Masstransit channels

Question

I configured MassTransit on my .NET core application as follows:

public void ConfigureServices(IServiceCollection services)
{
    [...]

    // producer
    services.AddMassTransit(x =>
    {
        x.AddBus(provider => Bus.Factory.CreateUsingRabbitMq(cfg =>
        {    
            cfg.Host(new Uri(_configuration["RabbitMQ:URI"] + _configuration["RabbitMQ:VirtualHost"]), $"ENG {_configuration["SiteID"]} Producer", h =>
            {
                h.Username(_configuration["RabbitMQ:UserName"]);
                h.Password(_configuration["RabbitMQ:Password"]);
            });

            cfg.Publish<NormUpdate>(x =>
            {
                x.Durable = true;
                x.AutoDelete = false;
                x.ExchangeType = "fanout"; // default, allows any valid exchange type
            });
            cfg.ConfigurePublish(x => x.UseExecute(x => 
            { 
                x.Headers.Set("SiteID", _configuration["SiteID"]); 
            }));
        }));
    });

    services.AddMassTransit<ISecondBus>(x =>
    {
        x.AddConsumer<NormConsumer>();
        x.AddBus(context => Bus.Factory.CreateUsingRabbitMq(cfg =>
        {
            cfg.UseMessageRetry(r => r.Intervals(100, 200, 500, 800, 1000));
            cfg.Host(new Uri(_configuration["RabbitMQ:URI"] + _configuration["RabbitMQ:VirtualHost"]), $"ENG {_configuration["SiteID"]} Consumer", h =>
            {
                h.Username(_configuration["RabbitMQ:UserName"]);
                h.Password(_configuration["RabbitMQ:Password"]);
            });

            cfg.ReceiveEndpoint($"norm-queue-{_configuration["SiteID"]}", e =>
            {
                e.Durable = true;
                e.AutoDelete = false;
                e.Consumer<NormConsumer>(context);
                e.UseConcurrencyLimit(1);
                e.ExchangeType = "fanout";
                e.PrefetchCount = 1;
            });
        }));
    });

    services.AddOptions<MassTransitHostOptions>().Configure(options =>
    {
        options.WaitUntilStarted = false;
        options.StopTimeout = TimeSpan.FromSeconds(30);
    });

[...]
}

public interface ISecondBus : IBus
{
}

I noticed that when connections are created, the consumer connection has 2 channels. Channel (1) with no attached consumers, channel (2) with one consumer.

I expected to have only one channel on receiver. Is this a normal behavior or am I doing something wrong?

Answer 1

You should have three channels:

1. One for the first bus you configured
2. One for the second bus you configured (MultiBus configures completely separate bus instances, nothing is shared)
3. One for the receive endpoint on the second bus you configured.

1 + 1 + 1 = 3

Q.E.D.

Yes, I was in Math club back in primary school.