如何访问Azure Webrole中的Signalr Hub

Question

I have a working SignalR Hub that contains some continuous running methods, they are managing sessions lifecycle, connecting sessions ... these continuous running methods are executed every X seconds using the Timer class. this is really not a good practice because of thread leaking, performance issues, locks ...

A better implementation would be to have a WebRole, and all those "worker methods" should go in the WebRole.cs file, witch makes a lot of sense, since this is the very purpose of roles in azure.

The probleme now, it can not get a working instance of the hub context using this code :

var hubContext = GlobalHost.ConnectionManager.GetHubContext<AppHub>();
hubContext.Clients.All.Message("hello from webrole");

hubContext is instantiated (so not null) but even so, still nothing is broadcasted to clients. No errors and no exceptions !

I guess this is happening because the WebRole.cs and Startup.cs are instantiated in different threads ?

How can I access hub context in the WebRole.cs ?

Thank you.

Answer 1

hubContext is instantiated (so not null) but even so, still nothing is broadcasted to clients. No errors and no exceptions !

I can reproduce same issue on my side. To broadcast the message to clients from WebRole.cs , you can try to install Microsoft.AspNet.SignalR.Client and invoke hub method to send message to clients. The following code works for me in the Compute Emulator, you can refer to it.

WebRole.cs

public class WebRole : RoleEntryPoint
{
    public override bool OnStart()
    {
        // For information on handling configuration changes
        // see the MSDN topic at https://go.microsoft.com/fwlink/?LinkId=166357.

        return base.OnStart();
    }

    public override void Run()
    {
        while (true)
        {
            System.Threading.Thread.Sleep(30000);

            var hub = new Microsoft.AspNet.SignalR.Client.HubConnection("http://localhost:57276/signalr/hubs");

            var proxy = hub.CreateHubProxy("ChatHub");
            hub.Start().Wait();

            //invoke hub method
            proxy.Invoke("mySend", "hello from webrole; " + DateTime.UtcNow.ToString());
        }         
    }


}

ChatHub.cs

public class ChatHub : Hub
{
    public void Send(string name, string message)
    {
        Clients.All.addNewMessageToPage(name, message);
    }

    public void mySend(string message)
    {
        Clients.All.addNewMessageToPage("webrole", message);
    }
}

Test result