OVNL3RouterPlugin register events in Neutron API workers

The ``OVNL3RouterPlugin`` class registers a set of OVN events in the
``_post_fork_initialize`` method. The event processing should be done
only by Neutron API workers (aka, ``WorkerService`` instances).

Conflicts:
  neutron/services/ovn_l3/plugin.py

Closes-Bug: #2152562
Signed-off-by: Rodolfo Alonso Hernandez <ralonsoh@redhat.com>
Change-Id: I206cd34b1d5559d52c8e841006cf4d6e1eb361ef
(cherry picked from commit 131d985)

Author: ralonsoh

neutron/services/ovn_l3/plugin.py

@@ -36,6 +36,7 @@
 
 from neutron._i18n import _
 from neutron.api.rpc.agentnotifiers import utils as notifier_utils
+from neutron.api import wsgi
 from neutron.common.ovn import constants as ovn_const
 from neutron.common.ovn import extensions
 from neutron.common.ovn import utils
@@ -185,11 +186,15 @@ def _post_fork_initialize(self, resource, event, trigger, payload=None):
         if not self._nb_ovn or not self._sb_ovn:
             raise ovn_l3_exc.MechanismDriverOVNNotReady()
 
-        # Register needed events.
-        self._nb_ovn.idl.notify_handler.watch_events([
-            ovsdb_monitor.LogicalRouterPortEvent(self),
-            ovsdb_monitor.LogicalRouterPortGatewayChassisEvent(self),
-        ])
+        # Register needed events, only for the Neutron API workers.
+        # TODO(ralonsoh): once [1] is released and required in Neutron, it
+        # won't be needed the ``get_method_class`` method.
+        # [1] https://review.opendev.org/c/openstack/neutron-lib/+/988563
+        if utils.get_method_class(trigger) == wsgi.WorkerService:
+            self._nb_ovn.idl.notify_handler.watch_events([
+                ovsdb_monitor.LogicalRouterPortEvent(self),
+                ovsdb_monitor.LogicalRouterPortGatewayChassisEvent(self),
+            ])
 
     def _add_neutron_router_interface(self, context, router_id,
                                       interface_info):

neutron/tests/functional/services/ovn_l3/test_ovsdb_monitor.py

@@ -18,6 +18,7 @@
 from neutron_lib.plugins import constants as plugin_constants
 from neutron_lib.plugins import directory
 
+from neutron.api import wsgi
 from neutron.common.ovn import utils as ovn_utils
 from neutron.common import utils as n_utils
 from neutron.services.bgp import constants as bgp_constants
@@ -34,7 +35,8 @@ def setUp(self, **kwargs):
         super().setUp(**kwargs)
         self.chassis = self.add_fake_chassis('ovs-host1')
         self.l3_plugin = directory.get_plugin(plugin_constants.L3)
-        self.l3_plugin._post_fork_initialize(mock.ANY, mock.ANY, mock.ANY)
+        self.l3_plugin._post_fork_initialize(
+            mock.ANY, mock.ANY, wsgi.WorkerService)
         self.ext_api = test_extensions.setup_extensions_middleware(
             test_l3.L3TestExtensionManager())
         kwargs = {'arg_list': (external_net.EXTERNAL,),
@@ -201,7 +203,8 @@ def setUp(self, **kwargs):
         super().setUp(**kwargs)
         self.chassis = self.add_fake_chassis('ovs-host1')
         self.l3_plugin = directory.get_plugin(plugin_constants.L3)
-        self.l3_plugin._post_fork_initialize(mock.ANY, mock.ANY, mock.ANY)
+        self.l3_plugin._post_fork_initialize(
+            mock.ANY, mock.ANY, wsgi.WorkerService)
         self.ext_api = test_extensions.setup_extensions_middleware(
             test_l3.L3TestExtensionManager())
         kwargs = {'arg_list': (external_net.EXTERNAL,),

releasenotes/notes/ovnl3routerplugin-register-events-api-workers-4444a36464c3390b.yaml

@@ -0,0 +1,9 @@
+---
+fixes:
+  - |
+    The ``OVNL3RouterPlugin`` now registers OVN OVSDB events
+    (``LogicalRouterPortEvent`` and ``RouterHAChassisGroupEvent``) only in
+    Neutron API workers (``WorkerService`` instances). Previously these events
+    were registered by every worker type that called
+    ``_post_fork_initialize``, which could lead to unexpected event processing
+    in maintenance or other non-API workers.