while42.org #1 paris event

1. HOW TO
SCALE YOUR
APP AND WIN
THE CLOUD
CHALLENGE
QUENTIN ADAM
@WAXZCE
2013

2. Quentin ADAM
Clever Cloud CEO
@waxzce on twitter
http://www.waxzce.org
WHO I AM ?

3. Java, scala, python, nodejs, php… apps scaling automatically in the cloud.
We cover your ass, you can focus on your own stuff
http://www.clever-cloud.com
PAAS PROVIDER

4. WHEN YOU
NEED TO
SCALE
THERE ARE 2 WAYS

5. GROWING AND GROWING
UNTIL YOU EXPLODE OR
BECOME WEIRD

6. OR SPLIT THE WORK AND
MAKE YOUR SOFTWARE
WORK AS A TEAM

7. Build an army of fat app
YOU CAN DO BOTH

8. SO WE NEED TO BE ABLE
TO DISPATCH THE WORK
SCALE OUT
• Many workers
doing the same
thing
• No SPOF
• Growing is more
easy
• Introduce best
practice
SCALE UP
• 1 Fat instance
• 1 Fat application
• SPOF (single point
of failure)
• Hard to maintain
• Always has a limit
• Short term
meaning

9. SO, HOW TO
SCALE OUT
?
JUST SOME FACTS

10. SPLIT PROCESS AND
STORAGE
Storage
• Databases
• Files
• Sessions
• Events
• …
Code
• Can be replicated
• Stateless
• Process

11. Picking one instance or another doesn’t matter
STATELESSNESS IS THE KEY

12. CONSIDER MORE
THINGS AS DATA
• User account
• Users data
• Files
• Sessions
• Events

13. CHOOSE
DATASTORE
WISELY
YOU CAN SHOULD USE MANY DATASTORES

14. DATASTORE CHOICES
ARE DRIVEN BY USAGE
Make
decisions
based on
needs
Do I need
atomicity of
requests ?
Do I need
concurrent
access ?
Do I mostly
read or
write ?
Do I need
relational ?
Do I need
big storage
capacity ?
Do I need
high
availability ?

15. • Not a big volume
• DB have to manage
data TTL
• Data model : K/V
• Multiple writes at the
same time
• High availability
I need to store sessions
QUICK EXAMPLE

16. • Not a big volume
It’s OK, PG can handle
small quantity of data
• DB have to manage
data TTL
No, I have to do it
manually
• Data model : K/V
No, PG is relational
(mainly)
• Multiple writes at the
same time
No, PG is Atomic
• High availability
PG is awesome ;-) Use
of PG bouncer or
similar allow good
clustering
I need to store sessions
QUICK EXAMPLE

17. • Not a big volume
It’s OK, redis can
handle small quantity
of data
• DB have to manage
data TTL
Yes Redis can do it
• Data model : K/V Yes
• Multiple writes at the
same time
No, redis is pseudo
Atomic (master/slave)
• High availability
Redis is great, but
cauterization is rude…
I need to store sessions
QUICK EXAMPLE

18. • Not a big volume
It’s OK, CB can handle
small quantity of data
• DB have to manage
data TTL
Yes CB can do it
• Data model : K/V Yes
• Multiple writes at the
same time
OK, this is possible
with memcached
protocol
• High availability
Clustering is built in, no
downtime 
I need to store sessions
QUICK EXAMPLE

19. USE ONLINE
DATABASE / BE
READY TO TEST
IN JUST A FEW
MINUTES
NO NEED TO TRASH YOUR COMPUTER

20. DON’T BE THAT GUY

21. DO NOT USE A
TECHNOLOGY BECAUSE
YOU <3 IT OR BECAUSE
IT’S HYPE : USE IT
BECAUSE IT FITS YOUR
NEEDS
BALANCE YOUR LEARNING CURVE WITH
THE TIME SAVED

22. DO NOT CREATE MONSTERS

23. COMMON MISTAKES

24. DO NOT USE
MEMORY AS
DATABASE
LIKE : SHARED / GLOBAL VARIABLE,
CACHE “IN THE CODE”, INTENSIVE
SESSION USAGE…

26. DO NOT USE A VARIABLE
FOR MORE THAN ONE
REQUEST

27. 2 + 2 = 4
FOR SAME INPUT, SAME OUTPUT

28. GET do not change data on server
BE HTTP CONSISTENT

29. And data will be lost
CODE WILL FAIL

30. DO NOT USE FILE
SYSTEM AS DATASTORE
File system are POSIX compliant
• POSIX is ACID
• POSIX is powerful but is bottleneck
• File System is nightmare of ops
• File System is create coupling (host provider/OS/language)
• Free SPOF multi tenant File System is a unicorn
STORE IN DATABASE, OR DATASTORE LIKE S3 (AWS)
DEDICATED TO FILE MANAGEMENT

31. CAREFUL USE OF
DARK MAGIC

32. SPLIT THE CODE :
MODULES
• Smallest code
base
• Deploy as
service for
each other
• Focus on best
technology for
a problem

33. SCALE YOUR TEAM
MODULARIZE YOUR TEAM

34. USE EVENT BROKER TO
MODULARIZE YOUR APP
• AMQP
• Celery
• 0MQ
• Redis
• JMS
• Some case : hadoop, akka…
• …
CRON is not an event queue

35. MAKE HARD
COMPUTATION ASYNC

36. ALWAYS USE A
REVERSE PROXY
Y U NOT USE ONE ?

37. DO NOT BUILD “THE
SERVER” WITH NO DOC

38. USE PROCESS
DEPLOYMENT

39. EASY MOVING OR
INCIDENT MANAGEMENT

40. KEEP CALM UNDER FIRE

41. TRACK BUG & GET METRICS

42. Quentin ADAM
Twitter : @waxzce
THX FOR LISTENING
& QUESTIONS TIME