Engine

The central orchestrator of a iii system — routes triggers to workers, manages modules, and tracks all registered functions.

The Engine is the central orchestrator of a iii system. It maintains a registry of every connected Worker and every registered Function, and routes trigger() calls to the correct Worker — regardless of language, location, or runtime.

Responsibilities

Responsibility	Description
Function registry	Tracks all `registerFunction` calls across connected Workers
Worker registry	Tracks connected Workers, their status, and metadata
Trigger dispatch	Receives `trigger()` (sync or fire-and-forget via `TriggerAction.Void()`) and routes to the correct Worker
Module orchestration	Loads and initializes Modules from `iii-config.yaml`
Worker cleanup	When a Worker disconnects, automatically removes all its registered functions and triggers

Configuration

The Engine is configured via iii-config.yaml at the root of your project.

Ports

The Engine uses two separate ports:

Port	Default	Purpose
Engine WebSocket	`49134`	Workers connect here via the SDK
HTTP API	`3111`	HTTP endpoints registered by the HTTP module

port: 49134   # WebSocket bridge port — workers connect here

modules:
  - class: modules::rest_api::RestApiModule
    config:
      port: 3111   # HTTP port for registered endpoints

  - class: modules::state::StateModule
    config:
      adapter:
        class: modules::state::adapters::KvStore
        config:
          store_method: file_based
          file_path: ./data/state

  - class: modules::queue::QueueModule
    config:
      adapter:
        class: modules::queue::BuiltinQueueAdapter

  - class: modules::observability::ObservabilityModule
    config:
      exporter: memory

Discovery

The Engine exposes built-in functions for querying the current system state:

// All registered functions across all workers
const functions = await iii.listFunctions()
// or: await iii.trigger({ function_id: 'engine::functions::list', payload: {} })

// All connected workers and their status
const workers = await iii.listWorkers()
// or: await iii.trigger({ function_id: 'engine::workers::list', payload: {} })

Worker Disconnect Cleanup

When a Worker disconnects — whether cleanly or due to a crash — the Engine automatically:

Removes all functions the Worker registered
Cancels all in-flight invocations routed to that Worker
Unregisters all triggers bound to that Worker's functions
Fires the engine::workers-available trigger to notify other Workers

Workers reconnect automatically via the SDK's built-in reconnection logic. On reconnect, all registerFunction and registerTrigger calls are re-sent automatically.

Architecture Agnostic

iii makes no distinction between cloud providers, colocated servers, serverless functions, or different languages. A Function registered on Worker A can trigger() a Function on Worker B without knowing where Worker B is running.