netty - 如何在 Netty 4+ 中使用 ChannelTrafficShapingHandler？

Question

我需要向客户端推送一个大文件，但是我想限制速度(比如100Kb/s)，如何使用ChannelTrafficShapingHandler？

ServerBootstrap b = new ServerBootstrap();
              b.group(bossGroup, workerGroup)
               .channel(NioServerSocketChannel.class)
               .option(ChannelOption.SO_BACKLOG, 100)
               .handler(new LoggingHandler(LogLevel.INFO))
               .childHandler(new ChannelInitializer<SocketChannel>() {
                   @Override
                   public void initChannel(SocketChannel ch) throws Exception {
                       ChannelPipeline p = ch.pipeline();

                       p.addLast(
                               new StringEncoder(CharsetUtil.UTF_8),
                               new LineBasedFrameDecoder(8192),
                               new StringDecoder(CharsetUtil.UTF_8),
                               new ChannelTrafficShapingHandler(1,1,10L),
                               new ChunkedWriteHandler(),
                               new FileServerHandler()
                               );
                   }
               });

这个演示不起作用，为什么？

Answer 1

您是否在 FileServerHandler 中管理 channel 写入功能？

如 Netty API 中所述 ChannelTrafficShapingHandler

In your handler, you should consider to use the channel.isWritable() and channelWritabilityChanged(ctx) to handle writability, or through future.addListener(new GenericFutureListener()) on the future returned by ctx.write().

You shall also consider to have object size in read or write operations relatively adapted to the bandwidth you required: for instance having 10 MB objects for 10KB/s will lead to burst effect, while having 100 KB objects for 1 MB/s should be smoothly handle by this TrafficShaping handler.

和初始化:

• 第一项是以 B/s 为单位的写入限制(这里强烈不推荐 1，接近 1024 的东西是最小的，对于 1KB/s)
• 第二项是B/S中的Read limit(这里强烈不推荐1，接近1024的最小值，1KB/s，0则无限制)
• 第一项是以毫秒为单位的间隔检查(这里的 1L 表示每毫秒，强烈不推荐，接近 1000 的东西是最小的，每 1 秒)

可以看一个例子(使用Discard的例子)here ，特别是:

• for the server initialization
• for the client handler part (which is similar to the server handler part) on how to use channel writability