@Override
  public TGetClusterIdResp getClusterId() {
    TGetClusterIdResp resp = new TGetClusterIdResp();
    String clusterId = configManager.getClusterManager().getClusterId();
    if (clusterId == null) {
      LOGGER.error("clusterId not generated yet, should never happen.");
      return resp.setClusterId("")
          .setStatus(new TSStatus(TSStatusCode.GET_CLUSTER_ID_ERROR.getStatusCode()));
    }
    resp.setClusterId(clusterId).setStatus(RpcUtils.SUCCESS_STATUS);
    LOGGER.info("Execute getClusterId with result {}", resp);
    return resp;
  }
ConfigNodeRPCServer exposes the interface that interacts with the DataNode
iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/service/thrift/ConfigNodeRPCServiceProcessor.java