Tornado is an open source version of the scalable, non-blocking web server and tools that power FriendFeed. The FriendFeed application is written using a web framework that looks a bit like or Google’s webapp, but with additional tools and optimizations to take advantage of the underlying non-blocking infrastructure.

The framework is distinct from most mainstream web server frameworks (and certainly most Python frameworks) because it is non-blocking and reasonably fast. Because it is non-blocking and uses epoll, it can handle thousands of simultaneous standing connections, which means it is ideal for real-time web services. We built the web server specifically to handle FriendFeed’s real-time features — every active user of FriendFeed maintains an open connection to the FriendFeed servers. (For more information on scaling servers to support thousands of clients.

See the Tornado documentation for a detailed walkthrough of the framework.

Download and install

Download: tornado-0.2.tar.gz

tar xvzf tornado-0.2.tar.gz
cd tornado-0.2
python build
sudo python install

The Tornado source code is hosted on GitHub.


Tornado has been tested on Python 2.5 and 2.6. To use all of the features of Tornado, you need to have PycURL and a JSON library like simplejson installed. Complete installation instructions for Mac OS X and Ubuntu are included below for convenience.

Mac OS X 10.5/10.6

sudo easy_install setuptools pycurl== simplejson

Ubuntu Linux

sudo apt-get install python-dev python-pycurl python-simplejson

Hello, world

Here is the canonical “Hello, world” example app for Tornado:

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)

See the Tornado documentation for a detailed walkthrough of the framework.

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