Queue Publishers

External event publishing.

The queue module provides the EventPublisher trait and two feature-gated implementations for publishing AgentEvent values to external message brokers.

EventPublisher trait

#[async_trait]
pub trait EventPublisher: Send + Sync {
    async fn publish(&self, event: &AgentEvent) -> Result<(), QueueError>;
    async fn health_check(&self) -> Result<(), QueueError>;
}

Backends

Backend	Feature	Mechanism
NATS	nats + queue	NATS JetStream publish per run
Redis Streams	redis + queue	XADD per run stream
No-op	queue (core)	Discards events (for testing)

How it works

A tokio::spawn task enqueues a PublishToQueue job after each event is persisted. The publisher receives the event and pushes it to the configured broker. Failures are logged and counted; the run loop does not block on publish failures.

When to use

• Fan-out observability to external systems.
• Triggering downstream workflows on run completion.
• Cross-instance event synchronisation.

See also

• AgentEvent — the event type.
• Feature Flags — the queue and nats features.