1.
Rapid Web Development with
Tornado Web and MongoDB
Ikai Lan
Twitter: @ikai
Friday, June 10, 2011

2.
About the speaker
• Developer Relations at Google
• Software Engineering background
• Lives in San Francisco, CA
• Writes Java, Python on a day to day basis
• Twitter: @ikai
Friday, June 10, 2011

3.
This talk
• Why Tornado Web and MongoDB?
• Whirlwind tour of Tornado (get it?!)
• Intro to MongoDB
• Brief look at a demo app
Friday, June 10, 2011

4.
What I won’t be talking
about
• Scalability - loaded topic
• Reliability - another loaded topic
Friday, June 10, 2011

5.
So why tornado/
mongo?
Friday, June 10, 2011

6.
Joy.
Friday, June 10, 2011

7.
Where does this joy
come from?
Friday, June 10, 2011

8.
Freedom.
Friday, June 10, 2011

9.
So really, my talk should
have been called “The
Joy of Tornado Web and
Mongo DB”
Friday, June 10, 2011

10.
Intangibles
• Tornado - fast development, very few rules
• MongoDB - freedom from a predefined
schema
• Python, of course. Dynamically typed
variables, duck typing plus everything else
that is cool about the language
Friday, June 10, 2011

11.
Tornado Web history
• Open Sourced by Facebook
• ... formerly of FriendFeed
• ... former Googlers (that’s why the
framework looks like App Engine’s webapp
- they wrote it)
• Tornado Web powers FriendFeed
Friday, June 10, 2011

12.
A whirlwind tour
Friday, June 10, 2011

13.
Tornado features
• Out of the box auth with Twitter,
Facebook, Google and FriendFeed
• Out of box support for localized strings
• Simple templating that allows arbitrary
Python code
• Asynchronous requests
• Small codebase
Friday, June 10, 2011

14.
Simple handlers
import tornado.ioloop
import tornado.web
class HelloHandler(tornado.web.RequestHandler):
def get(self):
self.write("Hello, world :)")
class GoodbyeHandler(tornado.web.RequestHandler):
def get(self):
self.render("goodbye.html",
message=”Goodbye, world”)
application = tornado.web.Application([
(r"/hello", HelloHandler),
(r"/goodbye", GoodbyeHandler),
])
if __name__ == "__main__":
application.listen(8888)
tornado.ioloop.IOLoop.instance().start()
Friday, June 10, 2011

15.
Asynchronous nature
class MainHandler(tornado.web.RequestHandler):
@tornado.web.asynchronous
def get(self):
http = tornado.httpclient.AsyncHTTPClient()
http.fetch("http://friendfeed-api.com/v2/feed/bret",
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 "
"from the FriendFeed API")
self.finish()
Friday, June 10, 2011

16.
Unrestrictive templating
{% for student in [p for p in people if p.student and p.age > 23] %}
<li>{{ escape(student.name) }}</li>
{% end %}
# Sample of arbitrary functions in templates
def add(x, y):
return x + y
template.execute(add=add)
### The template
{{ add(1, 2) }}
Friday, June 10, 2011

17.
Lies, damn lies and benchmarks
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18.
Saving data
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19.
MongoDB is an object
database
• No schema - anything that can be a JSON
object can be stored
• You can define new collections on the fly
Friday, June 10, 2011

20.
Getting started with
Mongo in 4 steps
• Download a binary for your system
• Create a data directory (mkdir -p /data/db)
• Run mongod
• Install pymongo
• ... start writing code!
Friday, June 10, 2011

21.
Pymongo code sample
connection = pymongo.Connection()
database = connection["your_database"]
def get_or_create_location_by_id(location_id):
"""
Attempts to fetch location data from database. If it doesn't exist,
create it. Note that this is NOT concurrency safe.
"""
location_data = database["locations"].find_one({ "_id" : location_id })
if location_data is None:
location_data = { "_id" : location_id,
"guards": [],
"owner" : None,
"history" : [],
"last_extort_time" : None
}
database.location.save(location_data, safe=True)
return location_data
Friday, June 10, 2011

22.
Pymongo queries
# Add Tyson as a guard to every location owned by “Joe Smith”
locations = database["locations"].find({ "owner" : "Joe Smith" })
for location in locations:
location["guards"].append("Tyson")
database["locations"].save(location)
# Find everyone who has Tyson as a guard
locations = database["locations"].find({"guards" : "Tyson"})
# Find everyone who has *ONLY* Tyson as a guard
locations = database["locations"].find({"guards" : ["Tyson"]}) # Note []s
# Find everyone who has Tyson as a guard whose owner is “Ikai Lan”
locations = database["locations"].find({"guards" : "Tyson",
"owner" : "Ikai Lan" })
Friday, June 10, 2011

23.
Mold as you go along
Friday, June 10, 2011

24.
Freedom from
• ... waiting to get started
• ... predefining a schema
• ... worrying about complex data structures
that don’t fit well into the SQL box.
Anything that is JSON can be stored!
Friday, June 10, 2011

25.
More MongoDB
features
• Simple Geospatial indexing
• GridFS - distributed filesystem running on
MongoDB
• Out of the box mapreduce
• Out of the box replication, data partitioning
Friday, June 10, 2011

26.
Putting it all together
• MobSquare, a location based game that
uses the Facebook API.
• Mashup: Mafia Wars + FourSquare
• https://github.com/ikai/mobsquare-demo
• “Check in” to locations, take them over,
extort money and fight other gangs
Friday, June 10, 2011

27.
Why are Tornado/
Mongo a fit?
• If I haven’t said it enough yet, they’re fun
• Facebook API performance varies -
asynchronous so we can serve requests
while waiting
• Highly structured player data
Friday, June 10, 2011

28.
OAuth 2 upgrade flow
class OnLoginHandler(tornado.web.RequestHandler):
@tornado.web.asynchronous
def get(self):
# Store this somewhere
code = self.get_argument("code")
access_token_url = ACCESS_TOKEN_URL_TPL + code
client = httpclient.AsyncHTTPClient()
client.fetch(access_token_url, self.on_fetched_token)
def on_fetched_token(self, response):
""" Callback inokved when the auth_token is fetched """
matches = ACCESS_TOKEN_REGEX.search(response.body)
if matches:
access_token = matches.group(1)
client = httpclient.AsyncHTTPClient()
# lambda is effectively a function factory for us
client.fetch(API["profile"] % access_token,
lambda response: self.on_profile_fetch(response, access_token))
def on_profile_fetch(self, response, access_token):
""" Callback invoked when we have fetched the user's profile """
profile = json.loads(response.body)
profile["access_token"] = access_token
profile_id = db.save_profile(profile)
self.set_secure_cookie("user_id", str(profile_id))
self.redirect("/") # implictly calls self.finish()
Friday, June 10, 2011

29.
Known gotchas
• Immaturity of frameworks, tools
• Tornado templating errors result in
somewhat useless stack traces
• MongoDB nuances
• Tornado community fairly small
Friday, June 10, 2011

30.
Questions?
• Ikai Lan - @ikai on Twitter
• Github: https://github.com/ikai
• Google Profile: https://profiles.google.com/
ikai.lan/about
• Thank you for having me at Pycon!
Friday, June 10, 2011

31.
Attributions
• Slide 6: Kirstin Jennings - “big smile!” http://www.flickr.com/photos/methyl_lives/2973265796/
• Slide 8: Tony Blay - “I am a bird now!” http://www.flickr.com/photos/toniblay/59415205/
• Slide 12: Antonio Sofi - “whirlwind” http://www.flickr.com/photos/webgol/36546734
• Slide 17: Tornado Web documentation - http://www.tornadoweb.org/documentation
• Slide 18: Christine of Robot Brainz - “Cassette” http://www.flickr.com/photos/robotbrainz/
2786347158/
• Slide 23: Samuel Stroube - “Play-Doh on a Picnic Table” http://www.flickr.com/photos/samoube/
203586664
Friday, June 10, 2011