hyper-v: Logs tips on PortBindingFailed

When spawning an Hyper-V instance with NICs having the vif_type "hyperv",
neutron will fail to bind the port to the Hyper-V host if the neutron
server doesn't have the "hyperv" mechanism driver installed and configured,
resulting in a PortBindingFailed exception on the nova-compute side.

When this exception is encountered, the logs will say to check the
neutron-server logs, but the problem and its solution are not obvious
or clear, resulting in plenty of questions / reports, all having the
same solution: is there an L2 agent on the host alive and reporting to
neutron, and if neutron Hyper-V agent is used, make sure to install
networking-hyperv and configure neutron-server to use the "hyperv"
mechanism_driver.

Change-Id: Idceeb08e1452413e3b10ecd0a65f71d4d82866e0
Closes-Bug: #1744032
(cherry picked from commit b80c245ba5)

nova/tests/unit/virt/hyperv/test_vmops.py

@@ -503,6 +503,18 @@ class VMOpsTestCase(test_base.HyperVBaseTestCase):
             deadline=CONF.vif_plugging_timeout,
             error_callback=self._vmops._neutron_failed_callback)
 
+    @mock.patch.object(vmops.VMOps, '_get_neutron_events')
+    def test_wait_vif_plug_events_port_binding_failed(self, mock_get_events):
+        mock_get_events.side_effect = exception.PortBindingFailed(
+            port_id='fake_id')
+
+        def _context_user():
+            with self._vmops.wait_vif_plug_events(mock.sentinel.instance,
+                                                  mock.sentinel.network_info):
+                pass
+
+        self.assertRaises(exception.PortBindingFailed, _context_user)
+
     def test_neutron_failed_callback(self):
         self.flags(vif_plugging_is_fatal=True)
         self.assertRaises(exception.VirtualInterfaceCreateException,

nova/virt/hyperv/vmops.py

@@ -306,9 +306,11 @@ class VMOps(object):
     @contextlib.contextmanager
     def wait_vif_plug_events(self, instance, network_info):
         timeout = CONF.vif_plugging_timeout
-        events = self._get_neutron_events(network_info)
 
         try:
+            # NOTE(claudiub): async calls to bind the neutron ports will be
+            # done when network_info is being accessed.
+            events = self._get_neutron_events(network_info)
             with self._virtapi.wait_for_instance_event(
                     instance, events, deadline=timeout,
                     error_callback=self._neutron_failed_callback):
@@ -319,6 +321,17 @@ class VMOps(object):
                         'instance.', instance=instance)
             if CONF.vif_plugging_is_fatal:
                 raise exception.VirtualInterfaceCreateException()
+        except exception.PortBindingFailed:
+            LOG.warning(
+                "Neutron failed to bind a port to this host. Make sure that "
+                "an L2 agent is alive and registered from this node (neutron "
+                "Open vSwitch agent or Hyper-V agent), or make sure that "
+                "neutron is configured with a mechanism driver that is able "
+                "to bind ports to this host (OVN). If you are using neutron "
+                "Hyper-V agent, make sure that networking-hyperv is installed "
+                "on the neutron controller, and that the neutron-server was "
+                "configured to use the 'hyperv' mechanism_driver.")
+            raise
 
     def _neutron_failed_callback(self, event_name, instance):
         LOG.error('Neutron Reported failure on event %s',