apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/service/ClusterService.java/ClusterService/createDefaultCluster
class ClusterService:  @Transactional
  public void createDefaultCluster(String appId, String createBy) {
    if (!isClusterNameUnique(appId, ConfigConsts.CLUSTER_NAME_DEFAULT)) {
      throw new ServiceException("cluster not unique");
    }
    Cluster cluster = new Cluster();
    cluster.setName(ConfigConsts.CLUSTER_NAME_DEFAULT);
    cluster.setAppId(appId);
    cluster.setDataChangeCreatedBy(createBy);
    cluster.setDataChangeLastModifiedBy(createBy);
    clusterRepository.save(cluster);

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