Delete the "Chassis_Private" register when deleting an agent

The method ``delete_agent`` [1] now deletes both the OVN SB
"Chassis" and "Chassis_Private" registers when called.

[1]https://github.com/openstack/neutron/blob/ad81687e2955f494c28e2122763a2332afd3d26d/neutron/plugins/ml2/drivers/ovn/mech_driver/mech_driver.py#L1400-L1401

Closes-Bug: #2023171
Change-Id: Ibb1285f61c172d2b6e281f41315415ce8b8526e7
(cherry picked from commit 9ca0e34)

Author: ralonsoh

neutron/plugins/ml2/drivers/ovn/mech_driver/mech_driver.py

@@ -40,6 +40,7 @@
 from oslo_db import exception as os_db_exc
 from oslo_log import log
 from oslo_utils import timeutils
+from ovsdbapp.backend.ovs_idl import idlutils
 
 from neutron._i18n import _
 from neutron.common.ovn import acl as ovn_acl
@@ -1322,6 +1323,14 @@ def delete_agent(self, context, id, _driver=None):
     chassis_name = agent['configurations']['chassis_name']
     _driver.sb_ovn.chassis_del(chassis_name, if_exists=True).execute(
         check_error=True)
+    if _driver.sb_ovn.is_table_present('Chassis_Private'):
+        # TODO(ralonsoh): implement the corresponding chassis_private
+        # commands in ovsdbapp.
+        try:
+            _driver.sb_ovn.db_destroy('Chassis_Private', chassis_name).execute(
+                check_error=True)
+        except idlutils.RowNotFound:
+            pass
     # Send a specific event that all API workers can get to delete the agent
     # from their caches. Ideally we could send a single transaction that both
     # created and deleted the key, but alas python-ovs is too "smart"

neutron/tests/functional/plugins/ml2/drivers/ovn/mech_driver/test_mech_driver.py

@@ -1169,6 +1169,19 @@ def _create_test_agent(self):
         _, status = self.plugin.create_or_update_agent(self.context, agent)
         return status['id']
 
+    def _check_chassis_registers(self, present=True):
+        chassis = self.sb_api.lookup('Chassis', self.chassis, default=None)
+        chassis_name = chassis.name if chassis else None
+        if self.sb_api.is_table_present('Chassis_Private'):
+            ch_private = self.sb_api.lookup(
+                'Chassis_Private', self.chassis, default=None)
+            ch_private_name = ch_private.name if ch_private else None
+            self.assertEqual(chassis_name, ch_private_name)
+        if present:
+            self.assertEqual(self.chassis, chassis_name)
+        else:
+            self.assertIsNone(chassis)
+
     def test_agent_show(self):
         for agent_id in self.agent_types.values():
             self.assertTrue(self.plugin.get_agent(self.context, agent_id))
@@ -1217,12 +1230,15 @@ def test_agent_delete(self):
         self.assertRaises(agent_exc.AgentNotFound, self.plugin.get_agent,
                           self.context, agent_id)
 
-        # OVN controller agent deletion, that triggers the "Chassis" register
-        # deletion. The "Chassis" register deletion triggers the host OVN
-        # agents deletion, both controller and metadata if present.
+        # OVN controller agent deletion, that triggers the "Chassis" and
+        # "Chassis_Private" registers deletion. The registers deletion triggers
+        # the host OVN agents deletion, both controller and metadata if
+        # present.
         controller_id = self.agent_types[ovn_const.OVN_CONTROLLER_AGENT]
         metadata_id = self.agent_types[ovn_const.OVN_METADATA_AGENT]
+        self._check_chassis_registers()
         self.plugin.delete_agent(self.context, controller_id)
+        self._check_chassis_registers(present=False)
         self.assertRaises(agent_exc.AgentNotFound, self.plugin.get_agent,
                           self.context, controller_id)
         self.assertEqual(