超时后中断任务的ExecutorService

Question

我正在寻找可以提供超时的 ExecutorService 实现。如果提交给 ExecutorService 的任务运行时间超过超时时间，它们将被中断。实现这样一个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。

这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();
        }
    }
}

原文由 Edward Dale 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

您可以为此使用 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，然后将取消（即中断）该特定任务。

原文由 John Vint 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

不幸的是，解决方案是有缺陷的。 ScheduledThreadPoolExecutor 有一种错误，也在 这个问题 中报告：取消提交的任务不会完全释放与任务相关的内存资源；只有在任务到期时才会释放资源。

因此，如果您创建一个 TimeoutThreadPoolExecutor 具有相当长的到期时间（典型用法），并且提交任务的速度足够快，您最终会填满内存 - 即使任务实际上已成功完成。

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();
    }
}

该程序会耗尽可用内存，尽管它会等待生成的 Runnable 完成。

我想了一会儿，但不幸的是我想不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 中得到修复。

原文由 Flavio 发布，翻译遵循 CC BY-SA 4.0 许可协议