Functions & Triggers

Comparable to: Serverless function runtimes, Lambda, Cloud Functions

Key Concepts

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

A Function is an async handler registered with a unique ID
A Trigger binds an event source to a function — types include http, queue, cron, state, stream, and subscribe
Functions invoke other functions via
```
trigger()
```
regardless of language or worker location
The engine handles serialization, routing, and delivery automatically
HTTP-invoked functions wrap external endpoints as callable function IDs
Functions can declare request/response formats for documentation and discovery — auto-generated from types in Rust (via
```
schemars::JsonSchema
```
) and Python (via type hints / Pydantic), or manually provided in Node.js

Architecture

registerWorker()

connects the worker to the engine,

registerFunction

defines handlers,

registerTrigger

binds event sources to those handlers, and the engine routes incoming events to the correct function. Functions can invoke other functions across workers and languages via

trigger()

iii Primitives Used

Primitive	Purpose
`registerWorker(url, options?)`	Connect worker to engine
`registerFunction({ id }, handler)`	Define a function handler
`registerTrigger({ type, function_id, config })`	Bind an event source to a function
`trigger({ function_id, payload })`	Invoke a function synchronously
`trigger({ ..., action: TriggerAction.Void() })`	Fire-and-forget invocation
`trigger({ ..., action: TriggerAction.Enqueue({ queue }) })`	Durable async invocation via queue

Reference Implementation

TypeScript: ../references/functions-and-triggers.js
Python: ../references/functions-and-triggers.py
Rust: ../references/functions-and-triggers.rs

Each reference shows the same patterns (function registration, trigger binding, cross-function invocation) in its respective language.

Common Patterns

Code using this pattern commonly includes, when relevant:

registerWorker('ws://localhost:49134', { workerName: 'my-worker' })

— connect to the engine

registerFunction({ id: 'namespace::name' }, async (input) => { ... })

— register a handler

registerTrigger({ type: 'http', function_id, config: { api_path, http_method } })

— HTTP trigger

registerTrigger({ type: 'queue', function_id, config: { topic } })

— queue trigger

registerTrigger({ type: 'cron', function_id, config: { expression } })

— cron trigger

registerTrigger({ type: 'state', function_id, config: { scope, key } })

— state change trigger

registerTrigger({ type: 'stream', function_id, config: { stream } })

— stream trigger

registerTrigger({ type: 'subscribe', function_id, config: { topic } })

— pubsub subscriber

Cross-language invocation: a TypeScript function can trigger a Python or Rust function by ID

Request/Response Format (Auto-Registration)

Functions can declare their input/output schemas for documentation and discovery:

Rust: Derive
```
schemars::JsonSchema
```
on handler input/output types —
```
RegisterFunction::new()
```
auto-generates JSON Schema (Draft 7) from the type
Python: Use type hints (Pydantic models or primitives) on handler parameters and return types —
```
register_function()
```
auto-extracts JSON Schema (Draft 2020-12)
Node.js: Pass
```
request_format
```
/
```
response_format
```
manually in the registration message (e.g., via Zod's
```
toJSONSchema()
```
)

Adapting This Pattern

Use the adaptations below when they apply to the task.

Replace placeholder handler logic with real business logic (API calls, DB queries, LLM calls)
Use
```
namespace::name
```
convention for function IDs to group related functions
For HTTP endpoints, configure
```
api_path
```
and
```
http_method
```
in the trigger config
For durable async work, use
```
TriggerAction.Enqueue({ queue })
```
instead of synchronous trigger
For fire-and-forget side effects, use
```
TriggerAction.Void()
```
Multiple workers in different languages can register functions that invoke each other by ID

Pattern Boundaries

For HTTP endpoint specifics (request/response format, path params), prefer
```
iii-http-endpoints
```
.
For queue processing details (retries, concurrency, FIFO), prefer
```
iii-queue-processing
```
.
For cron scheduling details (expressions, timezones), prefer
```
iii-cron-scheduling
```
.
For invocation modes (sync vs void vs enqueue), prefer
```
iii-trigger-actions
```
.
Stay with
```
iii-functions-and-triggers
```
when the primary problem is registering functions, binding triggers, or cross-language invocation.

When to Use

Use this skill when the task is primarily about
```
iii-functions-and-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.

iii-functions-and-triggers

NPX Install

Tags

SKILL.md Content