Revert "[HA] Do not add initial state change delay in HA router"

This reverts commit c20f2e5136.

The fix of bug #1945512 reintroduced bug #1837635 as after
the initial backup state ha router can transition to
'primary' state on multiple hosts and due to this
delay multiple routers get into 'active' ha_state even
if one of the host quickly transition to backup after
the primary state.
The issue got visible since ha router fullstack tests
are added as part of [1].

[1] https://review.opendev.org/c/openstack/neutron/+/917429

Related-Bug: #1837635
Related-Bug: #1945512
Related-Bug: #2083609
Change-Id: I83b53a07362861da98b8361dafd95e94e5048322
(cherry picked from commit a3689956dd)
Conflicts:
	neutron/agent/l3/ha.py
	neutron/tests/unit/agent/l3/test_agent.py

neutron/agent/l3/ha.py

@@ -17,9 +17,6 @@ import os
 import threading
 
 import eventlet
-from neutron_lib.callbacks import events
-from neutron_lib.callbacks import registry
-from neutron_lib.callbacks import resources
 from neutron_lib import constants
 from oslo_log import log as logging
 from oslo_utils import fileutils
@@ -79,7 +76,6 @@ class L3AgentKeepalivedStateChangeServer(object):
         server.wait()
 
 
-@registry.has_registry_receivers
 class AgentMixin(object):
     def __init__(self, host):
         self._init_ha_conf_path()
@@ -91,13 +87,6 @@ class AgentMixin(object):
         eventlet.spawn(self._start_keepalived_notifications_server)
         self._transition_states = {}
         self._transition_state_mutex = threading.Lock()
-        self._initial_state_change_per_router = set()
-
-    def initial_state_change(self, router_id):
-        initial_state = router_id not in self._initial_state_change_per_router
-        if initial_state:
-            self._initial_state_change_per_router.add(router_id)
-        return initial_state
 
     def _get_router_info(self, router_id):
         try:
@@ -106,13 +95,6 @@ class AgentMixin(object):
             LOG.info('Router %s is not managed by this agent. It was '
                      'possibly deleted concurrently.', router_id)
 
-    @registry.receives(resources.ROUTER, [events.AFTER_DELETE])
-    def _delete_router(self, resource, event, trigger, payload):
-        try:
-            self._initial_state_change_per_router.remove(payload.resource_id)
-        except KeyError:
-            pass
-
     def check_ha_state_for_router(self, router_id, current_state):
         ri = self._get_router_info(router_id)
         if not ri:
@@ -166,7 +148,7 @@ class AgentMixin(object):
 
     def _enqueue_state_change(self, router_id, state):
         # NOTE(ralonsoh): move 'primary' and 'backup' constants to n-lib
-        if state == 'primary' and not self.initial_state_change(router_id):
+        if state == 'primary':
             eventlet.sleep(self.conf.ha_vrrp_advert_int)
         transition_state = self._update_transition_state(router_id)
         if transition_state != state:

neutron/tests/unit/agent/l3/test_agent.py

@@ -274,15 +274,7 @@ class TestBasicRouterOperations(BasicRouterOperationsFramework):
         self._enqueue_state_change_transitions(['backup'], 1)
 
     def test_enqueue_state_change_from_none_to_primary_to_backup(self):
-        # First transition (to primary), won't have a delay.
-        self._enqueue_state_change_transitions(['primary', 'backup'], 2)
-
-    def test_enqueue_state_change_from_none_to_primary_to_backup_twice(self):
-        # Second transition to primary will have a delay and will be overridden
-        # by the second transition to backup; that means the transition from
-        # backup (second state) to primary (third state) is dismissed.
-        self._enqueue_state_change_transitions(
-            ['primary', 'backup', 'primary', 'backup'], 2)
+        self._enqueue_state_change_transitions(['primary', 'backup'], 0)
 
     def test_enqueue_state_change_from_none_to_backup_to_primary(self):
         self._enqueue_state_change_transitions(['backup', 'primary'], 2)
@@ -2630,21 +2622,6 @@ class TestBasicRouterOperations(BasicRouterOperationsFramework):
         agent.router_removed_from_agent(None, {'router_id': FAKE_ID})
         self.assertEqual(1, agent._queue.add.call_count)
 
-    @mock.patch.object(metadata_driver.MetadataDriver,
-                       'destroy_monitored_metadata_proxy')
-    def test__router_removed(self, *args):
-        agent = l3_agent.L3NATAgent(HOSTNAME, self.conf)
-        ri = mock.Mock(router={'id': 'router_id'})
-        agent._initial_state_change_per_router.add('router_id')
-        self.assertEqual({'router_id'}, agent._initial_state_change_per_router)
-        for _ in range(2):
-            # The second call will trigger a KeyError exception in
-            # AgentMixin._delete_router that should be dismissed.
-            agent.router_info['router_id'] = mock.ANY
-            agent.pd = mock.Mock(routers={'router_id': {'subnets': []}})
-            agent._router_removed(ri, 'router_id')
-            self.assertEqual(set([]), agent._initial_state_change_per_router)
-
     def test_added_to_agent(self):
         agent = l3_agent.L3NATAgent(HOSTNAME, self.conf)
         agent._queue = mock.Mock()