Azure Service Bus integration with SignalR

Question

This question is not about Scaleout with SignalR and Azure Service Bus. I want to build a Service Bus listener (e.g. OnMessage) into my SignalR web socket app that then distributes the message accordingly to connected users. Messages will be posted from various separately running services into the centralized Service Bus and the UI/browser connected to the web socket servers should receive these.

Option 1: I can add an async Task into a hub method to subscribe to a Service Bus and filter by the connected user. The problem with this is it uses an extra thread from the thread pool and will do this for every socket connection the user has started. Our app can easily start 5-10 or more sockets for every tab open.

Option 2: I can add a single task to the SignalR Startup.Configuration method that then receives all messages and distributes them to the proper connected users. The problem I've encountered here is that I don't have access to the Clients object used for sending to the browser.

I feel like SignalR and Service Bus are a good complement to each other to enable near real-time communications but I can find very little to implement a scenario like this. And I feel like this should be a common enough scenario. Perhaps I'm missing some obvious design patterns that would be a better solution.

flooptreque flooptreque · Accepted Answer · 2016-08-04T21:02:18

I was able to figure this out. In the SignalR Startup.Configuration method I added a method to start the listener and in that method I called GlobalHost.ConnectionManager.GetHubContext. Currently this doesn't send to individual users but I'll add a connection manager of some sort to handle that.

public void startServiceBusListener()
{

    // setup subcsription
    var namespaceManager = NamespaceManager.CreateFromConnectionString(connectionString);
    if (!namespaceManager.SubscriptionExists("myTopic", Environment.MachineName))
        namespaceManager.CreateSubscription("myTopic", Environment.MachineName);

    SubscriptionClient busClient = SubscriptionClient.CreateFromConnectionString(connectionString, "myTopic", Environment.MachineName);

    // Configure the callback options.
    OnMessageOptions options = new OnMessageOptions();
    options.AutoComplete = false;
    options.AutoRenewTimeout = TimeSpan.FromMinutes(1);

    receiveTask = Task.Run(() =>
    {
        // handle new messages
        busClient.OnMessage((message) =>
        {
            try
            {
                Notification note = message.GetBody<Notification>();
                string notification = JsonConvert.SerializeObject(note);
                GlobalHost.ConnectionManager.GetHubContext<DispatchHub>().Clients.All.notify(notification);
                // Remove message from subscription.
                message.Complete();
            }
            catch (Exception)
            {
                // Indicates a problem, unlock message in subscription.
                message.Abandon();
            }
        }, options);
    }, cts.Token);
}

Azure Service Bus integration with SignalR

1 Answers