apollo-configservice/src/main/java/com/ctrip/framework/apollo/configservice/service/AppNamespaceServiceWithCache.java/AppNamespaceServiceWithCache/afterPropertiesSet
class AppNamespaceServiceWithCache:  @Override
  public void afterPropertiesSet() throws Exception {
    populateDataBaseInterval();
    scanNewAppNamespaces(); //block the startup process until load finished
    scheduledExecutorService.scheduleAtFixedRate(() -> {
      Transaction transaction = Tracer.newTransaction("Apollo.AppNamespaceServiceWithCache",
          "rebuildCache");
      try {
        this.updateAndDeleteCache();
        transaction.setStatus(Transaction.SUCCESS);
      } catch (Throwable ex) {
        transaction.setStatus(ex);
        logger.error("Rebuild cache failed", ex);
      } finally {
        transaction.complete();
      }
    }, rebuildInterval, rebuildInterval, rebuildIntervalTimeUnit);
    scheduledExecutorService.scheduleWithFixedDelay(this::scanNewAppNamespaces, scanInterval,
        scanInterval, scanIntervalTimeUnit);
  }