Rask.Outbox 0.23.1-alpha.0.271

Rask.Outbox

A transactional outbox for Rask.Data aggregates. It runs a handler durably, on the app's own database, with no broker or Redis.

• Give a handler IDurableHandler<T> and the event is written to an OutboxMessage table in the same transaction as the change that raised it. It is never lost, and it never fires for a change that rolled back. Plain IEventHandler<T>s of the same event keep running in memory; each handler chooses.
• A background OutboxProcessor is woken by every save that wrote rows and runs each row's handler, at least once, with retries and an attempt count. Each durable handler is its own row, retried on its own.
• Published messages are purged after Retention (default 7 days) so the table doesn't grow forever. Dead letters are never purged, because they have no ProcessedAt for the predicate to match.
• Metrics on the Rask.Outbox meter: processed / failed / dead-lettered counters, a duration histogram, and pending / dead-letter gauges. rask.outbox.deadletters is the one to alert on.

Use

[LocalOnly]                                                    // only the server says a sale happened
public sealed record OrderPlaced(Guid Id) : IEvent;           // raised on your aggregate

public sealed class SendReceipt : IDurableHandler<OrderPlaced>
{
    public Task Handle(OrderPlaced e) => …;                    // through the outbox: atomic, retried
}

// Program.cs
builder.Services.AddRaskCqrs();
builder.Services.AddRaskOutbox<AppDbContext>(o => o.PollInterval = 5.Seconds);

builder.Services.AddDbContextFactory<AppDbContext>((sp, o) => o
    .UseSqlite("Data Source=app.db")
    .AddInterceptors(sp.GetServices<ISaveChangesInterceptor>()));

// AppDbContext.OnModelCreating
modelBuilder.AddRaskOutbox(); // maps the OutboxMessage table

In a multi-tenant app each message records the tenant the change was saved in, and the processor re-enters it before running the handler, so a handler reading a tenant-scoped table sees that tenant. The user travels the same way (Current.UserId), and Jobs.Enqueue(…) or Mail.Send(…) work inside a handler. OutboxMessage.Where(…) queries the table with no context of your own.

Server-side. The processor is a hosted BackgroundService and the store is your EF Core database (SQLite by default). Part of the Rask framework. MIT licensed.