main.rb

def run
  EventMachine::run {
    Signal.trap("INT")  { EventMachine.stop }
    Signal.trap("TERM") { EventMachine.stop }

    client = Faye::Client.new('http://tangpin.dev:6901/pulling')

    store = Store.new
    ws = WebSocket.new(client, store)
    ws.subscribe
  }
end

store.rb

class Store
  def initialize()
    @redis = EM::Hiredis.connect("redis://localhost:6379/0")
  end

  def set_online_user(user_id, current_user_id)
    k = key(current_user_id)
    @redis.set(k, user_id).callback {
      @redis.expire(k, 10)
    }
  end

  def key(id)
    "faye:online:user:#{id}"
  end
end

websocket.rb

class WebSocket
  def initialize(client, store)
    @client = client
    @store  = store
  end

  def subscribe
    @client.subscribe('/message_heartbeat') do |message|
      user_id         = message['user_id']
      current_user_id = message['current_user_id']

      case mark
      when 'online'
        if !user_id.nil? && !current_user_id.nil?
          @store.set_online_user(user_id, current_user_id)
        end
      end
    end
  end
end