Module messaging 

Event consumer mesh — the inbound half of the event architecture.

The transactional outbox (data::outbox) made producing events safe; this module gives consuming them the same framework-grade guarantees, with NestJS-style ergonomics:

pub struct OrderEventsConsumer;

#[EventConsumer]
impl OrderEventsConsumer {
    #[EventPattern("order.confirmed")]
    async fn on_confirmed(ctx: EventContext) -> Result<(), String> {
        let evt: OrderConfirmed = ctx.payload()?;
        ctx.inject::<InventoryService>().reserve(evt.order_id).await
    }
}

Guarantees

• Frozen dispatch — #[EventPattern] handlers register through inventory (the same link-time mechanism as #[Controller]); the topic→handler map is built once at runtime start and never mutated.
• At-least-once + dedupe — when an IdempotencyStore is in the DI container, each idempotency_key is consumed exactly once per TTL.
• Bounded retries → DLQ — a failing message is nacked and retried up to max_retries, then dead-lettered with the failure reason; one poison message can never wedge a topic.
• Trace continuity — the envelope’s traceparent (stamped by the outbox producer) becomes this hop’s parent span; async hops chain in the trace UI instead of starting orphan roots.

The transport (Kafka / AMQP / NATS / in-process bridge) is app-provided via MessageTransport — the same boundary rule as every other driver.

Re-exports

pub use runtime::ConsumerRuntime;

Modules

event

In-process async event bus — actually lock-free on the emit path.

runtime

Consumer runtime: poll → dedupe → dispatch → ack / retry / dead-letter.

Structs

EventContext

What an #[EventPattern] handler receives — DI + payload + trace, no HTTP types anywhere.

EventHandlerDescriptor

Static descriptor emitted by the #[EventPattern] expansion and collected at link time — the runtime freezes these into its dispatch map at start.

InboundMessage

One inbound message, transport-agnostic.

Enums

EventError

What the mesh should do with a failed message. Handlers may keep returning Result<(), String> (strings convert to EventError::Retry) or return EventError directly to decide the message’s fate:

Traits

MessageTransport

Type Aliases

BoxError

App-provided broker adapter (Kafka / AMQP / NATS / in-process bridge). Boxed error for infrastructure trait contracts (transports, sinks, publishers). String and &str convert via .into(), so simple implementations stay simple while real ones keep their source chain.