.agent.common.ovs_lib.OVSBridge.db_get_val',
+                   side_effect=_mock_db_get_val).start()
+        br = self.br_int_cls('br-int')
+        # make sure that in case of any misconfiguration when no datapath is
+        # found a proper exception, not a TypeError is raised
+        self.assertRaises(RuntimeError, br._get_dp)