Netty源码随笔-NioEventLoop

此章是NioEventLoop的源码学习
还是先上demo

EventLoopGroup bossGroup = new NioEventLoopGroup();
        try{
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(new ObjectDecoder(1024*1024,ClassResolvers.weakCachingConcurrentResolver(this.getClass().getClassLoader())));
                            ch.pipeline().addLast(new ObjectEncoder());
                            ch.pipeline().addLast(new DubboServerHandler());
                        }
                    })
                    .option(ChannelOption.SO_BACKLOG,128)
                    .childOption(ChannelOption.SO_KEEPALIVE,true);
            ChannelFuture f = b.bind(port).sync();
            f.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
        }

NioEventLoop在EventLoopGroup的构造函数中被创建 从NioEventLoopGroup的空构造方法开始

public NioEventLoopGroup() {
      //默认线程数为0
        this(0);
    }
public NioEventLoopGroup(int nThreads) {
        //默认线程数为0，线程池为null
        this(nThreads, (Executor) null);
    }
public NioEventLoopGroup(int nThreads, Executor executor) {
        //默认线程数为0，线程池为null，用来创建NIOSelector的provider
        this(nThreads, executor, SelectorProvider.provider());
    }
public NioEventLoopGroup(
            int nThreads, Executor executor, final SelectorProvider selectorProvider) {
        //默认线程数为0，线程池为null，用来创建NIOSelector的provider，
        this(nThreads, executor, selectorProvider, DefaultSelectStrategyFactory.INSTANCE);
    }
public NioEventLoopGroup(int nThreads, Executor executor, final SelectorProvider selectorProvider,
                             final SelectStrategyFactory selectStrategyFactory) {
        super(nThreads, executor, selectorProvider, selectStrategyFactory, RejectedExecutionHandlers.reject());
    }
protected MultithreadEventLoopGroup(int nThreads, Executor executor, Object... args) {
//如果为0的话则默认为2倍的CPU核数        
super(nThreads == 0 ? DEFAULT_EVENT_LOOP_THREADS : nThreads, executor, args);
    }
protected MultithreadEventExecutorGroup(int nThreads, Executor executor, Object... args) {
//DefaultEventExecutorChooserFactory.INSTANCE负责创建线程选择器
        this(nThreads, executor, DefaultEventExecutorChooserFactory.INSTANCE, args);
    }

此处主要是对EventEventGroup的各种参数进行默认赋值 在深入就进入了大段代码

protected MultithreadEventExecutorGroup(int nThreads, Executor executor,
                                            EventExecutorChooserFactory chooserFactory, Object... args) {
        if (nThreads <= 0) {
            throw new IllegalArgumentException(String.format("nThreads: %d (expected: > 0)", nThreads));
        }
        //创建线程执行器
        if (executor == null) {
            executor = new ThreadPerTaskExecutor(newDefaultThreadFactory());
        }

        children = new EventExecutor[nThreads];
        //通过For循环创建EventLoop
        for (int i = 0; i < nThreads; i ++) {
            boolean success = false;
            try {
                children[i] = newChild(executor, args);
                success = true;
            } catch (Exception e) {
                // TODO: Think about if this is a good exception type
                throw new IllegalStateException("failed to create a child event loop", e);
            } finally {
                if (!success) {
                    for (int j = 0; j < i; j ++) {
                        children[j].shutdownGracefully();
                    }

                    for (int j = 0; j < i; j ++) {
                        EventExecutor e = children[j];
                        try {
                            while (!e.isTerminated()) {
                                e.awaitTermination(Integer.MAX_VALUE, TimeUnit.SECONDS);
                            }
                        } catch (InterruptedException interrupted) {
                            // Let the caller handle the interruption.
                            Thread.currentThread().interrupt();
                            break;
                        }
                    }
                }
            }
        }
//创建线程选择器
        chooser = chooserFactory.newChooser(children);

        final FutureListener