BuildingBlocks.EventBus

public interface IEventBus
{
    Task PublishAsync(IntegrationEvent @event, CancellationToken cancellationToken = default);
}

public static IEventBusBuilder AddMassTransitSubscription<T, TH>(this IEventBusBuilder builder)
    where T : IntegrationEvent
    where TH : class, IIntegrationEventHandler<T>
{
    // BuildingBlocks.EventBus registry'sine ekler (KeyedService + EventTypes)
    EventBusBuilderExtensions.AddSubscription<T, TH>(builder);
    // MassTransit consumer'ını scope'a kaydeder
    builder.Services.AddScoped<IntegrationEventConsumer<T>>();
    return builder;
}

// Program.cs
builder.Services
    .AddMassTransitRabbitMqEventBus(builder.Configuration, x =>
    {
        // EF Outbox — MassTransit.EntityFrameworkCore
        // messaging.outbox_message / outbox_state / inbox_state tabloları
    })
    .AddMassTransitSubscription<UserCreatedIntegrationEvent, SendWelcomeEmailHandler>()
    .AddMassTransitSubscription<UserCreatedIntegrationEvent, NotifyAdminHandler>();

{
  "EventBus": {
    "SubscriptionClientName": "DiyanetCleanArchitecture",
    "ConcurrentMessageLimit": 10
  },
  "MassTransitRabbitMq": {
    "Host": "rabbitmq",
    "VirtualHost": "/",
    "Username": "guest",
    "Password": "guest",
    "ExchangeName": "integration_event_bus",
    "ExchangeType": "topic",
    "RoutingKeyPrefix": "integration.event",
    "RetryCount": 3,
    "RetryIntervalSeconds": 2,
    "RedeliveryIntervalsMinutes": [0.16, 1, 5]
  }
}

// Event tanımı (Contracts.Events'te)
public class UserCreatedIntegrationEvent : IntegrationEvent
{
    public Guid UserId { get; set; }
    public string Email { get; set; } = default!;

    public UserCreatedIntegrationEvent() { }
    public UserCreatedIntegrationEvent(Guid userId, string email)
        => (UserId, Email) = (userId, email);
}

// Yayınlama — domain event handler'dan (UserCreatedDomainEventHandler)
public class UserCreatedDomainEventHandler(IEventBus bus)
    : INotificationHandler<UserCreatedDomainEvent>
{
    public Task Handle(UserCreatedDomainEvent e, CancellationToken ct)
        => bus.PublishAsync(new UserCreatedIntegrationEvent(e.UserId, e.Email), ct);
}

// Tüketme — idempotent
public class SendWelcomeEmailHandler(IEmailService email)
    : IIntegrationEventHandler<UserCreatedIntegrationEvent>
{
    public async Task Handle(UserCreatedIntegrationEvent @event)
    {
        if (string.IsNullOrEmpty(@event.Email)) return;
        await email.SendWelcomeAsync(@event.Email);
    }
}