入口還是initAndRegister
final ChannelFuture initAndRegister() {
Channel channel = null;
try {
channel = channelFactory.newChannel();
init(channel);
} catch (Throwable t) {
if (channel != null) {
// channel can be null if newChannel crashed (eg SocketException("too many open files"))
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);
}
// 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);
}
//config().group()返回的是一個NioEventLoopGroup 就是我們在bind代碼是後寫的bossGroup
//debug一下發現是一個MultiThreadEventLoopGroup（他是NioEventLoopGroup的子類）
//真正執行register的卻是是SingleThreadEventLoop 看下下面的實現next方法
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;
}
//這裏說下loopGroup怎麼變成loop來實現
這個loop選擇器有點意思，如果loop的個數是2的指數和非2的指數是不通的選擇器實現 不過都是基於round-robin輪訓的
一個是運算符操作，一個是取模操作。代碼就不貼了 有興趣自己看看config().group().register(channel);
@Override
public ChannelFuture register(Channel channel) {
return next().register(channel);
}
@Override
public EventExecutor next() {
return chooser.next();
}
init之後就是register片段，這個是SingleThreadEventLoop中的方法
@Override
public ChannelFuture register(final ChannelPromise promise) {
ObjectUtil.checkNotNull(promise, "promise");
promise.channel().unsafe().register(this, promise);
return promise;
}
執行是 abstractChannel的內部類abstarctUnsafe類
下面代碼核心就是說 如果是當前線程直接執行 else提交給eventLoop執行。
register會被包轉成task塞到一個阻塞隊列中，負責處理他的線程會不停的去隊列中取內容執行。（netty線程安全的奧祕）
Channel 實例一旦 register 到了 NioEventLoopGroup 實例中的某個 NioEventLoop 實例，那麼後續該 Channel 的所有操作都是由該 NioEventLoop 實例來完成。
@Override
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;
if (eventLoop.inEventLoop()) {
register0(promise);
} else {
try {
eventLoop.execute(new Runnable() {
@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);
}
}
}
幹活的代碼 很重要的代碼 把channel註冊到register 添加handle
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;
//跟進的代碼 就是channel註冊到selector
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.
//ctx.handler().handlerAdded(ctx); 把ChannelInitializer中的handle全部添加到pipeline
//跟下代碼 會發現執行到ChannelInitializer的initChannel方法中，一般自定義的channelInitalizer中就是添加各種自己需要的handler
//這個代碼會走到 ChannelInitializer的initChannel方法中
pipeline.invokeHandlerAddedIfNeeded();
safeSetSuccess(promise);
//pipeline中的handle開始傳遞這個register事件
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);
}
}
//正真的操作 就是調用了java 的註冊nio
@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;
}
}
}
}
註冊事件傳播
static void invokeChannelRegistered(final AbstractChannelHandlerContext next) {
EventExecutor executor = next.executor();
if (executor.inEventLoop()) {
next.invokeChannelRegistered();
} else {
executor.execute(new Runnable() {
@Override
public void run() {
next.invokeChannelRegistered();
}
});
}
}
private void invokeChannelRegistered() {
if (invokeHandler()) {
try {
((ChannelInboundHandler) handler()).channelRegistered(this);
} catch (Throwable t) {
notifyHandlerException(t);
}
} else {
fireChannelRegistered();
}
}
//這個是headerHandler
public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
//這個已經做了 可以無視
invokeHandlerAddedIfNeeded();
ctx.fireChannelRegistered();
}
public ChannelHandlerContext fireChannelRegistered() {
invokeChannelRegistered(findContextInbound());
return this;
}
重點看下findContextInBound 鏈表裏面next inboundHandle
private AbstractChannelHandlerContext findContextInbound() {
AbstractChannelHandlerContext ctx = this;
do {
ctx = ctx.next;
} while (!ctx.inbound);
return ctx;
}
//這裏發現一個輪迴結束
static void invokeChannelRegistered(final AbstractChannelHandlerContext next) {
EventExecutor executor = next.executor();
if (executor.inEventLoop()) {
next.invokeChannelRegistered();
} else {
executor.execute(new Runnable() {
@Override
public void run() {
next.invokeChannelRegistered();
}
});
}
}