Never raise an exception in notify()

notify() is called from python-ovs code which is not built to
recover from an exception in this user-overriden code. If there
is an exception (e.g. the DB server is down when we process
the hash ring), this exception can cause an unrecoverable error
in processing OVSDB messages, rendering the neutron worker useless.

Change-Id: I5f703d82175d71a222c76df37a82b5ccad890d14
(cherry picked from commit 67e616b2380d6549308a15077b2043721dbea5d0)
(cherry picked from commit 848787785eb1140ee7d0eac72f3967b39345e625)
Conflicts: neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovsdb_monitor.py
(cherry picked from commit 3566cc065eb7e811822a472bd40e37ecf7668971)

1 files changed, 34 insertions, 30 deletions

diff --git a/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovsdb_monitor.py b/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovsdb_monitor.py
index 9962be8973..50323bc4d8 100644
--- a/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovsdb_monitor.py
+++ b/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovsdb_monitor.py
@@ -567,38 +567,42 @@ class OvnIdlDistributedLock(BaseOvnIdl):
         self._last_touch = None
 
     def notify(self, event, row, updates=None):
-        self.notify_handler.notify(event, row, updates, global_=True)
         try:
-            target_node = self._hash_ring.get_node(str(row.uuid))
-        except exceptions.HashRingIsEmpty as e:
-            LOG.error('HashRing is empty, error: %s', e)
-            return
-        if target_node != self._node_uuid:
-            return
-
-        # If the worker hasn't been health checked by the maintenance
-        # thread (see bug #1834498), indicate that it's alive here
-        time_now = timeutils.utcnow()
-        touch_timeout = time_now - datetime.timedelta(
-            seconds=ovn_const.HASH_RING_TOUCH_INTERVAL)
-        if not self._last_touch or touch_timeout >= self._last_touch:
-            # NOTE(lucasagomes): Guard the db operation with an exception
-            # handler. If heartbeating fails for whatever reason, log
-            # the error and continue with processing the event
+            self.notify_handler.notify(event, row, updates, global_=True)
             try:
-                ctx = neutron_context.get_admin_context()
-                ovn_hash_ring_db.touch_node(ctx, self._node_uuid)
-                self._last_touch = time_now
-            except Exception:
-                LOG.exception('Hash Ring node %s failed to heartbeat',
-                              self._node_uuid)
-
-        LOG.debug('Hash Ring: Node %(node)s (host: %(hostname)s) '
-                  'handling event "%(event)s" for row %(row)s '
-                  '(table: %(table)s)',
-                  {'node': self._node_uuid, 'hostname': CONF.host,
-                   'event': event, 'row': row.uuid, 'table': row._table.name})
-        self.notify_handler.notify(event, row, updates)
+                target_node = self._hash_ring.get_node(str(row.uuid))
+            except exceptions.HashRingIsEmpty as e:
+                LOG.error('HashRing is empty, error: %s', e)
+                return
+            if target_node != self._node_uuid:
+                return
+
+            # If the worker hasn't been health checked by the maintenance
+            # thread (see bug #1834498), indicate that it's alive here
+            time_now = timeutils.utcnow()
+            touch_timeout = time_now - datetime.timedelta(
+                seconds=ovn_const.HASH_RING_TOUCH_INTERVAL)
+            if not self._last_touch or touch_timeout >= self._last_touch:
+                # NOTE(lucasagomes): Guard the db operation with an exception
+                # handler. If heartbeating fails for whatever reason, log
+                # the error and continue with processing the event
+                try:
+                    ctx = neutron_context.get_admin_context()
+                    ovn_hash_ring_db.touch_node(ctx, self._node_uuid)
+                    self._last_touch = time_now
+                except Exception:
+                    LOG.exception('Hash Ring node %s failed to heartbeat',
+                                  self._node_uuid)
+
+            LOG.debug('Hash Ring: Node %(node)s (host: %(hostname)s) '
+                      'handling event "%(event)s" for row %(row)s '
+                      '(table: %(table)s)',
+                      {'node': self._node_uuid, 'hostname': CONF.host,
+                       'event': event, 'row': row.uuid,
+                       'table': row._table.name})
+            self.notify_handler.notify(event, row, updates)
+        except Exception as e:
+            LOG.exception(e)
 
     @abc.abstractmethod
     def post_connect(self):