那些遇到过的问题

Java - 在ExecutorCompletionService中定义Callable的超时

use*_*186 7 java multithreading timeout callable executorservice

我使用ExecutorCompletionService遇到了以下问题.我想在不同的线程中调用很多Callable.这些Callable不会彼此共享任何信息.我需要为每个Callable定义一个超时,例如.运行时间不要超过5秒.每个Callable都可以在启动时不知道的不同时间运行.在超时之后,线程应该被停止/杀死,结果对我来说不再有趣.不应该影响其他"正常"运行的线程.

因此,让我们以简单的可调用和我当前的Java代码为例.

import java.util.Date;
import java.util.concurrent.Callable;

public class Job implements Callable<Integer> {

    int returnValue = 0;
    long millis = 0;

    public Job(long millis, int value) {
        this.millis = millis;
        this.returnValue = value;
    }

    @Override
    public Integer call() throws Exception, InterruptedException {
        try {
            System.out.println(new Date() + " " + returnValue + " started");
            Thread.sleep(millis);
            System.out.println(new Date() + " " + returnValue + " finished");
            return returnValue;
        } catch (InterruptedException e) {
            System.out.println(new Date() + " " + returnValue + " interrupted");
            throw e;
        }        
    }
}
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以及使用Callable的其他类.

import java.util.ArrayList;
import java.util.Date;
import java.util.concurrent.*;

public class CallableTest {

    public static void main(String[] args) {
        ExecutorService newFixedThreadPool = Executors.newFixedThreadPool(2);
        CompletionService<Integer> pool = new ExecutorCompletionService<Integer>(newFixedThreadPool);

        for (int i = 10; i > 0; i--) {
            Job job = new Job(i * 1000, i);
            pool.submit(job);
        }

        ArrayList<Integer> results = new ArrayList<Integer>();
        for (int i = 1; i < 11; ++i) {
            try {
                Future<Integer> future = pool.take();
                Integer content = future.get(5, TimeUnit.SECONDS);
                results.add(content);
                System.out.println(new Date() + " added " + content);
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (TimeoutException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        newFixedThreadPool.shutdownNow();

        System.out.println(new Date() + " results:");
        for (int j : results) {
            System.out.println(new Date() + " " + j);
        }
    }
}
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输出是这样的:

Sun Jun 29 08:01:00 CEST 2014 10 started
Sun Jun 29 08:01:00 CEST 2014 9 started
Sun Jun 29 08:01:09 CEST 2014 9 finished
Sun Jun 29 08:01:09 CEST 2014 added 9
Sun Jun 29 08:01:09 CEST 2014 8 started
Sun Jun 29 08:01:10 CEST 2014 10 finished
Sun Jun 29 08:01:10 CEST 2014 7 started
Sun Jun 29 08:01:10 CEST 2014 added 10
Sun Jun 29 08:01:17 CEST 2014 7 finished
Sun Jun 29 08:01:17 CEST 2014 6 started
Sun Jun 29 08:01:17 CEST 2014 added 7
Sun Jun 29 08:01:17 CEST 2014 8 finished
Sun Jun 29 08:01:17 CEST 2014 added 8
Sun Jun 29 08:01:17 CEST 2014 5 started
Sun Jun 29 08:01:22 CEST 2014 5 finished
Sun Jun 29 08:01:22 CEST 2014 added 5
Sun Jun 29 08:01:22 CEST 2014 4 started
Sun Jun 29 08:01:23 CEST 2014 6 finished
Sun Jun 29 08:01:23 CEST 2014 3 started
Sun Jun 29 08:01:23 CEST 2014 added 6
Sun Jun 29 08:01:26 CEST 2014 3 finished
Sun Jun 29 08:01:26 CEST 2014 2 started
Sun Jun 29 08:01:26 CEST 2014 added 3
Sun Jun 29 08:01:26 CEST 2014 4 finished
Sun Jun 29 08:01:26 CEST 2014 1 started
Sun Jun 29 08:01:26 CEST 2014 added 4
Sun Jun 29 08:01:27 CEST 2014 1 finished
Sun Jun 29 08:01:27 CEST 2014 added 1
Sun Jun 29 08:01:28 CEST 2014 2 finished
Sun Jun 29 08:01:28 CEST 2014 added 2
Sun Jun 29 08:01:28 CEST 2014 results:
Sun Jun 29 08:01:28 CEST 2014 9
Sun Jun 29 08:01:28 CEST 2014 10
Sun Jun 29 08:01:28 CEST 2014 7
Sun Jun 29 08:01:28 CEST 2014 8
Sun Jun 29 08:01:28 CEST 2014 5
Sun Jun 29 08:01:28 CEST 2014 6
Sun Jun 29 08:01:28 CEST 2014 3
Sun Jun 29 08:01:28 CEST 2014 4
Sun Jun 29 08:01:28 CEST 2014 1
Sun Jun 29 08:01:28 CEST 2014 2
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这不像我想要的那样有效.我希望每个Callable运行时间超过5秒应该终止/结束/ interruped只有Callable运行低于5秒才能给我一个有效的结果.

我也尝试过没有ExecutorCompletionService

public class CallableTest2 {
    public static void main(String[] args) {
        ExecutorService newFixedThreadPool = Executors.newFixedThreadPool(2);
        List<Future<Integer>> futures = new ArrayList<Future<Integer>>();

        for (int i = 10; i > 0; i--) {
            Job job = new Job(i * 1000, i);
            futures.add(newFixedThreadPool.submit(job));
        }

        ArrayList<Integer> results = new ArrayList<Integer>();
        for (Future<Integer> future: futures) {
            try {
                Integer content = future.get(5, TimeUnit.SECONDS);
                results.add(content);
                System.out.println(new Date() + " added " + content);
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (TimeoutException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        newFixedThreadPool.shutdownNow();

        System.out.println(new Date() + " results:");
        for (int j : results) {
            System.out.println(new Date() + " " + j);
        }
    }
}
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结果如下:

Sun Jun 29 08:33:19 CEST 2014 9 started
Sun Jun 29 08:33:19 CEST 2014 10 started
java.util.concurrent.TimeoutException
    at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:228)
    at java.util.concurrent.FutureTask.get(FutureTask.java:91)
    at callabletest.CallableTest2.main(CallableTest2.java:29)
Sun Jun 29 08:33:28 CEST 2014 9 finished
Sun Jun 29 08:33:28 CEST 2014 8 started
Sun Jun 29 08:33:28 CEST 2014 added 9
Sun Jun 29 08:33:29 CEST 2014 10 finished
Sun Jun 29 08:33:29 CEST 2014 7 started
java.util.concurrent.TimeoutException
    at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:228)
    at java.util.concurrent.FutureTask.get(FutureTask.java:91)
    at callabletest.CallableTest2.main(CallableTest2.java:29)
Sun Jun 29 08:33:36 CEST 2014 7 finished
Sun Jun 29 08:33:36 CEST 2014 added 7
Sun Jun 29 08:33:36 CEST 2014 6 started
Sun Jun 29 08:33:36 CEST 2014 8 finished
Sun Jun 29 08:33:36 CEST 2014 5 started
java.util.concurrent.TimeoutException
    at java.util.concurrent.FutureTask$Sync.innerGet(Sun Jun 29 08:33:41 CEST 2014 5 finished
FutureTask.java:228)
Sun Jun 29 08:33:41 CEST 2014 added 5
    at java.util.concurrent.FutureTask.get(FutureTask.java:91)
Sun Jun 29 08:33:41 CEST 2014 4 started
    at callabletest.CallableTest2.main(CallableTest2.java:29)
Sun Jun 29 08:33:42 CEST 2014 6 finished
Sun Jun 29 08:33:42 CEST 2014 3 started
Sun Jun 29 08:33:45 CEST 2014 3 finished
Sun Jun 29 08:33:45 CEST 2014 2 started
Sun Jun 29 08:33:45 CEST 2014 4 finished
Sun Jun 29 08:33:45 CEST 2014 added 4
Sun Jun 29 08:33:45 CEST 2014 added 3
Sun Jun 29 08:33:45 CEST 2014 1 started
Sun Jun 29 08:33:46 CEST 2014 1 finished
Sun Jun 29 08:33:47 CEST 2014 2 finished
Sun Jun 29 08:33:47 CEST 2014 added 2
Sun Jun 29 08:33:47 CEST 2014 added 1
Sun Jun 29 08:33:47 CEST 2014 results:
Sun Jun 29 08:33:47 CEST 2014 9
Sun Jun 29 08:33:47 CEST 2014 7
Sun Jun 29 08:33:47 CEST 2014 5
Sun Jun 29 08:33:47 CEST 2014 4
Sun Jun 29 08:33:47 CEST 2014 3
Sun Jun 29 08:33:47 CEST 2014 2
Sun Jun 29 08:33:47 CEST 2014 1
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现在我得到一些TimeoutExceptions,但也不是我期望的那些.例如.Callable运行9和7秒不会抛出异常!

我需要在代码中更改什么,才能获得短期运行的线程的结果并杀死长时间运行的线程.在示例中仅结果1-5没有6-10.

我已经测试了很多东西,但我无法让它发挥作用.请帮忙

这是使用ScheduledExecutorService的bstar55帖子的答案.

我将有关您的提示的代码更改为:

public class CallableTest3 {

    public static void main(String[] args) {
        ScheduledExecutorService executor = Executors.newScheduledThreadPool(2);
        List<Future<Integer>> futures = new ArrayList<Future<Integer>>();

        for (int i = 10; i > 0; i--) {
            Job job = new Job(i * 1000, i);
            final Future handler = executor.submit(job);
            final int x = i;
            executor.schedule(new Runnable() {

                public void run() {
                    boolean cancel = handler.cancel(true);
                    if(cancel){
                        System.out.println(new Date() + " job " + x + " cancelled");
                    }else{
                        System.out.println(new Date() + " job " + x + " not cancelled");
                    }
                }
            }, 5000, TimeUnit.MILLISECONDS);
            futures.add(handler);
        }

        ArrayList<Integer> results = new ArrayList<Integer>();
        for (Future<Integer> future : futures) {
            try {
                Integer content = future.get(5, TimeUnit.SECONDS);
                results.add(content);
                System.out.println(new Date() + " added " + content);
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (TimeoutException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        executor.shutdown();

        System.out.println(new Date() + " results:");
        for (int j : results) {
            System.out.println(new Date() + " --- " + j);
        }
    }
}
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但这也不能按预期工作.结果:

Sun Jun 29 10:27:41 CEST 2014 9 started
Sun Jun 29 10:27:41 CEST 2014 10 started
java.util.concurrent.TimeoutException
    at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:228)
    at java.util.concurrent.FutureTask.get(FutureTask.java:91)
    at callabletest.CallableTest3.main(CallableTest3.java:43)
Sun Jun 29 10:27:50 CEST 2014 9 finished
Sun Jun 29 10:27:50 CEST 2014 added 9
Sun Jun 29 10:27:50 CEST 2014 8 started
Sun Jun 29 10:27:51 CEST 2014 10 finished
Sun Jun 29 10:27:51 CEST 2014 7 started
java.util.concurrent.TimeoutException
    at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:228)
    at java.util.concurrent.FutureTask.get(FutureTask.java:91)
    at callabletest.CallableTest3.main(CallableTest3.java:43)
Sun Jun 29 10:27:58 CEST 2014 8 finished
Sun Jun 29 10:27:58 CEST 2014 6 started
Sun Jun 29 10:27:58 CEST 2014 7 finished
Sun Jun 29 10:27:58 CEST 2014 5 started
Sun Jun 29 10:27:58 CEST 2014 added 7
Sun Jun 29 10:28:03 CEST 2014 5 finished
Sun Jun 29 10:28:03 CEST 2014 4 started
java.util.concurrent.TimeoutException
    at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:228)
    at java.util.concurrent.FutureTask.get(FutureTask.java:91)
Sun Jun 29 10:28:03 CEST 2014 added 5
    at callabletest.CallableTest3.main(CallableTest3.java:43)
Sun Jun 29 10:28:04 CEST 2014 6 finished
Sun Jun 29 10:28:04 CEST 2014 3 started
Sun Jun 29 10:28:07 CEST 2014 3 finished
Sun Jun 29 10:28:07 CEST 2014 2 started
Sun Jun 29 10:28:07 CEST 2014 4 finished
Sun Jun 29 10:28:07 CEST 2014 added 4
Sun Jun 29 10:28:07 CEST 2014 added 3
Sun Jun 29 10:28:07 CEST 2014 1 started
java.util.concurrent.CancellationException
    at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:230)
    at java.util.concurrent.FutureTask.get(FutureTask.java:91)
    at callabletest.CallableTest3.main(CallableTest3.java:43)
Sun Jun 29 10:28:08 CEST 2014 1 finished
Sun Jun 29 10:28:08 CEST 2014 job 10 not cancelled
Sun Jun 29 10:28:08 CEST 2014 job 9 not cancelled
Sun Jun 29 10:28:08 CEST 2014 job 8 not cancelled
Sun Jun 29 10:28:08 CEST 2014 job 7 not cancelled
Sun Jun 29 10:28:08 CEST 2014 job 6 not cancelled
Sun Jun 29 10:28:08 CEST 2014 job 5 not cancelled
Sun Jun 29 10:28:08 CEST 2014 job 4 not cancelled
Sun Jun 29 10:28:08 CEST 2014 job 3 not cancelled
Sun Jun 29 10:28:08 CEST 2014 2 interrupted
Sun Jun 29 10:28:08 CEST 2014 job 1 not cancelled
Sun Jun 29 10:28:08 CEST 2014 added 1
Sun Jun 29 10:28:08 CEST 2014 results:
Sun Jun 29 10:28:08 CEST 2014 --- 9
Sun Jun 29 10:28:08 CEST 2014 --- 7
Sun Jun 29 10:28:08 CEST 2014 --- 5
Sun Jun 29 10:28:08 CEST 2014 --- 4
Sun Jun 29 10:28:08 CEST 2014 --- 3
Sun Jun 29 10:28:08 CEST 2014 --- 1
Sun Jun 29 10:28:08 CEST 2014 job 2 cancelled
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但相反,工作2被取消了!

小智 7

我建议您将问题分为两个独立的问题：

  1. 在多个线程上运行
  2. 为每个操作使用超时

对于第一个（多线程），您已经使用了可以在 2 个线程上管理它的服务执行器：Executors.newFixedThreadPool(2)。如果您在此处应用超时，则超时适用于所有任务的运行，但每个作业都需要超时。

对于超时问题，您可以通过类中每个作业的新服务执行器来管理它：JobManager。

package com.stackoverflow.q24473796;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

public class JobManager implements Callable<Integer> {

protected long timeout;
protected TimeUnit timeUnit;
protected Callable<Integer> job;

public JobManager(long timeout, TimeUnit timeUnit, Callable<Integer> job) {
this.timeout = timeout;
this.timeUnit = timeUnit;
this.job = job;
}

@Override
public Integer call() {
    Integer result = new Integer(-1); // default, this could be adapted
    ExecutorService exec = Executors.newSingleThreadExecutor();

    try {
        result = exec.submit(job).get(timeout, timeUnit);
    } catch (InterruptedException | ExecutionException | TimeoutException e) {
        // Whatever you want
        if (e instanceof TimeoutException) {
            System.out.println("Timeout get for " + job.toString());
        } else {
            System.out.println("exception get for " + job.toString() + " : " + e.getMessage());
        }

    }
    exec.shutdown();
    return result;
    }
}
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然后，您可以从主线程调用任务，如下所示：

    Job job = new Job(i * 1000, i);
    Future<Integer> future = newFixedThreadPool.submit(new JobManager(5, TimeUnit.SECONDS, job));
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我调整了您的 CallableTest：包 com.stackoverflow.q24473796;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

public class CallableTest {

    public static void main(String[] args) {
        ExecutorService newFixedThreadPool = Executors.newFixedThreadPool(2);

        List<Future<Integer>> futures = new ArrayList<Future<Integer>>();
        for (int i = 10; i > 0; i--) {
            Job job = new Job(i * 1000, i);
            Future<Integer> future = newFixedThreadPool.submit(new   JobManager(5, TimeUnit.SECONDS, job));
            futures.add(future);
        }

        ArrayList<Integer> results = new ArrayList<Integer>();
        for (Future<Integer> future : futures) {
            Integer result = new Integer(-1);
            try {
                result = future.get();
            } catch (InterruptedException | ExecutionException e) {
                e.printStackTrace();
            }
            if (result != -1) {
                results.add(result);
            }
        }

        newFixedThreadPool.shutdown();

        try {
            newFixedThreadPool.awaitTermination(60, TimeUnit.SECONDS); //Global Timeout
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.println(new Date() + " results:");
        for (int j : results) {
            System.out.println(new Date() + " " + j);
        }
    }
}
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您将得到以下输出：

Wed Apr 29 10:51:02 CEST 2015 10 started
Wed Apr 29 10:51:02 CEST 2015 9 started
Timeout get for com.stackoverflow.q24473796.Job@249fe45c
Timeout get for com.stackoverflow.q24473796.Job@249fe45c
Wed Apr 29 10:51:07 CEST 2015 8 started
Wed Apr 29 10:51:07 CEST 2015 7 started
Wed Apr 29 10:51:11 CEST 2015 9 finished
Timeout get for com.stackoverflow.q24473796.Job@3cd4c5a0
Timeout get for com.stackoverflow.q24473796.Job@3cd4c5a0
Wed Apr 29 10:51:12 CEST 2015 6 started
Wed Apr 29 10:51:12 CEST 2015 5 started
Wed Apr 29 10:51:12 CEST 2015 10 finished
Wed Apr 29 10:51:14 CEST 2015 7 finished
Wed Apr 29 10:51:15 CEST 2015 8 finished
Wed Apr 29 10:51:17 CEST 2015 5 finished
Wed Apr 29 10:51:17 CEST 2015 4 started
Timeout get for com.stackoverflow.q24473796.Job@2a0fded2
Wed Apr 29 10:51:17 CEST 2015 3 started
Wed Apr 29 10:51:18 CEST 2015 6 finished
Wed Apr 29 10:51:20 CEST 2015 3 finished
Wed Apr 29 10:51:20 CEST 2015 2 started
Wed Apr 29 10:51:21 CEST 2015 4 finished
Wed Apr 29 10:51:21 CEST 2015 1 started
Wed Apr 29 10:51:22 CEST 2015 1 finished
Wed Apr 29 10:51:22 CEST 2015 2 finished
Wed Apr 29 10:51:22 CEST 2015 results:
Wed Apr 29 10:51:22 CEST 2015 5
Wed Apr 29 10:51:22 CEST 2015 4
Wed Apr 29 10:51:22 CEST 2015 3
Wed Apr 29 10:51:22 CEST 2015 2
Wed Apr 29 10:51:22 CEST 2015 1
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War*_*Dew 0

也许最好的方法是在 Callable 的 call() 方法中处理计时。当您输入方法时，记录时间。在 call() 方法中分割时间 - 在示例情况下，不是完全休眠，而是一次休眠一秒 - 并且每次都检查自进入时间以来是否已经过了最长时间。如果有，则中止处理并正常退出。

如果您绝对无法按时定期检查 Callable 的代码 - 或者像其他人建议的那样根据外部停止通知进行检查 - 有一种方法可以从线程外部执行的代码终止它。然而，这种方式已被弃用，因为它几乎肯定会导致无法修复的错误。本质上，当线程启动时 - 即当进入 call() 方法时 - 启动一个 TimerTask 子类并给它一个指向线程的指针。当 TimerTask 触发时，它会在线程上调用 Thread.stop()。同样，这是非常不安全的，因为它可能会使对象处于损坏状态，如 Oracle 文档中所述：

http://docs.oracle.com/javase/8/docs/technotes/guides/concurrency/threadPrimitiveDeprecation.html

唯一可行的方法是，如果您的 Callable 的代码永远不需要同步，并且永远不会在任何对象上实际同步，即使在库调用中也是如此，并且将来永远不会更改这样做。这是非常难以确保的，因此最好找到一种方法来分解 Callable 的代码，以便它可以定期检查时间并在超时时优雅地退出。

最后一点：如果您确实认为 Callable 的代码永远不需要同步来共享内存中的对象，那么它是在外部进程中执行的一个很好的候选者，而不是在主进程中的线程中。这样做的优点是您可以相对安全地终止外部进程。基本上，外部进程中的 TimerTask 会调用工作进程中的 System.exit()，而不是工作线程中的 Thread.stop()。

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