iii-pubsub

Topic-based publish/subscribe messaging. Publish an event to a named topic with the publish engine function and every registered subscribe trigger whose topic matches gets invoked with the raw payload — no envelope, no persistence, no retries. The worker is fire-and-forget broadcast: subscribers receive each event as it arrives, missed events are gone.

The worker exposes one callable function (publish, no namespace prefix — the function id is literally the string "publish") and one trigger type (subscribe). Two adapters: local (in-memory broadcast channels; only delivers to subscribers running in this engine process; no external dependencies) and redis (redis_url: ${REDIS_URL:redis://localhost:6379}; uses Redis Pub/Sub so events propagate across multiple engine instances).

This worker is the right tool for real-time notifications that consumers may miss without consequence (UI live updates, ephemeral signals, telemetry mirroring). For reliable fan-out with retries and dead-letter handling, use the iii-queue worker's topic-based queue mode instead. The trade-off summary: iii-pubsub is broadcast to every subscriber, no persistence, no ordering, fire-and-forget — best for real-time notifications and ephemeral fan-out. The queue worker's topic mode is fan-out with retries and DLQ, FIFO within a topic, and durable delivery — best for reliable fan-out where every consumer must process every event.

• publish function — broadcast an event to a topic. Empty topic returns topic_not_set.
• subscribe trigger — register a function to fire on every publish to a configured topic.

How-tos

publish

• publish — broadcast an event to a topic so every registered subscriber receives the payload.

subscribe triggers

• React to topic publishes — register a subscribe trigger to invoke a handler on every publish to a configured topic; the handler receives the raw data value directly.