if (trace) { log.trace(this + "'s downcache is full (" + downCache.size() + " messages)"); }
   protected void addToDownCache(MessageReference ref) throws Exception   {      //Non reliable refs can be cached in a down cache and then flushed to storage      //in blocks      downCache.add(ref);            if (downCache.size() == downCacheSize)      {         flushDownCache();      }   }