code: @SuppressWarnings("FutureReturnValueIgnored")
    private void failWrites(Throwable cause) {
      if (failCause == null) {
        failCause = cause;
      } else {
        logger.log(Level.FINE, "Ignoring duplicate failure", cause);
      }
      while (!bufferedWrites.isEmpty()) {
        ChannelWrite write = bufferedWrites.poll();
        write.promise.setFailure(cause);
        ReferenceCountUtil.release(write.msg);
      }
    }
docs: Propagate failures to all buffered writes.