Chip - A subject registry library

Chip is a performant local registry that can hold to a set of subjects to later retrieve or dispatch tasks to.

Example

Lets assemble a simple counter actor:

import gleam/erlang/process
import gleam/otp/actor

pub type Message {
  Inc
  Current(client: process.Subject(Int))
}

fn loop(message: Message, count: Int) {
  case message {
    Inc -> {
      actor.continue(count + 1)
    }

    Current(client) -> {
      process.send(client, count)
      actor.continue(count)
    }
  }
}

We start our registry and create new instances of the counter:

import chip
import gleam/otp/actor

pub fn main() {
  let assert Ok(registry) = chip.start()

  let assert Ok(counter_1) = actor.start(0, loop)
  let assert Ok(counter_2) = actor.start(0, loop)
  let assert Ok(counter_3) = actor.start(0, loop)

  chip.register(registry, chip.new(counter_1) |> chip.tag(1))
  chip.register(registry, chip.new(counter_2) |> chip.tag(2))
  chip.register(registry, chip.new(counter_3) |> chip.tag(3))
  
  process.sleep_forever()
}

Later, we may retrieve a member:

let assert Ok(counter) = chip.find(registry, 2)
let assert 0 = actor.call(counter, Current(_), 10)

Or dispatch a task to all members or group:

chip.dispatch(registry, fn(counter) {
  actor.send(counter, Inc)
}) 

let assert Ok(counter) = chip.find(registry, 2)
let assert 1 = actor.call(counter, Current(_), 10)

Chip will also automatically delist dead processes.

The road towards V1

Feature-wise this is near beign complete. Still planning to integrate:

• Adjust the API to be more in-line with other Registry libraries like elixir’s Registry, erlang’s pg or Syn.
• Document modules.
• Basic test case scenarios.
• Should play well with gleam style of supervisors.
• Document guides and use-cases.
• Build a benchmark that measures performance.
• Build a benchmark that measures memory consuption.
• Implement an ETS backend.
• Benchmark in-process backend vs ETS backend.

Couple of adjustments and cleanup left for V1!

Tentative features

• A broadcast(registry, message) function to send message types to subjects.
• Add metadata field to be set when a subject is registered or dispatched to.

Previous Art and other Gleam registry alternatives

This registry takes and combines some ideas from Elixir’s Registry, Erlang’s pg and Syn.

Singularity is a gleam library that offers registry capabilities but focusing more on singleton actors, therefore it is better suited for keeping track of actors that need to be passed around as configuration through your app.

Installation

gleam add chip