Check for agent restarted after checking for DVR port

This is a stable-only fix since code around the change was removed 
in master: https://review.opendev.org/#/c/641866

Commit a5244d6d44 changed the check
order so regular non-dvr ports are checked for agent restarted.
However regular ports may be unbound already, which leads to the
error in the bug description: agent_restarted check is done against
a 'None' agent.
This patch fixed logic back - only check agent_restarted for dvr ports.

This also adds some logging to have a clue why update port up/down fails.

Change-Id: I3ad59864eeb42916d2cf15a5292d5aa9484f6e91
Closes-Bug: #1835731
(cherry picked from commit c3a3031f78)

neutron/plugins/ml2/rpc.py

@@ -315,11 +315,13 @@ class RpcCallbacks(type_tunnel.TunnelRpcCallbackMixin):
         # and so we don't need to update it again here. But, l2pop did not
         # handle DVR ports while restart neutron-*-agent, we need to handle
         # it here.
-        if agent_restarted is None:
-            agent_restarted = l2pop_driver.obj.agent_restarted(port_context)
-        if (port['device_owner'] == n_const.DEVICE_OWNER_DVR_INTERFACE and
-                not agent_restarted):
-            return
+        if port['device_owner'] == n_const.DEVICE_OWNER_DVR_INTERFACE:
+            if agent_restarted is None:
+                agent_restarted = l2pop_driver.obj.agent_restarted(
+                    port_context)
+            if not agent_restarted:
+                return
+
         port = port_context.current
         if (port['device_owner'] != n_const.DEVICE_OWNER_DVR_INTERFACE and
             status == n_const.PORT_STATUS_ACTIVE and
@@ -351,9 +353,9 @@ class RpcCallbacks(type_tunnel.TunnelRpcCallbackMixin):
                         rpc_context,
                         device=device,
                         **kwargs)
-                except Exception:
+                except Exception as e:
                     failed_devices_up.append(device)
-                    LOG.error("Failed to update device %s up", device)
+                    LOG.error("Failed to update device %s up: %s", device, e)
                 else:
                     devices_up.append(device)
 
@@ -365,9 +367,9 @@ class RpcCallbacks(type_tunnel.TunnelRpcCallbackMixin):
                         rpc_context,
                         device=device,
                         **kwargs)
-                except Exception:
+                except Exception as e:
                     failed_devices_down.append(device)
-                    LOG.error("Failed to update device %s down", device)
+                    LOG.error("Failed to update device %s down: %s", device, e)
                 else:
                     devices_down.append(dev)
 

neutron/tests/unit/plugins/ml2/test_rpc.py

@@ -249,6 +249,16 @@ class RpcCallbacksTestCase(base.BaseTestCase):
             mock.ANY, 'fake_port_id', constants.PORT_STATUS_DOWN,
             'fake_host')
 
+    def test_notify_l2pop_port_wiring_non_dvr_port(self):
+        port = {'device_owner': constants.DEVICE_OWNER_COMPUTE_PREFIX}
+        l2pop_driver = (
+            self.plugin.mechanism_manager.mech_drivers.get.return_value)
+        with mock.patch.object(ml2_db, 'get_port') as ml2_db_get_port:
+            ml2_db_get_port.return_value = port
+            self.callbacks.notify_l2pop_port_wiring(
+                'port_id', mock.Mock(), 'DOWN', 'host', agent_restarted=None)
+            self.assertFalse(l2pop_driver.obj.agent_restarted.called)
+
     def test_update_device_down_call_update_port_status_failed(self):
         self.plugin.update_port_status.side_effect = exc.StaleDataError
         self.assertEqual({'device': 'fake_device', 'exists': False},