StimulusReflex with Standalone ActionCable server

config.ru

# cable/config.ru

require_relative "../config/environment"
Rails.application.eager_load!

app = Rack::Builder.new do
  use Rack::Session::Redis, redis_server: Rails.application.config.cache_store[1][:url], **Rails.application.config.session_options

  map "/" do
    run ActionCable.server
  end
end

run app

connection.rb

# app/channels/application_cable/connection.rb

module ApplicationCable
  class Connection < ActionCable::Connection::Base
    identified_by :current_user

    def connect
      self.current_user = user_from_session
    end

    private

    def user_from_session
      User.find_by(id: user_id)
    end

    def user_id
      connection_session.dig(1, "warden.user.user.key", 0, 0)
    end

    def connection_session
      return {} unless session_id

      ActionDispatch::Session::CacheStore.new(Rails.application).find_session(env, Rack::Session::SessionId.new(session_id))
    end

    def session_id
      env["rack.request.cookie_hash"][Rails.application.config.session_options[:key]]
    end
  end
end

development.rb

# app/config/environments/development.rb

Rails.application.configure do
  ...

  config.action_cable.mount_path = nil
  config.action_cable.url = "http://localhost:28080" # use wss:// in production
end

Gemfile.rb

...
  
gem "redis-rack"

Notes

When you run ActionCable in standalone mode, it's a stripped-down Rack app without all the usual Rails modules and middleware
like ActionDispatch and Rack::Session, so it doesn't load a session object by default, which is needed in StimulusReflex.

This example assumes the use of Redis as session store and devise for authentication.

Passing the user_id in a separate encrypted cookie is no longer necessary (as the suggested in the docs).

Start the standalone server locally with: `bundle exec puma -p 28080 cable/config.ru`

Standalone ActionCable docs here: https://guides.rubyonrails.org/action_cable_overview.html#standalone

The meta tag helper is required: https://guides.rubyonrails.org/action_cable_overview.html#consumer-configuration