基于Netty源代码版本：netty-all-4.1.33.Final
netty中的reactor线程
netty中最核心的东西莫过于两种类型的reactor线程，可以看作netty中两种类型的发动机，驱动着netty整个框架的运转
一种类型的reactor线程是boos线程组，专门用来接受新的连接，然后封装成channel对象扔给worker线程组；还有一种类型的reactor线程是worker线程组，专门用来处理连接的读写。
不管是boos线程还是worker线程，所做的事情均分为以下三个步骤
- 轮询出注册在selector上面的IO事件（select）
- 处理这些IO事件（process selected keys）
- 执行异步task
对于boos线程来说，第一步轮询出来的基本都是 accept 事件，表示有新的连接，而worker线程轮询出来的基本都是read/write事件，表示网络的读写事件
新连接的建立
简单来说，新连接的建立可以分为三个步骤：
- 1、检测到有新的连接
- 2、将新的连接注册到worker线程组
- 3、注册新连接的读事件
检测到有新连接进入
我们已经知道，当服务端绑启动之后，服务端的channel已经注册到boos reactor线程中，reactor不断检测有新的事件，直到检测出有accept事件发生
NioEventLoop.java
private void processSelectedKey(SelectionKey k, AbstractNioChannel ch) {
final AbstractNioChannel.NioUnsafe unsafe = ch.unsafe();
//检查该SelectionKey是否有效，如果无效，则关闭channel
if (!k.isValid()) {
final EventLoop eventLoop;
try {
eventLoop = ch.eventLoop();
} catch (Throwable ignored) {
// If the channel implementation throws an exception because there is no event loop, we ignore this
// because we are only trying to determine if ch is registered to this event loop and thus has authority
// to close ch.
return;
}
// Only close ch if ch is still registered to this EventLoop. ch could have deregistered from the event loop
// and thus the SelectionKey could be cancelled as part of the deregistration process, but the channel is
// still healthy and should not be closed.
// See https://github.com/netty/netty/issues/5125
if (eventLoop != this || eventLoop == null) {
return;
}
// close the channel if the key is not valid anymore
unsafe.close(unsafe.voidPromise());
return;
}
try {
int readyOps = k.readyOps();
// We first need to call finishConnect() before try to trigger a read(...) or write(...) as otherwise
// the NIO JDK channel implementation may throw a NotYetConnectedException.
// 如果是OP_CONNECT，则需要移除OP_CONNECT否则Selector.select(timeout)将立即返回不会有任何阻塞，这样可能会出现cpu 100%
if ((readyOps & SelectionKey.OP_CONNECT) != 0) {
// remove OP_CONNECT as otherwise Selector.select(..) will always return without blocking
// See https://github.com/netty/netty/issues/924
int ops = k.interestOps();
ops &= ~SelectionKey.OP_CONNECT;
k.interestOps(ops);
unsafe.finishConnect();
}
// Process OP_WRITE first as we may be able to write some queued buffers and so free memory.
// 如果准备好了WRITE则将缓冲区中的数据发送出去，如果缓冲区中数据都发送完成，则清除之前关注的OP_WRITE标记
if ((readyOps & SelectionKey.OP_WRITE) != 0) {
// Call forceFlush which will also take care of clear the OP_WRITE once there is nothing left to write
ch.unsafe().forceFlush();
}
// Also check for readOps of 0 to workaround possible JDK bug which may otherwise lead
// to a spin loop
// 如果准备好READ或ACCEPT则触发unsafe.read() ,检查是否为0，如上面的源码英文注释所说：解决JDK可能会产生死循环的一个bug。
if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {
unsafe.read();
}
} catch (CancelledKeyException ignored) {
unsafe.close(unsafe.voidPromise());
}
}
该方法主要是对SelectionKey k进行了检查，有如下几种不同的情况
- 1）OP_ACCEPT，接受客户端连接
- 2）OP_READ, 可读事件, 即 Channel 中收到了新数据可供上层读取。
- 3）OP_WRITE, 可写事件, 即上层可以向 Channel 写入数据。
- 4）OP_CONNECT, 连接建立事件, 即 TCP 连接已经建立, Channel 处于 active 状态。
主要来看下当boss线程 selector检测到OP_ACCEPT事件时，内部干了些什么。
// Also check for readOps of 0 to workaround possible JDK bug which may otherwise lead
// to a spin loop
// 如果准备好READ或ACCEPT则触发unsafe.read() ,检查是否为0，如上面的源码英文注释所说：解决JDK可能会产生死循环的一个bug。
if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {
unsafe.read();
}
boos reactor线程已经轮询到 SelectionKey.OP_ACCEPT 事件，说明有新的连接进入，此时将调用channel的 unsafe来进行实际的操作,此时的channel为 NioServerSocketChannel，则unsafe为NioServerSocketChannel的属性NioMessageUnsafe
那么，我们进入到它的read方法，进入新连接处理的第二步
注册到reactor线程
NioMessageUnsafe.java
private final List<Object> readBuf = new ArrayList<Object>();
@Override
public void read() {
assert eventLoop().inEventLoop();
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);
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));
}
readBuf.clear();
allocHandle.readComplete();
pipeline.fireChannelReadComplete();
if (exception != null) {
closed = closeOnReadError(exception);
pipeline.fireExceptionCaught(exception);
}
if (closed) {
inputShutdown = true;
if (isOpen()) {
close(voidPromise());
}
}
} finally {
// Check if there is a readPending which was not processed yet.
// This could be for two reasons:
// * The user called Channel.read() or ChannelHandlerContext.read() in channelRead(...) method
// * The user called Channel.read() or ChannelHandlerContext.read() in channelReadComplete(...) method
//
// See https://github.com/netty/netty/issues/2254
if (!readPending && !config.isAutoRead()) {
removeReadOp();
}
}
}
调用 doReadMessages 方法不断地读取消息，用 readBuf 作为容器，这里，其实可以猜到读取的是一个个连接，然后调用 pipeline.fireChannelRead()，将每条新连接经过一层服务端channel的洗礼，之后清理容器，触发 pipeline.fireChannelReadComplete()
下面我们具体看下这两个方法：
- 1、doReadMessages(List)
- 2、pipeline.fireChannelRead(NioSocketChannel)
doReadMessages()
@Override
protected int doReadMessages(List<Object> buf) throws Exception {
SocketChannel ch = SocketUtils.accept(javaChannel());
try {
if (ch != null) {
buf.add(new NioSocketChannel(this, ch));
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;
}
@Override
protected ServerSocketChannel javaChannel() {
return (ServerSocketChannel) super.javaChannel();
}
public final class SocketUtils {
@Override
protected int doReadMessages(List<Object> buf) throws Exception {
SocketChannel ch = SocketUtils.accept(javaChannel());
try {
if (ch != null) {
buf.add(new NioSocketChannel(this, ch));
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;
}
}
我们终于窥探到netty调用jdk底层nio的边界serverSocketChannel.accept();，由于netty中reactor线程第一步就扫描到有accept事件发生，因此，这里的accept方法是立即返回的，返回jdk底层nio创建的一条channel
ServerSocketChannel有阻塞和非阻塞两种模式：
- a、阻塞模式：ServerSocketChannel.accept() 方法监听新进来的连接，当 accept()方法返回的时候,它返回一个包含新进来的连接的 SocketChannel。阻塞模式下, accept()方法会一直阻塞到有新连接到达。
- b、非阻塞模式：accept() 方法会立刻返回，如果还没有新进来的连接,返回的将是null。 因此，需要检查返回的SocketChannel是否是null.
在NioServerSocketChannel的构造函数分析中，我们知道，其通过ch.configureBlocking(false);语句设置当前的ServerSocketChannel为非阻塞的。
在NioServerSocketChannel的构造函数分析中，我们知道，在其父类AbstractNioChannel的构造函数中通过ch.configureBlocking(false);语句设置当前的ServerSocketChannel为非阻塞的。
netty将jdk的 SocketChannel 封装成自定义的 NioSocketChannel，加入到list里面，这样外层就可以遍历该list，做后续处理
从上一篇文章中，我们已经知道服务端的创建过程中会创建netty中一系列的核心组件，包括pipeline,unsafe等等，那么，接受一条新连接的时候是否也会创建这一系列的组件呢？
带着这个疑问，我们跟进去
NioSocketChannel.java
public NioSocketChannel(Channel parent, SocketChannel socket) {
super(parent, socket);
config = new NioSocketChannelConfig(this, socket.socket());
}
我们重点分析 super(parent, socket)，NioSocketChannel的父类为 AbstractNioByteChannel
AbstractNioByteChannel.java
protected AbstractNioByteChannel(Channel parent, SelectableChannel ch) {
super(parent, ch, SelectionKey.OP_READ);
}
这里，我们看到jdk nio里面熟悉的影子—— SelectionKey.OP_READ，一般在原生的jdk nio编程中，也会注册这样一个事件，表示对channel的读感兴趣
我们继续往上，追踪到AbstractNioByteChannel的父类 AbstractNioChannel, 这里，我相信读了上一篇文章你对于这部分代码肯定是有印象的
protected AbstractNioChannel(Channel parent, SelectableChannel ch, int readInterestOp) {
super(parent);
this.ch = ch;
this.readInterestOp = readInterestOp;
try {
ch.configureBlocking(false);
} catch (IOException e) {
try {
ch.close();
} catch (IOException e2) {
if (logger.isWarnEnabled()) {
logger.warn(
"Failed to close a partially initialized socket.", e2);
}
}
throw new ChannelException("Failed to enter non-blocking mode.", e);
}
}
在创建服务端channel的时候，最终也会进入到这个方法，super(parent), 便是在AbstractChannel中创建一系列和该channel绑定的组件，如下
protected AbstractChannel(Channel parent) {
this.parent = parent;
id = newId();
unsafe = newUnsafe();
pipeline = newChannelPipeline();
}
而这里的 readInterestOp 表示该channel关心的事件是 SelectionKey.OP_READ，后续会将该事件注册到selector，之后设置该通道为非阻塞模式，在channel中创建 unsafe 和一条 pipeline
pipeline.fireChannelRead(NioSocketChannel)
对于 pipeline我们前面已经了解过，在netty的各种类型的channel中，都会包含一个pipeline，字面意思是管道，我们可以理解为一条流水线工艺，流水线工艺有起点，有结束，中间还有各种各样的流水线关卡，一件物品，在流水线起点开始处理，经过各个流水线关卡的加工，最终到流水线结束
对应到netty里面，流水线的开始就是HeadContxt，流水线的结束就是TailConext，HeadContxt中调用Unsafe做具体的操作，TailConext中用于向用户抛出pipeline中未处理异常以及对未处理消息的警告
通过前面的文章中，我们已经知道在服务端的channel初始化时，在pipeline中，已经自动添加了一个pipeline处理器 ServerBootstrapAcceptor, 并已经将用户代码中设置的一系列的参数传入了构造函数，接下来，我们就来看下ServerBootstrapAcceptor
ServerBootstrapAcceptor.java
private static class ServerBootstrapAcceptor extends ChannelInboundHandlerAdapter {
private final EventLoopGroup childGroup;
private final ChannelHandler childHandler;
private final Entry<ChannelOption<?>, Object>[] childOptions;
private final Entry<AttributeKey<?>, Object>[] childAttrs;
private final Runnable enableAutoReadTask;
ServerBootstrapAcceptor(
final Channel channel, EventLoopGroup childGroup, ChannelHandler childHandler,
Entry<ChannelOption<?>, Object>[] childOptions, Entry<AttributeKey<?>, Object>[] childAttrs) {
this.childGroup = childGroup;
this.childHandler = childHandler;
this.childOptions = childOptions;
this.childAttrs = childAttrs;
// Task which is scheduled to re-enable auto-read.
// It's important to create this Runnable before we try to submit it as otherwise the URLClassLoader may
// not be able to load the class because of the file limit it already reached.
//
// See https://github.com/netty/netty/issues/1328
enableAutoReadTask = new Runnable() {
@Override
public void run() {
channel.config().setAutoRead(true);
}
};
}
@Override
@SuppressWarnings("unchecked")
public void channelRead(ChannelHandlerContext ctx, Object msg) {
final Channel child = (Channel) msg;
child.pipeline().addLast(childHandler);
setChannelOptions(child, childOptions, logger);
for (Entry<AttributeKey<?>, Object> e: childAttrs) {
child.attr((AttributeKey<Object>) e.getKey()).set(e.getValue());
}
try {
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);
}
}
}
前面的 pipeline.fireChannelRead(NioSocketChannel); 最终通过head->unsafe->ServerBootstrapAcceptor的调用链，调用到这里的 ServerBootstrapAcceptor 的channelRead方法，而 channelRead 一上来就把这里的msg强制转换为 Channel
然后，拿到该channel，也就是我们之前new出来的 NioSocketChannel中对应的pipeline，将用户代码中的 childHandler，添加到pipeline，这里的 childHandler 在用户代码中的体现为
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast(new EchoServerHandler());
}
});
其实对应的是 ChannelInitializer，到了这里，NioSocketChannel中pipeline对应的处理器为 head->ChannelInitializer->tail，牢记，后面会再次提到！
接着，设置 NioSocketChannel 对应的 attr和option，然后进入到 childGroup.register(child)，这里的childGroup就是我们在启动代码中new出来的NioEventLoopGroup
我们进入到NioEventLoopGroup的register方法，代理到其父类MultithreadEventLoopGroup
MultithreadEventLoopGroup.java
@Override
public ChannelFuture register(Channel channel) {
return next().register(channel);
}
这里又扯出来一个 next()方法，我们跟进去
@Override
public EventLoop next() {
return (EventLoop) super.next();
}
回到其父类
MultithreadEventExecutorGroup.java
private final EventExecutorChooserFactory.EventExecutorChooser chooser;
@Override
public EventExecutor next() {
return chooser.next();
}
protected MultithreadEventExecutorGroup(int nThreads, Executor executor, EventExecutorChooserFactory chooserFactory, Object... args) {
chooser = chooserFactory.newChooser(children);
}
这里的chooser对应的类为 EventExecutorChooser，字面意思为事件执行器选择器，放到我们这里的上下文中的作用就是从worker reactor线程组中选择一个reactor线程
@UnstableApi
public interface EventExecutorChooserFactory {
/**
* Returns a new {@link EventExecutorChooser}.
*/
EventExecutorChooser newChooser(EventExecutor[] executors);
/**
* Chooses the next {@link EventExecutor} to use.
*/
@UnstableApi
interface EventExecutorChooser {
/**
* Returns the new {@link EventExecutor} to use.
*/
EventExecutor next();
}
}
chooser的实现有两种
@UnstableApi
public final class DefaultEventExecutorChooserFactory implements EventExecutorChooserFactory {
public static final DefaultEventExecutorChooserFactory INSTANCE = new DefaultEventExecutorChooserFactory();
private DefaultEventExecutorChooserFactory() { }
@SuppressWarnings("unchecked")
@Override
public EventExecutorChooser newChooser(EventExecutor[] executors) {
if (isPowerOfTwo(executors.length)) {
return new PowerOfTwoEventExecutorChooser(executors);
} else {
return new GenericEventExecutorChooser(executors);
}
}
private static boolean isPowerOfTwo(int val) {
return (val & -val) == val;
}
private static final class PowerOfTwoEventExecutorChooser implements EventExecutorChooser {
private final AtomicInteger idx = new AtomicInteger();
private final EventExecutor[] executors;
PowerOfTwoEventExecutorChooser(EventExecutor[] executors) {
this.executors = executors;
}
@Override
public EventExecutor next() {
return executors[idx.getAndIncrement() & executors.length - 1];
}
}
private static final class GenericEventExecutorChooser implements EventExecutorChooser {
private final AtomicInteger idx = new AtomicInteger();
private final EventExecutor[] executors;
GenericEventExecutorChooser(EventExecutor[] executors) {
this.executors = executors;
}
@Override
public EventExecutor next() {
return executors[Math.abs(idx.getAndIncrement() % executors.length)];
}
}
}
默认情况下，chooser通过 DefaultEventExecutorChooserFactory被创建，在创建reactor线程选择器的时候，会判断reactor线程的个数，如果是2的幂，就创建PowerOfTowEventExecutorChooser，否则，创建GenericEventExecutorChooser
两种类型的选择器在选择reactor线程的时候，都是通过Round-Robin的方式选择reactor线程，唯一不同的是，PowerOfTowEventExecutorChooser是通过与运算，而GenericEventExecutorChooser是通过取余运算，与运算的效率要高于求余运算
选择完一个reactor线程，即 NioEventLoop 之后，我们回到注册的地方
public ChannelFuture register(Channel channel) {
return next().register(channel);
}
SingleThreadEventLoop.java
@Override
public ChannelFuture register(Channel channel) {
return register(new DefaultChannelPromise(channel, this));
}
其实，这里已经和服务端启动的过程一样了，可以参考我前面的文章
AbstractChannel$AbstractUnsafe
private void register0(ChannelPromise promise) {
try {
// check if the channel is still open as it could be closed in the mean time when the register
// call was outside of the eventLoop
if (!promise.setUncancellable() || !ensureOpen(promise)) {
return;
}
boolean firstRegistration = neverRegistered;
doRegister();
neverRegistered = false;
registered = true;
// Ensure we call handlerAdded(...) before we actually notify the promise. This is needed as the
// user may already fire events through the pipeline in the ChannelFutureListener.
pipeline.invokeHandlerAddedIfNeeded();
safeSetSuccess(promise);
pipeline.fireChannelRegistered();
// Only fire a channelActive if the channel has never been registered. This prevents firing
// multiple channel actives if the channel is deregistered and re-registered.
if (isActive()) {
if (firstRegistration) {
pipeline.fireChannelActive();
} else if (config().isAutoRead()) {
// This channel was registered before and autoRead() is set. This means we need to begin read
// again so that we process inbound data.
//
// See https://github.com/netty/netty/issues/4805
beginRead();
}
}
} catch (Throwable t) {
// Close the channel directly to avoid FD leak.
closeForcibly();
closeFuture.setClosed();
safeSetFailure(promise, t);
}
}
和服务端启动过程一样，先是调用 doRegister();做真正的注册过程，如下
AbstractNioChannel
@Override
protected void doRegister() throws Exception {
boolean selected = false;
for (;;) {
try {
selectionKey = javaChannel().register(eventLoop().unwrappedSelector(), 0, this);
return;
} catch (CancelledKeyException e) {
if (!selected) {
// Force the Selector to select now as the "canceled" SelectionKey may still be
// cached and not removed because no Select.select(..) operation was called yet.
eventLoop().selectNow();
selected = true;
} else {
// We forced a select operation on the selector before but the SelectionKey is still cached
// for whatever reason. JDK bug ?
throw e;
}
}
}
}
将该条channel绑定到一个selector上去，一个selector被一个reactor线程使用，后续该channel的事件轮询，以及事件处理，异步task执行都是由此reactor线程来负责
绑定完reactor线程之后，调用 pipeline.invokeHandlerAddedIfNeeded()
前面我们说到，到目前为止NioSocketChannel 的pipeline中有三个处理器，head->ChannelInitializer->tail，最终会调用到 ChannelInitializer 的 handlerAdded 方法
@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
if (ctx.channel().isRegistered()) {
// This should always be true with our current DefaultChannelPipeline implementation.
// The good thing about calling initChannel(...) in handlerAdded(...) is that there will be no ordering
// surprises if a ChannelInitializer will add another ChannelInitializer. This is as all handlers
// will be added in the expected order.
if (initChannel(ctx)) {
// We are done with init the Channel, removing the initializer now.
removeState(ctx);
}
}
}
handlerAdded方法调用 initChannel 方法之后，调用remove(ctx);将自身删除
private boolean initChannel(ChannelHandlerContext ctx) throws Exception {
if (initMap.add(ctx)) { // Guard against re-entrance.
try {
initChannel((C) ctx.channel());
} catch (Throwable cause) {
// Explicitly call exceptionCaught(...) as we removed the handler before calling initChannel(...).
// We do so to prevent multiple calls to initChannel(...).
exceptionCaught(ctx, cause);
} finally {
ChannelPipeline pipeline = ctx.pipeline();
if (pipeline.context(this) != null) {
pipeline.remove(this);
}
}
return true;
}
return false;
}
而这里的 initChannel 方法又是神马玩意？让我们回到用户方法，比如下面这段用户代码
用户代码
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.option(ChannelOption.SO_BACKLOG, 100)
.handler(new LoggingHandler(LogLevel.INFO))
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast(new LoggingHandler(LogLevel.INFO));
pipeline.addLast(new EchoServerHandler());
}
});
原来最终跑到我们自己的代码里去了啊！完了之后，NioSocketChannel绑定的pipeline的处理器就包括 head->LoggingHandler->EchoServerHandler->tail
注册读事件
接下来，我们还剩下这些代码没有分析完
AbstractChannel$AbstractUnsafe
private void register0(ChannelPromise promise) {
try {
// check if the channel is still open as it could be closed in the mean time when the register
// call was outside of the eventLoop
if (!promise.setUncancellable() || !ensureOpen(promise)) {
return;
}
boolean firstRegistration = neverRegistered;
doRegister();
neverRegistered = false;
registered = true;
// Ensure we call handlerAdded(...) before we actually notify the promise. This is needed as the
// user may already fire events through the pipeline in the ChannelFutureListener.
pipeline.invokeHandlerAddedIfNeeded();
safeSetSuccess(promise);
pipeline.fireChannelRegistered();
// Only fire a channelActive if the channel has never been registered. This prevents firing
// multiple channel actives if the channel is deregistered and re-registered.
if (isActive()) {
if (firstRegistration) {
pipeline.fireChannelActive();
} else if (config().isAutoRead()) {
// This channel was registered before and autoRead() is set. This means we need to begin read
// again so that we process inbound data.
//
// See https://github.com/netty/netty/issues/4805
beginRead();
}
}
} catch (Throwable t) {
// Close the channel directly to avoid FD leak.
closeForcibly();
closeFuture.setClosed();
safeSetFailure(promise, t);
}
}
pipeline.fireChannelRegistered();，其实没有干啥有意义的事情，最终无非是再调用一下业务pipeline中每个处理器的 ChannelHandlerAdded方法处理下回调
isActive()在连接已经建立的情况下返回true，所以进入方法块，进入到 pipeline.fireChannelActive();在这里我详细步骤先省略，直接进入到关键环节
@Override
public final void beginRead() {
assertEventLoop();
if (!isActive()) {
return;
}
try {
doBeginRead();
} catch (final Exception e) {
invokeLater(new Runnable() {
@Override
public void run() {
pipeline.fireExceptionCaught(e);
}
});
close(voidPromise());
}
}
AbstractNioChannel
public abstract class AbstractNioChannel extends AbstractChannel {
@Override
protected void doBeginRead() throws Exception {
// Channel.read() or ChannelHandlerContext.read() was called
final SelectionKey selectionKey = this.selectionKey;
if (!selectionKey.isValid()) {
return;
}
readPending = true;
final int interestOps = selectionKey.interestOps();
if ((interestOps & readInterestOp) == 0) {
selectionKey.interestOps(interestOps | readInterestOp);
}
}
}
这里其实就是将 SelectionKey.OP_READ事件注册到selector中去，表示这条通道已经可以开始处理read事件了
至此，netty中关于新连接的处理已经向你展示完了，我们做下总结
- 1、boos reactor线程轮询到有新的连接进入
- 2、通过封装jdk底层的channel创建 NioSocketChannel以及一系列的netty核心组件
- 3、将该条连接通过chooser，选择一条worker reactor线程绑定上去
- 4、注册读事件，开始新连接的读写
参考：
https://www.cnblogs.com/java-chen-hao/p/11477358.html
