apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/service/ConfigsExportService.java/ConfigsExportService/exportCluster
class ConfigsExportService:  private void exportCluster(final Env env, final App exportApp, ZipOutputStream zipOutputStream) {
    final List<ClusterDTO> exportClusters = clusterService.findClusters(env, exportApp.getAppId());

    if (CollectionUtils.isEmpty(exportClusters)) {
      return;
    }

    //write cluster info to zip
    writeClusterInfoToZip(env, exportApp, exportClusters, zipOutputStream);

    //export namespaces
    exportClusters.parallelStream().forEach(cluster -> {
      try {
        this.exportNamespaces(env, exportApp, cluster, zipOutputStream);
      } catch (BadRequestException badRequestException) {
        //ignore
      } catch (Exception e) {
        logger.error("export namespace error. appId = {}, cluster = {}", exportApp.getAppId(), cluster, e);
      }
    });
  }