There are many ways to configure MassTransit consumers and register them. A nice way I've found is to create an extension class and setup MassTransit configuration.

In this post I'll show how to register a consumer using the AddConsumer method and have a separate class for the consumer definition so I can configure it individually.

Configuration extension

Use ServiceCollection extension pattern to keep the host builder clean and tidy.

public static class MassTransit
{
    public static void AddMassTransitConfiguration(this IServiceCollection services)
    {
        services.AddMassTransit(x =>
        {
            x.AddConsumer<ProcessBurgerOrderConsumer>(typeof(ProcessBurgerOrderConsumerDefinition));

            x.UsingRabbitMq((context, cfg) =>
            {
                cfg.Host("rabbitmq", "/", h =>
                {
                    h.Username("guest");
                    h.Password("guest");
                });

                cfg.ConfigureEndpoints(context);
            });
        });
    }
}

Consumer definition

Create a consumer definition.

public class SubmitBurgerOrderConsumerDefinition : ConsumerDefinition<SubmitBurgerOrderConsumer>
{
    public SubmitBurgerOrderConsumerDefinition()
    {
        // limit the number of messages consumed concurrently
        // this applies to the consumer only, not the endpoint
        ConcurrentMessageLimit = 8;
    }

    protected override void ConfigureConsumer(
      IReceiveEndpointConfigurator endpointConfigurator,
      IConsumerConfigurator<SubmitBurgerOrderConsumer> consumerConfigurator)
    {
        // configure message retry with millisecond intervals
        endpointConfigurator.UseMessageRetry(r => r.Intervals(100, 200, 500, 800, 1000));

        // use the outbox to prevent duplicate events from being published
        endpointConfigurator.UseInMemoryOutbox();
    }
}

Hook up

Simply bring it all together.

public class Program
{
    public static void Main(string[] args)
    {
        CreateHostBuilder(args).Build().Run();
    }

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureServices((hostContext, services) =>
            {
                services.AddMassTransitConfiguration();
                services.AddMassTransitHostedService();
            });
  }