SignalR client does not receive message through Masstransit

Question

I had a problem sending messages to clients via MassTransit and SignalR

Startup:

        //SignalR
        services.AddSignalR().AddMassTransitBackplane();     
        #region MassTransit RabbitMq

        services.AddScoped<SendCosistListToScaleConsumer>();
        services.AddScoped<CreateConsistListConsumer>();

        services.AddMassTransit(x => 
        {
            x.AddSignalRHubConsumers<NotifyHub>();

            x.AddBus(provider => Bus.Factory.CreateUsingRabbitMq(conf =>
            {
                conf.Host(Configuration["Rabbit:Host"], host => {
                    host.Username(Configuration["Rabbit:Username"]);
                    host.Password(Configuration["Rabbit:Password"]);
                });                   

               conf.ReceiveEndpoint(Configuration["Rabbit:ReceiveEndpoint"], e => {
                    e.PrefetchCount = 16;
                    e.UseMessageRetry(n => n.Interval(3, 100));

                    #region Consumers
                    e.Consumer<SendCosistListToScaleConsumer>();
                    e.Consumer<CreateConsistListConsumer>();
                   #endregion
               });
                conf.AddSignalRHubEndpoints<NotifyHub>(provider);
            }));
        });
        services.AddMassTransitHostedService();
        #endregion

....

app.UseSignalR(endpoints =>
{
    endpoints.MapHub<NotifyHub>("/notify");
});

Consumer:

public class CreateConsistListConsumer : IConsumer<ICreateConsistList>
    {
        IReadOnlyList<IHubProtocol> protocols = new IHubProtocol[] { new JsonHubProtocol() };
        public Task Consume(ConsumeContext<ICreateConsistList> context)
        {
            context.Publish<All<NotifyHub>>(
               new
               {
                   Message = protocols.ToProtocolDictionary("SendMessageToAllUsers", new object[] { "CompanyId", context.Message.CompanyId })
               });
            return Task.CompletedTask;
        }
    }

Console App (SignalR Client):

   hubConnection.On<Object>("SendMessageToAllUsers", param => {
        Console.WriteLine(param);
     });

If I understand correctly how MassTransii and SignalR work, then this code is enough to send messages to clients. With the help of debugging, I looked that CreateConsistListConsumer is working, but clients do not receive reporting.   At the same time, the client connects to the hub and correctly receives messages from other sources, but not from MassTransit.

What am I doing wrong?

Answer 1

I have been facing the same issue last week.

It seem SignalR is doing some special work with handling hubs, and couldn't make Masstransit SignalR service to work.

I ended up using a static hub reference as described here.

Basically, I am just calling Core DI to get my hub context, then store it into a static property (as in the sample in the Github issue listed above).

When needed, I call the reference from within my MassTransit Consumer, and I am done.