MassTransit 5.2, SignalR: How can i get the IHubContext inside my Consumer? - asp.net-core

Question

My main problem is to get the right instance of the SignalR hub.
Context: Im building a webapplication which communicates with a couple of external systems. CRUD operations in my application result in updating the databases of the external systems.
In this example i have 3 services running:
ExternalSystem | StateMachine | .NET CORE WebAPI
When i post the 'create employee' form, a RabbitMQ message will be sent from the WebAPI to the statemachine. The statemachine then sends a couple of create messages to my external system service which updates the database. Thereafter, it updates the statemachine to keep track of the createoperation.
Form -> API -> StateMachine -> ExternalSystem -> StateMachine -> API
So far so good. Now i would like to use SignalR to send the status updates to the client. So i've implemented this consumer in the API:
public class UpdatesConsumer :
IConsumer<IExternalSystemUpdateMessage>
{
private readonly IHubContext<UpdatesHub> _updaterHubContext;
public UpdatesConsumer(IHubContext<UpdatesHub> hubContext)
{
_updaterHubContext = hubContext;
}
public Task Consume(ConsumeContext<IExternalSystemUpdateMessage> context)
{
//return _updaterHubContext.Clients.Group(context.Message.CorrelationId.ToString()).SendAsync("SEND_UPDATE", context.Message.Message);// this.SendUpdate(context.Message.CorrelationId, context.Message.Message);
return _updaterHubContext.Clients.All.SendAsync("SEND_UPDATE", context.Message.Message);
}
}
This is my SignalR hub:
public class UpdatesHub :
Hub
{
public Task SendUpdate(Guid correlationId, string message)
{
return Clients.Group(correlationId.ToString()).SendAsync("SEND_UPDATE", message);
}
}
And this is how the Bus and consumer is instantiated:
public void ConfigureServices(IServiceCollection services)
{
_services = services;
services.AddMvc();
services.AddSignalR();
//services.AddSingleton<IHubContext<UpdatesHub>>();
WebAPI.CreateBus();
}
public static IServiceCollection _services;
static IBusControl _busControl;
public static IBusControl Bus
{
get
{
return _busControl;
}
}
public static void CreateBus()
{
IRMQConnection rmqSettings = Config.GetRMQConnectionConfig("rmq-settings.json", "connection");
_busControl = MassTransit.Bus.Factory.CreateUsingRabbitMq(x =>
{
var host = x.Host(BusInitializer.GetUri("", rmqSettings), h =>
{
h.Username(rmqSettings.UserName);
h.Password(rmqSettings.Password);
});
x.ReceiveEndpoint(host, "externalsystems.update",
e => { e.Consumer(() => new UpdatesConsumer((IHubContext<UpdatesHub>)Startup.__serviceProvider.GetService(typeof(IHubContext<UpdatesHub>)))); });
});
TaskUtil.Await(() => _busControl.StartAsync());
}
=========================================================================
So the problem is that _updaterHubContext.Clients in my Consumer class, always turn out to be empty. I've tested accessing the hub in a controller, and the clients do show up:
public class TestController : Controller
{
private readonly IHubContext<UpdatesHub> _hubContext;
public TestController(IHubContext<UpdatesHub> hubContext)
{
_hubContext = hubContext;
}
[HttpGet]
[Route("api/Test/")]
public IActionResult Index()
{
return View();
}
}
How can i get the right instance of the hub in my Consumer class? Or how can i access the IServiceCollection that .net is using?
Thnx in advance!

Answer 1

You can register your consumer so that MassTransit will resolve it from the IServiceProvider using the support provided in the MassTransit.Extensions.DependencyInjection package.
x.ReceiveEndpoint(host, "externalsystems.update", e =>
{
e.Consumer<UpdatesConsumer>(_serviceProvider);
});
Be sure to register your UpdatesConsumer in the container as well. This should resolve a new instance of the consumer for each message received on the endpoint.

Answer 2

Why not register Bus using Microsoft Dependency Injection. It should fix your issue, it will Resolve your consumer using IServiceProvider