netty 客户端初始化 and 注册过程分析

一、BootStrap.connect() 分析

 public ChannelFuture connect(SocketAddress remoteAddress, SocketAddress localAddress) {        ........................................        参数校验        ........................................        validate();        ........................................        解析与连接        ........................................         return doResolveAndConnect(remoteAddress, localAddress);    }   

• doResolveAndConnect 方法

    private ChannelFuture doResolveAndConnect(final SocketAddress remoteAddress, final SocketAddress localAddress) {        ...........         ........................................        初始化和注册        ........................................        final ChannelFuture regFuture = initAndRegister();        ...........        }    }

• initAndRegister方法

    final ChannelFuture initAndRegister() {        Channel channel = null;        try {            ..................................................            1. 实例化NioSocketChannel            ..................................................            channel = channelFactory.newChannel();            ..................................................            2. NioSocketChannel的 option方法设置 & atrr 方法设置            ..................................................            init(channel);        } catch (Throwable t) {            if (channel != null) {                channel.unsafe().closeForcibly();            }            GlobalEventExecutor.INSTANCE).setFailure(t);        }        ..................................................        3. config().group()为 NioEventLoopGroup的实例        config().group().register()的实现为MultiThreadEventLoopGroup.register 方法        ..................................................        ChannelFuture regFuture = config().group().register(channel);    }

二、MultiThreadEventLoopGroup.register(Channel channel)

    @Override    public EventLoop next() {        return (EventLoop) super.next();    }    @Override    public ChannelFuture register(Channel channel) {        .......................................       register 方法为：SingleThreadEventLoop.register(Channel)        .......................................        return next().register(channel);    }

三、SingleThreadEventLoop .register(Channel) 方法

    @Override    public ChannelFuture register(Channel channel) {        return register(new DefaultChannelPromise(channel, this));    }    @Override    public ChannelFuture register(final ChannelPromise promise) {        ObjectUtil.checkNotNull(promise, "promise");        .......................................        promise.channel().unsafe() 为  NioSocketChannelUnsafe 实例        实际调用方法为 AbstractUnsafe.register        .......................................        promise.channel().unsafe().register(this, promise);        return promise;    }

四、 AbstractUnsafe. register

  public final void register(EventLoop eventLoop, final ChannelPromise promise) {        ......         ..........................         设置NioSocketChannel 的eventloop =SingleThreadEventLoop         ..........................         AbstractChannel.this.eventLoop = eventLoop;         ..........................         eventLoop.execute()：启动一个新的线程然后执行         实际调用方法为 SingleThreadEventLoop.execute         ..........................        eventLoop.execute(new Runnable() {            @Override            public void run() {                register0(promise);            }        });        ......    }

1. register0 过程

 .......................... AbstractUnsafe 标记为已注册 ..........................boolean firstRegistration = neverRegistered;  ....................................................doRegister();neverRegistered = false; .......................... NioSocketChannel 标记为已注册 ..........................registered = true; ....................................................pipeline.invokeHandlerAddedIfNeeded();....................................................safeSetSuccess(promise);....................................................pipeline.fireChannelRegistered();

1.1 doRegister（）分析

实际调用方法为 NioSochetChannel 的 doRegister

    @Override    protected void doRegister() throws Exception {        for (;;) {            try {             ..........................              将jdk的 socketChannel 注册到多路复用器上             ..........................                selectionKey = javaChannel().register(eventLoop().unwrappedSelector(), 0, this);                return;            }         }    }

2. eventLoop.execute(Runnable） 过程

这里的eventLoop 为SingleThreadEventLoop实例

实际调用方法 SingleThreadEventExecutor.execute，代码如下：

     public void execute(Runnable task) {         boolean inEventLoop = inEventLoop();         ..........................         启动线程         ..........................         startThread();         ..........................         将任务添加到 taskQueue中         ..........................         addTask(task);        } 

2.1 startThread();

    private void startThread() {        doStartThread();    }

2.1.1 doStartThread();

        executor.execute(new Runnable() {            @Override            public void run() {            ... .....                 ..........................                  为了标记 eventLoo 是否已经启动                 ..........................                thread = Thread.currentThread();                 boolean success = false;                updateLastExecutionTime();                try {                    SingleThreadEventExecutor.this.run();                    success = true;                }                 }            ....  ....         });

2.1.1.1 executor.execute(runnable)

实现方法为ThreadPerTaskExecutor.execute

public void execute(Runnable command) {        threadFactory.newThread(command).start();    }

2.1.1.2 SingleThreadEventExecutor.this.run()

此方法非常关键,是eventLoop的核心

实现方法为 ：NioEventLoop.run（）方法

    @Override    protected void run() {        for (;;) {             ..........................             查询就绪的selectedKey             ..........................            select(wakenUp.getAndSet(false));            ..........................            执行就绪的selectedKey            ..........................            processSelectedKeys();            ..........................            执行任务            ..........................            runAllTasks();        }    }

• processSelectedKeys();

  processSelectedKeysOptimized 方法

    private void processSelectedKeysOptimized() {        for (int i = 0; i < selectedKeys.size; ++i) {            final SelectionKey k = selectedKeys.keys[i];            selectedKeys.keys[i] = null;            final Object a = k.attachment();            if (a instanceof AbstractNioChannel) {                processSelectedKey(k, (AbstractNioChannel) a);            } else {                @SuppressWarnings("unchecked")                NioTask<SelectableChannel> task = (NioTask<SelectableChannel>) a;                processSelectedKey(k, task);            }            if (needsToSelectAgain) {                selectedKeys.reset(i + 1);                selectAgain();                i = -1;            }        }    }

processSelectedKey 方法

    int readyOps = k.readyOps();     ..........................     处理 connnect 事件     ..........................    if ((readyOps & SelectionKey.OP_CONNECT) != 0) {        int ops = k.interestOps();        ops &= ~SelectionKey.OP_CONNECT;        k.interestOps(ops);        unsafe.finishConnect();    }     ..........................     处理 write 事件     ..........................    if ((readyOps & SelectionKey.OP_WRITE) != 0) {        ch.unsafe().forceFlush();    }     ..........................     处理 read  和  accept 事件     ..........................    if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {        unsafe.read();    }

• runAllTasks();

    protected boolean runAllTasks() {        assert inEventLoop();        boolean fetchedAll;        boolean ranAtLeastOne = false;        do {         ..........................         ScheduledTaskQueue 中的task 放入 taskQueue 中         ..........................            fetchedAll = fetchFromScheduledTaskQueue();         ..........................          执行taskQueue中的任务         ..........................            if (runAllTasksFrom(taskQueue)) {                ranAtLeastOne = true;            }        } while (!fetchedAll);          ..........................          执行tailQueue中的任务         ..........................        afterRunningAllTasks();        return ranAtLeastOne;    }

2.2 addTask(task);

    protected void addTask(Runnable task) {         ..........................          taskQueue 中增加task         ..........................        if (!offerTask(task)) {            reject(task);        }    }