deepcopy binding and binding levels avoid expiration

Perform a deepcopy on the sqla objects passed into the PortContext
so we get detached versions of them safe to reference forever.
This is necessary because the PortContexts outlive the
transaction context managers they are creating in which means an
object can be expired and result in a query after a commit
(e.g. in bind_port_if_needed) that will fail and result in an
exception.

This required a few additional explicit session.merge calls to deal
with cases where touching the mech context was implicitly expected
to modify the DB state on the next commit.

Conflicts:
	neutron/plugins/ml2/driver_context.py
	neutron/plugins/ml2/plugin.py
	neutron/tests/unit/plugins/ml2/test_port_binding.py

Closes-Bug: #1669528
Change-Id: Ib5ba2daa80acba53c082bade1f61a3ee44ca41fc
(cherry picked from commit 20c1de9dc8)

neutron/plugins/ml2/driver_context.py

@@ -13,6 +13,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import copy
+
 from neutron_lib import constants
 from oslo_log import log
 from oslo_serialization import jsonutils
@@ -96,8 +98,10 @@ class PortContext(MechanismDriverContext, api.PortContext):
         else:
             self._network_context = NetworkContext(
                 plugin, plugin_context, network) if network else None
-        self._binding = binding
-        self._binding_levels = binding_levels
+        # NOTE(kevinbenton): these copys can go away once we are working with
+        # OVO objects here instead of native SQLA objects.
+        self._binding = copy.deepcopy(binding)
+        self._binding_levels = copy.deepcopy(binding_levels)
         self._segments_to_bind = None
         self._new_bound_segment = None
         self._next_segments_to_bind = None

neutron/plugins/ml2/plugin.py

@@ -13,6 +13,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import copy
+
 from eventlet import greenthread
 from neutron_lib.api import validators
 from neutron_lib import constants as const
@@ -348,6 +350,10 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
             binding.host = ''
 
         self._update_port_dict_binding(port, binding)
+        # merging here brings binding changes into the session so they can be
+        # committed since the binding attached to the context is detached from
+        # the session
+        mech_context._plugin_context.session.merge(binding)
         return changes
 
     def _bind_port_if_needed(self, context, allow_notify=False,
@@ -510,6 +516,8 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
                 cur_binding.vif_details = new_binding.vif_details
                 db.clear_binding_levels(session, port_id, cur_binding.host)
                 db.set_binding_levels(session, bind_context._binding_levels)
+                # refresh context with a snapshot of updated state
+                cur_context._binding = copy.deepcopy(cur_binding)
                 cur_context._binding_levels = bind_context._binding_levels
 
                 # Update PortContext's port dictionary to reflect the
@@ -1414,6 +1422,8 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
         self._update_port_dict_binding(port, binding)
         binding.host = attrs and attrs.get(portbindings.HOST_ID)
         binding.router_id = attrs and attrs.get('device_id')
+        # merge into session to reflect changes
+        mech_context._plugin_context.session.merge(binding)
 
     @utils.transaction_guard
     @db_api.retry_if_session_inactive()
@@ -1635,8 +1645,7 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
                     session, port['id'], host)
                 if not binding:
                     return
-                binding['status'] = status
-                binding.update(binding)
+                binding.status = status
                 updated = True
 
         if (updated and

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

@@ -1596,7 +1596,8 @@ class TestMl2PortBinding(Ml2PluginV2TestCase,
             plugin = manager.NeutronManager.get_plugin()
             binding = ml2_db.get_locked_port_and_binding(self.context.session,
                                                          port['port']['id'])[1]
-            binding['host'] = 'test'
+            with self.context.session.begin(subtransactions=True):
+                binding.host = 'test'
             mech_context = driver_context.PortContext(
                 plugin, self.context, port['port'],
                 plugin.get_network(self.context, port['port']['network_id']),
@@ -1604,7 +1605,9 @@ class TestMl2PortBinding(Ml2PluginV2TestCase,
         with mock.patch('neutron.plugins.ml2.plugin.Ml2Plugin.'
                         '_update_port_dict_binding') as update_mock:
             attrs = {portbindings.HOST_ID: None}
-            plugin._process_port_binding(mech_context, attrs)
+            self.assertEqual('test', binding.host)
+            with self.context.session.begin(subtransactions=True):
+                plugin._process_port_binding(mech_context, attrs)
             self.assertTrue(update_mock.mock_calls)
             self.assertEqual('', binding.host)
 
@@ -2507,7 +2510,7 @@ class TestMl2PluginCreateUpdateDeletePort(base.BaseTestCase):
         binding.host = 'vm_host'
         binding.vnic_type = portbindings.VNIC_NORMAL
         binding.profile = ''
-        binding.vif_type = ''
+        binding.vif_type = 'unbound'
         binding.vif_details = ''
 
         with mock.patch.object(ml2_plugin.Ml2Plugin, '__init__') as init,\

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

@@ -15,6 +15,7 @@
 
 import mock
 from neutron_lib import constants as const
+from oslo_serialization import jsonutils
 
 from neutron import context
 from neutron.extensions import portbindings
@@ -194,7 +195,7 @@ class PortBindingTestCase(test_plugin.NeutronDbPluginV2TestCase):
                 port_id=original_port['id'],
                 host=original_port['binding:host_id'],
                 vnic_type=original_port['binding:vnic_type'],
-                profile=original_port['binding:profile'],
+                profile=jsonutils.dumps(original_port['binding:profile']),
                 vif_type=original_port['binding:vif_type'],
                 vif_details=original_port['binding:vif_details'])
             levels = 1