A Gleam actor registry that manages actors by key, similar to Discord's gen_registry in Elixir. It provides a way to look up or start actors on demand ensuring only one actor exists per key, while automatically cleaning up dead processes.
gleam add reki
import gleam/erlang/process import gleam/list import gleam/option import gleam/otp/actor import gleam/otp/static_supervisor as supervisor import reki pub type ChannelMsg { Subscribe(process.Subject(String)) Publish(String) } pub type ChannelState { ChannelState(name: String, subscribers: List(process.Subject(String))) } fn start_channel(name: String) { actor.new(ChannelState(name:, subscribers: [])) |> actor.on_message(fn(state, msg) { println("Channel" <> state.name <> " received message: " <> inspect(msg)) case msg { Subscribe(sub) -> actor.continue(ChannelState(..state, subscribers: [sub, ..state.subscribers])) Publish(text) -> { list.each(state.subscribers, process.send(_, text)) actor.continue(state) } } }) |> actor.start } pub fn main() { let channels = reki.new() let assert Ok(_) = supervisor.new(supervisor.OneForOne) |> supervisor.add(reki.supervised(channels)) |> supervisor.start let assert Ok(general) = reki.lookup_or_start(channels, "general", start_channel) let inbox = process.new_subject() process.send(general, Subscribe(inbox)) process.send(general, Publish("Hello!")) let assert Ok(same_channel) = reki.lookup_or_start(channels, "general", start_channel) process.send(same_channel, Publish("Also hello!")) // You can also lookup without starting case reki.lookup(channels, "general") { option.Some(channel) -> process.send(channel, Publish("Found it!")) option.None -> { // channel not found ... todo } } }
Like gen_registry, reki is an Erlang gen_server that stores {key, subject} mappings in ETS for fast O(1) lookups. The gen_server serializes "lookup or start" operations to prevent races when multiple processes request the same key simultaneously.
- Fast reads: Existing actors are looked up directly from ETS, bypassing the gen_server
- Automatic cleanup: The registry links to child processes and traps exits, removing entries from ETS when they die
- Concurrent safety: Start operations are serialized through the gen_server