Finding Connection by UserId in SignalR

Question

I have a webpage that uses ajax polling to get stock market updates from the server. I'd like to use SignalR instead, but I'm having trouble understanding how/if it would work. ok, it's not really stock market updates, but the analogy works. The SignalR examples I've seen send messages to either the current connection, all connections, or groups. In my example the stock updates happen outside of the current connection, so there's no such thing as the 'current connection'. And a user's account is associated with a few stocks, so sending a stock notification to all connections or to groups doesn't work either. I need to be able to find a connection associated with a certain userId. Here's a fake code example: ``` foreach(var stock in StockService.GetStocksWithBigNews()) { var userIds = UserService.GetUserIdsThatCareAboutStock(stock); var connections = /* find connections associated with user ids */; foreach(var connection in connections) { connection.Send(...); } } ``` In this question…

Accepted Answer

I created a little project last night to learn this also. I used 1.0 alpha and it was Straight forward. I created a Hub and from there on it just worked :)

I my project i have N Compute Units(some servers processing work), when they start up they invoke the ComputeUnitRegister.

```
await HubProxy.Invoke("ComputeUnitReqisted", _ComputeGuid);
```

and every time they do something they call

```
HubProxy.Invoke("Running", _ComputeGuid);
```

where HubProxy is :

```
HubConnection Hub = new HubConnection(RoleEnvironment.IsAvailable ?
                    RoleEnvironment.GetConfigurationSettingValue("SignalREndPoint"):
                    "http://taskqueue.cloudapp.net/");
IHubProxy HubProxy = Hub.CreateHubProxy("ComputeUnits"); 
```

I used RoleEnviroment.IsAvailable because i can now run this as a Azure Role , a Console App or what ever in .NET 4.5. The Hub is placed in a MVC4 Website project and is started like this:

```
        GlobalHost.Configuration.ConnectionTimeout = TimeSpan.FromSeconds(50);
        RouteTable.Routes.MapHubs();

public class ComputeUnits : Hub
{
     public Task Running(Guid MyGuid)
     {
         return Clients.Group(MyGuid.ToString()).ComputeUnitHeartBeat(MyGuid,
                DateTime.UtcNow.ToEpochMilliseconds());            
     }
     public Task ComputeUnitReqister(Guid MyGuid)
     {
         Groups.Add(Context.ConnectionId, "ComputeUnits").Wait(); 
         return Clients.Others.ComputeUnitCameOnline(new { Guid = MyGuid,
                HeartBeat = DateTime.UtcNow.ToEpochMilliseconds() });           
     }
     public void SubscribeToHeartBeats(Guid MyGuid)
     {
         Groups.Add(Context.ConnectionId, MyGuid.ToString());
     }
}
```

My clients are Javascript clients, that have methods for(let me know if you need to see the code for this also). But basicly they listhen for the `ComputeUnitCameOnline` and when its run they call on the server `SubscribeToHeartBeats`. This means that whenever the server compute unit is doing some work it will call Running, which will trigger a `ComputeUnitHeartBeat` on javascript clients.

I hope you can use this to see how Groups and Connections can be used. And last, its also scaled out over multiply azure roles by adding a few lines of code:

```
    GlobalHost.HubPipeline.EnableAutoRejoiningGroups();
    GlobalHost.DependencyResolver.UseServiceBus(
        serviceBusConnectionString,
        2,
        3,
        GetRoleInstanceNumber(),
          topicPathPrefix /* the prefix applied to the name of each topic used */
        );
```

You can get the connection string on the servicebus on azure, remember the Provider=SharedSecret. But when adding the nuget packaged the connectionstring syntax is also pasted into your web.config. 2 is how many topics to split it about. Topics can contain 1Gb of data, so depending on performance you can increase it. 3 is the number of nodes to split it out on. I used 3 because i have 2 Azure Instances, and my localhost. You can get the RoleNumber like this (note that i hard coded my localhost to 2).

```
private static int GetRoleInstanceNumber()
{
    if (!RoleEnvironment.IsAvailable)
        return 2;

var roleInstanceId = RoleEnvironment.CurrentRoleInstance.Id;
    var li1 = roleInstanceId.LastIndexOf(".");
    var li2 = roleInstanceId.LastIndexOf("_");
    var roleInstanceNo = roleInstanceId.Substring(Math.Max(li1, li2) + 1);
    return Int32.Parse(roleInstanceNo);
}
```

You can see it all live at : http://taskqueue.cloudapp.net/#/compute-units

Finding Connection by UserId in SignalR

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