Using Server-send Events with Rails

create.js.coffee

document.getElementById('new_message').reset()

development.rb

Hermes::Application.configure do
  config.cache_classes = true
  config.eager_load = true
end

Gemfile

gem 'puma'
gem 'redis'

index.html.erb

<ul id="messages">
  <%= content_tag_for :li, @messages do |message| %>
    <%= message.content %>
    <%= link_to "Destroy", message, method: :delete, remote: true %>
  <% end %>
</ul>

<%= form_for Message.new, remote: true do |f| %>
  <%= f.text_field :content, autofocus: true, autocomplete: 'off' %>
<% end %>

messages.js.coffee

source = new EventSource('/messages/events')

source.addEventListener 'messages:create', (e) ->
  message = JSON.parse(e.data)
  li = document.createElement('li')
  li.id = "message_#{message.id}"
  li.className = 'message'
  li.innerText = message.content
  document.getElementById('messages').appendChild(li)
  
source.addEventListener 'messages:destroy', (e) ->
  message = JSON.parse(e.data)
  document.getElementById("message_#{message.id}").remove()

messages_controller.rb

class MessagesController < ApplicationController
  include ActionController::Live

  def index
    response.headers['Content-Type'] = 'text/html'
    @messages = Message.all
  end

  def create
    response.headers['Content-Type'] = 'text/javascript'
    message = Message.create!(message_params)
    redis_publish message
  end
  
  def destroy
    response.headers['Content-Type'] = 'text/javascript'
    message = Message.find(params[:id]).tap(&:destroy!)
    redis_publish message
    head :ok
  end

  def events
    response.header['Content-Type'] = 'text/event-stream'
    redis = Redis.new
    redis.psubscribe('messages:*') do |on|
      on.pmessage do |pattern, event, data|
        response.stream.write "event: #{event}\n"
        response.stream.write "data: #{data}\n\n"
      end
    end
  rescue IOError
    logger.info "Stream Closed"
  ensure
    response.stream.close
  end

  private

  def message_params
    params.require(:message).permit(:content)
  end
  
  def redis_publish(message)
    $redis.publish "messages:#{action_name}", message.to_json
  end
end

redis.rb

$redis = Redis.new(host: 'localhost', port: 6379)

routes.rb

Hermes::Application.routes.draw do
  resources :messages do
    collection { get :events }
  end
end