checkNotNull(future);
    try {
      return getUninterruptibly(future);
    } catch (ExecutionException wrapper) {
      if (wrapper.getCause() instanceof Error) {
        throw new ExecutionError((Error) wrapper.getCause());
      }
      /*
       * It's an Exception. (Or it's a non-Error, non-Exception Throwable. From my survey of such

     */
    protected String detailedMessage(final Throwable t) {
        if (t == null) {
            return "Unknown";
        }
        Throwable target = t;
        if (target.getCause() == null) {
            return target.getClass().getSimpleName() + "[" + target.getMessage() + "]";
        }
        final StringBuilder sb = new StringBuilder();
        while (target != null) {

            try (final InputStream is = new BufferedInputStream(responseData.getResponseBody())) {
                out.write(is);
            } catch (final IOException e) {
                if (!(e.getCause() instanceof ClientAbortException)) {
                    throw new FessSystemException("Failed to write a content. configId: " + configId + ", url: " + url, e);
                }
            } finally {

                  started.countDown();
                  try {
                    return method.invoke(delegate, args);
                  } catch (InvocationTargetException e) {
                    throw e.getCause();
                  } finally {
                    awaitUninterruptibly(canReturn);
                    returned.countDown();
                  }
                }
              });