Custom Triggers

Comparable to: Custom event adapters, webhook receivers

Key Concepts

Use the concepts below when they fit the task. Not every custom trigger needs all of them.

• registerTriggerType(id, handler) defines a new trigger type with registerTrigger and unregisterTrigger callbacks
• The handler receives a TriggerConfig containing id, function_id, and config
• When the external event fires, call iii.trigger(function_id, event) to invoke the registered function
• unregisterTriggerType cleans up when the trigger type is no longer needed
• Do not reuse built-in trigger type names: http, cron, queue, state, stream, subscribe

Architecture

External event source (webhook, file watcher, IoT, CDC, etc.)
  → Custom trigger handler (registerTriggerType)
    → iii.trigger(function_id, event)
      → Registered function processes the event

iii Primitives Used

Primitive	Purpose
registerTriggerType(id, handler)	Define a new trigger type with lifecycle hooks
unregisterTriggerType(id)	Clean up a custom trigger type
TriggerConfig: { id, function_id, config }	Configuration passed to the trigger handler
iii.trigger(function_id, event)	Fire the registered function when the event occurs

Reference Implementation

See ../references/custom-triggers.js for the full working example — a custom trigger type that listens for external events and routes them to registered functions.

Also available in Python: ../references/custom-triggers.py

Also available in Rust: ../references/custom-triggers.rs

Common Patterns

Code using this pattern commonly includes, when relevant:

• registerWorker(url, { workerName }) — worker initialization
• registerTriggerType(id, { registerTrigger, unregisterTrigger }) — define the custom trigger
• registerTrigger(config) — called by iii when a function subscribes to this trigger type
• unregisterTrigger(config) — called by iii when a function unsubscribes
• iii.trigger(config.function_id, eventPayload) — fire the target function
• Cleanup logic in unregisterTrigger (close connections, remove listeners, clear intervals)
• const logger = new Logger() — structured logging

Adapting This Pattern

Use the adaptations below when they apply to the task.

• Choose a unique trigger type name that describes your event source (e.g. file-watcher, mqtt, db-cdc)
• In registerTrigger, start the listener (open socket, poll endpoint, subscribe to topic)
• In unregisterTrigger, tear down the listener to avoid resource leaks
• Store active listeners in a map keyed by config.id for clean unregistration
• Pass relevant event data in the payload when calling iii.trigger(function_id, event)

Pattern Boundaries

• If the task uses built-in HTTP routes, prefer iii-http-endpoints.
• If the task uses built-in cron schedules, prefer iii-cron-scheduling.
• If the task uses built-in queue triggers, prefer iii-queue-processing.
• Stay with iii-custom-triggers when iii has no built-in trigger type for the event source.

When to Use

• Use this skill when the task is primarily about iii-custom-triggers in the iii engine.
• Triggers when the request directly asks for this pattern or an equivalent implementation.

Boundaries

• Never use this skill as a generic fallback for unrelated tasks.
• You must not apply this skill when a more specific iii skill is a better fit.
• Always verify environment and safety constraints before applying examples from this skill.