关闭Netty服务器本身

Question

I'm using Netty server to solve this: reading a big file line by line and processing it. Doing it on single machine is still slow, so I've decided to use server to serve chunks of data to clients. That already works, but what I also want is that server shut downs itself when processed whole file. The source code I'm using right now is:

public static void main(String[] args) {
    new Thread(() -> {
        //reading the big file and populating 'dq' - data queue
    }).start();

    final EventLoopGroup bGrp = new NioEventLoopGroup(1);
    final EventLoopGroup wGrp = new NioEventLoopGroup();
    try {
        ServerBootstrap b = new ServerBootstrap();
        b.group(bossGroup, workerGroup)
                .channel(NioServerSocketChannel.class)
                .option(ChannelOption.SO_BACKLOG, 100)
                .childHandler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    public void initChannel(SocketChannel ch) {
                        ChannelPipeline p = ch.pipeline();
                        p.addLast(new StringDecoder());
                        p.addLast(new StringEncoder());
                        p.addLast(new ServerHandler(dq, bGrp, wGrp));
                    }
                });
        ChannelFuture f = b.bind(PORT).sync();
        f.channel().closeFuture().sync();
    } finally {
        workerGroup.shutdownGracefully();
        bossGroup.shutdownGracefully();
    }
}

class ServerHandler extends ChannelInboundHandlerAdapter {
    public ServerHandler(dq, bGrp, wGrp) {
        //assigning params to instance fields
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        //creating bulk of data from 'dq' and sending to client
        /* e.g.
        ctx.write(dq.get());
         */
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        if (dq.isEmpty() /*or other check that file was processed*/ ) {
            try {
                ctx.channel().closeFuture().sync();
            } catch (InterruptedException ie) {
                //...
            }
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        ctx.close();
        ctx.executor().parent().shutdownGracefully();
    }
}

Is the server shutdown in channelReadComplete(...) method correct? What I'm afraid is that there can still be another served client (eg sending big bulk in other client and with current client reached the end of 'dq').

The base code is from netty EchoServer/DiscardServer examples.

The question is : how to shut down netty server (from handler) when reached specific condition.

Thanks

Answer 1

You can not shutdown a server from a handler. What you could do is signal to a different thread that it should shutdown the server.