C#生产者/消费者

Question

我最近遇到了生产者/消费者模式的 C# 实现。它非常简单(至少对我而言)非常优雅。

好像是2006年左右设计的，所以我想知道这个实现是不是
- 安全
- 仍然适用

代码如下(原代码引用http://bytes.com/topic/net/answers/575276-producer-consumer#post2251375)

using System;  
using System.Collections;  
using System.Threading;

public class Test
{  
    static ProducerConsumer queue;

    static void Main()
    {
        queue = new ProducerConsumer();
        new Thread(new ThreadStart(ConsumerJob)).Start();

        Random rng = new Random(0);
        for (int i=0; i < 10; i++)
        {
            Console.WriteLine ("Producing {0}", i);
            queue.Produce(i);
            Thread.Sleep(rng.Next(1000));
        }
    }

    static void ConsumerJob()
    {
        // Make sure we get a different random seed from the
        // first thread
        Random rng = new Random(1);
        // We happen to know we've only got 10 
        // items to receive
        for (int i=0; i < 10; i++)
        {
            object o = queue.Consume();
            Console.WriteLine ("\t\t\t\tConsuming {0}", o);
            Thread.Sleep(rng.Next(1000));
        }
    }
}

public class ProducerConsumer
{
    readonly object listLock = new object();
    Queue queue = new Queue();

    public void Produce(object o)
    {
        lock (listLock)
        {
            queue.Enqueue(o);

            // We always need to pulse, even if the queue wasn't
            // empty before. Otherwise, if we add several items
            // in quick succession, we may only pulse once, waking
            // a single thread up, even if there are multiple threads
            // waiting for items.            
            Monitor.Pulse(listLock);
        }
    }

    public object Consume()
    {
        lock (listLock)
        {
            // If the queue is empty, wait for an item to be added
            // Note that this is a while loop, as we may be pulsed
            // but not wake up before another thread has come in and
            // consumed the newly added object. In that case, we'll
            // have to wait for another pulse.
            while (queue.Count==0)
            {
                // This releases listLock, only reacquiring it
                // after being woken up by a call to Pulse
                Monitor.Wait(listLock);
            }
            return queue.Dequeue();
        }
    }
}

Answer 1

代码比那个更旧 - 我在 .NET 2.0 出现之前的某个时间写了它。生产者/消费者队列的概念比那个方式更古老:)

是的，据我所知，该代码是安全的 - 但它有一些缺陷:

• 它不是通用的。现代版本肯定是通用的。
• 它无法停止队列。停止队列(以便所有消费者线程退出)的一种简单方法是拥有一个可以放入队列的“停止工作” token 。然后，您可以添加与线程一样多的标记。或者，您有一个单独的标志来指示您要停止。 (这允许其他线程在完成队列中的所有当前工作之前停止。)
• 如果作业非常小，一次处理一个作业可能不是最有效的做法。

老实说，代码背后的思想比代码本身更重要。