code: public synchronized void pushExternalCacheFragment(ExternalInvalidation externalCacheFragment, DCache cache) {
          BatchUpdateList bul = getUpdateList(cache);
          bul.pushECFEvents.add(externalCacheFragment);
      }
docs: This allows an external cache fragment to be added to the
  BatchUpdateDaemon.
  
  @param cacheEntry The external cache fragment to be added.