ThreadPoolExecutor：拉出挂起的任务

Question

我已经实现了ThreadPoolExecutor来调用任务。而且，由于核心/队列大小的错误配置，任务似乎挂起在I/O上。我想拉出挂起的线程，以便队列中的其他线程开始执行。

有没有办法列出threadpoolexecutor中的线程并拉出挂起的线程？

Answer 1

您可以控制所使用的执行器，您可以使用ThreadPoolExecutor的beforeExecute和afterExecute方法来跟踪正在运行的任务，并使用它来创建getActiveTasks方法。

import java.util.Set;
import java.util.concurrent.*;


public class ActiveTasksThreadPool extends ThreadPoolExecutor {

private final ConcurrentHashMap<Runnable, Boolean> activeTasks = new ConcurrentHashMap<>();

public ActiveTasksThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {
    super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
}

@Override
protected void beforeExecute(Thread t, Runnable r) {

    activeTasks.put(r, Boolean.TRUE);
    super.beforeExecute(t, r);
}

@Override
protected void afterExecute(Runnable r, Throwable t) {

    super.afterExecute(r, t);
    activeTasks.remove(r);
}

public Set<Runnable> getActiveTasks() {
    // the returned set will not throw a ConcurrentModificationException.
    return activeTasks.keySet();
}

要使用Future设置线程任务超时，请执行以下操作：

 ActiveTasksThreadPool executor = new ActiveTasksThreadPool(maxTasks, maxTasks, 10, TimeUnit.SECONDS, new SynchronousQueue<Runnable>());Executors.newFixedThreadPool(2);

      List<Future<Integer>> resultList = new ArrayList<>();

      Random random = new Random();

      for (int i=0; i<4; i++)
      {
          Integer number = random.nextInt(10);
          FactorialCalculator calculator  = new FactorialCalculator(number);
          Future<Integer> result = executor.submit(calculator);
          result .get(100, TimeUnit.MILLISECONDS); // here is a timeout of 100 milisecond
      }