An overview on social network technologies: are they "typical" website? Or do they work in a different way? How many and what technologies do Facebook and Instagram use? Presentation made for the Multimedia Languages and Environments course at Politecnico di Torino (academic year 2013/2014).

1. Social Network
Technologies
An overview Luigi De Russis

2. Prerequisite
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Did you know…
 the data center definition?
 the difference between a logical server and
a physical server?
 the difference between cache and
database access?

3. Let’s think!
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Social Networks Technologies

4. Social network
A “typical” web site?
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Social Networks Technologies
Traditional web
site

5. Social network
A “typical” web site?
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Social Networks Technologies
Traditional web
site
In the beginning, probably…

6. Social network
A “typical” web site?
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Social Networks Technologies
Traditional web
site
… but soon or later…

7. Why?

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What tools and technologies are we
using for building a website?
Web site: tools and technologies

9. Web site: tools and technologies
 JVM + JDK + J2EE
 Tomcat (or similar)
 MySQL (or similar)
 PHP
 Apache
 MySQL (or similar)
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Social Networks Technologies
Java/JSP PHP
For example…

10. Web site: tools and technologies
 JVM + JDK + J2EE
 MySQL (or similar)
 Tomcat (or similar)
 PHP
 MySQL (or similar)
 Apache server
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Social Networks Technologies
Java/JSP PHP
Typically, a vertical stack
(with one programming language)

11. Now let’s try with these sites…
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12. Now let’s try with these sites…
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PHP
MySQL
Apache
Rails
MySQL
Unicorn
Django
MySQL
Gunicorn
Django
PostgreSQL
Gunicorn

13. Now let’s try with these sites…
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PHP
MySQL
Apache
Rails
MySQL
Unicorn
Django
MySQL
Gunicorn
Django
PostgreSQL
Gunicorn
Are you really, really sure?

14. Not so sure?!
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Social Networks Technologies
https://github.com/twitter https://github.com/facebook
Let’s have a look at some pages and projects…
https://enginnering.twitter.com/opensource/projects
What did you notice?
https://code.facebook.com/projects/

15. What did you notice?
 Twitter
 tracing system, package manager, various servers,
NoSQL database, caching system, etc.
 Facebook
 code-related tools, code transformer, various servers,
distributed file system, caching system, NoSQL
database, etc.
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Social Networks Technologies
A lot of different components

16. What did you notice?
 Twitter
 Java, Scala, Ruby, C++, C, Objective-C, Shell scripting,
Python, JavaScript
 Facebook
 PHP, OCAml, C++, JavaScript, Python, Java,
Objective-C, Processing, C, Ruby, Shell scripting,
Haskell, Emacs Lisp, ActionScript
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Social Networks Technologies
A lot of different languages

17. Now, have a look again at this…
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Social Networks Technologies
Impressive?!

18. This is ONLY the tip of the iceberg…

19. Social Network Characteristics
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 Wildly popular over last few years
 Facebook has more than 1 billion (monthly active) users
 Twitter has more than 600M users
 Distributed across the planet
 Changed how content is created and consumed
 Explosion of smartphones
 photos and video are now easy to shoot and share
 e.g., Facebook has more than 350M photos uploaded
each day

20. Facebook as an example…
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Social Networks Technologies

21. On December 2013…
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More than 3.9 trillion
feed actions processed
per day
More than 1 billion
monthly active users
100 million search
queries per day
More than 200 billion
monthly page views
2,5 billion content
items shared per day
2.7 billion
‘Likes’ per day
350 million
photos uploaded
per day
Over 500 TB new
data ingested per day
757 million active
users per day

22. Growth Rate
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0
200
400
600
800
1000
1200
1400
December2004
December2005
December2006
April2007
October2007
August2008
January2009
February2009
April2009
July2009
September2009
December2009
February2010
July2010
September2010
January2011
February2011
June2011
September2011
February2012
April2012
July2012
October2012
January2013
April2013
July2013
October2013
January2014
Millions of Users

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Social Networks Technologies
Each active user wants to write and upload something NOW
No perceptible delay is allowed, in any case
No matter how “big” the content is
Reality Check
Data and services have to be available 24/7, everywhere

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Social Networks Technologies
Moreover, new features and applications are added
continuously to Facebook
Reality Check
No perceptible delay is allowed, in any case
Each active user wants to see and share something NOW
(she sees the recent status of her friends and pages, anyway)
No matter where the information is (geographically speaking)

25. Reality Check
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“Rendering a single page of Facebook
involves hundreds of machines examining
tens of thousands of pieces of data from
dozen of services - all in real time.”
- from the Infrastructure page of the Facebook Newsroom

26. Reality Check
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27. The main problem
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Scalability
The ability of a system, network or process to handle a growing
amount of work in a capable manner or its ability to be enlarged
to accommodate that growth.

28. The main problem
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Scalability
The ability of a system, network or process to handle a growing
amount of work in a capable manner or its ability to be enlarged
to accommodate that growth.
Affected by
several factors

29. How to handle such situations?
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Social Networks Technologies

30. Solution
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 No standard solutions…
 … each social network made different choices
 strongly dependent from the original core
 We are in the Cloud Computing realm
 We are going to analyze briefly the Facebook
and the Instagram cases

31. Facebook architecture at 100 feet
How to handle such situations?
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Social Networks Technologies

32. Servers and Data Centers
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 Facebook has 4 data centers
 Prineville, Oregon
 Forest City, North Carolina
 Luleå, Sweden
 Altoona, Iowa (in construction)
 They build their servers and
data centers from the ground up (efficiently)
 Servers and data center design is open source
 see The Open Compute Project (http://opencompute.org)

33. Complex Infrastructure
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 Large number of software components
 Multiple storage systems
 Multiple caching systems
 Hundreds of specialized services
 Failure is routine!
Keep things as simple as possible!

34. Software Architecture
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35. Web Tier
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 Gather Data from the other Tiers
 Runs PHP code
 Widely used for web development
 One single source tree for all the entire code
 Same “binary” on every web tier box

36. Web Tier
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 At the beginning: Zend Interpreter for PHP
 reasonably fast (for an interpreter)
 rapid development
 no recompiling
 but, at scale, performance matters!
 Then: HipHop compiler for PHP
 400% faster
 but slow down development
 they add an HipHop interpreter
 but compiler and interpreter sometime disagree

37. Web Tier
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 Now: HipHop Virtual Machine
 The best of both worlds
 9x increase in web request throughput
 5x reduction in memory consumption
 All this is open source
 e.g., you can find HipHop Virtual Machine at
http://hhvm.com

38. Storage Tier
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 Multiple storage systems
 MySQL
 Hbase (NoSQL) - Messaging and Insight
 Haystack (BLOBS)
 BLOB: Binary Large Objects (Photos, Videos, Email
attachments, etc.)
 large files, no updates/appends, sequential reads

39. Cache Tier
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 Memcache
 speak only with the Web Tier
 do one thing very well
 improved performance by 10x
 key-value store

40. Cache Tier
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 Tao
 abstract the Storage Tier
 in production for more than a 3-4 years
 higher CPU load than memcache
 used for the social graph

41. Service Tier
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42. Service Tier
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 Example: News Feed
 one of the hundreds of services at Facebook
 Characteristics
 real-time distribution
 writers can potentially broadcast to very large
audience
 readers wants (and have) different and dynamic ways
to filter data
 The service should maintain an index and rank the
data (in multiple ways)

43. News Feed Service
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- write one location

44. News Feed Service
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 1000s of machines
 leafs are in multiple sets, and each set has the entire index
 Dealing with (daily) failures
 hardware/software, server/network,
intermittent/permanent, etc.
 if a leaf is inaccessible, failover request to a different set
 if an aggregator is inaccessible, “just” pick another
 More leafs than aggregators
 Reads are more expensive than writes
 High network load between aggregator and leafs
 fundamental to keep a full leaf set within a single rack on
machines

45. Software architecture
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46. Instagram architecture at 100 feet
How to handle such situations?
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Social Networks Technologies

47. Infrastructure
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 Instagram follows some core principle when
choosing a system:
 keep it very simple
 don’t re-invent the wheel
 go with proven and solid technologies when you can
 It runs Ubuntu on Amazon EC2

48. Software Architecture
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 Web Tier
 Django (Python) on more than 25 Amazon High-CPU
Extra-Large machines
 Gunicorn is the chosen Web Server
 Storage Tier
 PostgreSQL
 Redis (key-value storage)
 Amazon S3 for photos
 Cache Tier
 memcache

49. Conclusions
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Social Networks Technologies

50. Conclusions
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 Most Social Networks starts like “traditional”
website
 They change and/or evolve their hardware and
software infrastructure when:
 users growth
 some functionalities are added/revised
 Scalability is a relevant problem…
 They are complex entities and, sometimes, required
complex or innovative solutions

51. References
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 Instagram Engineering Blog, http://instagram-
engineering.tumblr.com
 Facebook Newsroom, http://newsroom.fb.com
 Facebook Investor Relations, http://investor.fb.com
 HPCA 2012 Facebook Keynote,
http://www.ece.lsu.edu/hpca-
18/files/HPCA2012_Facebook_Keynote.pdf

52. License
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