Module @prelude/remote-actor

Remote actor module

Talk to an @prelude/actor that lives on the other side of a message boundary — a worker, a MessagePort, a socket — through the same send/ask interface as a local one.

serve(actor, transport) answers frames from the transport.
new RemoteActor(transport) is a Ref: send, ask (with timeout and signal), close.
Frames are plain data; any transport that can carry JSON or structured clones works. fromPort adapts MessagePort-like objects, pair() connects two ends in memory, channel multiplexes several actors over one transport.
Remote handler errors reject ask with a RemoteError carrying the remote error's name, message and code.

Usage

npm i -E @prelude/remote-actor

Serving side (e.g. inside a worker):

import * as Actor from '@prelude/actor'
import * as Remote from '@prelude/remote-actor'

const counter = Actor.of(() => ({ count: 0 }), (message: Message, state) => { /* … */ })
Remote.serve(counter, Remote.fromPort(self))

Calling side:

import * as Remote from '@prelude/remote-actor'

const counter = new Remote.RemoteActor<Message, number>(Remote.fromPort(worker))
await counter.send({ type: 'inc', value: 5 })
console.log(await counter.ask({ type: 'get' }, { timeout: 1000 })) // 5
counter.close()

Several actors over one connection:

Remote.serve(users, Remote.channel(port, 'users'))
Remote.serve(orders, Remote.channel(port, 'orders'))

const users = new Remote.RemoteActor(Remote.channel(port, 'users'))

Transport

interface Transport {
  post(frame: Frame): void | Promise<void>
  subscribe(listener: (frame: Frame) => void): () => void
}

Implement it over anything ordered and bidirectional. RemoteActor and serve ignore frames they do not understand, so a transport may carry other traffic.

Semantics

send resolves when the transport has accepted the frame; delivery is not acknowledged. A message to a stopped remote actor is dead-lettered there.
ask resolves with the handler's return value or rejects with a RemoteError (code: 'remote'), an ActorError (code: 'timeout'), the abort reason, or a RemoteError (code: 'closed') if the client is closed.
Frames from one client stay in issue order.
One RemoteActor per served actor (or per channel key); two clients sharing a channel would collide on ask ids.