AxisBus 2.2.0

AxisBus — Documentation

🌐 Português (documentação navegável)

A one-method event bus port — IAxisBus.PublishAsync<TEvent>(@event, params topics) returning an AxisResult that aggregates every handler failure. Drop in AxisMemoryBus for in-process broadcasting; swap it for a Kafka, RabbitMQ, Service Bus or transactional-outbox adapter without touching application code.

public Task<AxisResult<CreateOrderResponse>> HandleAsync(CreateOrderCommand cmd)
    => orderFactory.CreateAsync(cmd)
        .ThenAsync(order => bus.PublishAsync(new OrderCreatedEvent(order.OrderId)))   // enqueue in the outbox…
        .ThenAsync(order => unitOfWork.SaveChangesAsync())                            // …then one commit persists the order AND the event
        .MapAsync(order => new CreateOrderResponse { OrderId = order.OrderId });

The event never leaves the unit of work. With an outbox adapter (see Custom adapter), PublishAsync enqueues the event on the unit of work's connection before the commit — the single SaveChangesAsync then persists the state change and the event together, atomically, or neither. There is no commit-then-publish dual-write, so the classic race — state committed but the event lost, or the event broadcast for a state change that then rolls back — cannot happen. In-memory fan-out for tolerant side effects (cache, email) is a separate role → see PublishAsync.

Use this page as a map: read the trunk below (~5 min) and jump straight to the detail of the group you need — without reading hundreds of lines.

The trunk (read first)

The interface in 60 seconds

public interface IAxisBus
{
    Task<AxisResult> PublishAsync<TEvent>(TEvent @event, params string[] topics)
        where TEvent : IAxisEvent;
}

One method. The bus fans the event out to every registered IAxisEventHandler<TEvent>, runs them in parallel, and aggregates the results with AxisResult.Combine — every handler's errors are surfaced together. Routing details (topics, partition keys, exchanges) are the adapter's problem, not the caller's. → The IAxisBus contract

Events and handlers

The contracts come from AxisMediator:

public interface IAxisEvent
{
    string? OrderingKey => null;   // optional; the durable outbox's FIFO partition key
}

public interface IAxisEventHandler<in TEvent> where TEvent : IAxisEvent
{
    Task<AxisResult> HandleAsync(TEvent @event);
}

Define a record that implements IAxisEvent, write a handler for it, register it in DI, and the bus picks it up. → Defining events and handlers

In-memory adapter

AxisMemoryBus registers IAxisBus against in-process handlers, runs them in parallel and aggregates their results:

services.AddAxisMemoryBus();   // wires IAxisBus → MemoryBusAdapter + scans for handlers

→ AxisMemoryBus adapter

Durable outbox adapter (bundled)

AxisBus.Repository ships a production-ready transactional outbox over Postgres/MySQL: publishing enqueues on the unit of work, a commit drains it atomically with the business state, and a background dispatcher delivers it after the commit — no status column, claim-by-lease, at-least-once:

services.AddAxisBusPostgres(new AxisBusRepositorySettings { ConnectionString = "..." });   // or AddAxisBusMySql

→ API reference (see "Durable outbox adapter")

Installation

dotnet add package AxisBus           # the abstraction (depends on AxisResult)
dotnet add package AxisMemoryBus     # in-process adapter

→ Full guide: Getting started

The map (jump to what you need)

Start here: Getting started · The IAxisBus contract · Why AxisBus?

Fundamentals: Publish · PublishAsync · Defining events and handlers · AxisMemoryBus adapter

Reference & extras: Custom adapter · API reference

Design principles

1. One method. A publish-only port keeps the application out of the transport's vocabulary. Subscriptions live in the adapter or the broker, not in the abstraction.
2. Errors aggregate, not crash. Every handler's failure becomes an entry in the combined AxisResult. The publisher sees the whole picture, not the first thing that blew up.
3. Handlers run in parallel. The in-memory adapter awaits all handlers concurrently. Side effects must be independent.
4. Routing belongs to the adapter. Topics, partition keys and exchanges are vendor concepts. The port accepts a params string[] topics so callers can hint, but interpretation is the adapter's call.
5. Events are dumb records. IAxisEvent is a marker interface. Add the fields the consumers need; nothing more.
6. Domain events ride the unit of work. A domain event is staged inside the transaction that persists the state change — an outbox adapter writes the event row on the same connection, and the commit makes both durable atomically. Never SaveChanges first and Publish after: that dual-write can commit the state while losing the event. In-memory fan-out is reserved for post-commit side effects that tolerate loss.

License

Apache 2.0