超时后中断任务的执行程序服务更新

concurrency multithreading java executorservice

2022-08-31 09:35:33

我正在寻找一个可以提供超时的执行器服务实现。如果提交到 ExecutorService 的任务运行时间超过超时时间，则会中断这些任务。实现这样的野兽并不是一项艰巨的任务，但我想知道是否有人知道现有的实现。

以下是我根据下面的一些讨论得出的结论。任何意见？

import java.util.List;
import java.util.concurrent.*;

public class TimeoutThreadPoolExecutor extends ThreadPoolExecutor {
    private final long timeout;
    private final TimeUnit timeoutUnit;

    private final ScheduledExecutorService timeoutExecutor = Executors.newSingleThreadScheduledExecutor();
    private final ConcurrentMap<Runnable, ScheduledFuture> runningTasks = new ConcurrentHashMap<Runnable, ScheduledFuture>();

    public TimeoutThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, long timeout, TimeUnit timeoutUnit) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
        this.timeout = timeout;
        this.timeoutUnit = timeoutUnit;
    }

    public TimeoutThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, long timeout, TimeUnit timeoutUnit) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory);
        this.timeout = timeout;
        this.timeoutUnit = timeoutUnit;
    }

    public TimeoutThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, RejectedExecutionHandler handler, long timeout, TimeUnit timeoutUnit) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, handler);
        this.timeout = timeout;
        this.timeoutUnit = timeoutUnit;
    }

    public TimeoutThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler, long timeout, TimeUnit timeoutUnit) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
        this.timeout = timeout;
        this.timeoutUnit = timeoutUnit;
    }

    @Override
    public void shutdown() {
        timeoutExecutor.shutdown();
        super.shutdown();
    }

    @Override
    public List<Runnable> shutdownNow() {
        timeoutExecutor.shutdownNow();
        return super.shutdownNow();
    }

    @Override
    protected void beforeExecute(Thread t, Runnable r) {
        if(timeout > 0) {
            final ScheduledFuture<?> scheduled = timeoutExecutor.schedule(new TimeoutTask(t), timeout, timeoutUnit);
            runningTasks.put(r, scheduled);
        }
    }

    @Override
    protected void afterExecute(Runnable r, Throwable t) {
        ScheduledFuture timeoutTask = runningTasks.remove(r);
        if(timeoutTask != null) {
            timeoutTask.cancel(false);
        }
    }

    class TimeoutTask implements Runnable {
        private final Thread thread;

        public TimeoutTask(Thread thread) {
            this.thread = thread;
        }

        @Override
        public void run() {
            thread.interrupt();
        }
    }
}

答案 1

为此，您可以使用 ScheduledExecutorService。首先，您只需提交一次即可立即开始并保留创建的未来。之后，您可以提交一个新任务，该任务将在一段时间后取消保留的未来。

 ScheduledExecutorService executor = Executors.newScheduledThreadPool(2); 
 final Future handler = executor.submit(new Callable(){ ... });
 executor.schedule(new Runnable(){
     public void run(){
         handler.cancel();
     }      
 }, 10000, TimeUnit.MILLISECONDS);

这将执行您的处理程序（要中断的主要功能）10秒，然后取消（即中断）该特定任务。

答案 2

不幸的是，解决方案是有缺陷的。在此问题中也报告了一种 bug：取消提交的任务不会完全释放与该任务关联的内存资源;仅当任务过期时，才会释放资源。ScheduledThreadPoolExecutor

因此，如果您创建了具有相当长的过期时间（典型用法）的 a，并且提交任务的速度足够快，则最终会填满内存 - 即使任务实际上已成功完成。TimeoutThreadPoolExecutor

您可以通过以下（非常粗糙的）测试程序看到问题：

public static void main(String[] args) throws InterruptedException {
    ExecutorService service = new TimeoutThreadPoolExecutor(1, 1, 10, TimeUnit.SECONDS, 
            new LinkedBlockingQueue<Runnable>(), 10, TimeUnit.MINUTES);
    //ExecutorService service = Executors.newFixedThreadPool(1);
    try {
        final AtomicInteger counter = new AtomicInteger();
        for (long i = 0; i < 10000000; i++) {
            service.submit(new Runnable() {
                @Override
                public void run() {
                    counter.incrementAndGet();
                }
            });
            if (i % 10000 == 0) {
                System.out.println(i + "/" + counter.get());
                while (i > counter.get()) {
                    Thread.sleep(10);
                }
            }
        }
    } finally {
        service.shutdown();
    }
}

程序会耗尽可用内存，尽管它会等待生成的 s 完成。Runnable

虽然有一段时间我这样，但不幸的是，我无法想出一个好的解决方案。

更新

我发现这个问题被报告为JDK错误6602600，并且似乎已在Java 7中修复。