text: UPDATE database_instance SET master_port=22294 where port not in (22293, 22294);
  -- topology:
  --
  -- 22293
  -- + 22294
  --   + 22295
  --   + 22296
  --   + 22297
  --
  UPDATE database_instance SET data_center='seattle', physical_environment='prod';
  UPDATE database_instance SET data_center='ny', physical_environment='prod' where port in (22293, 22296);
  
  INSERT INTO candidate_database_instance (hostname, port, promotion_rule) VALUES ('testhost', 22295, 'prefer');
  