hash-ring: Retry all DB operations if inactive

Neutron should be resilient to scenarios where connectivity to a service
Neutron depends on is lost. SQL database is one of it and hash ring DB
operations is used very early in the Neutron startup process.

If the connection is lost right after new API worker was spawned then
OVN IDLs are not instantiated and Neutron silently hangs on each request
that uses OVN DB because the event signaling OVN is ready never happens.

Closes-bug: #2029297
Change-Id: Id5bc24b76b7aa510d4066fbc5f7b8037cc8c740d
Signed-off-by: Jakub Libosvar <[email protected]>
(cherry picked from commit a505ff7)

Author: cubeek

neutron/db/ovn_hash_ring_db.py

@@ -29,6 +29,7 @@
 
 # NOTE(ralonsoh): this was migrated from networking-ovn to neutron and should
 #                 be refactored to be integrated in a OVO.
+@db_api.retry_if_session_inactive()
 def add_node(context, group_name, node_uuid=None):
     if node_uuid is None:
         node_uuid = uuidutils.generate_uuid()
@@ -41,6 +42,7 @@ def add_node(context, group_name, node_uuid=None):
     return node_uuid
 
 
+@db_api.retry_if_session_inactive()
 def remove_nodes_from_host(context, group_name):
     with db_api.CONTEXT_WRITER.using(context):
         context.session.query(ovn_models.OVNHashRing).filter(
@@ -50,13 +52,15 @@ def remove_nodes_from_host(context, group_name):
              CONF.host, group_name)
 
 
+@db_api.retry_if_session_inactive()
 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)
 
 
+@db_api.retry_if_session_inactive()
 def _touch(context, updated_at=None, **filter_args):
     if updated_at is None:
         updated_at = timeutils.utcnow()
@@ -90,19 +94,22 @@ def _get_nodes_query(context, interval, group_name, offline=False,
     return query
 
 
+@db_api.retry_if_session_inactive()
 @db_api.CONTEXT_READER
 def get_active_nodes(context, interval, group_name, from_host=False):
     query = _get_nodes_query(context, interval, group_name,
                              from_host=from_host)
     return query.all()
 
 
+@db_api.retry_if_session_inactive()
 @db_api.CONTEXT_READER
 def count_offline_nodes(context, interval, group_name):
     query = _get_nodes_query(context, interval, group_name, offline=True)
     return query.count()
 
 
+@db_api.retry_if_session_inactive()
 @db_api.CONTEXT_READER
 def count_nodes_from_host(context, group_name):
     query = context.session.query(ovn_models.OVNHashRing).filter(