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首页 > 解决方案 > 具有提到 timeOut 的未来对象为下一个线程不断增加（timeOut 未申请 Java 中 ThreadPool 中的所有线程）

java - 具有提到 timeOut 的未来对象为下一个线程不断增加（timeOut 未申请 Java 中 ThreadPool 中的所有线程）

问题描述

工作线程在此处定义，运行方法中的繁重任务为 10 秒

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

public class WorkerThread implements Callable {

private String command;
private long startTime;
public WorkerThread(String s){
    this.command=s;
}

@Override
public Object call() throws Exception {
    startTime = System.currentTimeMillis();
    System.out.println(new Date()+"::::"+Thread.currentThread().getName()+" Start. Command = "+command);
    Random generator = new Random(); 
    Integer randomNumber = generator.nextInt(5); 
    processCommand();
    System.out.println(new Date()+ ":::"+Thread.currentThread().getName()+" End.::"+command+"::"+ (System.currentTimeMillis()-startTime));
    return randomNumber+"::"+this.command;
}

private void processCommand() {
    try {
        Thread.sleep(10000);
    } 
    catch (Exception e) {

        System.out.println("Interrupted::;Process Command:::"+this.command);
    }
}

@Override
public String toString(){
    return this.command;
}

}

将我的 WorkerPool 定义为 Future get Timeout 为 1 秒。

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
public class WorkerPool {

        static BlockingQueue queue=new LinkedBlockingQueue(2);
        static RejectedExecutionHandlerImpl rejectionHandler = new RejectedExecutionHandlerImpl();
        static ThreadFactory threadFactory = Executors.defaultThreadFactory();
        static ThreadPoolExecutor executorPool = new ThreadPoolExecutor(4, 4, 11, TimeUnit.SECONDS, queue, threadFactory, rejectionHandler);
        static MyMonitorThread monitor = new MyMonitorThread(executorPool, 3);
        public static void main(String args[]) throws InterruptedException, TimeoutException{
            List<Future<Integer>> list = new ArrayList<Future<Integer>>();
            for(int i=1; i< 5; i++){
                WorkerThread worker = new WorkerThread("WorkerThread:::_"+i);
                Future<Integer> future = executorPool.submit(worker);
                list.add(future);
            }

            for(Future<Integer> future : list){
                try {
                    try {
                        future.get(1000, TimeUnit.MILLISECONDS);
                    } catch (TimeoutException e) {
                        future.cancel(true);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            executorPool.shutdown();
        }

    }

线程的超时对于未来的线程不断增加，我的期望应该是，如果所有线程都花费超过 1 秒，那么应该在 ! 第二。

在 aboce 场景中，工作线程需要 10 秒来处理，但我在 1 秒内超时了我的所有 4 个线程，但每个线程时间每个任务增加 1 秒。

第一个 thred timeOut 是 1 第二个 second thred timeOut 是 2 Second 第三个 thred timeOut 是 3 秒。

为什么所有线程都不会在 1 秒内中断？我的代码有问题吗？

标签： javatimeoutjava-7futureexecutorservice

解决方案

Because you are waiting sequentially in a loop in this section:

for(Future<Integer> future : list) {
  ...
  future.get(1000, TimeUnit.MILLISECONDS);
  ...
}

Basically the flow is:

 - all workers 1 .. 4 start
 - you wait for worker A to finish
 - 1 second passes, TimeoutException (worker A was alive for 1 second)
 - you wait for worker B to finish
 - 1 second passes, TimeoutException (worker B was alive for 2 seconds)
 - you wait for worker C to finish
 - 1 second passes, TimeoutException (worker C was alive for 3 seconds)
 - ... same for D ...

If you want to wait for at most 1 second for all workers you need to count how much time you spent waiting so far, and then wait for remaining time. Something like the pseudocode:

long quota = 1000
for (Future future : futures) {
  long start = System.currentTimeMillis
  try {
    future.get(quota, MILLISECONDS)
  }
  catch (TimeoutException e) {
    future.cancel(true)
  }
  finally {
    long spent = System.currentTimeMillis() - start
    quota -= spent
    if (quota < 0) {quota = 0} // the whole block is going to execute longer than .get() only
  }
}

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