CleanMessageBus.Abstractions 2.0.1

CleanMessageBus

This package provides an abstraction layer for message busses for easy integration of events.

Publishing Events

• Event object must inherit from class Integrationevent for integration events ot DomainEvent for domain events

• Inject IMessageBus to desired service

• Publish event by using IMessageBus.PublishAsync(event)

• Automatic creation of producer resource on message bus

• Example:

public class UserRegisteredEvent(string Username, string Email) : Integrationevent;

var integrationEvent = new UserRegisteredEvent("JohnDoe", "john@doe.com");
await messageBus.PublishAsync(integrationevent);

Change event name name

• Use attribute [EventName(<Name>)] to set producer name

Handling Events

• Handler must inherit from IntegrationEventHandlerBase<TIntegrationEvent> class for integration events or from DomainEventHandlerBase<TDomainEvent> for domain events
• Integration event handlers must specify the name of the application, that published the event using the [SourceApplication(<Name>)] attribute. This is not allowed for domain event handlers, as the application of the event and the event handler must match.
• Generic type specifies domain event type to receive
• Implementation logic must be implemented in the Handle method
• Registration happens automatically via dependency injection
• Integration of CleanDomainValidation result types

Example:

[SourceApplication("MyApp.Authorization")]
public class UserRegisteredEventHandler : IntegrationEventHandlerBase<UserRegisteredEvent>
{
    public override async Task<CanFail> Handle(UserRegisteredEvent @event, CancellationToken cancellationToken)
    {
        Console.WriteLine($"User {@event.Username} with email {@event.Email} has been registered.");
        
        //TODO furhter logic in here
        
        return CanFail.Success;
    }
}

Change event handler name

• Use attribute [EventHandlerName(<Name>)] to set event handler name

Use serialized message handling

• Ideal for long running / rate limited tasks, that should be split across multiple instances
• Use attribute [Serialized(MaxQueueSize = 1)] to set the max amount of messages that is being loaded in the application simultaniously
• Event handlers with this attribute are only called if the previous handler has completed processing the event
• Rate limiting may be implemented in the handler itself

Configuration via dependency injection

• Define assemblies containing events and handlers
• Define name of the current application (defaults to name of the entry assembly)
• Select and configure message broker

Example:

builder.Services.AddCleanMessageBus(config => config
    .WithApplicationName("MyApp")
    .RegisterIntegrationEventsFromAssembly(Assembly.GetExecutingAssembly())
    .RegisterDomainEventsFromAssemby(Assembly.GetExecutingAssembly())
    .RegisterHandlersFromAssemby(Assembly.GetExecutingAssembly())
    .Use... //Use concrete implementation like rabbbitmq