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Netty-主从Reactor多线程模式的源码实现

Netty--主从Reactor多线程模式的源码实现

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Netty-主从Reactor多线程模式的源码实现

EventLoopGroup到底是什么?

EventLoopGroup是一个存储EventLoop的容器,同时他应该具备线程池的功能。

graph BT; EventLoopGroup --> EventExecutorGroup; EventExecutorGroup --> ScheduledExecutorService;

由于EventLoopGroup间接继承ScheduledExecutorService接口,因此其实现类应该具备线程池的功能。

看一下NioEventLoopGroup的核心属性

// 默认的线程池大小
    private static final int DEFAULT_EVENT_LOOP_THREADS;

    static {
        DEFAULT_EVENT_LOOP_THREADS = Math.max(1, SystemPropertyUtil.getInt(
                "io.netty.eventLoopThreads", NettyRuntime.availableProcessors() * 2)); // CPU核数 x 2
    }
    
    // 存储EventLoop的数组
    private final EventExecutor[] children;

构造方法

// 如果传入的nThread为空,那么使用默认的线程池大小(CPU核数 x 2)
    protected MultithreadEventLoopGroup(int nThreads, ThreadFactory threadFactory, Object... args) {
        super(nThreads == 0 ? DEFAULT_EVENT_LOOP_THREADS : nThreads, threadFactory, args);
    }

    // 最终的构建方法
    protected MultithreadEventExecutorGroup(int nThreads, Executor executor,
                                            EventExecutorChooserFactory chooserFactory, Object... args) {
        // ......省略

        children = new EventExecutor[nThreads]; // 初始化EventExecutor数组的大小

        for (int i = 0; i < nThreads; i ++) {
            boolean success = false;
            try {
                children[i] = newChild(executor, args); // 初始化EventLoop
                success = true;
            } catch (Exception e) {
                throw new IllegalStateException("failed to create a child event loop", e);
            } finally {
                // ......省略
            }
        }
        // ......省略
    }

当创建NioEventLoopGroup实例后,就已经初始化好其EventExecutor数组的大小以及其存储的EventLoop。

graph TB; NioEventLoopGroup --> array[EventExecutor数组]; array --> E1[EventLoop]; array --CPU核数 x 2--> E2[EventLoop]; array --> E3[EventLoop...];

EventLoop又是什么?

graph BT; EventLoop --> EventExecutor; NioEventLoop --> EventLoop;

EventLoop是EventExecutor的子接口。

看一下NioEventLoop的核心属性

private Selector selector;
  
  private volatile Thread thread;
  
  private final Executor executor;
  
  private final Queue<Runnable> taskQueue;
  
  static final int DEFAULT_MAX_PENDING_EXECUTOR_TASKS = Math.max(16,
            SystemPropertyUtil.getInt("io.netty.eventexecutor.maxPendingTasks", Integer.MAX_VALUE));

每一个NioEventLoop都有一个Selector、Thread、Executor、Queue属性,当创建EventLoop实例后其thread属性仍为NULL,还没有创建线程。

Channel

看一下Channel的核心属性

private volatile EventLoop eventLoop; // 指向EventLoop的引用

每一个Channel都有一个指向EventLoop的引用,也就是说每一个Channel都会与一个EventLoop进行绑定,其eventLoop()方法返回此Channel绑定的EventLoop。

graph TB; EventLoop --> A[Channel]; EventLoop --> B[Channel]; EventLoop --> C[Channel...];

Netty启动服务器后的核心流程

// 创建bossGroup和workerGroup
  EventLoopGroup bossGroup = new NioEventLoopGroup();
  EventLoopGroup workerGroup = new NioEventLoopGroup();
// 绑定端口,启动服务
  serverBootstrap.bind(8888).sync();

AbstarctBootstrap的doBind()方法

private ChannelFuture doBind(final SocketAddress localAddress) {
        final ChannelFuture regFuture = initAndRegister(); // 初始化Channel并将Channel注册到bossGroup中的EventLoop中的Selector
        final Channel channel = regFuture.channel();
        if (regFuture.cause() != null) {
            return regFuture;
        }

        if (regFuture.isDone()) {
            ChannelPromise promise = channel.newPromise();
            doBind0(regFuture, channel, localAddress, promise);
            return promise;
        } else {
            final PendingRegistrationPromise promise = new PendingRegistrationPromise(channel);
            regFuture.addListener(new ChannelFutureListener() { 
                @Override
                public void operationComplete(ChannelFuture future) throws Exception {  // 当initAndRegister()方法完成后,由IO线程自动调用
                    Throwable cause = future.cause();
                    if (cause != null) {
                        promise.setFailure(cause);
                    } else {
                        promise.registered();
                        doBind0(regFuture, channel, localAddress, promise);   // 进行绑定操作
                    }
                }
            });
            return promise;
        }
    }
final ChannelFuture initAndRegister() {
        Channel channel = null;
        try {
            channel = channelFactory.newChannel(); // 创建NioServerSocketChannel
            init(channel); // 初始化Channel
        } catch (Throwable t) {
            if (channel != null) {
                channel.unsafe().closeForcibly();
                return new DefaultChannelPromise(channel, GlobalEventExecutor.INSTANCE).setFailure(t);
            }
            return new DefaultChannelPromise(new FailedChannel(), GlobalEventExecutor.INSTANCE).setFailure(t);
        }
        
        // config()方法返回AbstractBootStrap
        // AbstractBootStrap存储bossGroup,ServerBootStrap存储workerGroup
        ChannelFuture regFuture = config().group().register(channel); 
        if (regFuture.cause() != null) {
            if (channel.isRegistered()) {
                channel.close();
            } else {
                channel.unsafe().closeForcibly();
            }
        }
        return regFuture;
    }

EventLoopGroup的register()方法会通过选择器从EventLoopGroup中取出一个EventLoop,然后调用EventLoop的register()方法

// EventLoopGroup的register()方法
    public ChannelFuture register(Channel channel) {
        return next().register(channel); // 调用EventLoop的register()方法
    }
    
    /**
     * 通过选择器从EventLoopGroup中取出一个EventLoop
     */
    public EventExecutor next() {
        return chooser.next();
    }

SingleThreadEventLoop的register()方法

public ChannelFuture register(final ChannelPromise promise) {
        ObjectUtil.checkNotNull(promise, "promise");
        promise.channel().unsafe().register(this, promise); // 调用Channel的register()方法,传递当前对象,即当前EventLoop实例
        return promise;
    }

AbstarctChannel的register()方法

public final void register(EventLoop eventLoop, final ChannelPromise promise) {
        if (eventLoop == null) {
            throw new NullPointerException("eventLoop");
        }
        if (isRegistered()) {
            promise.setFailure(new IllegalStateException("registered to an event loop already"));
            return;
        }
        if (!isCompatible(eventLoop)) {
            promise.setFailure(new IllegalStateException("incompatible event loop type: " + eventLoop.getClass().getName()));
            return;
        }

        AbstractChannel.this.eventLoop = eventLoop; // 初始化Channel的EventLoop属性
           
        // 第一次调用时,EventLoop中的thread为空,因此inEventLoop()返回false
        if (eventLoop.inEventLoop()) { 
            register0(promise); 
        } else {
            try {
                eventLoop.execute(new Runnable() { // 调用EventLoop的execute()方法,并将注册操作作为一个任务,放入到Runnable实例中
                @Override
                public void run() {
                    // register0()方法最终将会调用doRegister()方法,将Channel注册到EventLoop中的Selector
                    register0(promise);
                    }
                });
            } catch (Throwable t) {
                logger.warn("Force-closing a channel whose registration task was not accepted by an event loop: {}",AbstractChannel.this, t);
                closeForcibly();
                closeFuture.setClosed();
                safeSetFailure(promise, t);
           }
        }
     }

SingleThreadEventExecutor的execute()方法

public void execute(Runnable task) {
         if (task == null) {
             throw new NullPointerException("task");
         }
 
         boolean inEventLoop = inEventLoop(); 
         addTask(task); // 将任务放入到当前EventLoop的任务队列中
         if (!inEventLoop) {
             startThread(); // 开启一个线程,最终调用doStartThread()方法
             if (isShutdown()) {
                 boolean reject = false;
                 try {
                     if (removeTask(task)) {
                         reject = true;
                     }
                 } catch (UnsupportedOperationException e) {
                 
                 }
                 if (reject) {
                     reject();
                 }
             }
         }

         if (!addTaskWakesUp && wakesUpForTask(task)) {
             wakeup(inEventLoop);
         }
     }

SingleThreadEventExecutor的doStartThread()方法

private void doStartThread() {
         assert thread == null; // 当前EventLoop中的thread为空,输出结果肯定为true
         executor.execute(new Runnable() { // 向线程池中提交一个任务,到这里才创建线程同时异步执行
             @Override
             public void run() {
                 thread = Thread.currentThread(); // 初始化EventLoop中的thread属性,即线程池中执行该任务的线程
                 if (interrupted) {
                     thread.interrupt();
                 }

                 boolean success = false;
                 updateLastExecutionTime();
                 try {
                     SingleThreadEventExecutor.this.run(); // 核心方法(当前对象为NioEventLoop)
                     success = true;
                 } catch (Throwable t) {
                     logger.warn("Unexpected exception from an event executor: ", t);
                 } finally {
                     // ......省略
                 }
             }
         });
     }

NioEventLoop的run()方法

protected void run() {
         for (;;) { // 死循环
             try {
                 try {
                     switch (selectStrategy.calculateStrategy(selectNowSupplier, hasTasks())) {
                     case SelectStrategy.CONTINUE:
                         continue;

                     case SelectStrategy.BUSY_WAIT:

                     case SelectStrategy.SELECT:
                         select(wakenUp.getAndSet(false));

                         if (wakenUp.get()) {
                             selector.wakeup();
                         }
                     default:
                     }
                 } catch (IOException e) {
                     rebuildSelector0();
                     handleLoopException(e);
                     continue;
                 }

                 cancelledKeys = 0;
                 needsToSelectAgain = false;
                 final int ioRatio = this.ioRatio;
                 if (ioRatio == 100) {
                     try {
                         processSelectedKeys(); // 处理Channel的就绪事件,最终调用processSelectedKeysOptimized()方法
                     } finally {
                         runAllTasks(); // 执行保存在任务队列中的所有任务
                     }
                 } else {
                     final long ioStartTime = System.nanoTime();
                     try {
                         processSelectedKeys();
                     } finally {
                         // Ensure we always run tasks.
                         final long ioTime = System.nanoTime() - ioStartTime;
                         runAllTasks(ioTime * (100 - ioRatio) / ioRatio);
                     }
                 }
             } catch (Throwable t) {
                 handleLoopException(t);
             }
             try {
                 if (isShuttingDown()) {
                     closeAll();
                     if (confirmShutdown()) {
                         return;
                     }
                 }
             } catch (Throwable t) {
                 handleLoopException(t);
             }
         }
     }
private void processSelectedKeysOptimized() {
         for (int i = 0; i < selectedKeys.size; ++i) { // 遍历就绪的Channel对应的SelectionKey集合,如果Channel没有事件就绪则集合为空
             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;
             }
         }
     }

NioEventLoop的processSelectedKey()方法

private void processSelectedKey(SelectionKey k, AbstractNioChannel ch) {
         final AbstractNioChannel.NioUnsafe unsafe = ch.unsafe();
         if (!k.isValid()) {
             final EventLoop eventLoop;
             try {
                 eventLoop = ch.eventLoop();
             } catch (Throwable ignored) {
                 return;
             }
             if (eventLoop != this || eventLoop == null) {
                 return;
             }
             unsafe.close(unsafe.voidPromise());
             return;
         }

         try {
             int readyOps = k.readyOps(); // 就绪的事件
             if ((readyOps & SelectionKey.OP_CONNECT) != 0) { // 连接就绪
                 int ops = k.interestOps();
                 ops &= ~SelectionKey.OP_CONNECT;
                 k.interestOps(ops);
                 unsafe.finishConnect(); // 处理连接就绪
             }
           
            if ((readyOps & SelectionKey.OP_WRITE) != 0) { // 写就绪
                 ch.unsafe().forceFlush(); // 处理写就绪
             }
           
            if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) { // 接收和读就绪
                 unsafe.read(); // 处理接收和读就绪
             }
         } catch (CancelledKeyException ignored) {
             unsafe.close(unsafe.voidPromise());
         }
     }

当EventLoop中的线程处理完Channel的就绪事件后将会执行保存在任务队列中的所有任务,此时注册任务将被执行

private void register0(ChannelPromise promise) {
         try {
             if (!promise.setUncancellable() || !ensureOpen(promise)) {
                 return;
             }
             boolean firstRegistration = neverRegistered;
             doRegister(); // 执行注册操作
             neverRegistered = false;
             registered = true;

             pipeline.invokeHandlerAddedIfNeeded();

             safeSetSuccess(promise); // ChannelFuture设置成成功状态,同时isDone()方法将返回true
             pipeline.fireChannelRegistered();
             if (isActive()) {
                 if (firstRegistration) {
                     pipeline.fireChannelActive();
                 } else if (config().isAutoRead()) {
                     beginRead();
                 }
             }
          } catch (Throwable t) {
             closeForcibly();
             closeFuture.setClosed();
             safeSetFailure(promise, t); // ChannelFuture设置成失败状态,同时isDone()方法将返回true
          }
     }

AbstractNioChannel的doRegister()方法

protected void doRegister() throws Exception {
         boolean selected = false;
         for (;;) {
             try {
                 // 将Channel注册到EventLoop中的Selector
                 selectionKey = javaChannel().register(eventLoop().unwrappedSelector(), 0, this); // 将Channel注册到Selector当中,当Channel执行完相应操作后,再向Selector传递需要监听此Channel的事件类型
                 return;
             } catch (CancelledKeyException e) {
                 if (!selected) {
                     eventLoop().selectNow();
                     selected = true;
                 } else {
                     throw e;
                 }
             }
         }
     }

回到一开始的AbstarctBootstrap的doBind()方法

private ChannelFuture doBind(final SocketAddress localAddress) {
         final ChannelFuture regFuture = initAndRegister(); 
         final Channel channel = regFuture.channel(); 
         if (regFuture.cause() != null) {
             return regFuture;
         }

         if (regFuture.isDone()) { // 由于注册任务是异步执行的,此时任务还未被执行,因此isDone()方法将返回false
             ChannelPromise promise = channel.newPromise();
             doBind0(regFuture, channel, localAddress, promise);
             return promise;
         } else {
             final PendingRegistrationPromise promise = new PendingRegistrationPromise(channel);
             regFuture.addListener(new ChannelFutureListener() { 
                 @Override
                 public void operationComplete(ChannelFuture future) throws Exception {  // 当注册任务被执行完毕后,由IO线程自动
                     Throwable cause = future.cause();
                     if (cause != null) {
                         promise.setFailure(cause);
                     } else {
                         promise.registered();
                         doBind0(regFuture, channel, localAddress, promise); // 进行绑定操作
                     }
                 }
             });
             return promise;
         }
     }
private static void doBind0(
         final ChannelFuture regFuture, final Channel channel,
         final SocketAddress localAddress, final ChannelPromise promise) {

         channel.eventLoop().execute(new Runnable() { // 同样的,获取Channel绑定的EventLoop,调用EventLoop的execute()方法,并将绑定操作作为一个任务,放入到Runnable实例中
         @Override
         public void run() {
             if (regFuture.isSuccess()) {
                   channel.bind(localAddress, promise).addListener(ChannelFutureListener.CLOSE_ON_FAILURE);
                } else {
                   promise.setFailure(regFuture.cause());
             }
         }
        });
      }
public void execute(Runnable task) {
         if (task == null) {
             throw new NullPointerException("task");
         }

         boolean inEventLoop = inEventLoop(); // 由于当前方法是被处理注册任务的那个线程调用的,即EventLoop中的那个线程,因此inEventLoop()方法返回true
         addTask(task); // 将任务放入到队列中,等待被执行
         if (!inEventLoop) { // 不会执行,到目前为止仍然只开启了一个线程
             startThread();
             if (isShutdown()) {
                 boolean reject = false;
                 try {
                     if (removeTask(task)) {
                         reject = true;
                     }
                 } catch (UnsupportedOperationException e) {
                    
                 }
                 if (reject) {
                     reject();
                 }
             }
         }

         if (!addTaskWakesUp && wakesUpForTask(task)) {
             wakeup(inEventLoop);
         }
     }

这就是Netty启动服务端后的核心流程

1.创建ServerSocketChannel并进行初始化。

2.调用bossGroup的register()方法,方法内部通过选择器从bossGroup中取出一个EventLoop,然后调用EventLoop的register()方法。

3.最终调用Channel的register()方法,方法中初始化Channel的eventLoop属性,然后将Channel注册到bossGroup中的EventLoop中的Selector作为一个任务,放入到Runnable实例中,然后调用EventLoop的execute(Runnable)方法。

4.execute()方法将任务放入到任务队列当中,然后向线程池中提交一个任务,此时才创建一个线程,同时初始化EventLoop中的thread属性。

5.任务中初始化EventLoop的thread属性,然后调用NioEventLoop的run()方法,死循环去处理Channel的就绪事件以及执行保存在任务队列中的所有任务。

6.当注册任务被执行完毕后,该线程会回调ChannelFutureListener中的operationComplete()方法,将绑定操作作为一个任务,然后调用EventLoop的execute(Runnable)方法。

7.重复第4步骤,将任务放入到任务队列中,由于当前线程就是EventLoop中的thread,因此inEventLoop()方法返回true,不会向线程池中提交任务,任务等待被EventLoop中的线程执行。

Netty处理接收和读就绪事件的核心流程

BossGroup中的EventLoop中的Thread正在死循环的处理Channel的就绪事件以及执行保存在任务队列中的所有任务

// 创建一个连接
SocketChannel socketChannel = SocketChannel.open();
socketChannel.connect(new InetSocketAddress(InetAddress.getLocalHost(), 8888));

BossGroup中的EventLoop中的Selector监听到ServerSocketChannel有接收就绪事件

// NioEventLoop的processSelectedKey()方法
        if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {
            unsafe.read();
        }
        
        public void read() {
            assert eventLoop().inEventLoop(); // 肯定是true
            final ChannelConfig config = config();
            final ChannelPipeline pipeline = pipeline();
            final RecvByteBufAllocator.Handle allocHandle = unsafe().recvBufAllocHandle();
            allocHandle.reset(config);

            boolean closed = false;
            Throwable exception = null;
            try {
                try {
                    do {
                        int localRead = doReadMessages(readBuf); // 读取Channel中的数据
                        if (localRead == 0) {
                            break;
                        }
                        if (localRead < 0) {
                            closed = true;
                            break;
                        }

                        allocHandle.incMessagesRead(localRead);
                    } while (allocHandle.continueReading());
                } catch (Throwable t) {
                    exception = t;
                }

                int size = readBuf.size();
                for (int i = 0; i < size; i ++) {
                    readPending = false;
                    pipeline.fireChannelRead(readBuf.get(i)); // 最终会调用ServerBootStrap的register()方法
                }
                readBuf.clear();
                allocHandle.readComplete();
                pipeline.fireChannelReadComplete();

                if (exception != null) {
                    closed = closeOnReadError(exception);

                    pipeline.fireExceptionCaught(exception);
                }

                if (closed) {
                    inputShutdown = true;
                    if (isOpen()) {
                        close(voidPromise());
                    }
                }
            } finally {
                if (!readPending && !config.isAutoRead()) {
                    removeReadOp();
                }
            }
        }

NioServerSocketChannel的doReadMessage()方法

protected int doReadMessages(List<Object> buf) throws Exception {
         SocketChannel ch = SocketUtils.accept(javaChannel()); // 接收连接,调用ServerSocketChannel的accept()方法

         try {
             if (ch != null) {
                 buf.add(new NioSocketChannel(this, ch)); // 将接收到连接放入到buffer中
                 return 1;
             }
         } catch (Throwable t) {
             logger.warn("Failed to create a new channel from an accepted socket.", t);

             try {
                 ch.close();
             } catch (Throwable t2) {
                 logger.warn("Failed to close a socket.", t2);
             }
         }

         return 0;
     }

ServerBootstrap的register()方法

public void channelRead(ChannelHandlerContext ctx, Object msg) {
        final Channel child = (Channel) msg;

         child.pipeline().addLast(childHandler);

         setChannelOptions(child, childOptions, logger);
         setAttributes(child, childAttrs);

         try {
              // 调用workerGroup的register()方法,方法内部通过选择器从workerGroup中取出一个EventLoop,然后调用EventLoop的register()方法,最终调用AbstractChannel的register()方法
              childGroup.register(child).addListener(new ChannelFutureListener() {
              @Override
              public void operationComplete(ChannelFuture future) throws Exception {
                  if (!future.isSuccess()) {
                        forceClose(child, future.cause());
                  }
              }
             });
          } catch (Throwable t) {
              forceClose(child, t);
          }
      }

AbstractChannel的register()方法

public final void register(EventLoop eventLoop, final ChannelPromise promise) {
        if (eventLoop == null) {
                throw new NullPointerException("eventLoop");
        }
        if (isRegistered()) {
              promise.setFailure(new IllegalStateException("registered to an event loop already"));
              return;
        }
        if (!isCompatible(eventLoop)) {
              promise.setFailure(
                     new IllegalStateException("incompatible event loop type: " + eventLoop.getClass().getName()));
              return;
        }

        AbstractChannel.this.eventLoop = eventLoop; // 初始化Channel的eventLoop属性

        // 如果取出的是新的EventLoop,那么其thread属性为空,当前线程总是bossGroup中的EventLoop中的thread,因此inEventLoop()返回false。
        // 如果取出的是旧的EventLoop,那么其thread属性不为空,当前线程总是bossGroup中的EventLoop中的thread,因此inEventLoop()返回false。
        if (eventLoop.inEventLoop()) { // 总是返回false,当前线程总是bossGroup中的EventLoop中的thread,肯定与workerGroup中的任意一个EventLoop中的thread都不相等。
              register0(promise);
         } else {
             try {
                 eventLoop.execute(new Runnable() { // 总是会执行该方法
                     @Override
                     public void run() {
                        register0(promise);
                     }
                  });
             } catch (Throwable t) {
                  logger.warn("Force-closing a channel whose registration task was not accepted by an event loop: {}",AbstractChannel.this, t);
                  closeForcibly();
                  closeFuture.setClosed();
                  safeSetFailure(promise, t);
             }
        }
     }
public void execute(Runnable task) {
         if (task == null) {
             throw new NullPointerException("task");
         }

         boolean inEventLoop = inEventLoop();
         addTask(task); // 将任务放入到队列当中
         if (!inEventLoop) { 
             startThread(); // 不管是新的还是旧的EventLoop都会调用该方法 
             if (isShutdown()) {
                 boolean reject = false;
                 try {
                     if (removeTask(task)) {
                         reject = true;
                     }
                 } catch (UnsupportedOperationException e) {
                
                 }
                 if (reject) {
                     reject();
                 }
             }
         }

         if (!addTaskWakesUp && wakesUpForTask(task)) {
             wakeup(inEventLoop);
         }
     }
private void startThread() {
         if (state == ST_NOT_STARTED) { // 如果取出的是旧的EventLoop,那么其thread属性本身就不为空,因此其state属性就不等于ST_NOT_STARTED,因此不会开启新的线程,注册任务等待被EventLoop中的线程执行
             if (STATE_UPDATER.compareAndSet(this, ST_NOT_STARTED, ST_STARTED)) {
                 boolean success = false;
                 try {
                     doStartThread(); // 取出的是新的EventLoop,其thread属性为null,同时其state等于ST_NOT_STARTED,因此需要开启线程,向线程池中提交一个任务,死循环去处理Channel的就绪事件以及执行保存在任务队列中的所有任务
                     success = true;
                 } finally {
                     if (!success) {
                         STATE_UPDATER.compareAndSet(this, ST_STARTED, ST_NOT_STARTED);
                     }
                 }
             }
         }
     }

这就是Netty处理接收和读就绪事件的核心流程

1.客户端建立SocketChannel并进行连接。

2.bossGroup中的EventLoop中的Selector监听到ServerSocketChannel有接收就绪事件。

3.接收连接,最终调用workerGroup的register()方法,方法内部通过选择器从workGroup中取出一个EventLoop,然后调用EventLoop的register()方法。

4.最终调用Channel的register()方法,方法中初始化Channel的eventLoop属性,然后将Channel注册到bossGroup中的EventLoop中的Selector作为一个任务,放入到Runnable实例中,然后调用EventLoop的execute(Runnable)方法。

5.execute()方法将任务放入到任务队列中,如果取出的是新的EventLoop,那么其thread属性为空,此时将会开启线程,向线程池中提交一个任务,死循环去处理Channel的就绪事件以及执行保存在任务队列中的所有任务,如果取出的是旧的EventLoop,那么其thread属性不为空,任务等待被EventLoop中的线程执行。

总结

1.当创建NioEventLoopGroup实例后,就已经初始化好其EventExecutor数组的大小以及其存储的EventLoop。

2.每一个NioEventLoop都有一个Selector、Thread、Executor、Queue属性,当创建NioEventLoop实例后,其thread属性仍为空。

3.每一个Channel都会与一个EventLoop进行绑定,其eventLoop()方法返回其绑定的EventLoop,同时该Channel会注册到其绑定的EventLoop的Selector中。

4.EventLoopGroup的register()方法会通过选择器从EventLoopGroup中取出一个EventLoop,然后调用EventLoop的register()方法。

5.EventLoop的execute()方法会将任务放入到任务队列当中,如果inEventLoop()方法返回false同时其thread属性为空,则创建一个线程,向线程池中提交一个任务(任务中初始化EventLoop中的thread属性,然后死循环去处理Channel的就绪事件以及执行保存在任务队列中的所有任务)

原文  http://www.cnblogs.com/funyoung/p/11984630.html
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