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社区首页 >问答首页 >按顺序执行锁(使用ConcurrentQueue和lock)

问按顺序执行锁(使用ConcurrentQueue和lock)
EN

Stack Overflow用户
提问于 2021-10-26 23:21:06
回答 1查看 56关注 0票数 1

我在API中有一个端点，它处理数据并使用锁。由于有许多用户在使用系统，有时请求不会按顺序处理，如果有许多请求在等待，可能会抛出超时。我们已经尝试了两种不同的方法，第一种是这个类：

代码语言：javascript
复制
public class QueuedFunctions<T>
    {
        private readonly object _internalSyncronizer = new object();
        private readonly ConcurrentQueue<Func<T>> _funcQueue = new ConcurrentQueue<Func<T>>();

        public T Execute(Func<T> func)
        {
            _funcQueue.Enqueue(func);
            Console.WriteLine("Queuing: " + Thread.CurrentThread.ManagedThreadId);
            Console.WriteLine(Monitor.IsEntered(_internalSyncronizer));
            lock (_internalSyncronizer)
            {
                Console.WriteLine("Locked: " + Thread.CurrentThread.ManagedThreadId);
                Func<T> nextFunc;
                if (_funcQueue.TryDequeue(out nextFunc))
                {
                    return nextFunc();
                }
                else
                {
                    throw new Exception("Something is wrong. How come there is nothing in the queue?");
                }
            }
        }
    }

我用下面的单元测试对此进行了测试：

代码语言：javascript
复制
var threadsQuantity = 50;

            for (int i = 0; i < threadsQuantity; i++)
            {
                var t = new Thread(async () =>
                {
                    Console.WriteLine("Started Thread: " + Thread.CurrentThread.ManagedThreadId);
                    await queuedActions.Execute(() =>
                    {
                        Console.WriteLine("Thread: " + Thread.CurrentThread.ManagedThreadId);
                        return Task.FromResult<object>(null);
                    });
                });

                t.Start();
            }

输出如下所示

代码语言：javascript
复制
Started Thread: 16
Started Thread: 13
Started Thread: 15
Started Thread: 17
Started Thread: 14
Started Thread: 18
Started Thread: 19
Started Thread: 20
Started Thread: 21
Queuing: 21
Locked: 21
Queuing: 13
Queuing: 18
Queuing: 15
Queuing: 16
Queuing: 17
Queuing: 14
Queuing: 19
Queuing: 20
Started Thread: 22
Queuing: 22
Thread: 21
Locked: 13
Thread: 13
Locked: 15
Started Thread: 23
Thread: 15
Queuing: 23
Locked: 23
Thread: 23
Locked: 18
Thread: 18
Locked: 17
Thread: 17
Locked: 16
Thread: 16
Locked: 14
Thread: 14
Locked: 19
Thread: 19
Locked: 20
Thread: 20
Locked: 22
Thread: 22
Started Thread: 24
Queuing: 24
Locked: 24
Thread: 24
Started Thread: 25
Queuing: 25
Locked: 25
Thread: 25
Started Thread: 26
Queuing: 26
Locked: 26
Thread: 26
Started Thread: 27
Queuing: 27
Locked: 27
Thread: 27
Started Thread: 28
Queuing: 28
Locked: 28
Thread: 28
Started Thread: 29
Queuing: 29
Locked: 29
Thread: 29
Started Thread: 30
Queuing: 30
Locked: 30
Thread: 30
Started Thread: 31
Queuing: 31
Locked: 31
Thread: 31
Started Thread: 32
Queuing: 32
Locked: 32
Thread: 32
Started Thread: 33
Queuing: 33
Locked: 33
Thread: 33
Started Thread: 34
Queuing: 34
Locked: 34
Thread: 34
Started Thread: 35
Queuing: 35
Locked: 35
Thread: 35
Started Thread: 36
Queuing: 36
Locked: 36
Thread: 36
Started Thread: 37
Queuing: 37
Locked: 37
Thread: 37
Started Thread: 38
Queuing: 38
Locked: 38
Thread: 38
Started Thread: 39
Queuing: 39
Locked: 39
Thread: 39
Started Thread: 40
Queuing: 40
Locked: 40
Thread: 40
Started Thread: 41
Queuing: 41
Locked: 41
Thread: 41
Started Thread: 42
Queuing: 42
Locked: 42
Thread: 42
Started Thread: 43
Queuing: 43
Locked: 43
Thread: 43
Started Thread: 44
Queuing: 44
Locked: 44
Thread: 44
Started Thread: 45
Queuing: 45
Locked: 45
Thread: 45
Started Thread: 46
Queuing: 46
Locked: 46
Thread: 46
Started Thread: 47
Queuing: 47
Locked: 47
Thread: 47
Started Thread: 48
Queuing: 48
Locked: 48
Thread: 48
Started Thread: 49
Queuing: 49
Locked: 49
Thread: 49
Started Thread: 50
Queuing: 50
Locked: 50
Thread: 50
Started Thread: 51
Queuing: 51
Locked: 51
Thread: 51
Started Thread: 52
Queuing: 52
Locked: 52
Thread: 52
Started Thread: 53
Queuing: 53
Locked: 53
Thread: 53
Started Thread: 54
Queuing: 54
Locked: 54
Thread: 54
Started Thread: 55
Queuing: 55
Locked: 55
Thread: 55
Started Thread: 56
Queuing: 56
Locked: 56
Thread: 56
Started Thread: 57
Queuing: 57
Locked: 57
Thread: 57
Started Thread: 58
Queuing: 58
Locked: 58
Thread: 58
Started Thread: 59
Queuing: 59
Locked: 59
Thread: 59
Started Thread: 60
Queuing: 60
Locked: 60
Thread: 60
Started Thread: 61
Queuing: 61
Locked: 61
Thread: 61
Started Thread: 62
Queuing: 62
Locked: 62
Thread: 62

如您所见，代码对线程21进行排队，锁定线程21，然后对线程13进行排队，对线程13进行锁定，对线程18进行排队，然后对线程15进行锁定，线程15是下一个要处理的线程。

此外，我们还测试了我们在这个论坛上找到的另一个类：

代码语言：javascript
复制
   public sealed class QueuedLock
{
    private class SyncObject : IDisposable
    {
        private Action m_action = null;
        private static readonly object locker = new object();

        public SyncObject(Action action)
        {
            m_action = action;
        }

        public void Dispose()
        {
            lock (locker)
            {
                var action = m_action;
                m_action = null;
                action?.Invoke();
            }
        }
    }

    private static readonly object m_innerLock = new Object();
    private volatile int m_ticketsCount = 0;
    private volatile int m_ticketToRide = 1;

    public bool Enter()
    {
        if (Monitor.IsEntered(m_innerLock))
        {
            return false;
        }

        var myTicket = Interlocked.Increment(ref m_ticketsCount);
        Monitor.Enter(m_innerLock);
        Console.WriteLine("Locked: " + Thread.CurrentThread.ManagedThreadId);
        while (true)
        {
            if (myTicket == m_ticketToRide)
            {
                return true;
            }

            Monitor.Wait(m_innerLock);
        }
    }

    public void Exit()
    {
        Interlocked.Increment(ref m_ticketToRide);
        Monitor.PulseAll(m_innerLock);
        Monitor.Exit(m_innerLock);
    }

    public IDisposable GetLock()
    {
        if (Enter())
        {
            return new SyncObject(Exit);
        }

        return new SyncObject(null);
    }
}

测试方法：

代码语言：javascript
复制
static QueuedLock queuedLock = new QueuedLock();
        [TestMethod]
        public void QueuedLockTest_ShouldRunInOrder()
        {
            var threadsQuantity = 50;

            for (int i = 0; i < threadsQuantity; i++)
            {
                var t = new Thread(() =>
                {
                    Console.WriteLine("Started Thread: " + Thread.CurrentThread.ManagedThreadId);
                    try
                    {
                        queuedLock.Enter();
                        Console.WriteLine("Thread: " + Thread.CurrentThread.ManagedThreadId);
                    }
                    finally
                    {
                        queuedLock.Exit();
                    }
                });

                t.Start();
            }
        }

而且输出也没有排序：

代码语言：javascript
复制
    Started Thread: 15
Started Thread: 14
Started Thread: 13
Started Thread: 16
Started Thread: 17
Started Thread: 18
Locked: 18
Started Thread: 19
Thread: 18
Locked: 15
Thread: 15
Locked: 14
Locked: 13
Locked: 19
Thread: 19
Locked: 16
Thread: 14
Locked: 17
Thread: 13
Thread: 16
Thread: 17
Started Thread: 20
Locked: 20
Thread: 20
Started Thread: 21
Locked: 21
Thread: 21
Started Thread: 22
Locked: 22
Thread: 22
Started Thread: 23
Locked: 23
Thread: 23
Started Thread: 24
Locked: 24
Thread: 24
Started Thread: 25
Locked: 25
Thread: 25
Started Thread: 26
Locked: 26
Thread: 26
Started Thread: 27
Locked: 27
Thread: 27
Started Thread: 28
Locked: 28
Thread: 28
Started Thread: 29
Locked: 29
Thread: 29
Started Thread: 30
Locked: 30
Thread: 30
Started Thread: 31
Locked: 31
Thread: 31
Started Thread: 32
Locked: 32
Thread: 32
Started Thread: 33
Locked: 33
Thread: 33
Started Thread: 34
Locked: 34
Thread: 34
Started Thread: 35
Locked: 35
Thread: 35
Started Thread: 36
Locked: 36
Thread: 36
Started Thread: 37
Locked: 37
Thread: 37
Started Thread: 38
Locked: 38
Thread: 38
Started Thread: 39
Locked: 39
Thread: 39
Started Thread: 40
Locked: 40
Thread: 40
Started Thread: 41
Locked: 41
Thread: 41
Started Thread: 42
Locked: 42
Thread: 42
Started Thread: 43
Locked: 43
Thread: 43
Started Thread: 44
Locked: 44
Thread: 44
Started Thread: 45
Locked: 45
Thread: 45
Started Thread: 46
Locked: 46
Thread: 46
Started Thread: 47
Locked: 47
Thread: 47
Started Thread: 48
Locked: 48
Thread: 48
Started Thread: 49
Locked: 49
Thread: 49
Started Thread: 50
Locked: 50
Thread: 50
Started Thread: 51
Locked: 51
Thread: 51
Started Thread: 52
Locked: 52
Thread: 52
Started Thread: 53
Locked: 53
Thread: 53
Started Thread: 54
Locked: 54
Thread: 54
Started Thread: 55
Locked: 55
Thread: 55
Started Thread: 56
Locked: 56
Thread: 56
Started Thread: 57
Locked: 57
Thread: 57
Started Thread: 58
Locked: 58
Thread: 58
Started Thread: 59
Locked: 59
Thread: 59
Started Thread: 60
Locked: 60
Thread: 60
Started Thread: 61
Locked: 61
Thread: 61
Started Thread: 62
Locked: 62
Thread: 62

你能帮我把它修好吗？我找不到这些函数中的错误，而且它似乎也适用于其他人。

c#
concurrency
thread-safety
locking
monitor
EN

回答 1

Stack Overflow用户

回答已采纳

发布于 2021-10-27 07:26:19

看起来你的测试并没有生成有用的信息来证明或反驳正确的执行顺序。Thread.CurrentThread.ManagedThreadId只是一个ID，并不是订单的可靠指示。另外，在程序运行时写入Console可能会影响执行顺序，因为对静态Console类的所有访问都是同步的。

下面的测试使用自定义的先进先出(修改)类来确保执行顺序，并一致地报告QueuedLock行为。我在启动每个线程之前添加了一个Thread.Sleep(20)，以避免两个线程同时请求一个票证。在ThreadStart委托中还有一个Thread.Sleep(40)，以确保所有线程在进入QueuedLock之前都会被阻塞(除了每个批处理的第一个线程)。

代码语言：javascript
复制
public static void Main()
{
    QueuedLock queuedLock = new QueuedLock();
    foreach (var batch in Enumerable.Range(1, 10))
    {
        var sequence = Enumerable.Range(1, 10);
        var tickets = new List<int>();
        var threads = sequence.Select(item =>
        {
            Thread.Sleep(20);
            var thread = new Thread(() =>
            {
                queuedLock.Enter();
                try { tickets.Add(item); Thread.Sleep(40); }
                finally { queuedLock.Exit(); }
            });
            thread.Start();
            return thread;
        }).ToArray();
        foreach (var thread in threads) thread.Join();
        Console.WriteLine($"Batch #{batch}, tickets: {String.Join(", ", tickets)} - "
            + (tickets.SequenceEqual(sequence) ? "OK" : "NOT FIFO!"));
    }
}

public class QueuedLock
{
    private readonly object _locker = new object();
    private int _ticketsCount = 0;
    private int _ticketToRide = 1;

    public void Enter()
    {
        if (Monitor.IsEntered(_locker)) throw new InvalidOperationException();
        int myTicket = Interlocked.Increment(ref _ticketsCount);
        Monitor.Enter(_locker);
        while (myTicket != _ticketToRide) Monitor.Wait(_locker);
    }

    public void Exit()
    {
        if (!Monitor.IsEntered(_locker)) throw new InvalidOperationException();
        _ticketToRide++;
        Monitor.PulseAll(_locker);
        Monitor.Exit(_locker);
    }
}

输出：

代码语言：javascript
复制
Batch #1, tickets: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 - OK
Batch #2, tickets: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 - OK
Batch #3, tickets: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 - OK
Batch #4, tickets: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 - OK
Batch #5, tickets: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 - OK
Batch #6, tickets: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 - OK
Batch #7, tickets: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 - OK
Batch #8, tickets: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 - OK
Batch #9, tickets: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 - OK
Batch #10, tickets: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 - OK

Try it on Fiddle。

票数 1
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：

https://stackoverflow.com/questions/69731000

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