This document discusses the Tornado web server framework. It provides an overview of Tornado, including that it is a non-blocking and scalable web server that was used by FriendFeed and is now open-sourced by Facebook. It describes Tornado's architecture, which uses an IOLoop and callbacks instead of threads to remain asynchronous and non-blocking. An example "Hello World" application in Tornado is also provided. Performance comparisons show Tornado outperforming other frameworks like Node.js and Twisted.

1. Tornado Rocking the Non-Blocking Web Contact: Twitter: Kurtiss Hare, CTO & Co-Founder of playhaven.com @kurtiss

2. What is Tornado? Scalable, Non-blocking Web Server Powered www.friendfeed.com Now open-sourced by Facebook after FF acquisition

3. Why Tornado?

4. Why Tornado? Paul Buchheit

5. Why Tornado? Don’t Be Paul Buchheit

6. Why Tornado? Processor/Thread Model CherryPy, Mod_WSGI, uWSGI, … Lightweight Threads Gevent, Eventlet, … IOLoop/Callback Model Tornado, Cogen, … What are you trying to do?

7. Why Tornado? Trying to address the c10k problem? 10,000 concurrent connections Processor/thread is known to fall over Trying to enable real-time/long-polling, WebSockets? Different problem than handling many short-lived, pipelined requests. Want to extend your arsenal with a tool that addresses these problems? Tornado might be for you.

8. Tornado’s Architecture ~2000 clients tornado.ioloop._poll tornado.web.RequestHandler tornado.httpserver.HTTPServer socket.socket tornado.ioloop.IOStream tornado.httpserver.HTTPConnection tornado.web.Application Routing/MVC tornado.ioloop

9. Tornado’s Architecture tornado.ioloop._poll Edge-triggered when possible (epoll/kqueue) Falls back on level triggered (select) Handles: Callback registration New connections Connections with new data Heart of Tornado’s approach to c10k

10. Hello, world import tornado.httpserver import tornado.ioloop import tornado.web class MainHandler(tornado.web.RequestHandler): def get(self): self.write("Hello, world") application = tornado.web.Application([ (r"/", MainHandler), ]) if __name__ == "__main__”: http_server = tornado.httpserver.HTTPServer(application) http_server.listen(8888) tornado.ioloop.IOLoop.instance().start()

11. Rocking the Non-Block class MainHandler(tornado.web.RequestHandler): @tornado.web.asynchronous def get(self): http = tornado.httpclient.AsyncHTTPClient() http.fetch("http://friendfeed-api.com/v2/feed/kurtiss", callback=self.async_callback(self.on_response)) def on_response(self, response): if response.error: raise tornado.web.HTTPError(500) json = tornado.escape.json_decode(response.body) self.write("Fetched " + str(len(json["entries"])) + " entries ”) self.finish()

12. Performance Notes Source: http://developers.facebook.com/blog/post/301

13. Performance Notes Better Comparisons Node.js – Tornado by 110% throughput [0] Twisted.Web – Tornado by 84% shorter average response time [1] Caveat Emptor, OK? http://nichol.as/benchmark-of-python-web-servers Of note, “Server Latency,” vs. gEvent, uWSGI Likely due to CPU availability Nothing beats a load test on your own environment PlayHaven’s use is modest, but growing: <500 concurrent web requests No long polling … yet. [0] http://news.ycombinator.com/item?id=1089340 [1] http://www.apparatusproject.org/blog/2009/09/twisted-web-vs-tornado-part-deux/

14. Let’s Code

15. Questions? Beer?