Ruby Server Side Events Server implementation with Goliath

server_side_events.rb

require 'goliath'
require 'em-synchrony/em-http'

# After a connect the server streams 10 bomb ticks and then stops with a BOOM. The
# event source needs to listen to source.addEventListener 'bomb', .. to retrieve
# the ticks.
class Stream < Goliath::API
  
  def response(env)
    
    i = 0
    # Tick every second until the boom
    bomb_timer = EM.add_periodic_timer(1) do
      env.stream_send "event: bomb\n"
      env.stream_send("data: #{i}\n\n")
      i += 1
    end
    
    # Cancel bomb timer after 10 seconds with a BOOM
    EM.add_timer(10) do
      bomb_timer.cancel
      env.stream_send "event: bomb\n"
      env.stream_send("data: !! BOOM !!\n\n")
    end
    
    # Stream response to client
    streaming_response(200, {'Content-Type' => 'text/event-stream', 'Cache-Control' => 'no-cache', 'Connection' => 'keep-alive'})
  end
end


# As the client and server must follow the same origin rule, the proxy simply
# redirects all requests not "/stream" to another server that e.g. hosts the
# javascript with the EventSource code. Feel free to adapt the proxy destination
# to your needs
class Proxy < Goliath::API
  
  def response(env)
    url = "http://localhost:9292#{env['REQUEST_PATH']}?#{env['QUERY_STRING']}"
    logger.info "Proxying #{url}"
    http = EM::HttpRequest.new(url).get
    [http.response_header.status, {'Content-Type' => http.response_header["CONTENT_TYPE"] }, http.response]
  end
  
end

# Maps the requests to stream to the Server Side Events stream, and sends everything
# else to the proxy
class Routes < Goliath::API
  get "/stream" , Stream
  not_found "/" do run Proxy.new end
end

# Start with: ruby server_side_events_server.rb -sv