Will Shulman, from MongoLab, shows us how to to persist our mobile app data in the cloud using a super-scalable and amazingly developer-friendly MongoDB back-end.

1. MongoDB for mobile app
backends
sf android meetup
08.31.2010

2. I’ve written my mobile app…
where should I store my data ?
?

3. Mobile apps do not exist
in a vacuum
• user profile data
• logging
• location-based data collection
• game data (stats, high scores)
• polls and surveys
• user feedback

4. Do I want to host this
myself ?
Java + Spring + Hibernate ?
Ruby on Rails ?
Hmmm… I will probably
need to build a REST API…

5. GET, POST, PUT, DELETE
•EC2
•Rackspace
•App Engine*
•MySQL
•SQLServer
•Postgres
•RoR
•J2EE
General approach
REST API

6. How can this be even simpler and
more awesome?

7. • “Scalable, open-source, high-
performance, document-oriented
database” - 10gen
• “The database your database could
smell like” - old spice guy

8. MongoDB is designed to address
two modern DB problems
1. object / relational “impedance mismatch”
2. horizontal scalability

9. Native drivers in almost every
language
• Java
• Javascript
• Python
• Ruby
• C#
• PHP
• and more…

10. A paradigm shift…
• Traditional RDMS
– database
– table
– row
• MongoDB
– database
– collection
– document / object

11. Documents (a.k.a. Objects)
{
_id: 1234,
author: { name: “Bob Jones”, email: “b@b.com” },
post: “In these troubled times I like to …“,
date: { $date: “2010-07-12 13:23UTC” },
location: [ -121.2322, 42.1223222 ],
rating: 2.2,
comments: [
{ user: “jgs32@hotmail.com”,
upVotes: 22,
downVotes: 14,
text: “Great point! I agree” },
{ user: “holly.davidson@gmail.com”,
upVotes: 421,
downVotes: 22,
text: “You are a moron” }
]
}

12. {
_id: 1234,
author: { name: “Bob Jones”, email: “b@b.com” },
post: “In these troubled times I like to …“,
date: { $date: “2010-07-12 13:23UTC” },
location: [ -121.2322, 42.1223222 ],
rating: 2.2,
comments: [
{ user: “jgs32@hotmail.com”,
upVotes: 22,
downVotes: 14,
text: “Great point! I agree” },
{ user: “holly.davidson@gmail.com”,
upVotes: 421,
downVotes: 22,
text: “You are a moron” }
],
tags: [ “politics”, “Virginia” ]
}
Flexible “schemas”

13. db.posts.find({ author.name: “mike” })
Dynamic queries
db.posts.find({ rating: { $gt: 2 }})
db.posts.find({ tags: “software” })
db.posts.find().sort({date: -1}).limit(10)

14. Comment c = {author: “will”,
date: new Date(),
text: “great post!”}
db.posts.update({_id: post._id},
{$push: {comments: c}})
Atomic update operators

15. Aggregation and Map/Reduce

16. Focus on scalability and
performance

17. depth of functionality
scalabilityandperformance
•memcached
•key / value
•RDBMS
•

18. High performance, fault tolerant
clusters made easy
• master / slave replication
• replica sets
• auto-sharding

19. MongoDB is great for mobile
• everything is JSON!
– storage model is JSON
– queries are in JSON
– update operators are in JSON
• geospatial indexing built-in
• GridFS

20. Geospatial indexing
• index on geo coordinate pairs
• search by
– bounding box
– bounding circle (point, radius)

21. Geospatial indexing
db.places.ensureIndex( { loc: “2d” } )
db.places.find({ loc: { $near : [50, 50] } }).limit(10)
db.places.find({loc: {$within : {$box : [[40,40],[60,60]]}}})
db.places.find({loc: {$within : {$center : [[40,40],10]}}})

22. Geospatial indexing at
Foursquare
• ~1.3M registered users
• ~615k check-ins a day
• “Who’s here” service tracks last 3 hours for
every user; uses mongo exclusively
• all checkins, tips and venues written to
mongo; reads a mix of mongo / legacy
postgres

23. GridFS
• distributed filesystem inside MongoDB
• stores large files by splitting them into
smaller documents
• leverages existing sharding and
replication configuration
• stores metadata along with files
• works well behind a CDN

24. Street cred
• Shutterfly
• Foursquare
• bit.ly
• Sourceforge
• Etsy
• The New York Times
• Business Insider
• Github
• Gilt Groupe
• Sugar CRM
• Electronic Arts
• Evite
• CollegeHumor
• Disqus
• Justin.tv
• Chartbeat
• Hot potato
• Eventbrite

25. Not so good for
• Complex / multi-operation
transactions
• When you (really) need joins

26. How can this be even simpler and
more awesome?

27. • MongoLab provides cloud-hosted
MongoDB
• It’s EC2 hosting + MongoDB + REST
API + awesome admin tools
• http://mongolab.com

28. GET, POST, PUT, DELETE
EC2
MongoDB
Two ways to use MongoLab
REST API
method 1: REST API
method 2: MongoDB driver
Your application

29. /databases/<d>/collections
GET
/databases/<d>/collections/<c>
GET
POST
/databases/<d>/collections/<c>/<_id>
GET
PUT
DELETE
/databases/<d>/collections/<c>?[q=<query>]
[&f=<fields>]
[&s=<order>]
[&sk=<skip>]
[&l=<limit>]
GET
MongoLab API

30. Example app:
GeoPost
• add a GeoPost (email, date, message, location)
• list nearby GeoPosts

31. Example app:
GeoPost
• POST
URL: https://mongolab.com/api/1/databases/demo/collections/geoposts
data: { “email” : “will@mongolab.com”,
“date” : { “$date” : “2010-02-03 10:21:21 UTC” },
“location” : { “lat” : 41, “long” : -82 },
“message” : “Hello Cleveland!” }
• GET
URL: https://…/geoposts?q={"location":{"$near":{"lat":38,"long":-122}}}

33. Android SDK makes client-side
easy
• JSON: org.json.*
• REST: org.apache.http.*
HttpClient client = new DefaultHttpClient()
HttpGet request = new HttpGet(url);
HttpResponse response = client.execute(request);
HttpEntity entity = response.getEntity();
InputStream in = entity.getContent();
String json = convertStreamToString(in);
JSONObject o = new JSONObject(json);

34. For more info…
• MongoDB / 10Gen
– http://mongodb.org
– http://10gen.com
• MongoLab
– http://mongolab.com
– will@mongolab.com