apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/service/ClusterService.java/ClusterService/saveWithoutInstanceOfAppNamespaces
class ClusterService:  @Transactional
  public Cluster saveWithoutInstanceOfAppNamespaces(Cluster entity) {
    if (!isClusterNameUnique(entity.getAppId(), entity.getName())) {
      throw new BadRequestException("cluster not unique");
    }
    entity.setId(0);//protection
    Cluster cluster = clusterRepository.save(entity);

    auditService.audit(Cluster.class.getSimpleName(), cluster.getId(), Audit.OP.INSERT,
                       cluster.getDataChangeCreatedBy());

    return cluster;
  }