Add metadata proxy router_update callback handler

This patch implements the callback handler for router update events;
This checks if the proxy process monitor is active, and if not, starts
the proxy.

This is particularly important if the metadata driver misses to receive
a create notification due to failures, which in turn generates an update
event because of a resync step.

Closes-bug: #1623732

Change-Id: I296a37daff1e5f018ae11eb8661c77ad346b8075

neutron/agent/metadata/driver.py

@@ -33,11 +33,15 @@ METADATA_SERVICE_NAME = 'metadata-proxy'
 
 class MetadataDriver(object):
 
+    monitors = {}
+
     def __init__(self, l3_agent):
         self.metadata_port = l3_agent.conf.metadata_port
         self.metadata_access_mark = l3_agent.conf.metadata_access_mark
         registry.subscribe(
             after_router_added, resources.ROUTER, events.AFTER_CREATE)
+        registry.subscribe(
+            after_router_updated, resources.ROUTER, events.AFTER_UPDATE)
         registry.subscribe(
             before_router_removed, resources.ROUTER, events.BEFORE_DELETE)
 
@@ -122,6 +126,7 @@ class MetadataDriver(object):
                                                      callback=callback)
         pm.enable()
         monitor.register(uuid, METADATA_SERVICE_NAME, pm)
+        cls.monitors[router_id] = pm
 
     @classmethod
     def destroy_monitored_metadata_proxy(cls, monitor, uuid, conf):
@@ -129,6 +134,7 @@ class MetadataDriver(object):
         # No need to pass ns name as it's not needed for disable()
         pm = cls._get_metadata_proxy_process_manager(uuid, conf)
         pm.disable()
+        cls.monitors.pop(uuid, None)
 
     @classmethod
     def _get_metadata_proxy_process_manager(cls, router_id, conf, ns_name=None,
@@ -161,6 +167,13 @@ def after_router_added(resource, event, l3_agent, **kwargs):
             router_id=router.router_id)
 
 
+def after_router_updated(resource, event, l3_agent, **kwargs):
+    router = kwargs['router']
+    proxy = l3_agent.metadata_driver
+    if not proxy.monitors.get(router.router_id):
+        after_router_added(resource, event, l3_agent, **kwargs)
+
+
 def before_router_removed(resource, event, l3_agent, **kwargs):
     router = kwargs['router']
     proxy = l3_agent.metadata_driver

neutron/tests/unit/agent/metadata/test_driver.py

@@ -20,6 +20,7 @@ from oslo_utils import uuidutils
 from neutron.agent.common import config as agent_config
 from neutron.agent.l3 import agent as l3_agent
 from neutron.agent.l3 import ha as l3_ha_agent
+from neutron.agent.l3 import router_info
 from neutron.agent.metadata import config
 from neutron.agent.metadata import driver as metadata_driver
 from neutron.common import constants
@@ -79,6 +80,19 @@ class TestMetadataDriverProcess(base.BaseTestCase):
         cfg.CONF.register_opts(config.SHARED_OPTS)
         cfg.CONF.register_opts(config.DRIVER_OPTS)
 
+    def test_after_router_updated_called_on_agent_process_update(self):
+        with mock.patch.object(metadata_driver, 'after_router_updated') as f,\
+                mock.patch.object(router_info.RouterInfo, 'process'):
+            agent = l3_agent.L3NATAgent('localhost')
+            router_id = _uuid()
+            router = {'id': router_id}
+            ri = router_info.RouterInfo(router_id, router,
+                                        agent.conf, mock.ANY)
+            agent.router_info[router_id] = ri
+            agent._process_updated_router(router)
+            f.assert_called_once_with(
+                'router', 'after_update', agent, router=ri)
+
     def _test_spawn_metadata_proxy(self, expected_user, expected_group,
                                    user='', group='', watch_log=True):
         router_id = _uuid()