* CacheLoader#reload}
   * to obtain a future of the new value. If the returned future is already complete, it is returned
   * immediately. Otherwise, the old value is returned.
   *
   * <p><b>Note:</b> <i>all exceptions thrown during refresh will be logged and then swallowed</i>.
   *
   * @param duration the length of time after an entry is created that it should be considered

   * occurs. The request triggering refresh will make a synchronous call to {@link
   * CacheLoader#reload}
   * and immediately return the new value if the returned future is complete, and the old value
   * otherwise.
   *
   * <p><b>Note:</b> <i>all exceptions thrown during refresh will be logged and then swallowed</i>.
   *