Question

我有生产者 - 消费者模式。 1个生产者（做一些工作）和7个消费者（8个核心机器上）。制作人打算一次下载7个文件（2000年以后）并等待7个线程处理它们，然后继续下一个7.设置大致如下：

            ExecutorService threadPool = Executors.newFixedThreadPool(8);

        int pollWait = 4; 
        int queSize = 7;
        Broker broker = new Broker(queSize,pollWait);

Broker实现了一个容量为7的LinkedBlockingQueue。

        Producer producer = new Producer(); 
        producer.setBroker(broker);
        Future<Integer> producerStatus = threadPool.submit(producer);

        int numConsumerThreads = 7;

        ArrayList<Future<Integer>> consumers = new ArrayList<Future<Integer>>();

        for(int c=0; c < numConsumerThreads;c++)
        {
            String threadName = "consumer-"+(c+1);
            Consumer consumer = new Consumer(threadName);
            consumer.setBroker(broker);

            Future<Integer> consumerStatus = threadPool.submit(consumer);
            consumers.add(consumerStatus);                            
        }   

        if(producerStatus.isDone())
        {
            Integer numFilesRead = producerStatus.get();
            System.out.println("[INFO] Total number of files downloaded by producer: " + numFilesRead);
        }

        int k=0,numIndexedByThread=0;
        while(!consumers.isEmpty())
        {
            final Iterator<Future<Integer>> i = consumers.iterator();
            while (i.hasNext())
            {                   
               Future<Integer> f = i.next();
               if (f.isDone())
               {
                  i.remove();
                  numIndexedByThread = f.get();
                  k += numIndexedByThread;
               } 
             }
        }
        System.out.println("[INFO] Total number of files indexed: " + k);
        threadPool.shutdown();

我看到的问题是程序没有执行。

Answer 1

您已将序列化处理结果

以下行阻止并序列化结果的整个处理：

Integer numConsumedByThread = consumerStatus.get();

正确的习惯用法是检查每一个isDone()并仅在.get()返回true时调用isDone()，否则.get()会阻止循环，直到返回结果为止

Pseudocodeish

while(!listOfFutures.isEmpty())
{
    final Iterator<Future> i = listofFutures.iterator;
    while (i.hasNext())
    {
       Future f = i.next();
       if (f.isDone())
       {
          i.remove();
          // call .get() and process the completed result 
       } 
     }
}

阅读Future.get()

的JavaDocs

ExecutorService中的线程未完成

1 个答案:

您已将序列化处理结果

Pseudocodeish