序

本文主要研究一下sentinel的NettyHttpCommandCenter

NettyHttpCommandCenter

com/alibaba/csp/sentinel/transport/command/NettyHttpCommandCenter.java

public class NettyHttpCommandCenter implements CommandCenter {    private final HttpServer server = new HttpServer();    private final ExecutorService pool = Executors.newSingleThreadExecutor(        new NamedThreadFactory("sentinel-netty-command-center-executor"));    @Override    public void start() throws Exception {        pool.submit(new Runnable() {            @Override            public void run() {                try {                    server.start();                } catch (Exception ex) {                    RecordLog.info("Start netty server error", ex);                    ex.printStackTrace();                    System.exit(-1);                }            }        });    }    @Override    public void stop() throws Exception {        server.close();        pool.shutdownNow();    }    @Override    public void beforeStart() throws Exception {        // Register handlers        Map
    
      handlers = CommandHandlerProvider.getInstance().namedHandlers();        server.registerCommands(handlers);    }}
    

• 这里特意newSingleThreadExecutor，用来异步启动HttpServer
• 在启动之前调用CommandHandlerProvider.getInstance().namedHandlers()，触发收集命令及handler
• 然后调用server.registerCommands(handlers)来注册这些handler

HttpServer

com/alibaba/csp/sentinel/transport/command/netty/HttpServer.java

public final class HttpServer {    private static final int DEFAULT_PORT = 8719;    private Channel channel;    final static Map
    
      handlerMap = new ConcurrentHashMap
     
      ();    public void start() throws Exception {        EventLoopGroup bossGroup = new NioEventLoopGroup(1);        EventLoopGroup workerGroup = new NioEventLoopGroup();        try {            ServerBootstrap b = new ServerBootstrap();            b.group(bossGroup, workerGroup)                .channel(NioServerSocketChannel.class)                .childHandler(new HttpServerInitializer());            int port;            try {                if (StringUtil.isEmpty(TransportConfig.getPort())) {                    CommandCenterLog.info("Port not configured, using default port: " + DEFAULT_PORT);                    port = DEFAULT_PORT;                } else {                    port = Integer.parseInt(TransportConfig.getPort());                }            } catch (Exception e) {                throw new IllegalArgumentException("Illegal port: " + TransportConfig.getPort());            }            channel = b.bind(port).sync().channel();            channel.closeFuture().sync();        } finally {            workerGroup.shutdownGracefully();            bossGroup.shutdownGracefully();        }    }    public void close() {        channel.close();    }    public void registerCommand(String commandName, CommandHandler handler) {        if (StringUtil.isEmpty(commandName) || handler == null) {            return;        }        if (handlerMap.containsKey(commandName)) {            CommandCenterLog.info("Register failed (duplicate command): " + commandName);            return;        }        handlerMap.put(commandName, handler);    }    public void registerCommands(Map
      
        handlerMap) {        if (handlerMap != null) {            for (Entry
       
         e : handlerMap.entrySet()) {                registerCommand(e.getKey(), e.getValue());            }        }    }}
       
      
     
    

• 这里使用netty构造nio server，处理handler为HttpServerInitializer

HttpServerInitializer

com/alibaba/csp/sentinel/transport/command/netty/HttpServerInitializer.java

public class HttpServerInitializer extends ChannelInitializer
    
      {    @Override    protected void initChannel(SocketChannel socketChannel) throws Exception {        ChannelPipeline p = socketChannel.pipeline();        p.addLast(new HttpRequestDecoder());        p.addLast(new HttpObjectAggregator(1024 * 1024));        p.addLast(new HttpResponseEncoder());        p.addLast(new HttpServerHandler());    }}
    

• 设置了HttpRequestDecoder、HttpObjectAggregator、HttpResponseEncoder、HttpServerHandler，前三个为netty自带的组件

HttpServerHandler

com/alibaba/csp/sentinel/transport/command/netty/HttpServerHandler.java

public class HttpServerHandler extends SimpleChannelInboundHandler

• 继承SimpleChannelInboundHandler
• channelRead0方法主要是解析CommandRequest，然后获取响应commandName，调用对应的commandHandler，最后写入结果

小结

NettyHttpCommandCenter提供的是基于netty的http实现，sentinel-transport还有一个SimpleHttpCommandCenter，是基于java socket的bio外加工作线程池模式的实现。

doc