Correctly call is_distributed_router()

A recent change to _notify_l3_agent_port_update() was
making a call to is_distributed_router() via the l3plugin,
but since that method lives in l3_dvr_db.py it was
failing.  This was not caught by the unit test since it
was mocking the return value.

Had to modify things to get the router first since the
object is required for the check.

Change-Id: I2289f882b692b375d1b40d7a50d206d72da66155
Closes-bug: #1785848

neutron/db/l3_dvrscheduler_db.py

@@ -19,6 +19,7 @@ from neutron_lib.callbacks import events
 from neutron_lib.callbacks import registry
 from neutron_lib.callbacks import resources
 from neutron_lib import constants as n_const
+from neutron_lib.exceptions import l3 as l3_exc
 from neutron_lib.plugins import constants as plugin_constants
 from neutron_lib.plugins import directory
 from oslo_log import log as logging
@@ -28,6 +29,7 @@ from neutron.common import utils as n_utils
 
 from neutron.db import agentschedulers_db
 from neutron.db import l3_agentschedulers_db as l3agent_sch_db
+from neutron.db import l3_dvr_db
 from neutron.db import models_v2
 from neutron.objects import l3agent as rb_obj
 from neutron.plugins.ml2 import db as ml2_db
@@ -453,13 +455,20 @@ def _notify_l3_agent_port_update(resource, event, trigger, **kwargs):
             fips = l3plugin._get_floatingips_by_port_id(
                 context, port_id=original_port['id'])
             fip = fips[0] if fips else None
-            removed_router_ids = [
-                info['router_id'] for info in removed_routers
-            ]
-            if (fip and
-                l3plugin.is_distributed_router(fip['router_id']) and
-                not (removed_routers and
-                     fip['router_id'] in removed_router_ids)):
+
+            def _should_notify_on_fip_update():
+                if not fip:
+                    return False
+                for info in removed_routers:
+                    if info['router_id'] == fip['router_id']:
+                        return False
+                try:
+                    router = l3plugin._get_router(context, fip['router_id'])
+                except l3_exc.RouterNotFound:
+                    return False
+                return l3_dvr_db.is_distributed_router(router)
+
+            if _should_notify_on_fip_update():
                 l3plugin.l3_rpc_notifier.routers_updated_on_host(
                     context, [fip['router_id']],
                     original_port[portbindings.HOST_ID])

neutron/tests/unit/scheduler/test_l3_agent_scheduler.py

@@ -34,6 +34,7 @@ import testtools
 
 from neutron.db import db_base_plugin_v2 as db_v2
 from neutron.db import l3_db
+from neutron.db import l3_dvr_db
 from neutron.db import l3_dvr_ha_scheduler_db
 from neutron.db import l3_dvrscheduler_db
 from neutron.db import l3_hamode_db
@@ -1084,7 +1085,7 @@ class L3DvrSchedulerTestCase(L3SchedulerBaseMixin,
                                if routers_to_remove else []),\
                 mock.patch.object(l3plugin, '_get_floatingips_by_port_id',
                                   return_value=[fip] if fip else []),\
-                mock.patch.object(l3plugin, 'is_distributed_router',
+                mock.patch.object(l3_dvr_db, 'is_distributed_router',
                                   return_value=is_distributed):
             l3_dvrscheduler_db._notify_l3_agent_port_update(
                 'port', 'after_update', mock.ANY, **kwargs)