Merge "[OVN] Hash Ring: Better handle Neutron worker failures" into stable/yoga

Author: Zuul

neutron/cmd/ovn/neutron_ovn_db_sync_util.py

@@ -57,12 +57,12 @@ def post_fork_initialize(self, resource, event, trigger, **kwargs):
     def ovn_client(self):
         return self._ovn_client
 
-    def _set_hash_ring_nodes_offline(self):
-        """Don't set hash ring nodes as offline.
+    def _remove_node_from_hash_ring(self):
+        """Don't remove the node from the Hash Ring.
 
         If this method was not overridden, cleanup would be performed when
-        calling the db sync and running neutron server would mark all the
-        nodes from the ring as offline.
+        calling the db sync and running neutron server would remove the
+        nodes from the Hash Ring.
         """
 
     # Since we are not using the ovn mechanism driver while syncing,

neutron/db/ovn_hash_ring_db.py

@@ -50,6 +50,13 @@ def remove_nodes_from_host(context, group_name):
              CONF.host, group_name)
 
 
+def remove_node_by_uuid(context, node_uuid):
+    with db_api.CONTEXT_WRITER.using(context):
+        context.session.query(ovn_models.OVNHashRing).filter(
+            ovn_models.OVNHashRing.node_uuid == node_uuid).delete()
+    LOG.info('Node "%s" removed from the Hash Ring', node_uuid)
+
+
 def _touch(context, updated_at=None, **filter_args):
     if updated_at is None:
         updated_at = timeutils.utcnow()
@@ -96,7 +103,9 @@ def count_offline_nodes(context, interval, group_name):
     return query.count()
 
 
-def set_nodes_from_host_as_offline(context, group_name):
-    timestamp = datetime.datetime(day=26, month=10, year=1985, hour=9)
-    _touch(context, updated_at=timestamp, hostname=CONF.host,
-           group_name=group_name)
+@db_api.CONTEXT_READER
+def count_nodes_from_host(context, group_name):
+    query = context.session.query(ovn_models.OVNHashRing).filter(
+        ovn_models.OVNHashRing.group_name == group_name,
+        ovn_models.OVNHashRing.hostname == CONF.host)
+    return query.count()

neutron/plugins/ml2/drivers/ovn/mech_driver/mech_driver.py

@@ -270,17 +270,17 @@ def subscribe(self):
                                resources.SECURITY_GROUP_RULE,
                                events.BEFORE_DELETE)
 
-    def _set_hash_ring_nodes_offline(self, *args, **kwargs):
+    def _remove_node_from_hash_ring(self, *args, **kwargs):
+        # The node_uuid attribute will be empty for worker types
+        # that are not added to the Hash Ring and can be skipped
+        if self.node_uuid is None:
+            return
         admin_context = n_context.get_admin_context()
-        ovn_hash_ring_db.set_nodes_from_host_as_offline(
-            admin_context, self.hash_ring_group)
-        LOG.info('Hash Ring nodes from host "%s" marked as offline',
-                 cfg.CONF.host)
+        ovn_hash_ring_db.remove_node_by_uuid(
+            admin_context, self.node_uuid)
 
     def pre_fork_initialize(self, resource, event, trigger, payload=None):
         """Pre-initialize the ML2/OVN driver."""
-        atexit.register(self._set_hash_ring_nodes_offline)
-        signal.signal(signal.SIGTERM, self._set_hash_ring_nodes_offline)
         ovn_utils.create_neutron_pg_drop()
 
     @staticmethod
@@ -298,6 +298,10 @@ def _setup_hash_ring(self):
         thread for this host. Subsequently workers just need to register
         themselves to the hash ring.
         """
+        # Attempt to remove the node from the ring when the worker stops
+        atexit.register(self._remove_node_from_hash_ring)
+        signal.signal(signal.SIGTERM, self._remove_node_from_hash_ring)
+
         admin_context = n_context.get_admin_context()
         if not self._hash_ring_probe_event.is_set():
             # Clear existing entries

neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/maintenance.py

@@ -42,6 +42,7 @@
 from neutron.db import segments_db
 from neutron.objects import router as router_obj
 from neutron.plugins.ml2.drivers.ovn.mech_driver.ovsdb import ovn_db_sync
+from neutron import service
 from neutron.services.logapi.drivers.ovn import driver as log_driver
 
 
@@ -1067,3 +1068,20 @@ def touch_hash_ring_nodes(self):
         # here because we want the maintenance tasks from each instance to
         # execute this task.
         hash_ring_db.touch_nodes_from_host(self.ctx, self._group)
+
+        # Check the number of the nodes in the ring and log a message in
+        # case they are out of sync. See LP #2024205 for more information
+        # on this issue.
+        api_workers = service._get_api_workers()
+        num_nodes = hash_ring_db.count_nodes_from_host(self.ctx, self._group)
+
+        if num_nodes > api_workers:
+            LOG.critical(
+                'The number of nodes in the Hash Ring (%d) is higher than '
+                'the number of API workers (%d) for host "%s". Something is '
+                'not right and OVSDB events could be missed because of this. '
+                'Please check the status of the Neutron processes, this can '
+                'happen when the API workers are killed and restarted. '
+                'Restarting the service should fix the issue, see LP '
+                '#2024205 for more information.',
+                num_nodes, api_workers, cfg.CONF.host)

neutron/tests/functional/base.py

@@ -363,7 +363,7 @@ def trigger(self):
         # NOTE(ralonsoh): do not access to the DB at exit when the SQL
         # connection is already closed, to avoid useless exception messages.
         mock.patch.object(
-            self.mech_driver, '_set_hash_ring_nodes_offline').start()
+            self.mech_driver, '_remove_node_from_hash_ring').start()
         self.mech_driver.pre_fork_initialize(
             mock.ANY, mock.ANY, trigger_cls.trigger)
 

neutron/tests/unit/db/test_ovn_hash_ring_db.py

@@ -270,16 +270,18 @@ def test_count_offline_nodes(self):
         self.assertEqual(0, ovn_hash_ring_db.count_offline_nodes(
             self.admin_ctx, interval=60, group_name=HASH_RING_TEST_GROUP))
 
-    def test_set_nodes_from_host_as_offline(self):
+    def test_remove_node_by_uuid(self):
         self._add_nodes_and_assert_exists(count=3)
 
         active_nodes = ovn_hash_ring_db.get_active_nodes(
             self.admin_ctx, interval=60, group_name=HASH_RING_TEST_GROUP)
         self.assertEqual(3, len(active_nodes))
 
-        ovn_hash_ring_db.set_nodes_from_host_as_offline(
-                self.admin_ctx, HASH_RING_TEST_GROUP)
+        node_to_remove = active_nodes[0].node_uuid
+        ovn_hash_ring_db.remove_node_by_uuid(
+                self.admin_ctx, node_to_remove)
 
         active_nodes = ovn_hash_ring_db.get_active_nodes(
             self.admin_ctx, interval=60, group_name=HASH_RING_TEST_GROUP)
-        self.assertEqual(0, len(active_nodes))
+        self.assertEqual(2, len(active_nodes))
+        self.assertNotIn(node_to_remove, [n.node_uuid for n in active_nodes])