signalr send group notification with delay

Question

I have a signal r application. I have an issue of concurrent connection maxing out on iis. To avoid that i want my hub to send notification to groups created by in pack of 25 with delay of suppose 500ms. I add users to group as they connect. After count of 25 i add them to next group.Need help with how shall i send notification to each group with delay of 500ms. I have looped through the number of groups and used

Thread.Sleep(500);

but all connected users do not receive the notification

At the very least use `await Task.Delay(500);`, *not* Thread.Sleep — Panagiotis Kanavos, Dec 18 '14 at 08:41
You may try to change settings : http://stackoverflow.com/questions/11667799/while-using-signalr-will-there-be-any-connection-limits-on-iis — Guillaume, Dec 18 '14 at 08:55
How does delaying notifications reduce the number of concurrent connections? — halter73, Dec 18 '14 at 22:52

score 0 · Answer 1 · answered Dec 18 '14 at 09:01

Your question almost describes the solution - buffer the notifications fro 500ms then send an array of all of them.

You could do that by pushing the notification in a queue or list and and use a timer to send the notifications every 500ms.

A far better solution though would be to use Reactive Extensions and the Observable.Buffer(Timespan) method, thus avoiding queues and timers.

Subject<string> _subject;

.....
public void InitSubject()
{
    _subject=new Subject<string>();
    _subject.Buffer(Timespan.FromMilliseconds(500))
            .Subscribe(notifications=>SendBatch(notifications));
}
....
public void SendBatch(IList<string> notifications)
{
    //Get hold of the SignalR context and send the notifications here
}

public void QueueNotification(string notification)
{
    _subject.OnNext(notification);
}

Buffer also allows you to batch a specific number of notifications, or use both a timespan and item limit to send a batch whenever one of the limits is reached.

Your code should call QueueNotification instead of sending the notification directly. Reactive Extensions also provide LINQ extensions, so you could apply filtering with the Where() method, eg to use different delays for different user groups, bypass buffering completely, or use any other combination.

You should note that since a Hub is transient, you can't put your subject inside the hub, although you can put QueueNotification in there, provided you provide a reference to the subject somewhere, eg by using Dependency injection to initialize the hub

signalr send group notification with delay

1 Answers1