Tornado web

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

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

Why Tornado?

Why Tornado?
Paul Buchheit

Why Tornado?
Don’t
Be
Paul Buchheit

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

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.

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

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

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()

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()

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

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/

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Tornado web

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