[英]Shutdown hook is not killing executor
我有以下代码:
public class Driver {
private ExecutorService executor = Executors.newCachedThreadPool();
public static void main(String[] args) {
Driver d = new Driver();
d.run();
}
private void run() {
final Timer timer = new Timer();
final TimerTask task = new TimerTask() {
@Override
public void run() {
System.out.println("Task is running!");
}
};
Runnable worker = new Runnable() {
@Override
public void run() {
timer.scheduleAtFixedRate(task, new Date(), 5 * 1000);
}
};
Runtime.getRuntime().addShutdownHook(new Thread() {
@Override
public void run() {
System.out.println("Shutdown hook is being invoked!");
try {
if(executor.awaitTermination(20, TimeUnit.SECONDS))
System.out.println("All workers shutdown properly.");
else {
System.out.println(String.format("Maximum time limit of %s reached " +
"when trying to shut down workers. Forcing shutdown.", 20));
executor.shutdownNow();
}
} catch (InterruptedException interrupt) {
System.out.println("Shutdown hook interrupted by exception: " +
interrupt.getMessage());
}
System.out.println("Shutdown hook is finished!");
}
});
executor.submit(worker);
System.out.println("Initializing shutdown...");
}
}
当运行时,我得到以下控制台输出:
Initializing shutdown...
Task is running!
Task is running!
Task is running!
Task is running!
Task is running!
Task is running!
Task is running!
... (this keeps going non-stop)
当我运行此程序时,应用程序永不终止。 相反,每隔5秒,我会看到一个新的println“任务正在运行!”。 我本来希望主线程到达main
方法的末尾,打印“ Initializing shutdown ...”,调用添加的shutdown钩子,杀死执行程序,最后打印出“ Shutdown钩子完成!”。
相反,“任务正在运行”只会不断打印,程序永远不会终止。 这里发生了什么?
我不是专家,但是AFAIK您必须终止所有非守护进程线程,才能使关闭挂接 “插入”。 在原始示例中,您有3个非守护进程:
Timer(true)
覆盖 因此,我认为您应该做的是创建一个ThreadFactory并在初始化“执行程序”时使用它。
创建一个将是ThreadFactory的类 :
private class WorkerThreadFactory implements ThreadFactory {
@Override
public Thread newThread(Runnable r) {
Thread t = new Thread(r, "Worker");
t.setDaemon(true);
return t;
}
}
-当然重要的是setDaemon
:)
将其实例作为参数传递给newCachedThreadPool
方法:
private ExecutorService executor = Executors.newCachedThreadPool(new WorkerThreadFactory());
应用这2个更改对我来说很成功,所以我做到了:
Maximum time limit of 20 reached when trying to shut down workers. Forcing shutdown.
Shutdown hook is finished!
希望能帮助到你,
伊兹克
golan2@hotmail.com
它没有关闭,因为Timer()
创建并启动了一个非守护线程...然后永不停止。
有两种情况可以导致JVM自行关闭:
System.exit()
(或Runtime.halt()
) 由于您创建了第二个非守护进程线程(除了运行main()
的线程之外),因此将不满足第二个条件。
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