Question

重要：有关结果的说明和更多详情，请查看我的回答

我需要对通常复制的一系列对象/事件进行分组和过滤，并使用TimeSpan间隔缓冲它们。我尝试用大理石图解释它更好：

X-X-X-X-X-Y-Y-Y-Z-Z-Z-Z-X-X-Y-Z-Z

会产生

X---Y---Z---X---Y---Z

其中X，Y和Z是不同的事件类型，' - '表示间隔。另外，我还想通过一个关键属性区分它可用于所有类型，因为它们有一个共同的基类：

X, Y, Z : A

和A包含属性Key。使用符号X.a表示X.Key = a，最终样本将是：

X.a-X.b-X.a-Y.b-Y.c-Z.a-Z.a-Z.c-Z.b-Z.c

会产生

X.a-X.b---Y.b-Y.c-Z.a-Z.c-Z.b

有人可以帮我组合所需的Linq运算符（可能是DistinctUntilChanged和Buffer）来实现这种行为吗？感谢

更新18.08.12 ：

根据要求，我尝试给出更好的解释。我们有设备收集和发送事件到Web服务。这些设备有一个旧的逻辑（我们不能因为向后兼容而改变它），并且它们不断发送事件直到它们收到确认;在确认之后，他们将下一个事件发送到队列中，依此类推。事件包含单元的网络地址和一些其他属性，用于区分每个设备的队列中的事件。事件如下所示：

class Event
{
    public string NetworkAddress { get; }

    public string EventCode { get; }

    public string AdditionalAttribute { get; }
}

目标是每隔5秒处理从所有设备接收的区分事件，将信息存储在数据库中（这就是为什么我们不想批量执行）并将ack发送到设备。让我们举个例子，只有两个设备和一些事件：

Device 'a':
Event 1 (a1): NetworkAddress = '1', EventCode = A, AdditionalAttribute = 'x'
Event 2 (a2): NetworkAddress = '1', EventCode = A, AdditionalAttribute = 'y'
Event 3 (a3): NetworkAddress = '1', EventCode = B, AdditionalAttribute = 'x'

Device 'b':
Event 1 (b1): NetworkAddress = '2', EventCode = A, AdditionalAttribute = 'y'
Event 2 (b2): NetworkAddress = '2', EventCode = B, AdditionalAttribute = 'x'
Event 3 (b3): NetworkAddress = '2', EventCode = B, AdditionalAttribute = 'y'
Event 4 (b4): NetworkAddress = '2', EventCode = C, AdditionalAttribute = 'x'

Pn are the operations done by our server, explained later

可能的大理石图（输入流+输出流）：

Device 'a'          : -[a1]-[a1]-[a1]----------------[a2]-[a2]-[a2]-[a3]-[a3]-[a3]-...
Device 'b'          : ------[b1]-[b1]-[b2]-[b2]-[b2]------[b3]-[b3]-[b4]-[b4]-[b4]-...

Time                : ------------[1s]-----------[2s]------------[3s]------------[4s]-
DB/acks (rx output) : ------------[P1]-----------[P2]------------[P3]------------[P4]-

P1: Server stores and acknowledges [a1] and [b1]
P2: "      "      "   "            [b2]
P3: "      "      "   "            [a2] and [b3]
P4: "      "      "   "            [a3] and [b4]

最后我认为它可能是基本运算符的简单组合，但我是Rx的新手，我有点困惑，因为似乎有很多运算符（或运算符的组合）来获得相同的输出流。

更新19.08.12 ：

请记住，此代码在服务器上运行，它应该运行数天而不会出现内存泄漏...我不确定主题的行为。目前，对于每个事件，我调用一个服务上的push操作，该服务调用Subject的OnNext，我应该在其上构建查询（如果我对主题的使用没有错误的话）。

更新20.08.12 ：

目前的实施，包括验证测试;这就是我尝试过的，看起来@yamen

的建议也是如此

public interface IEventService
{
    // Persists the events
    void Add(IEnumerable<Event> events);
}

public class Event
{
    public string Description { get; set; }
}

/// <summary>
/// Implements the logic to handle events.
/// </summary>
public class EventManager : IDisposable
{
    private static readonly TimeSpan EventHandlingPeriod = TimeSpan.FromSeconds(5);

    private readonly Subject<EventMessage> subject = new Subject<EventMessage>();

    private readonly IDisposable subscription;

    private readonly object locker = new object();

    private readonly IEventService eventService;

    /// <summary>
    /// Initializes a new instance of the <see cref="EventManager"/> class.
    /// </summary>
    /// <param name="scheduler">The scheduler.</param>
    public EventManager(IEventService eventService, IScheduler scheduler)
    {
        this.eventService = eventService;
        this.subscription = this.CreateQuery(scheduler);
    }

    /// <summary>
    /// Pushes the event.
    /// </summary>
    /// <param name="eventMessage">The event message.</param>
    public void PushEvent(EventMessage eventMessage)
    {
        Contract.Requires(eventMessage != null);
        this.subject.OnNext(eventMessage);
    }

    /// <summary>
    /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
    /// </summary>
    /// <filterpriority>2</filterpriority>
    public void Dispose()
    {
        this.Dispose(true);
    }

    private void Dispose(bool disposing)
    {
        if (disposing)
        {
            // Dispose unmanaged resources
        }

        this.subject.Dispose();
        this.subscription.Dispose();
    }

    private IDisposable CreateQuery(IScheduler scheduler)
    {
        var buffered = this.subject
            .DistinctUntilChanged(new EventComparer())
            .Buffer(EventHandlingPeriod, scheduler);

        var query = buffered
            .Subscribe(this.HandleEvents);
        return query;
    }

    private void HandleEvents(IList<EventMessage> eventMessages)
    {
        Contract.Requires(eventMessages != null);
        var events = eventMessages.Select(this.SelectEvent);
        this.eventService.Add(events);
    }

    private Event SelectEvent(EventMessage message)
    {
        return new Event { Description = "evaluated description" };
    }

    private class EventComparer : IEqualityComparer<EventMessage>
    {
        public bool Equals(EventMessage x, EventMessage y)
        {
            return x.NetworkAddress == y.NetworkAddress && x.EventCode == y.EventCode && x.Attribute == y.Attribute;
        }

        public int GetHashCode(EventMessage obj)
        {
            var s = string.Concat(obj.NetworkAddress + "_" + obj.EventCode + "_" + obj.Attribute);
            return s.GetHashCode();
        }
    }
}

public class EventMessage
{
    public string NetworkAddress { get; set; }

    public byte EventCode { get; set; }

    public byte Attribute { get; set; }

    // Other properties
}

测试：

public void PushEventTest()
    {
        const string Address1 = "A:2.1.1";
        const string Address2 = "A:2.1.2";

        var eventServiceMock = new Mock<IEventService>();

        var scheduler = new TestScheduler();
        var target = new EventManager(eventServiceMock.Object, scheduler);
        var eventMessageA1 = new EventMessage { NetworkAddress = Address1, EventCode = 1, Attribute = 4 };
        var eventMessageB1 = new EventMessage { NetworkAddress = Address2, EventCode = 1, Attribute = 5 };
        var eventMessageA2 = new EventMessage { NetworkAddress = Address1, EventCode = 1, Attribute = 4 };
        scheduler.Schedule(() => target.PushEvent(eventMessageA1));
        scheduler.Schedule(TimeSpan.FromSeconds(1), () => target.PushEvent(eventMessageB1));
        scheduler.Schedule(TimeSpan.FromSeconds(2), () => target.PushEvent(eventMessageA1));

        scheduler.AdvanceTo(TimeSpan.FromSeconds(6).Ticks);

        eventServiceMock.Verify(s => s.Add(It.Is<List<Event>>(list => list.Count == 2)), Times.Once());

        scheduler.Schedule(TimeSpan.FromSeconds(3), () => target.PushEvent(eventMessageB1));

        scheduler.AdvanceTo(TimeSpan.FromSeconds(11).Ticks);

        eventServiceMock.Verify(s => s.Add(It.Is<List<Event>>(list => list.Count == 1)), Times.Once());
    }

此外，我再次评论说，软件可以运行几天没有问题，处理成千上万的消息非常重要。为了说清楚：测试没有通过当前的实现。

Answer 1

我不确定这是否完全符合您的要求，但您可能会使用group关键字明确对元素进行分组，然后分别操作各种IObservable重新组合它们。

E.g。如果我们有类定义，如

class A
{
    public char Key { get; set; }
}

class X : A { }
...

和Subject<A>

Subject<A> subject = new Subject<A>();

然后我们可以写

var buffered =
    from a in subject
    group a by new { Type = a.GetType(), Key = a.Key } into g
    from buffer in g.Buffer(TimeSpan.FromMilliseconds(300))
    where buffer.Any()
    select new
    {
        Count = buffer.Count,
        Type = buffer.First().GetType().Name,
        Key = buffer.First().Key
    };

buffered.Do(Console.WriteLine).Subscribe();

我们可以使用您提供的数据对此进行测试：

subject.OnNext(new X { Key = 'a' }); 
Thread.Sleep(100);
subject.OnNext(new X { Key = 'b' }); 
Thread.Sleep(100);
subject.OnNext(new X { Key = 'a' }); 
Thread.Sleep(100);
...
subject.OnCompleted();

获取您提供的输出：

{ Count = 2, Type = X, Key = a }
{ Count = 1, Type = X, Key = b }
{ Count = 1, Type = Y, Key = b }
{ Count = 1, Type = Y, Key = c }
{ Count = 2, Type = Z, Key = a }
{ Count = 2, Type = Z, Key = c }
{ Count = 1, Type = Z, Key = b }

Answer 2

不确定这是否正是您想要的，但它似乎支持您的用例。

首先，让我们定义要使用的基类（您可以根据需要轻松修改它）：

public class MyEvent
{
    public string NetworkAddress { set; get; }
    public string EventCode { set; get; }
}

让我们将您的设备设置为IObservable<MyEvent>的数组 - 您可能会以不同的方式提供这些设备，并且下面需要更改以适应当然。这些设备将产生一个随机延迟在0.5到1.5秒之间的值。

var deviceA = new MyEvent[] { new MyEvent() {NetworkAddress = "A", EventCode = "1"},
                              new MyEvent() {NetworkAddress = "A", EventCode = "1"},
                              new MyEvent() {NetworkAddress = "A", EventCode = "2"} };

var deviceB = new MyEvent[] { new MyEvent() {NetworkAddress = "B", EventCode = "1"},
                              new MyEvent() {NetworkAddress = "B", EventCode = "2"},
                              new MyEvent() {NetworkAddress = "B", EventCode = "2"},
                              new MyEvent() {NetworkAddress = "B", EventCode = "3"} };   

var random = new Random();                                 

var deviceARand = deviceA.ToObservable().Select(a => Observable.Return(a).Delay(TimeSpan.FromMilliseconds(random.Next(500,1500)))).Concat();
var deviceBRand = deviceB.ToObservable().Select(b => Observable.Return(b).Delay(TimeSpan.FromMilliseconds(random.Next(500,1500)))).Concat();

var devices = new IObservable<MyEvent>[] { deviceARand, deviceBRand };

现在让我们采用所有这些单独的设备流，使它们“不同”，并将它们合并为一个主流：

var stream = devices.Aggregate(Observable.Empty<MyEvent>(), (acc, device) => acc.DistinctUntilChanged(a => a.EventCode).Merge(device));

一旦你有了这个，定期使用这个流只是用Buffer来缓冲它：

stream.Buffer(TimeSpan.FromSeconds(1)).Subscribe(x => { /* code here works on a list of the filtered events per second */ });

Answer 3

在搜索和实验之后，我整理了一些产生我期望的输出的代码：

static void Main(string[] args)
    {
        const string Address1 = "A:2.1.1";
        const string Address2 = "A:2.1.2";
        var comparer = new EventComparer();
        var eventMessageA1 = new EventMessage { NetworkAddress = Address1, EventCode = 1, Attribute = 4 };
        var eventMessageB1 = new EventMessage { NetworkAddress = Address2, EventCode = 1, Attribute = 5 };
        var eventMessageA2 = new EventMessage { NetworkAddress = Address1, EventCode = 1, Attribute = 5 };
        var list = new[] { eventMessageA1, eventMessageA1, eventMessageB1, eventMessageA2, eventMessageA1, eventMessageA1 };

        var queue = new BlockingCollection<EventMessage>();
        Observable.Interval(TimeSpan.FromSeconds(2)).Subscribe
            (
                l => list.ToList().ForEach(m =>
                {
                    Console.WriteLine("Producing {0} on thread {1}", m, Thread.CurrentThread.ManagedThreadId);
                    queue.Add(m);
                })
            );

        // subscribing
        queue.GetConsumingEnumerable()
            .ToObservable()
             .Buffer(TimeSpan.FromSeconds(5))
             .Subscribe(e =>
                 {
                     Console.WriteLine("Queue contains {0} items", queue.Count);
                     e.Distinct(comparer).ToList().ForEach(m =>
                  Console.WriteLine("{0} - Consuming: {1} (queue contains {2} items)", DateTime.UtcNow, m, queue.Count));
                 }
             );

        Console.WriteLine("Type enter to exit");
        Console.ReadLine();
    }

    public class EventComparer : IEqualityComparer<EventMessage>
    {
        public bool Equals(EventMessage x, EventMessage y)
        {
            var result = x.NetworkAddress == y.NetworkAddress && x.EventCode == y.EventCode && x.Attribute == y.Attribute;
            return result;
        }

        public int GetHashCode(EventMessage obj)
        {
            var s = string.Concat(obj.NetworkAddress + "_" + obj.EventCode + "_" + obj.Attribute);
            return s.GetHashCode();
        }
    }

    public class EventMessage
    {
        public string NetworkAddress { get; set; }

        public byte EventCode { get; set; }

        public byte Attribute { get; set; }

        public override string ToString()
        {
            const string Format = "{0} ({1}, {2})";
            var s = string.Format(Format, this.NetworkAddress, this.EventCode, this.Attribute);
            return s;
        }
    }

无论如何，监控应用程序，似乎这会导致内存泄漏。我现在的问题是：

导致内存泄漏的原因是什么？ [请参阅下面的更新]
这是最好的方法（如果我将distinct放在第一个observable上，我不会在下一个缓冲区中获取其他事件，但每个缓冲区中的项应该与其他缓冲区隔离）？
如何使用测试调度程序编写测试？

<强>更新：

似乎内存增量只持续几分钟，然后值稳定。我会进行长时间的测试。当然，这将是绝对可以接受的行为。

更新26.08.12 ：

正如我在上一次更新中已经提到的，内存使用率在启动后的几分钟内仅增加（并且缓慢）。 8小时后，消耗的内存是稳定的，在几KB的范围内正常波动。
此question与我的非常相似，建议的Drain扩展可以很好地应用于我的问题（仍有待验证）

无论如何，我认为我的问题仍然适用于使用测试调度程序的单元测试。

感谢弗朗西斯

Rx运算符指向不同的序列

3 个答案: