Bring back dvr routers autoscheduling

Commit 1105d732b2cb6ec66d042c85968d47fe6d733f5f disabled
auto scheduling for dvr routers because of the complexity
of DVR scheduling itself which led to a number of logical
and DB issues. Now after blueprint improve-dvr-l3-agent-binding
is merged DVR scheduling is almost no different from legacy
scheduling (no extra DVR logic required for auto scheduling)
so we can bring auto scheduling for DVR routers back.
This is better for consistency and improves UX.

Closes-Bug: #1543513
Change-Id: Ibf0263a711f0dbaf42fb59799ada79b6e896eca1

neutron/scheduler/l3_agent_scheduler.py

@@ -91,29 +91,19 @@ class L3Scheduler(object):
                 context, filters={'id': unscheduled_router_ids})
         return []
 
-    def _get_routers_to_schedule(self, context, plugin,
-                                 router_ids=None, exclude_distributed=False):
+    def _get_routers_to_schedule(self, context, plugin, router_ids=None):
         """Verify that the routers specified need to be scheduled.
 
         :param context: the context
         :param plugin: the core plugin
         :param router_ids: the list of routers to be checked for scheduling
-        :param exclude_distributed: whether or not to consider dvr routers
         :returns: the list of routers to be scheduled
         """
         if router_ids is not None:
             routers = plugin.get_routers(context, filters={'id': router_ids})
-            unscheduled_routers = self._filter_unscheduled_routers(
-                context, plugin, routers)
+            return self._filter_unscheduled_routers(context, plugin, routers)
         else:
-            unscheduled_routers = self._get_unscheduled_routers(context,
-                                                                plugin)
-
-        if exclude_distributed:
-            unscheduled_routers = [
-                r for r in unscheduled_routers if not r.get('distributed')
-            ]
-        return unscheduled_routers
+            return self._get_unscheduled_routers(context, plugin)
 
     def _get_routers_can_schedule(self, context, plugin, routers, l3_agent):
         """Get the subset of routers that can be scheduled on the L3 agent."""
@@ -143,11 +133,8 @@ class L3Scheduler(object):
         if not l3_agent:
             return False
 
-        # NOTE(armando-migliaccio): DVR routers should not be auto
-        # scheduled because auto-scheduling may interfere with the
-        # placement rules for IR and SNAT namespaces.
         unscheduled_routers = self._get_routers_to_schedule(
-            context, plugin, router_ids, exclude_distributed=True)
+            context, plugin, router_ids)
         if not unscheduled_routers:
             if utils.is_extension_supported(
                     plugin, constants.L3_HA_MODE_EXT_ALIAS):

neutron/tests/functional/services/l3_router/test_l3_dvr_ha_router_plugin.py

@@ -299,3 +299,6 @@ class L3DvrHATestCase(test_l3_dvr_router_plugin.L3DvrTestCase):
 
     def test__get_router_ids_for_agent(self):
         self.skipTest('Valid for DVR-only routers')
+
+    def test_router_auto_scheduling(self):
+        self.skipTest('Valid for DVR-only routers')

neutron/tests/functional/services/l3_router/test_l3_dvr_router_plugin.py

@@ -14,6 +14,7 @@
 
 import mock
 
+from neutron.api.rpc.handlers import l3_rpc
 from neutron.api.v2 import attributes
 from neutron.common import constants
 from neutron.common import topics
@@ -900,3 +901,18 @@ class L3DvrTestCase(ml2_test_base.ML2TestFramework):
 
             l3_notifier.router_removed_from_agent.assert_called_once_with(
                 self.context, router['id'], HOST1)
+
+    def test_router_auto_scheduling(self):
+        router = self._create_router()
+        agents = self.l3_plugin.list_l3_agents_hosting_router(
+                self.context, router['id'])
+        # router is not scheduled yet
+        self.assertEqual([], agents['agents'])
+
+        l3_rpc_handler = l3_rpc.L3RpcCallback()
+        # router should be auto scheduled once l3 agent requests router ids
+        l3_rpc_handler.get_router_ids(self.context, self.l3_agent['host'])
+        agents = self.l3_plugin.list_l3_agents_hosting_router(
+            self.context, router['id'])
+        self.assertEqual(1, len(agents['agents']))
+        self.assertEqual(self.l3_agent['id'], agents['agents'][0]['id'])

neutron/tests/unit/scheduler/test_l3_agent_scheduler.py

@@ -202,20 +202,6 @@ class L3SchedulerBaseTestCase(base.BaseTestCase):
         mock_get.assert_called_once_with(mock.ANY, self.plugin)
         self.assertEqual(expected_routers, unscheduled_routers)
 
-    def test__get_routers_to_schedule_exclude_distributed(self):
-        routers = [
-            {'id': 'foo_router1', 'distributed': True}, {'id': 'foo_router_2'}
-        ]
-        expected_routers = [{'id': 'foo_router_2'}]
-        with mock.patch.object(self.scheduler,
-                               '_get_unscheduled_routers') as mock_get:
-            mock_get.return_value = routers
-            unscheduled_routers = self.scheduler._get_routers_to_schedule(
-                mock.ANY, self.plugin,
-                router_ids=None, exclude_distributed=True)
-        mock_get.assert_called_once_with(mock.ANY, self.plugin)
-        self.assertEqual(expected_routers, unscheduled_routers)
-
     def _test__get_routers_can_schedule(self, routers, agent, target_routers):
         self.plugin.get_l3_agent_candidates.return_value = agent
         result = self.scheduler._get_routers_can_schedule(