NioEventLoopGroup继承关系图
从上图可以看出，
NioEventLoopGroup实现了
Executor、
ExecutorService、
ScheduledExecutorService、
Iterable、
EventExecutorGroup、
EventLoopGroup接口，另外三个抽象类
AbstractEventExecutorGroup、
MultithreadEventExecutorGroup、
MultithreadEventLoopGroup提供了接口的部分实现。
-
AbstractEventExecutorGroup实现了Executor、ExecutorService、ScheduledExecutorService中的部分方法，都是委托给next()方法返回的EventExecutor -
MultithreadEventExecutorGroup主要是创建了EventExecutor[] children数组，并将多个方法委托给children -
MultithreadEventLoopGroup将EventExecutor类型的chlild转化成EventLoop（EventExecutor的子接口），并将register()方法委托给EventLoop -
NioEventLoopGroup实现newChild()方法，返回NioEventLoop（EventLoop的实现类），并将几个方法委托给NioEventLoop
Executor
Executor接口比较简单，只有一个execute()方法，该方法在未来某个时间点执行参数Runnable实例，可以在当前线程、新建线程或线程池里面执行，取决于具体实现。
public interface Executor {
void execute(Runnable command);
}
ExecutorService
ExecutorService继承了Executor，是建立在Executor基础上的一个服务，它是Executor基础上增加了任务管理服务。
除了执行任务的基础功能外，ExecutorService还提供submit类方法，用于提交任务，并返回futrue实例（可以用于取消执行任务，或者等待执行完成）用于和任务进行通信。
同时，还支持对Executor进行shutdown()操作，这一步可以用于资源的释放。
public interface ExecutorService extends Executor {
//拒绝新任务，但在terminate之前可以执行先前提交的任务
void shutdown();
//拒绝新任务，并删除之前提交的正在等待执行的任务，同时会尝试终止正在执行的任务
List shutdownNow();
boolean isShutdown();
/**如果shutdown后所有任务都已完成，则返回true。
请注意，除非先调用shutdown或shutdownNow，否则isTerminated永远不会为真。**/
boolean isTerminated();
//阻塞，直到shutdown后剩下的所有任务被完成，或者等待超时，或者被中断（interrupted）
boolean awaitTermination(long timeout, TimeUnit unit)
throws InterruptedException;
//提交任务，返回的Future实例可以用于取消执行任务，或者等待执行完成
Future submit(Callable task);
Future submit(Runnable task, T result);
Future submit(Runnable task);
List> invokeAll(Collection> tasks)
throws InterruptedException;
List> invokeAll(Collection> tasks,
long timeout, TimeUnit unit)
throws InterruptedException;
T invokeAny(Collection> tasks)
throws InterruptedException, ExecutionException;
T invokeAny(Collection> tasks,
long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException;
}
Executors类提供ExecutorService类的多个工厂方法。
ScheduledExecutorService
ScheduledExecutorService可以在给定延时后执行任务，或者定期执行任务。
scheduleAtFixedRate和scheduleWithFixedDelay方法创建并执行定期运行的任务，直到被取消。
scheduleAtFixedRate表示每隔多少时间，执行一次任务。
scheduleWithFixedDelay等到前一个任务结束的时刻，才开始结算间隔时间，如0秒开始执行第一次任务，任务耗时5秒，任务间隔时间3秒，那么第二次任务执行的时间是在第8秒开始。
通过 Executor.execute(Runnable)和ExecutorService的submit()方法提交的任务延迟时间为0。
public interface ScheduledExecutorService extends ExecutorService {
public ScheduledFuture schedule(Runnable command,
long delay, TimeUnit unit);
public ScheduledFuture schedule(Callable callable,
long delay, TimeUnit unit);
public ScheduledFuture scheduleAtFixedRate(Runnable command,
long initialDelay,
long period,
TimeUnit unit);
public ScheduledFuture scheduleWithFixedDelay(Runnable command,
long initialDelay,
long delay,
TimeUnit unit);
}
EventExecutorGroup
EventExecutorGroup负责通过next()方法提供EventExecutor。 除此之外，它还负责处理它们的生命周期并允许以全局的方式关闭它们。
public interface EventExecutorGroup extends ScheduledExecutorService, Iterable {
//当被此EventExecutorGroup管理的所有EventExecutor被shutdown或者被shutdownGracefully时，返回true
boolean isShuttingDown();
//向executor发出关闭信号，此方法一旦被调用，isShuttingDown()就返回true，然后executor准备关闭自己
Future shutdownGracefully();
Future shutdownGracefully(long quietPeriod, long timeout, TimeUnit unit);
//返回一个future，当所有被当前这个EventExecutorGroup管理的EventExecutor被终止时，会通知这个future
Future terminationFuture();
//返回一个EventExecutor
EventExecutor next();
//被shutdownGracefully方法替代
@Override
@Deprecated
void shutdown();
//被shutdownGracefully方法替代
@Override
@Deprecated
List shutdownNow();
@Override
Iterator iterator();
@Override
Future submit(Runnable task);
@Override
Future submit(Runnable task, T result);
@Override
Future submit(Callable task);
@Override
ScheduledFuture schedule(Runnable command, long delay, TimeUnit unit);
@Override
ScheduledFuture schedule(Callable callable, long delay, TimeUnit unit);
@Override
ScheduledFuture scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit);
@Override
ScheduledFuture scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit);
}
EventLoopGroup
EventLoopGroup是特殊的EventExecutorGroup，它可以注册channel，被注册的channel会在事件循环（event loop）中被select和处理。
public interface EventLoopGroup extends EventExecutorGroup {
//返回下一个EventLoop
@Override
EventLoop next();
//注册Channel，返回的ChannelFuture会在注册完成时得到通知
ChannelFuture register(Channel channel);
ChannelFuture register(ChannelPromise promise);
@Deprecated
ChannelFuture register(Channel channel, ChannelPromise promise);
}
AbstractEventExecutorGroup
AbstractEventExecutorGroup只是将部分方法的实现的委托给next()方法返回的EventExecutor，但是没具体实现next()方法。
public abstract class AbstractEventExecutorGroup implements EventExecutorGroup {
@Override
public Future submit(Runnable task) {
return next().submit(task);
}
@Override
public Future submit(Runnable task, T result) {
return next().submit(task, result);
}
@Override
public Future submit(Callable task) {
return next().submit(task);
}
@Override
public ScheduledFuture schedule(Runnable command, long delay, TimeUnit unit) {
return next().schedule(command, delay, unit);
}
@Override
public ScheduledFuture schedule(Callable callable, long delay, TimeUnit unit) {
return next().schedule(callable, delay, unit);
}
@Override
public ScheduledFuture scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
return next().scheduleAtFixedRate(command, initialDelay, period, unit);
}
@Override
public ScheduledFuture scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
return next().scheduleWithFixedDelay(command, initialDelay, delay, unit);
}
@Override
public Future shutdownGracefully() {
return shutdownGracefully(DEFAULT_SHUTDOWN_QUIET_PERIOD, DEFAULT_SHUTDOWN_TIMEOUT, TimeUnit.SECONDS);
}
/**
* @deprecated {@link #shutdownGracefully(long, long, TimeUnit)} or {@link #shutdownGracefully()} instead.
*/
@Override
@Deprecated
public abstract void shutdown();
/**
* @deprecated {@link #shutdownGracefully(long, long, TimeUnit)} or {@link #shutdownGracefully()} instead.
*/
@Override
@Deprecated
public List shutdownNow() {
shutdown();
return Collections.emptyList();
}
@Override
public List> invokeAll(Collection> tasks)
throws InterruptedException {
return next().invokeAll(tasks);
}
@Override
public List> invokeAll(
Collection> tasks, long timeout, TimeUnit unit) throws InterruptedException {
return next().invokeAll(tasks, timeout, unit);
}
@Override
public T invokeAny(Collection> tasks) throws InterruptedException, ExecutionException {
return next().invokeAny(tasks);
}
@Override
public T invokeAny(Collection> tasks, long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
return next().invokeAny(tasks, timeout, unit);
}
@Override
public void execute(Runnable command) {
next().execute(command);
}
}
MultithreadEventExecutorGroup
MultithreadEventExecutorGroup主要是创建了EventExecutor[] children
数组，并将多个方法委托给children。
public abstract class MultithreadEventExecutorGroup extends AbstractEventExecutorGroup {
private final EventExecutor[] children;
private final Set readonlyChildren;
private final AtomicInteger terminatedChildren = new AtomicInteger();
private final Promise terminationFuture = new DefaultPromise(GlobalEventExecutor.INSTANCE);
private final EventExecutorChooserFactory.EventExecutorChooser chooser;
protected MultithreadEventExecutorGroup(int nThreads, ThreadFactory threadFactory, Object... args) {
this(nThreads, threadFactory == null ? null : new ThreadPerTaskExecutor(threadFactory), args);
}
protected MultithreadEventExecutorGroup(int nThreads, Executor executor, Object... args) {
this(nThreads, executor, DefaultEventExecutorChooserFactory.INSTANCE, args);
}
protected MultithreadEventExecutorGroup(int nThreads, Executor executor,
EventExecutorChooserFactory chooserFactory, Object... args) {
if (nThreads <= 0) {
throw new IllegalArgumentException(String.format("nThreads: %d (expected: > 0)", nThreads));
}
if (executor == null) {
executor = new ThreadPerTaskExecutor(newDefaultThreadFactory());
}
children = new EventExecutor[nThreads];
for (int i = 0; i < nThreads; i ++) {
boolean success = false;
try {
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 MultithreadEventLoopGroup
MultithreadEventLoopGroup将EventExecutor类型的chlild转化成EventLoop（EventExecutor的子接口），并将register()方法委托给EventLoop。
public abstract class MultithreadEventLoopGroup extends MultithreadEventExecutorGroup implements EventLoopGroup {
private static final InternalLogger logger = InternalLoggerFactory.getInstance(MultithreadEventLoopGroup.class);
private static final int DEFAULT_EVENT_LOOP_THREADS;
static {
DEFAULT_EVENT_LOOP_THREADS = Math.max(1, SystemPropertyUtil.getInt(
"io.netty.eventLoopThreads", NettyRuntime.availableProcessors() * 2));
if (logger.isDebugEnabled()) {
logger.debug("-Dio.netty.eventLoopThreads: {}", DEFAULT_EVENT_LOOP_THREADS);
}
}
protected MultithreadEventLoopGroup(int nThreads, Executor executor, Object... args) {
super(nThreads == 0 ? DEFAULT_EVENT_LOOP_THREADS : nThreads, executor, args);
}
protected MultithreadEventLoopGroup(int nThreads, ThreadFactory threadFactory, Object... args) {
super(nThreads == 0 ? DEFAULT_EVENT_LOOP_THREADS : nThreads, threadFactory, args);
}
protected MultithreadEventLoopGroup(int nThreads, Executor executor, EventExecutorChooserFactory chooserFactory,
Object... args) {
super(nThreads == 0 ? DEFAULT_EVENT_LOOP_THREADS : nThreads, executor, chooserFactory, args);
}
@Override
protected ThreadFactory newDefaultThreadFactory() {
return new DefaultThreadFactory(getClass(), Thread.MAX_PRIORITY);
}
@Override
public EventLoop next() {
return (EventLoop) super.next();
}
@Override
protected abstract EventLoop newChild(Executor executor, Object... args) throws Exception;
@Override
public ChannelFuture register(Channel channel) {
return next().register(channel);
}
@Override
public ChannelFuture register(ChannelPromise promise) {
return next().register(promise);
}
@Deprecated
@Override
public ChannelFuture register(Channel channel, ChannelPromise promise) {
return next().register(channel, promise);
}
}
NioEventLoopGroup
NioEventLoopGroup实现newChild()方法，返回NioEventLoop（EventLoop的实现类），并将几个方法委托给NioEventLoop。
public class NioEventLoopGroup extends MultithreadEventLoopGroup {
public NioEventLoopGroup() {
this(0);
}
public NioEventLoopGroup(int nThreads) {
this(nThreads, (Executor) null);
}
public NioEventLoopGroup(int nThreads, ThreadFactory threadFactory) {
this(nThreads, threadFactory, SelectorProvider.provider());
}
public NioEventLoopGroup(int nThreads, Executor executor) {
this(nThreads, executor, SelectorProvider.provider());
}
public NioEventLoopGroup(
int nThreads, ThreadFactory threadFactory, final SelectorProvider selectorProvider) {
this(nThreads, threadFactory, selectorProvider, DefaultSelectStrategyFactory.INSTANCE);
}
public NioEventLoopGroup(int nThreads, ThreadFactory threadFactory,
final SelectorProvider selectorProvider, final SelectStrategyFactory selectStrategyFactory) {
super(nThreads, threadFactory, selectorProvider, selectStrategyFactory, RejectedExecutionHandlers.reject());
}
public NioEventLoopGroup(
int nThreads, Executor executor, final SelectorProvider selectorProvider) {
this(nThreads, executor, selectorProvider, DefaultSelectStrategyFactory.INSTANCE);
}
public NioEventLoopGroup(int nThreads, Executor executor, final SelectorProvider selectorProvider,
final SelectStrategyFactory selectStrategyFactory) {
super(nThreads, executor, selectorProvider, selectStrategyFactory, RejectedExecutionHandlers.reject());
}
public NioEventLoopGroup(int nThreads, Executor executor, EventExecutorChooserFactory chooserFactory,
final SelectorProvider selectorProvider,
final SelectStrategyFactory selectStrategyFactory) {
super(nThreads, executor, chooserFactory, selectorProvider, selectStrategyFactory,
RejectedExecutionHandlers.reject());
}
public NioEventLoopGroup(int nThreads, Executor executor, EventExecutorChooserFactory chooserFactory,
final SelectorProvider selectorProvider,
final SelectStrategyFactory selectStrategyFactory,
final RejectedExecutionHandler rejectedExecutionHandler) {
super(nThreads, executor, chooserFactory, selectorProvider, selectStrategyFactory, rejectedExecutionHandler);
}
public void setIoRatio(int ioRatio) {
for (EventExecutor e: this) {
((NioEventLoop) e).setIoRatio(ioRatio);
}
}
public void rebuildSelectors() {
for (EventExecutor e: this) {
((NioEventLoop) e).rebuildSelector();
}
}
@Override
protected EventLoop newChild(Executor executor, Object... args) throws Exception {
return new NioEventLoop(this, executor, (SelectorProvider) args[0],
((SelectStrategyFactory) args[1]).newSelectStrategy(), (RejectedExecutionHandler) args[2]);
}
}