code: private void requestCacheUpdate() {
          log.debug("Cache update requested");
          if (updateRequested) {
              log.debug("Cache update, redundant request ignored.");
              return;
          }
  
          updateRequested = true;
  
          if (!updating) {
              updateCache();
          }
      }
docs: Just run updateCache one time if multiple requests come in while an update is already in progress...