Modules

Modules are the interface between the Engine and the rest of the application.

Modules are the interface between the Engine and the rest of the application. They are responsible for establishing connections to services, implementing trigger types, and supplying application Context.

Every capability in iii (HTTP endpoints, cron scheduling, state management, queues, streams, observability) is implemented as a Module. This modular architecture means the Engine itself stays small and focused on orchestration, while Modules handle all external concerns.

Built-in Modules

Module	Provides	Config key
HTTP	HTTP trigger type, request/response handling	rest_api
Queue	Async message processing with retries	queue
Cron	Scheduled task execution	cron
State	Key-value state storage with atomic updates	state
Stream	Real-time data streams with WebSocket push	stream
PubSub	Publish/subscribe messaging	pubsub
Observability	Structured logging, tracing, and metrics	observability
Exec	Shell command execution	exec
Bridge	WebSocket bridge for SDK connections	bridge

How Modules Work

A Module has two responsibilities:

1. Register trigger types: A Module can introduce new ways to invoke Functions. For example, the HTTP module registers the http trigger type, and the Cron module registers the cron trigger type.

2. Supply Context: A Module can add capabilities to the Context object that gets passed to every Function. For example, the State module adds state::get, state::set, and other state operations.

Modules are configured in config.yaml (the engine default). Use -c iii-config.yaml to specify a custom path:

modules:
  - class: modules::api::RestApiModule
    config:
      port: 3111
      host: 0.0.0.0
  - class: modules::state::StateModule
    config:
      adapter:
        class: modules::state::adapters::KvStore
        config:
          store_method: in_memory
  - class: modules::queue::QueueModule
    config:
      adapter:
        class: modules::queue::BuiltinQueueAdapter
        config:
          store_method: in_memory

You can build your own Modules to integrate any service or infrastructure. See Custom Modules for a detailed guide.