Tornado

A Python Web Framework

Asynchronous Networking
Scalable
Uses non-blocking network I/O
Fast (faster than Django, web.py, CherryPy)
Great for creating RESTful services

INstallation

Available in PyPI
Install with pip or easy_install
Source on GitHub
Runs on python 2.6+ and 3.2+
Supports Unix-Like environments
Not suggested for running on Mac OS X
(But who would host off of OS X anyways?)

INFORMATION

Created by FriendFeed
FF acquired by Facebook, tornado opensourced afterwards
Docs/Examples available at www.tornadoweb.org
In use here at Synacor!

The Basics

Tornado Application

Request Handlers

Arguments

Routing

Tornado Application

tornado.web.Application

Holds a mapping of URLs to Handlers
Used in conjunction with httpserver.HTTPServer
Can register static files as well
Even can handle virtual hosts!
Configuration also registered with Application

REQUEST HANDLERS

Accept a request
Main methods are HTTP verbs

GET
POST
PUT
DELETE
HEAD
OPTIONS

Request Handlers

Able to access request parameters
Does the communication heavy lifting
self.write() to send data to client
self.set_header() set appropriate headers
self.set_status() to modify HTTP status codes
self.redirect() to send user elsewhere

REQUEST HANDLERS

Can also use templating engine

Python embedded in templates
Sounds familiar

Localization is a breeze

If you use their templates, at least

REQUEST HANDLERS

import tornado.ioloopimport tornado.web
class BaseHandler(tornado.web.RequestHandler):    def get(self):        self.write("Hello, world")application = tornado.web.Application([    (r"/", BaseHandler),])if __name__ == "__main__":    application.listen(8080)    tornado.ioloop.IOLoop.instance.start()

Start a server on 8080

Respond to GET requests with "Hello, world"

Available on the url "/"

Arguments

(I'm right, you're wrong!)

Easy access to request arguments (GET and POST!)
self.get_argument('name')

?name=Matt
arg 'name' required
only returns last defined argument

self.get_argument('name', default='John Doe', strip=True)

arg 'name' defaults to 'John Doe', strips whitespace

self.get_arguments('name') -- return list of arguments 'name'

returns list of argument 'name'
?name[]=Matt&name[]=John

ARGUMENTS

File Uploads

Access via self.request
(also where headers and request body are found)
self.request.files['name'][0]
where 'name' is the field name
provides 'filename', and binary data in 'body'

Note: The file sits in RAM

the use of nginx's upload module is suggested

Arguments

class ArgumentHandler(tornado.RequestHandler):   def get(self):      #name is required      name = self.get_argument('name')      names = self.get_arguments('names') # empty list if not present      self.write('Hello, {0}<br />'.format(name))      if len(names) > 0:           self.write('Your list of names are: {0}'.format(                      ', '.join(names)))      else:           self.write("Provide a list of names in the 'names' argument!")

Routing

Registered within Application
Pairs a regular expression with a handler
Regex mapped to handler
Matches provided to handler as parameters
Can map as many Regex to a single Handler as you want

Routing

application = tornado.web.Application([
    (r"/", MainHandler),    (r"/hello/world/", HelloWorldHandler),    (r"/hello/([^/]+)/?"), HelloAnythingHandler),])

class HelloWorldHandler(tornado.web.RequestHandler):    def get(self):        self.write("Hello, World")

class HelloAnythingHandler(tornado.web.RequestHandler):    def get(self, anything):        self.write("Hello, {0}".format(anything))

Yes, I could drop the hello world handler and have the same functionality.

Some things to consider

@tornado.asynchronous decorator

means request is asynchronous

does not make code asynchronous

use a mongodb driver such as motor

motor allows for asynchronous mongo operations

if using decorator, must use self.finish

request will hang until client timesout otherwise

Demo Time

Let's see a working demo of a service!

Source code available at:

https://github.com/mattgen88/tornado-demo