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

modules:
  - class: modules::worker::WorkerModule
    config:
      port: 49134  # WebSocket protocol port — workers connect here

  - 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.

For deployment options and production configuration, see Deployment.