PubSub

Mistweaver's PubSub is built on Erlang's pg (process groups) module. Processes subscribe to named topics and receive messages when any process broadcasts to that topic.

Starting PubSub

Call pubsub.start() once at application boot, before mistweaver.start:

pub fn main() {
  pubsub.start()
  let assert Ok(_) = mistweaver.new_config() |> mistweaver.start(router)
  process.sleep_forever()
}

Subscribe and broadcast

import mistweaver/pubsub

// Subscribe the current process
pubsub.subscribe("room:lobby")

// Broadcast to all subscribers
pubsub.broadcast("room:lobby", MyMessage("hello"))

Messages arrive as raw Erlang messages {pubsub, topic, message}. Use process.new_selector() and process.selecting_anything to receive them in a typed actor.

Unsubscribe

pubsub.unsubscribe("room:lobby")

Dead processes are cleaned up automatically by the pg module — no manual cleanup needed when a process crashes.

LiveView integration

Subscribe a LiveView process in init and dispatch incoming messages as component updates:

pub fn init(user_id: Int) -> #(Model, lustre.Effect(Msg)) {
  let effect = lustre.effect(fn(_dispatch) {
    pubsub.subscribe("user:" <> int.to_string(user_id))
  })
  #(Model(...), effect)
}