Pusher Clone

Pusher is a glitzy websockets service for pushing messages from server to clients. I wondered how difficult it would be to copy their syntax.

The Clone

The server is a ruby rack application that must be run or mounted. It is accessed globally just like the real Pusher.

# config.ru

require 'faye'

class Pusher
  
  @server = Faye::RackAdapter.new(mount: '/faye', timeout: 25)
  
  def self.call(env)
    @server.call(env)
  end
  
  def self.trigger(channel, event, data = nil)
    @server.get_client.publish("/#{channel}", event: event, data: data)
  end
  
end

Assuming we're listening on 9292, the following code will get websockets working on the client.

var faye = new Faye.Client('http://localhost:9292/faye');
window.pusher = {
  subscribe: function(channel) {
    var handlers = {};
    faye.subscribe('/' + channel, function(message) {
      handlers[message.event](message.data);
    });
    function bind(evt, handler) { handlers[evt] = handler; }
    return { bind: bind };
  }
};

21 LOC.

Example Application

To cascade it with a sinatra app takes a few more lines of code, and serves as an example of a chat application.

# config.ru

require 'sinatra'

get '/' do
  erb :index
end

post '/messages' do
  Pusher.trigger('messages', 'create', params[:messages])
  'message created'
end

run Rack::Cascade.new([ Pusher, Sinatra::Application ])

Client subscriptions work the same as well.

<!-- views/index.html.erb -->

<script src="http://localhost:9292/faye.js"></script>
<script>
  var channel = pusher.subscribe('messages');
  channel.bind('create', function(message) {
    console.log(message);
  });
</script>

Trying It Out

Use the same syntax, and sub out Pusher for load-balanced redis-backed auto-scaling faye applications in production.

To test it out locally, run the cascaded app specifying the production environment. The puma web server deals with sockets nicely, and is multi-threaded.

$ gem install puma
$ puma config.ru -p 9292 -e production

Open http://localhost:9292 in a browser, and open the console.

$ curl localhost:9292/messages -d "message=hello"

The message "hello" should appear in the console of the web browser.