[英]Rx operator to distinct sequences
重要提示 :有关结果的描述和更多详细信息,请也查看我的答案
我需要对通常被复制的对象/事件序列进行分组和过滤,并以TimeSpan间隔对其进行缓冲。 我尝试用某种大理石图更好地解释它:
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,“ ---”表示时间间隔。 另外,我还想通过一个关键属性来区分它在所有类型上都可用,因为它们具有共同的基类:
X, Y, Z : A
并且A包含属性Key。 使用Xa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
有人可以帮助我将所需的Linq运算符(可能是DistinctUntilChanged和Buffer)放在一起以实现此行为吗? 谢谢
更新18.08.12 :
根据要求,我尝试给出更好的解释。 我们有收集事件并将事件发送到Web服务的设备。 这些设备具有旧的逻辑(由于向后兼容性,我们无法更改它),并且它们不断发送事件,直到收到确认为止。 确认后,他们将队列中的下一个事件发送,依此类推。 事件包含设备的网络地址和一些其他属性,这些属性区分每个设备的队列中的事件。 一个事件如下所示:
class Event
{
public string NetworkAddress { get; }
public string EventCode { get; }
public string AdditionalAttribute { get; }
}
目的是每5秒处理一次从所有设备收到的特殊事件,将信息存储在数据库中(这就是为什么我们不希望批量处理此信息)并将确认发送到设备。 让我们举一个仅包含两个设备和一些事件的示例:
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,我认为这可能是基本运算符的简单组合,但是我对Rx还是陌生的,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,所以我有点困惑。
更新19.08.12 :
请记住,此代码在服务器上运行,并且可以运行数天而不会导致内存泄漏...我不确定主题的行为。 目前,对于每个事件,我都会在服务上调用推送操作,该服务会调用Subject的OnNext,并在其之上构建查询(如果我对Subject的用法没错的话)。
更新20.08.12 :
当前实施,包括验证测试; 这是我尝试过的,似乎与@yamen建议的相同
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
}
和测试:
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,该软件可以连续运行数天而不会出现问题,处理数千条消息,这一点非常重要。 明确地说:测试未通过当前实现。
我不确定这是否确实符合您的要求,但是您可能要使用group
关键字对元素进行显式group
,然后在重新组合各个IObservable
之前分别对其进行操作。
例如,如果我们有类定义,例如
class A
{
public char Key { get; set; }
}
class X : A { }
...
和一个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();
要获得您提供的输出:
{ 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 }
不知道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(您可以轻松地对其进行修改以满足您的需求):
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使用这些设备,并且当然需要更改以下内容以适应这些情况。 这些设备将各自产生一个具有0.5到1.5秒之间的随机延迟的值。
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,使其“与众不同”,然后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));
一旦有了这些,就可以定期使用此流,而只需使用Buffer
对其进行Buffer
:
stream.Buffer(TimeSpan.FromSeconds(1)).Subscribe(x => { /* code here works on a list of the filtered events per second */ });
经过搜索和实验后,我整理了一些代码以产生期望的输出:
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,监视应用程序似乎会导致内存泄漏。 我的问题是:
更新 :
似乎内存增加仅持续几分钟,然后该值稳定。 我将进行长时间的测试。 当然,这将是绝对可接受的行为。
更新26.08.12 :
无论如何,我认为我的问题仍然对使用test Scheduler进行单元测试开放。
谢谢弗朗切斯科
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