20220330_netty事件循环NioEventLoopGroup多线程源码学习笔记.md
1概述
本文基于netty版本,V4.1.68.Final-SNAPSHOT。
事件循环EventLoop完全是一个Thread,本质是一个线程,继承了事件循环组接口EventLoopGroup和事件执行器接口OrderEventExecutor,但没有实现。
nioEventLoopGroup线程池创建的最大区别就是,netty自定义了ThreadPerTaskExecutor执行器进行线程的创建。而没有使用Jdk中的Executor(ThreadPoolExecutor),至于任务调度方式是一样的。
为了合理利用资源,根据配置和可用的内核，netty可用使用多个EventLoop即多个线程。
1.1相关类图
1.1.1EventLoop接口关系图
public interface EventLoop extends OrderedEventExecutor, EventLoopGroup {
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1.1.2SingleThreadEventLoop抽象类关系图
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1.1.2.1DefaultEventLoop类关系图
public DefaultEventLoop(EventLoopGroup parent, ThreadFactory threadFactory) {
// addTaskWakesUp:true,由JDK队列进行阻塞唤醒
super(parent, threadFactory, true);
}
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1.1.2.2NioEventLoop类(单线程)
NioEventLoop(NioEventLoopGroup parent, Executor executor, SelectorProvider selectorProvider,
SelectStrategy strategy, RejectedExecutionHandler rejectedExecutionHandler,
EventLoopTaskQueueFactory taskQueueFactory, EventLoopTaskQueueFactory tailTaskQueueFactory) {
// addTaskWakesUp:false,需要人为增加一个NOP队列任务唤醒IO任务
super(parent, executor, false, newTaskQueue(taskQueueFactory), newTaskQueue(tailTaskQueueFactory),
rejectedExecutionHandler);
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SingleThreadEventExecutor抽象类:延时任务,获取待执行和过期任务,并执行,内置Queue<Runnable> taskQueue。
-
SingleThreadEventLoop抽象类:实现EventLoopGroup接口中的next,注册等方法,内置额外的时间循环任务队列,tailTasks queue<Runnable>,作为参数给SingleThreadEventExecutor.runAllTasksFrom调用,问题来了,taskQueue不够吗?
protected final boolean runAllTasksFrom(Queue<Runnable> taskQueue) {。
- DefaultEventLoop:无限循环,实现从队列中取任务,执行任务等一些列的。
// E:\workdirectory\Dev\study\netty-4.1\transport\src\main\java\io\netty\channel\DefaultEventLoop.java
// 实现了SingleThreadEventExecutor抽象类的run方法。
@Override
protected void run() {
for (;;) {
// 1.调用SingleThreadEventExecutor.takeTask获取任务。
Runnable task = takeTask();
if (task != null) {
task.run();
// 3.调用SingleThreadEventExecutor.updateLastExecutionTime
updateLastExecutionTime();
}
// 3.调用SingleThreadEventExecutor.confirmShutdown
if (confirmShutdown()) {
break;
}
}
}
1.1.3MultithreadEventLoopGroup抽象类
public abstract class MultithreadEventLoopGroup extends MultithreadEventExecutorGroup implements EventLoopGroup {
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1.1.3.1NioEventLoopGroup类(多线程)
public class NioEventLoopGroup extends MultithreadEventLoopGroup {
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1.2多线程启动源码分析
1.2.1构建NioEventLoopGroup
// E:\workdirectory\Dev\study\netty-4.1\transport\src\main\java\io\netty\channel\nio\NioEventLoopGroup.java
public NioEventLoopGroup(int nThreads, Executor executor, final SelectorProvider selectorProvider,
final SelectStrategyFactory selectStrategyFactory) {
super(nThreads, executor, selectorProvider, selectStrategyFactory, RejectedExecutionHandlers.reject());
}
// E:\workdirectory\Dev\study\netty-4.1\transport\src\main\java\io\netty\channel\MultithreadEventLoopGroup.java
protected MultithreadEventLoopGroup(int nThreads, Executor executor, Object... args) {
super(nThreads == 0 ? DEFAULT_EVENT_LOOP_THREADS : nThreads, executor, args);
}
// E:\workdirectory\Dev\study\netty-4.1\common\src\main\java\io\netty\util\concurrent\MultithreadEventExecutorGroup.java
protected MultithreadEventExecutorGroup(int nThreads, Executor executor, Object... args) {
this(nThreads, executor, DefaultEventExecutorChooserFactory.INSTANCE, args);
}
1.2.2线程池的创建(非JDK方式)
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public abstract class MultithreadEventExecutorGroup extends AbstractEventExecutorGroup {
// 本质:NioEventLoop
private final EventExecutor[] children;
/**
* Create a new instance.
*
* @param nThreads the number of threads that will be used by this instance.
* @param executor the Executor to use, or {@code null} if the default should be used.
* @param chooserFactory the {@link EventExecutorChooserFactory} to use.
* @param args arguments which will passed to each {@link #newChild(Executor, Object...)} call
*/
protected MultithreadEventExecutorGroup(int nThreads, Executor executor,
EventExecutorChooserFactory chooserFactory, Object... args) {
checkPositive(nThreads, "nThreads");
// 1.构建 executor,ThreadPerTaskExecutor等同于 JDK ThreadPoolExecutor
if (executor == null) {
executor = new ThreadPerTaskExecutor(newDefaultThreadFactory());
}
// 2.创建指定线程数量的NioEventLoop
children = new EventExecutor[nThreads];
for (int i = 0; i < nThreads; i ++) {
boolean success = false;
try {
// 2.1.创建NioEventLoop,默执行器:ThreadPerTaskExecutor
children[i] = newChild(executor, args);
success = true;
} catch (Exception e) {
// TODO: Think about if this is a good exception type
throw new IllegalStateException("failed to create a child event loop", e);
} finally {
if (!success) {
for (int j = 0; j < i; j ++) {
children[j].shutdownGracefully();
}
for (int j = 0; j < i; j ++) {
EventExecutor e = children[j];
try {
while (!e.isTerminated()) {
e.awaitTermination(Integer.MAX_VALUE, TimeUnit.SECONDS);
}
} catch (InterruptedException interrupted) {
// Let the caller handle the interruption.
Thread.currentThread().interrupt();
break;
}
}
}
}
}
chooser = chooserFactory.newChooser(children);
final FutureListener<Object> terminationListener = new FutureListener<Object>() {
@Override
public void operationComplete(Future<Object> future) throws Exception {
if (terminatedChildren.incrementAndGet() == children.length) {
terminationFuture.setSuccess(null);
}
}
};
for (EventExecutor e: children) {
e.terminationFuture().addListener(terminationListener);
}
Set<EventExecutor> childrenSet = new LinkedHashSet<EventExecutor>(children.length);
Collections.addAll(childrenSet, children);
readonlyChildren = Collections.unmodifiableSet(childrenSet);
}
1.2.2.1创建线程(NioEventLoopGroup中实现方法)
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// E:\workdirectory\Dev\study\netty-4.1\common\src\main\java\io\netty\util\concurrent\MultithreadEventExecutorGroup.java
protected abstract EventExecutor newChild(Executor executor, Object... args) throws Exception;
// E:\workdirectory\Dev\study\netty-4.1\transport\src\main\java\io\netty\channel\nio\NioEventLoopGroup.java
@Override
protected EventLoop newChild(Executor executor, Object... args) throws Exception {
SelectorProvider selectorProvider = (SelectorProvider) args[0];
SelectStrategyFactory selectStrategyFactory = (SelectStrategyFactory) args[1];
RejectedExecutionHandler rejectedExecutionHandler = (RejectedExecutionHandler) args[2];
EventLoopTaskQueueFactory taskQueueFactory = null;
EventLoopTaskQueueFactory tailTaskQueueFactory = null;
int argsLength = args.length;
if (argsLength > 3) {
taskQueueFactory = (EventLoopTaskQueueFactory) args[3];
}
if (argsLength > 4) {
tailTaskQueueFactory = (EventLoopTaskQueueFactory) args[4];
}
// 看到没有,返回的类:NioEventLoop
// public abstract class AbstractEventExecutor extends AbstractExecutorService implements EventExecutor {
// -->SingleThreadEventLoop-->SingleThreadEventExecutor
// -->AbstractScheduledEventExecutor-->AbstractEventExecutor
return new NioEventLoop(this, executor, selectorProvider,
selectStrategyFactory.newSelectStrategy(),
rejectedExecutionHandler, taskQueueFactory, tailTaskQueueFactory);
}
1.2.2.2ThreadFactory
// C:\Program Files\Java\jdk1.8.0_60\src.zip!\java\util\concurrent\Executors.java
/**
* The default thread factory
*/
static class DefaultThreadFactory implements ThreadFactory {
// E:\workdirectory\Dev\study\netty-4.1\transport\src\main\java\io\netty\channel\MultithreadEventLoopGroup.java
@Override
protected ThreadFactory newDefaultThreadFactory() {
return new DefaultThreadFactory(getClass(), Thread.MAX_PRIORITY);
}
public class DefaultThreadFactory implements ThreadFactory {
1.2.2.3netty默认执行器ThreadPerTaskExecutor
public final class ThreadPerTaskExecutor implements Executor {
private final ThreadFactory threadFactory;
public ThreadPerTaskExecutor(ThreadFactory threadFactory) {
this.threadFactory = ObjectUtil.checkNotNull(threadFactory, "threadFactory");
}
@Override
public void execute(Runnable command) {
threadFactory.newThread(command).start();
}
}
1.2.2.4创建线程(任务首次提交NioEventLoop.execute的时候)
提交到某一个NioEventLoop中
1.2.2.4.1execute(无返回值)
NioEventLoopGroup group = new NioEventLoopGroup(1);
final NioEventLoop loop = (NioEventLoop) group.next()
loop.execute(task);
// E:\workdirectory\Dev\study\netty-4.1\common\src\main\java\io\netty\util\concurrent\SingleThreadEventExecutor.java
@Override
public void execute(Runnable task) {
ObjectUtil.checkNotNull(task, "task");
execute(task, !(task instanceof LazyRunnable) && wakesUpForTask(task));
}
private void execute(Runnable task, boolean immediate) {
boolean inEventLoop = inEventLoop();
addTask(task);
if (!inEventLoop) {
startThread();
private void doStartThread() {
assert thread == null;
// executor:
executor.execute(new Runnable() {
@Override
public void execute(Runnable command) {
// 这里是创建线程的地方
threadFactory.newThread(command).start();
}
1.2.2.4.2submit(支持异步获取)
NioEventLoopGroup group = new NioEventLoopGroup(1);
final NioEventLoop loop = (NioEventLoop) group.next()
loop.submit(task);
// E:\workdirectory\Dev\study\netty-4.1\common\src\main\java\io\netty\util\concurrent\AbstractEventExecutor.java
@Override
public Future<?> submit(Runnable task) {
return (Future<?>) super.submit(task);
}
// C:\Program Files\Java\jdk1.8.0_60\src.zip!\java\util\concurrent\AbstractExecutorService.java
public Future<?> submit(Runnable task) {
if (task == null) throw new NullPointerException();
// 包装成 Jdk.RunnableFuture,class is:Jdk.FutureTask
RunnableFuture<Void> ftask = newTaskFor(task, null);
execute(ftask);
return ftask;
}
protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
return new FutureTask<T>(runnable, value);
}
// E:\workdirectory\Dev\study\netty-4.1\common\src\main\java\io\netty\util\concurrent\SingleThreadEventExecutor.java
@Override
public void execute(Runnable task) { // task is:FutrueTask,可异步接收的
ObjectUtil.checkNotNull(task, "task");
execute(task, !(task instanceof LazyRunnable) && wakesUpForTask(task));
}
2代码示例
2.1testReregister
// E:\workdirectory\Dev\study\netty-4.1\transport\src\test\java\io\netty\channel\AbstractEventLoopTest.java
@Test
public void testReregister() {
EventLoopGroup group = newEventLoopGroup();
EventLoopGroup group2 = newEventLoopGroup();
final EventExecutorGroup eventExecutorGroup = new DefaultEventExecutorGroup(2);
ServerBootstrap bootstrap = new ServerBootstrap();
ChannelFuture future = bootstrap.channel(newChannel()).group(group)
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) {
}
}).handler(new ChannelInitializer<ServerSocketChannel>() {
@Override
public void initChannel(ServerSocketChannel ch) {
ch.pipeline().addLast(new TestChannelHandler());
ch.pipeline().addLast(eventExecutorGroup, new TestChannelHandler2());
}
})
.bind(0).awaitUninterruptibly();
EventExecutor executor = future.channel().pipeline().context(TestChannelHandler2.class).executor();
EventExecutor executor1 = future.channel().pipeline().context(TestChannelHandler.class).executor();
future.channel().deregister().awaitUninterruptibly();
Channel channel = group2.register(future.channel()).awaitUninterruptibly().channel();
EventExecutor executorNew = channel.pipeline().context(TestChannelHandler.class).executor();
assertNotSame(executor1, executorNew);
assertSame(executor, future.channel().pipeline().context(TestChannelHandler2.class).executor());
}
2.2testRegistrationAfterShutdown
@Test
@Timeout(value = 10000, unit = TimeUnit.MILLISECONDS)
@SuppressWarnings("deprecation")
public void testRegistrationAfterShutdown() throws Exception {
// 1.关闭线程池
loopA.shutdown();
// 2.禁用log
// Disable logging temporarily.
Logger root = (Logger) LoggerFactory.getLogger(org.slf4j.Logger.ROOT_LOGGER_NAME);
List<Appender<ILoggingEvent>> appenders = new ArrayList<Appender<ILoggingEvent>>();
for (Iterator<Appender<ILoggingEvent>> i = root.iteratorForAppenders(); i.hasNext();) {
Appender<ILoggingEvent> a = i.next();
appenders.add(a);
root.detachAppender(a);
}
try {
// throw new RejectedExecutionException("event executor terminated");
ChannelFuture f = loopA.register(new LocalChannel());
f.awaitUninterruptibly();
assertFalse(f.isSuccess());
assertThat(f.cause(), is(instanceOf(RejectedExecutionException.class)));
assertFalse(f.channel().isOpen());
} finally {
for (Appender<ILoggingEvent> a: appenders) {
root.addAppender(a);
}
}
}
