apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/service/ConfigsExportService.java/ConfigsExportService/writeClusterInfoToZip
class ConfigsExportService:  private void writeClusterInfoToZip(Env env, App app, List<ClusterDTO> exportClusters,
                                     ZipOutputStream zipOutputStream) {
    final Consumer<ClusterDTO> clusterConsumer =
        cluster -> {
          try {
            synchronized (zipOutputStream) {
              String fileName = ConfigFileUtils.genClusterInfoPath(app, env, cluster);
              String content = gson.toJson(cluster);

              writeToZip(fileName, content, zipOutputStream);
            }
          } catch (IOException e) {
            logger.error("Write error. {}", cluster);
            throw new ServiceException("Write error. {}", e);
          }
        };

    exportClusters.forEach(clusterConsumer);
  }