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 web.py 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 C10K problem.)
See the Tornado documentation for a detailed walkthrough of the framework.
Download and install
Automatic installation: Tornado is listed in PyPI and can be installed with pip
or easy_install
. If you do not already have libcurl installed you may need to install it separately; see the prerequisites section below. Note that the source distribution includes demo applications that are not present when Tornado is installed using pip
or easy_install
Manual installation: Download tornado-1.2.1.tar.gz
tar xvzf tornado-1.2.1.tar.gz
cd tornado-1.2.1
python setup.py build
sudo python setup.py install
The Tornado source code is hosted on GitHub. On Python 2.6+, it is also possible to simply add the tornado directory to your PYTHONPATH
instead of building with setup.py
, since the standard library includes epoll
support.
Prerequisites
Tornado has been tested on Python 2.5, 2.6, and 2.7. To use all of the features of Tornado, you need to have PycURL (version 7.18.2 or higher) and (for Python 2.5 only) simplejson installed (Python 2.6 includes JSON support in the standard library so simplejson is not needed). Complete installation instructions for Mac OS X and Ubuntu are included below for convenience.
Mac OS X 10.6 (Python 2.6+)
sudo easy_install setuptools pycurl
Ubuntu Linux (Python 2.6+)
sudo apt-get install python-pycurl
Ubuntu Linux (Python 2.5)
sudo apt-get install python-dev python-pycurl python-simplejson
Hello, world
Here is the canonical "Hello, world" example app for Tornado:
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__":
application.listen(8888)
tornado.ioloop.IOLoop.instance().start()
See the Tornado documentation for a detailed walkthrough of the framework.
Discussion and support
You can discuss Tornado and report bugs on the Tornado developer mailing list. Links to additional resources can be found on the Tornado wiki.