从绑定端口**bind()**方法开始
AbstractBootstrap.java 从构造方法一路跟踪
/**
* Create a new {@link Channel} and bind it.
*/
public ChannelFuture bind(int inetPort) {
return bind(new InetSocketAddress(inetPort));
}
/**
* Create a new {@link Channel} and bind it.
*/
public ChannelFuture bind(String inetHost, int inetPort) {
return bind(SocketUtils.socketAddress(inetHost, inetPort));
}
/**
* Create a new {@link Channel} and bind it.
*/
public ChannelFuture bind(InetAddress inetHost, int inetPort) {
return bind(new InetSocketAddress(inetHost, inetPort));
}
/**
* Create a new {@link Channel} and bind it.
*/
public ChannelFuture bind(SocketAddress localAddress) {
// 验证group与channelFactory属性是否为null
validate();
if (localAddress == null) {
throw new NullPointerException("localAddress");
}
return doBind(localAddress);
}
private ChannelFuture doBind(final SocketAddress localAddress) {
// 以异步的方式创建、初始化一个channel，并将其注册到selector
// 准备跟踪initAndRegister() 方法
final ChannelFuture regFuture = initAndRegister();
// 从future中获取channel
final Channel channel = regFuture.channel();
// 若在执行异步操作过程中出现了异常，则直接返回这个future
if (regFuture.cause() != null) {
return regFuture;
}
// 处理当前异步操作完成（任务正常结束，或执行过程中发生异常，或任务被取消）的情况
if (regFuture.isDone()) {
// At this point we know that the registration was complete and successful.
// 创建一个channelPromise实例
ChannelPromise promise = channel.newPromise();
// 继续绑定
doBind0(regFuture, channel, localAddress, promise);
return promise;
} else { // 处理当前异步操作目前尚未完成的情况
// Registration future is almost always fulfilled already, but just in case it's not.
// Pending，悬而未决的
final PendingRegistrationPromise promise = new PendingRegistrationPromise(channel);
// 为future添加监听，当异步操作完成时，会触发该回调的执行
regFuture.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) throws Exception {
Throwable cause = future.cause();
if (cause != null) {
// Registration on the EventLoop failed so fail the ChannelPromise directly to not cause an
// IllegalStateException once we try to access the EventLoop of the Channel.
// 修改promise的值
promise.setFailure(cause);
} else {
// Registration was successful, so set the correct executor to use.
// See https://github.com/netty/netty/issues/2586
promise.registered();
doBind0(regFuture, channel, localAddress, promise);
}
}
});
return promise;
}
}
初始化并注册ChannelFuture
final ChannelFuture initAndRegister() {
Channel channel = null;
try {
// 创建parentChannel
// 其实这里面是使用反射newInstance 创建出一个Channel无参对象
channel = channelFactory.newChannel();
// 对象创建完后，开始初始化该channel
init(channel);
} catch (Throwable t) {
if (channel != null) { // 若条件为true，说明channel创建成功，但初始化时出现问题
// channel can be null if newChannel crashed (eg SocketException("too many open files"))
// 将channel强制关闭
channel.unsafe().closeForcibly();
// as the Channel is not registered yet we need to force the usage of the GlobalEventExecutor
return new DefaultChannelPromise(channel, GlobalEventExecutor.INSTANCE).setFailure(t);
}
// 代码能走到这里，说明创建channel过程中出现了问题
// as the Channel is not registered yet we need to force the usage of the GlobalEventExecutor
return new DefaultChannelPromise(new FailedChannel(), GlobalEventExecutor.INSTANCE).setFailure(t);
}
// 注册parentChannel(该过程中从group中选择出了eventLoop与channel进行了绑定，并创建启动了这个线程）
ChannelFuture regFuture = config().group().register(channel);
if (regFuture.cause() != null) {
if (channel.isRegistered()) {
channel.close();
} else {
channel.unsafe().closeForcibly();
}
}
// If we are here and the promise is not failed, it's one of the following cases:
// 1) If we attempted registration from the event loop, the registration has been completed at this point.
// i.e. It's safe to attempt bind() or connect() now because the channel has been registered.
// 2) If we attempted registration from the other thread, the registration request has been successfully
// added to the event loop's task queue for later execution.
// i.e. It's safe to attempt bind() or connect() now:
// because bind() or connect() will be executed *after* the scheduled registration task is executed
// because register(), bind(), and connect() are all bound to the same thread.
return regFuture;
}
我们现在查看的源代码是服务端的，所以选择ServerBootstrap.java进行跟踪init() 初始化方法
@Override
void init(Channel channel) throws Exception {
// 获取ServerBootstrap中的options属性
final Map<ChannelOption<?>, Object> options = options0();
synchronized (options) {
//这个地方就是将options属性初始化到channel中，而这个channel就是我们
//.childHandler(new ChannelInitializer<SocketChannel>() {} 中设置channel
//准备跟踪
setChannelOptions(channel, options, logger);
}
// 获取ServerBootstrap中的attrs属性
final Map<AttributeKey<?>, Object> attrs = attrs0();
synchronized (attrs) {
// 逐个将attr属性写入到channel
for (Entry<AttributeKey<?>, Object> e: attrs.entrySet()) {
@SuppressWarnings("unchecked")
AttributeKey<Object> key = (AttributeKey<Object>) e.getKey();
channel.attr(key).set(e.getValue());
}
}
// 获取当前channel的pipeline
ChannelPipeline p = channel.pipeline();
// 将ServerBootstrap中所有以child开头的属性赋值给局部变量
final EventLoopGroup currentChildGroup = childGroup;
final ChannelHandler currentChildHandler = childHandler;
final Entry<ChannelOption<?>, Object>[] currentChildOptions;
final Entry<AttributeKey<?>, Object>[] currentChildAttrs;
synchronized (childOptions) {
currentChildOptions = childOptions.entrySet().toArray(newOptionArray(0));
}
synchronized (childAttrs) {
currentChildAttrs = childAttrs.entrySet().toArray(newAttrArray(0));
}
// 添加一个ChannelInitializer处理器到pipeline
p.addLast(new ChannelInitializer<Channel>() {
@Override
public void initChannel(final Channel ch) throws Exception {
final ChannelPipeline pipeline = ch.pipeline();
// 获取serverBootstrap的handler()属性值，并添加到pipeline
ChannelHandler handler = config.handler();
if (handler != null) {
pipeline.addLast(handler);
}
ch.eventLoop().execute(new Runnable() {
@Override
public void run() {
// ServerBootstrapAcceptor称为连接处理器
pipeline.addLast(new ServerBootstrapAcceptor(
ch, currentChildGroup, currentChildHandler, currentChildOptions, currentChildAttrs));
}
});
}
});
}
设置options的属性
static void setChannelOptions(Channel channel, Map<ChannelOption<?>, Object> options, InternalLogger logger) {
// 遍历options
for (Map.Entry<ChannelOption<?>, Object> e: options.entrySet()) {
// 将当前遍历的option初始化到channel
setChannelOption(channel, e.getKey(), e.getValue(), logger);
}
}
@SuppressWarnings("unchecked")
private static void setChannelOption(Channel channel, ChannelOption<?> option, Object value, InternalLogger logger) {
try {
// 将option写入到channel的config中
if (!channel.config().setOption((ChannelOption<Object>) option, value)) {
logger.warn("Unknown channel option '{}' for channel '{}'", option, channel);
}
} catch (Throwable t) {
logger.warn(
"Failed to set channel option '{}' with value '{}' for channel '{}'", option, value, channel, t);
}
}
static void setChannelOptions(Channel channel, Map.Entry<ChannelOption<?>, Object>[] options, InternalLogger logger) {
// 多个时，使用循环的方式增加
for (Map.Entry<ChannelOption<?>, Object> e: options) {
setChannelOption(channel, e.getKey(), e.getValue(), logger);
}
}
属性设置这一块算是跟踪完毕了，继续回到initAndRegister() 方法中跟踪
ChannelFuture regFuture = config().group().register(channel); 跟踪register 的注册细节。
MultithreadEventLoopGroup.java
@Override
public ChannelFuture register(Channel channel) {
// next()是从group中通过轮询方式选择出一个eventLoop
return next().register(channel);
}
SingleThreadEventLoop.java
@Override
public ChannelFuture register(final ChannelPromise promise) {
ObjectUtil.checkNotNull(promise, "promise");
promise.channel().unsafe().register(this, promise);
return promise;
}
AbstractChannel.java
@Override
public final void register(EventLoop eventLoop, final ChannelPromise promise) {
// 若eventLoop为null，则抛出异常。因为这里要将当前channel与eventLoop进行绑定
if (eventLoop == null) {
throw new NullPointerException("eventLoop");
}
// 若当前channel已经注册过了，则直接结束
if (isRegistered()) {
promise.setFailure(new IllegalStateException("registered to an event loop already"));
return;
}
// 若当前eventLoop与当前channel不兼容，则直接结束
if (!isCompatible(eventLoop)) {
promise.setFailure(
new IllegalStateException("incompatible event loop type: " + eventLoop.getClass().getName()));
return;
}
// 当前channel与eventLoop的绑定就发生在这里
AbstractChannel.this.eventLoop = eventLoop;
if (eventLoop.inEventLoop()) { // 判断当前正在执行的线程与eventLoop所绑定的线程是否是同一个
register0(promise);
} else {
try {
// eventLoop本质上是一个executor，这里调用的是它的execute()
eventLoop.execute(new Runnable() {
@Override
public void run() {
// 注册
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);
}
}
}
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;
// 注册
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);
}
}
AbstractNioChannel.java
@Override
protected void doRegister() throws Exception {
boolean selected = false;
for (;;) {
try {
// 完成NIO原生channel向NIO原生Selector的注册
// 第二个参数为0，表示当前channel没有关注的事件，为什么指定为0？
// 两个原因：
// 1)这是一个一般性方法，所有channel的注册均会调用该方法。所有channel包含三类：
// 1.1 服务端的parentChannel，其关注的事件应该为OP_ACCEPT，接收连接就绪事件
// 1.2 服务端的childChannel，其关注的事件应该为OP_READ或OP_WRITE，即读/写就绪事件
// 1.3 客户端的channel，其关注的事件应该为OP_CONNECT，即连接就绪事件
// 2)真正指定其所关注的事件，是在Netty封装的channel创建时指定的
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;
}
}
} // end-for
}
回到AbstractChannel.java中，跟踪线程创建 **eventLoop.execute(new Runnable() **
SingleThreadEventExecutor.java
@Override
public void execute(Runnable task) {
if (task == null) {
throw new NullPointerException("task");
}
// 若当前线程与当前eventLoop所绑定线程是同一个线程，则返回true，否则返回false
boolean inEventLoop = inEventLoop();
// 将task任务添加到任务队列
addTask(task);
if (!inEventLoop) {
// 创建并启动一个线程
startThread();
if (isShutdown()) {
boolean reject = false;
try {
if (removeTask(task)) {
reject = true;
}
} catch (UnsupportedOperationException e) {
// The task queue does not support removal so the best thing we can do is to just move on and
// hope we will be able to pick-up the task before its completely terminated.
// In worst case we will log on termination.
}
if (reject) {
reject();
}
}
}
if (!addTaskWakesUp && wakesUpForTask(task)) {
wakeup(inEventLoop);
}
}
private void startThread() {
if (state == ST_NOT_STARTED) {
if (STATE_UPDATER.compareAndSet(this, ST_NOT_STARTED, ST_STARTED)) {
try {
doStartThread();
} catch (Throwable cause) {
STATE_UPDATER.set(this, ST_NOT_STARTED);
PlatformDependent.throwException(cause);
}
}
}
}
private void doStartThread() {
assert thread == null;
// 调用子executor(即eventLoop所包含的executor)的execute()
// 该execute()完成了两项工作：
// 1）创建了一个线程
// 2）启动了这个线程
executor.execute(new Runnable() {
@Override
public void run() {
thread = Thread.currentThread();
if (interrupted) {
thread.interrupt();
}
boolean success = false;
updateLastExecutionTime();
try {
// 其会调用一个无限循环的for
SingleThreadEventExecutor.this.run();
success = true;
} catch (Throwable t) {
logger.warn("Unexpected exception from an event executor: ", t);
} finally {
for (;;) {
int oldState = state;
if (oldState >= ST_SHUTTING_DOWN || STATE_UPDATER.compareAndSet(
SingleThreadEventExecutor.this, oldState, ST_SHUTTING_DOWN)) {
break;
}
}
// Check if confirmShutdown() was called at the end of the loop.
if (success && gracefulShutdownStartTime == 0) {
if (logger.isErrorEnabled()) {
logger.error("Buggy " + EventExecutor.class.getSimpleName() + " implementation; " +
SingleThreadEventExecutor.class.getSimpleName() + ".confirmShutdown() must " +
"be called before run() implementation terminates.");
}
}
try {
// Run all remaining tasks and shutdown hooks.
for (;;) {
if (confirmShutdown()) {
break;
}
}
} finally {
try {
cleanup();
} finally {
// Lets remove all FastThreadLocals for the Thread as we are about to terminate and notify
// the future. The user may block on the future and once it unblocks the JVM may terminate
// and start unloading classes.
// See https://github.com/netty/netty/issues/6596.
FastThreadLocal.removeAll();
STATE_UPDATER.set(SingleThreadEventExecutor.this, ST_TERMINATED);
threadLock.release();
if (!taskQueue.isEmpty()) {
if (logger.isWarnEnabled()) {
logger.warn("An event executor terminated with " +
"non-empty task queue (" + taskQueue.size() + ')');
}
}
terminationFuture.setSuccess(null);
}
}
}
}
});
}
跟踪doStartThread() 方法中的 线程创建方法 execute
ThreadExecutorMap.java
public static Executor apply(final Executor executor, final EventExecutor eventExecutor) {
ObjectUtil.checkNotNull(executor, "executor");
ObjectUtil.checkNotNull(eventExecutor, "eventExecutor");
// 通过匿名内部类创建的一个executor
return new Executor() {
@Override
public void execute(final Runnable command) {
// 调用总executor的execute()
executor.execute(apply(command, eventExecutor));
}
};
}
继续跟execute()中的execute方法
ThreadPerTaskExecutor.java
@Override
public void execute(Runnable command) {
// newThread() 创建一个新的线程
// start() 启动该新线程，即调用该command的run()方法
threadFactory.newThread(command).start();
}
创建这个任务线程并返回这个线程。到这里该线程就创建完毕了
DefaultThreadFactory.java
@Override
public Thread newThread(Runnable r) {
// 创建了一个线程
Thread t = newThread(FastThreadLocalRunnable.wrap(r), prefix + nextId.incrementAndGet());
// 初始化线程
try {
if (t.isDaemon() != daemon) {
t.setDaemon(daemon);
}
if (t.getPriority() != priority) {
t.setPriority(priority);
}
} catch (Exception ignored) {
// Doesn't matter even if failed to set.
}
return t;
}
protected Thread newThread(Runnable r, String name) {
return new FastThreadLocalThread(threadGroup, r, name);
}
