How to set the maximum number of connections in Netty?

2 years ago
William Carter
1 minute

In Netty, the maximum number of connections can be set using the following method:

  1. Set the SO_BACKLOG parameter in ServerBootstrap using the option() method, which represents the maximum length of the queue for connections waiting to be accepted. An example code snippet is as follows:
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossGroup, workerGroup)
               .channel(NioServerSocketChannel.class)
               .option(ChannelOption.SO_BACKLOG, 100) // 设置最大连接数为100
               .childHandler(new MyChannelInitializer());
  1. In the initChannel() method of ChannelInitializer, add a ChannelInboundHandlerAdapter to the ChannelPipeline to monitor connection numbers and handle them. Example code is as follows:
public class MyChannelInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        pipeline.addLast(new ConnectionCountHandler()); // 添加连接数监听处理器
        pipeline.addLast(new MyHandler1());
        pipeline.addLast(new MyHandler2());
    }
}

public class ConnectionCountHandler extends ChannelInboundHandlerAdapter {
    private static AtomicInteger connectionCount = new AtomicInteger();

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        int currentCount = connectionCount.incrementAndGet();
        if (currentCount > 100) {
            ctx.channel().close(); // 关闭连接
        }
        super.channelActive(ctx);
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        connectionCount.decrementAndGet();
        super.channelInactive(ctx);
    }
}

By using the above method, you can set a maximum number of connections, monitor the number of connections, and close new connections when the maximum number is reached.

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