安徽省建设工程造价管理总站网站,旅游网站开发方案ppt,河南郑州房价,设计网免费前言#xff1a;在对ServerBootstrap 进行属性赋值之后#xff0c;通过bind 方法完成端口的绑定#xff0c;并开始在NioEventLoop中进行轮询进行事件的处理#xff1b;本文主要探究ServersocketChannel 在netty 中是如何完成注册#xff0c;以及端口的绑定
1 Nio selecto…前言在对ServerBootstrap 进行属性赋值之后通过bind 方法完成端口的绑定并开始在NioEventLoop中进行轮询进行事件的处理本文主要探究ServersocketChannel 在netty 中是如何完成注册以及端口的绑定
1 Nio selector 多路复用模型
为了更好的探究netty 的channel 的注册和端口的绑定先来回顾下Nio selector 的事件注册以及端口绑定步骤以及netty 步骤的对应 可以看到在 nio 中的步骤在netty 也都是有的然后对以上步骤的关键点在netty 中实现进行探究
2 跟踪bind 方法 server.bind(this.port).sync()
2.1 AbstractBootstrap 类 server.bind(this.port) AbstractBootstrap bind 完成端口的绑定和监听
public ChannelFuture bind(int inetPort) {return this.bind(new InetSocketAddress(inetPort));
}使用new InetSocketAddress(inetPort) 构建要监听的端口然后通过bind 方法进行绑定 AbstractBootstrap 的bind 方法
public ChannelFuture bind(SocketAddress localAddress) {// 验证父类事件处理 的EventLoopGroup 和NioServerSocketChannel 工厂类是否赋值this.validate();// 端口的绑定和启动return this.doBind((SocketAddress)ObjectUtil.checkNotNull(localAddress, localAddress));
}关键点 2.2 进入 AbstractBootstrap doBind在这里开始真正进行channel 管道的初始化注册占位事件完成端口的绑定
private ChannelFuture doBind(final SocketAddress localAddress) {
// 初始化NioServerSocketChannel 对象并赋值 regFuture final ChannelFuture regFuture this.initAndRegister();
// 得到NioServerSocketChannel channel 对象final Channel channel regFuture.channel();if (regFuture.cause() ! null) {return regFuture;} else if (regFuture.isDone()) {
// 通道初始化完成ChannelPromise promise channel.newPromise();
// 地址绑定doBind0(regFuture, channel, localAddress, promise);return promise;} else {final PendingRegistrationPromise promise new PendingRegistrationPromise(channel);regFuture.addListener(new ChannelFutureListener() {public void operationComplete(ChannelFuture future) throws Exception {Throwable cause future.cause();if (cause ! null) {promise.setFailure(cause);} else {promise.registered();AbstractBootstrap.doBind0(regFuture, channel, localAddress, promise);}}});return promise;}
}关键点 2.2.1 this.initAndRegister()NioServerSocketChannel 对象的初始化以及channel 管道的占位事件注册 AbstractBootstrap 类中 initAndRegister 方法
final ChannelFuture initAndRegister() {Channel channel null;try {
// 调用NioServerSocketChannel 无参构造方法 初始化 NioServerSocketChannel 对象channel this.channelFactory.newChannel();
// NioServerSocketChannel 对象初始化this.init(channel);} catch (Throwable var3) {if (channel ! null) {channel.unsafe().closeForcibly();return (new DefaultChannelPromise(channel, GlobalEventExecutor.INSTANCE)).setFailure(var3);}return (new DefaultChannelPromise(new FailedChannel(), GlobalEventExecutor.INSTANCE)).setFailure(var3);}
// 从父类group 中的EventLoopGroup 选出一个EventLoop 并注册到channel 管道上ChannelFuture regFuture this.config().group().register(channel);if (regFuture.cause() ! null) {
// 注册失败 关闭ServerSocketChannel 通道if (channel.isRegistered()) {channel.close();} else {channel.unsafe().closeForcibly();}}
// 返回注册的结果 由于是异步的方法 返回regFuture return regFuture;
}关键点 2.2.1.1 this.channelFactory.newChannel() 的方法NioServerSocketChannel 以及jdk 原生的ServerSocketChannel 对象创建
1 this.channelFactory.newChannel() 通过反射机制调用NioServerSocketChannel 的鬼样子方法中进行jdk 原生的ServerSocketChannel 对象创建
// 获取 WindowsSelectorProvider 的实例对象
private static final SelectorProvider DEFAULT_SELECTOR_PROVIDER SelectorProvider.provider();
public NioServerSocketChannel() {this(newSocket(DEFAULT_SELECTOR_PROVIDER));
}private static java.nio.channels.ServerSocketChannel newSocket(SelectorProvider provider) {try {// 返回ServerSocketChannelImpl 的实例对象return provider.openServerSocketChannel();} catch (IOException var2) {throw new ChannelException(Failed to open a server socket., var2);}
}this(newSocket(DEFAULT_SELECTOR_PROVIDER)); NioServerSocketChannel 的this 方法
public NioServerSocketChannel(java.nio.channels.ServerSocketChannel channel) {
// 父类方法对ServerSocketChannel 对象设置属性super((Channel)null, channel, 16);
// ServerSocketChannel 的config 对象进行初始化
// private final ServerSocketChannelConfig config;this.config new NioServerSocketChannelConfig(this, this.javaChannel().socket());
}super((Channel)null, channel, 16) 调用 AbstractNioMessageChannel这里可以看到把感兴趣的事件accept 16 作为参数进行了传递
// parent 为null ch 为ServerSocketChannel channel 对象
// readInterestOp为int OP_ACCEPT 1 4; 对应客户端连接服务器事件
protected AbstractNioMessageChannel(Channel parent, SelectableChannel ch, int readInterestOp) {super(parent, ch, readInterestOp);
}关键点2继续进父类的调用:AbstractNioChannel: 对java 原生的ServerSocketChannel 的channel 管道的非阻塞属性进行了设置
private static final InternalLogger logger InternalLoggerFactory.getInstance(AbstractNioChannel.class);
private final SelectableChannel ch;
protected final int readInterestOp;
volatile SelectionKey selectionKey;
boolean readPending;
private final Runnable clearReadPendingRunnable new Runnable() {public void run() {AbstractNioChannel.this.clearReadPending0();}
};
private ChannelPromise connectPromise;
private ScheduledFuture? connectTimeoutFuture;
private SocketAddress requestedRemoteAddress;protected AbstractNioChannel(Channel parent, SelectableChannel ch, int readInterestOp) {super(parent);
// 将ServerSocketChannel 对象进行赋值this.ch ch;
// 感兴趣的事件 进行赋值 16 final int OP_ACCEPT 1 4; 对应客户端连接服务器事件this.readInterestOp readInterestOp;try {// 设置管道非阻塞ch.configureBlocking(false);} catch (IOException var7) {try {ch.close();} catch (IOException var6) {logger.warn(Failed to close a partially initialized socket., var6);}throw new ChannelException(Failed to enter non-blocking mode., var7);}
}关键点3 super(parent); 调用父类AbstractChannel:这里对java 原生的ServerSocketChannel 的pipeline 进行双向链表的初始化以便后续加入对accept事件handler 的加入
private static final InternalLogger logger InternalLoggerFactory.getInstance(AbstractChannel.class);
private final Channel parent;
private final ChannelId id;
private final Channel.Unsafe unsafe;
private final DefaultChannelPipeline pipeline;
private final VoidChannelPromise unsafeVoidPromise new VoidChannelPromise(this, false);
private final CloseFuture closeFuture new CloseFuture(this);
private volatile SocketAddress localAddress;
private volatile SocketAddress remoteAddress;
private volatile EventLoop eventLoop;
private volatile boolean registered;
private boolean closeInitiated;
private Throwable initialCloseCause;
private boolean strValActive;
private String strVal;protected AbstractChannel(Channel parent) {
// parent 为nullthis.parent parent;
// chanel 通道设置idthis.id this.newId();
// chanel 通过设置文件描述this.unsafe this.newUnsafe();
// 当前通道初始 pipeline this.pipeline this.newChannelPipeline();
}this.newChannelPipeline()
protected DefaultChannelPipeline newChannelPipeline() {return new DefaultChannelPipeline(this);
}DefaultChannelPipeline 类中对pipeline 完成初始化
static final InternalLogger logger InternalLoggerFactory.getInstance(DefaultChannelPipeline.class);
private static final String HEAD_NAME generateName0(HeadContext.class);
private static final String TAIL_NAME generateName0(TailContext.class);
private static final FastThreadLocalMapClass?, String nameCaches new FastThreadLocalMapClass?, String() {protected MapClass?, String initialValue() {return new WeakHashMap();}
};
private static final AtomicReferenceFieldUpdaterDefaultChannelPipeline, MessageSizeEstimator.Handle ESTIMATOR AtomicReferenceFieldUpdater.newUpdater(DefaultChannelPipeline.class, MessageSizeEstimator.Handle.class, estimatorHandle);
final AbstractChannelHandlerContext head;
final AbstractChannelHandlerContext tail;
private final Channel channel;
private final ChannelFuture succeededFuture;
private final VoidChannelPromise voidPromise;
private final boolean touch ResourceLeakDetector.isEnabled();
private MapEventExecutorGroup, EventExecutor childExecutors;
private volatile MessageSizeEstimator.Handle estimatorHandle;
private boolean firstRegistration true;
private PendingHandlerCallback pendingHandlerCallbackHead;
private boolean registered;
// channel 为 NioServerSocketChannel对象
protected DefaultChannelPipeline(Channel channel) {
// chanel 赋值this.channel (Channel)ObjectUtil.checkNotNull(channel, channel);this.succeededFuture new SucceededChannelFuture(channel, (EventExecutor)null);
// 管道初始化异常 异常原因 promisethis.voidPromise new VoidChannelPromise(channel, true);
// pipeline 双向链表设置this.tail new TailContext(this);this.head new HeadContext(this);this.head.next this.tail;this.tail.prev this.head;
}4NioServerSocketChannel 的config 初始化在完成了对NioServerSocketChannel 对象的创建并初始化pipeline和设置其为非阻塞流之后回到 NioServerSocketChannel 类中
this.config new NioServerSocketChannelConfig(this, this.javaChannel().socket())private NioServerSocketChannelConfig(NioServerSocketChannel channel, ServerSocket javaSocket) {super(channel, javaSocket);
}super(channel, javaSocket) 方法调用到DefaultServerSocketChannelConfig 类
protected final ServerSocket javaSocket;
private volatile int backlog;public DefaultServerSocketChannelConfig(ServerSocketChannel channel, ServerSocket javaSocket) {super(channel);this.backlog NetUtil.SOMAXCONN;// ServerSocket 进行赋值this.javaSocket (ServerSocket)ObjectUtil.checkNotNull(javaSocket, javaSocket);
}继续super(channel);调用到 DefaultChannelConfig
// channel 为 ServerSocketChannel 对象
public DefaultChannelConfig(Channel channel) {this(channel, new AdaptiveRecvByteBufAllocator());
}
protected DefaultChannelConfig(Channel channel, RecvByteBufAllocator allocator) {
// channel NioServerSocketChannel allocator:通道所用的缓冲区this.allocator ByteBufAllocator.DEFAULT;this.msgSizeEstimator DEFAULT_MSG_SIZE_ESTIMATOR;
// 通道属性的赋值this.connectTimeoutMillis 30000;this.writeSpinCount 16;this.autoRead 1;this.autoClose true;this.writeBufferWaterMark WriteBufferWaterMark.DEFAULT;this.pinEventExecutor true;this.setRecvByteBufAllocator(allocator, channel.metadata());this.channel channel;
}2.2.1.2 继续看 initAndRegister() 中的this.init(channel) 方法
// channel为 NioServerSocketChannel 对象
void init(Channel channel) {// 将父类AbstractBootstrap 的options 属性赋值到 NioServerSocketChannel 对象setChannelOptions(channel, this.newOptionsArray(), logger);// 将父类AbstractBootstrap 的attrs属性赋值到 NioServerSocketChannel 对象setAttributes(channel, (Map.Entry[])this.attrs0().entrySet().toArray(EMPTY_ATTRIBUTE_ARRAY));
// 获取 ServerSocketChannel 初始化的pipeline DetaultChannelPipelineChannelPipeline p channel.pipeline();
// 获取 子事件轮询组final EventLoopGroup currentChildGroup this.childGroup;
// 获取子事件的 业务逻辑处理任务final ChannelHandler currentChildHandler this.childHandler;
// 获取的子事件中设置的配置项final Map.Entry[] currentChildOptions;synchronized(this.childOptions) {currentChildOptions (Map.Entry[])this.childOptions.entrySet().toArray(EMPTY_OPTION_ARRAY);}
// 子事件设置的属性final Map.EntryAttributeKey?, Object[] currentChildAttrs (Map.Entry[])this.childAttrs.entrySet().toArray(EMPTY_ATTRIBUTE_ARRAY);p.addLast(new ChannelHandler[]{new ChannelInitializerChannel() {public void initChannel(final Channel ch) {
// 获取 ServerSocketChannel 的pipelinefinal ChannelPipeline pipeline ch.pipeline();
// 添加 原有的handlerChannelHandler handler ServerBootstrap.this.config.handler();if (handler ! null) {pipeline.addLast(new ChannelHandler[]{handler});}
// 添加 Acceptor hadler 到 ServerSocketChannel 的pipeline 双向链表中ch.eventLoop().execute(new Runnable() {public void run() {pipeline.addLast(new ChannelHandler[]{new ServerBootstrapAcceptor(ch, currentChildGroup, currentChildHandler, currentChildOptions, currentChildAttrs)});}});}}});
}
关键点1下面代码向ServerSocketChannel 中的pipeline 在双向链表的尾部增加了一个处理客户端连接事件的handler并且可以看到这个添加handler 的操作是在ServerSocketChannel 初始化完成之后 由eventLoop 中的线程执行了任务handler 在增加之后双向链表的构造header-acceptor-tail
pipeline.addLast(new ChannelHandler[]{new ServerBootstrapAcceptor(ch, currentChildGroup, currentChildHandler, currentChildOptions, currentChildAttrs)})到这里可以做下小结
this.channelFactory.newChannel() 完成了对NioServerSocketChannel 的创建此处可以对应NIo 中的 SocketChannel socketChannel SocketChannel.open()this.init(channel); 对创建的SocketChannel 进行属性的初始化对于事件处理的Pipeline进行双向链表的初始化此处可以对应NIo 中的 socketChannel.configureBlocking(false);并且在ServerSocketChannel 真正完成初始化之后会有nio 的Eventloop 线程将ServerBootstrapAcceptor的handler 增加到ServerSocketChannel pipeline 链表中
2再回到 AbstractBootstrap 的 initAndRegister() 方法中看下事件是如果被注册到ServerSocketChannel 上
final ChannelFuture initAndRegister() {Channel channel null;try {
// 调用NioServerSocketChannel 无参构造方法 初始化 NioServerSocketChannel 对象channel this.channelFactory.newChannel();
// NioServerSocketChannel 对象初始化this.init(channel);} catch (Throwable var3) {if (channel ! null) {channel.unsafe().closeForcibly();return (new DefaultChannelPromise(channel, GlobalEventExecutor.INSTANCE)).setFailure(var3);}return (new DefaultChannelPromise(new FailedChannel(), GlobalEventExecutor.INSTANCE)).setFailure(var3);}
// 从父类group 中的EventLoopGroup 选出一个EventLoop 并注册到channel 管道上ChannelFuture regFuture this.config().group().register(channel);if (regFuture.cause() ! null) {
// 注册失败 关闭ServerSocketChannel 通道if (channel.isRegistered()) {channel.close();} else {channel.unsafe().closeForcibly();}}
// 返回注册的结果return regFuture;
}关键点3 ChannelFuture regFuture this.config().group().register(channel)事件轮询器注册到ServerSocketChannel 对象上 调用 MultithreadEventLoopGroup 中的register 方法
public ChannelFuture register(Channel channel) {return this.next().register(channel);
}next 方法 使用在new NioEventLoopGroup 时设置的 选择器从父类 EventExecutor[] children 数组中选择一个 EventExecutor 然后继续看register 方法 SingleThreadEventLoop 中的register
public ChannelFuture register(Channel channel) {
// 创建DefaultChannelPromise 的promise 对象 赋值 当前的ServerSocketChannel channel 和 子事件轮询器的EventExecutor 并返回包装类的ChannelPromisereturn this.register((ChannelPromise)(new DefaultChannelPromise(channel, this)));
}
public ChannelFuture register(ChannelPromise promise) {ObjectUtil.checkNotNull(promise, promise);
// NioServerSocketChannel 的channel 进行registerpromise.channel().unsafe().register(this, promise);return promise;
}继续进入AbstractChannel 类中的register 方法
public final void register(EventLoop eventLoop, final ChannelPromise promise) {ObjectUtil.checkNotNull(eventLoop, eventLoop);if (AbstractChannel.this.isRegistered()) {promise.setFailure(new IllegalStateException(registered to an event loop already));} else if (!AbstractChannel.this.isCompatible(eventLoop)) {promise.setFailure(new IllegalStateException(incompatible event loop type: eventLoop.getClass().getName()));} else {
// 子事件轮训器进行赋值AbstractChannel.this.eventLoop eventLoop;// eventLoop 是否有线程可以直接使用if (eventLoop.inEventLoop()) {this.register0(promise);} else {try {
// new 一个线程来执行registereventLoop.execute(new Runnable() {public void run() {AbstractUnsafe.this.register0(promise);}});} catch (Throwable var4) {// 注册失败设置异常原因AbstractChannel.logger.warn(Force-closing a channel whose registration task was not accepted by an event loop: {}, AbstractChannel.this, var4);this.closeForcibly();AbstractChannel.this.closeFuture.setClosed();this.safeSetFailure(promise, var4);}}}
}
关键点3.1 调用AbstractUnsafe register0 方法完成占位事件的注册
private voidregister0(ChannelPromise promise) {try {if (!promise.setUncancellable() || !this.ensureOpen(promise)) {return;}// 第一次注册boolean firstRegistration this.neverRegistered;// 事件注册AbstractChannel.this.doRegister();this.neverRegistered false;// 注册成功AbstractChannel.this.registered true;AbstractChannel.this.pipeline.invokeHandlerAddedIfNeeded();// promise 设置注册成功标识this.safeSetSuccess(promise);AbstractChannel.this.pipeline.fireChannelRegistered();if (AbstractChannel.this.isActive()) {if (firstRegistration) {AbstractChannel.this.pipeline.fireChannelActive();} else if (AbstractChannel.this.config().isAutoRead()) {this.beginRead();}}} catch (Throwable var3) {this.closeForcibly();AbstractChannel.this.closeFuture.setClosed();this.safeSetFailure(promise, var3);}}关键点3.2 AbstractChannel.this.doRegister()占位事件0完成注册 AbstractNioChannel 类中 doRegister 方法
protected void doRegister() throws Exception {boolean selected false;while(true) {try {// this.javaChannel() 为ServerSocketChannel对象// ServerSocketChannel对象 调用 register 方法this.selectionKey this.javaChannel().register(this.eventLoop().unwrappedSelector(), 0, this);return;} catch (CancelledKeyException var3) {if (selected) {throw var3;}this.eventLoop().selectNow();selected true;}}
}ServerSocketChannel对象 调用 register 方法 AbstractSelectableChannel 类中 register 方法
// Selector 为 从父事件NioEventLoopGroup 中选择出来的某个NioEventLoop 对应的 Selector 选择器器
// ops 感兴趣的事件 0
// att 属性NioServerSocketChannel 对象
public final SelectionKey register(Selector sel, int ops,Object att)throws ClosedChannelException
{synchronized (regLock) {if (!isOpen())throw new ClosedChannelException();if ((ops ~validOps()) ! 0)throw new IllegalArgumentException();if (blocking)throw new IllegalBlockingModeException();SelectionKey k findKey(sel);if (k ! null) {k.interestOps(ops);k.attach(att);}if (k null) {// New registrationsynchronized (keyLock) {if (!isOpen())throw new ClosedChannelException();k ((AbstractSelector)sel).register(this, ops, att);addKey(k);}}return k;}
}调用AbstractSelector 的 register 方法完成将事件注册到selector多路复用器中
protected final SelectionKey register(AbstractSelectableChannel var1, int var2, Object var3) {if (!(var1 instanceof SelChImpl)) {throw new IllegalSelectorException();} else {SelectionKeyImpl var4 new SelectionKeyImpl((SelChImpl)var1, this);var4.attach(var3);synchronized(this.publicKeys) {this.implRegister(var4);}var4.interestOps(var2);return var4;}
}关键点3.3 AbstractChannel.this.pipeline.invokeHandlerAddedIfNeeded() 在channel初始化完成之后回调到initAndRegister() 中的this.init(channel) 方法完成accept handler 的增加 可以看到具体进行accept 事件增加的处理是借由 EventLoop 中的execute 进行任务的提交
关键点关键点3.4 this.safeSetSuccess(promise) 为promise 设置成功结果后回调到AbstractBootstrap的doBind的operationComplete 方法进行端口号的绑定
关键点 2.2.1.3 ServerSocketChannel 管道初始化完成之后 进行doBind0 端口的板绑定
private ChannelFuture doBind(final SocketAddress localAddress) {final ChannelFuture regFuture this.initAndRegister();final Channel channel regFuture.channel();if (regFuture.cause() ! null) {return regFuture;} else if (regFuture.isDone()) {ChannelPromise promise channel.newPromise();doBind0(regFuture, channel, localAddress, promise);return promise;} else {final PendingRegistrationPromise promise new PendingRegistrationPromise(channel);// 监听注册完成的事件regFuture.addListener(new ChannelFutureListener() {public void operationComplete(ChannelFuture future) throws Exception {Throwable cause future.cause();if (cause ! null) {promise.setFailure(cause);} else {// 设置注册成功标识promise.registered();// 绑定端口AbstractBootstrap.doBind0(regFuture, channel, localAddress, promise);}}});return promise;}
}1 AbstractBootstrap 的doBind0 方法使用nio 线程进行channel 的绑定
// ChannelFuture 为 DefaultChannelPromise
// channel 为 NioServerSocketChannel
// localAddress为 0.0.0.0/0.0.0.0:8080
// promise为 AbstractBootstrap$PendingRegistrationPromise
private static void doBind0(final ChannelFuture regFuture, final Channel channel, final SocketAddress localAddress, final ChannelPromise promise) {channel.eventLoop().execute(new Runnable() {public void run() {if (regFuture.isSuccess()) {channel.bind(localAddress, promise).addListener(ChannelFutureListener.CLOSE_ON_FAILURE);} else {promise.setFailure(regFuture.cause());}}});
}AbstractChannel 的bind 方法
public ChannelFuture bind(SocketAddress localAddress, ChannelPromise promise) {// this.pipeline 取的 NioServerSocketChannel 的pipeline return this.pipeline.bind(localAddress, promise);
}DefaultChannelPipeline 类中bind 方法
public final ChannelFuture bind(SocketAddress localAddress, ChannelPromise promise) {return this.tail.bind(localAddress, promise);
}2 AbstractChannelHandlerContext 类中bind 方法 找到第一个Outbound handler head 节点完成端口绑定
public ChannelFuture bind(final SocketAddress localAddress, final ChannelPromise promise) {ObjectUtil.checkNotNull(localAddress, localAddress);if (this.isNotValidPromise(promise, false)) {return promise;} else {final AbstractChannelHandlerContext next this.findContextOutbound(512);EventExecutor executor next.executor();if (executor.inEventLoop()) {// 端口绑定next.invokeBind(localAddress, promise);} else {safeExecute(executor, new Runnable() {public void run() {next.invokeBind(localAddress, promise);}}, promise, (Object)null, false);}return promise;}
}AbstractChannelHandlerContext 类 invokeBind 方法
private void invokeBind(SocketAddress localAddress, ChannelPromise promise) {if (this.invokeHandler()) {try {((ChannelOutboundHandler)this.handler()).bind(this, localAddress, promise);} catch (Throwable var4) {notifyOutboundHandlerException(var4, promise);}} else {this.bind(localAddress, promise);}}关键点3 最终进入NioServerSocketChannel 中的doBind 进行端口的绑定 使用原生的java ServerSocketChannel 进行端口的绑定 关键点4 在dobind 之后判断channel 管道是否已经就绪了如果就绪 就依次调用 NioServerSocketChannel 的Pipeline 中的 每个handler 中的channelActive 方法 目前Pipeline 中有3个handler header-acceptor-tail 5 最终进入head 头节点的 DefaultChannelPipeline 中的channelActive方法 6 进入AbstractChannelHandlerContext read 方法从tail 向前找到Outbound 的handler 然后进行操作
关键点7进入到AbstractNioChannel中doBeginRead() 然后关注accept 事件 到这里我们看到了NioServerSocketChannel 对象的初始化以及非阻塞属性的设置已经最终对管道accept 事件 的注册
3 对于bind 方法总结
initAndRegister 分为init 和register init 中可以理解为 在main 线程中创建了创 NioServerSocketChannel 对象并且 在main 线程中 添加 NioServerSocketChannel 初始化 handler 并随后在NioServerSocketChannel 管道初始化完成之后使用nio 线程向NioServerSocketChannel 的Pipeline 增加accept 处理客户端连接的handler;register 中会切换到nio线程完成对NioServerSocketChannel 初始事件的绑定在dobind0 中 使用nio 线程完成NioServerSocketChannel 端口的绑定并触发NioServerSocketChannel active 事件 进入到head 节点selectionKey.interestOps(SelectionKey.OP ACCEPT): 对于accept 事件进行绑定这里nio 线程指的是我们声明的boss NioEventLoopGroup需要注意的是 NioEventLoopGroup 中存在多个NioEventLoop,每个NioEventLoop 都有自己的selector任务队列所以每个NioEventLoop 都可以处理io 事件普通任务和定时任务值得注意的是每个NioEventLoop 的处理任务的线程只有一个虽然有线程池但是也只有一个线程典型的多生产者一个消费者
