This document discusses scaling out a Yii2 application to handle increased traffic. It covers key considerations for load balancing, using a centralized database, managing sessions outside individual servers, storing files in a centralized system like S3, deploying assets through a build server and CDN, and automating deployments. The goal is to build a stateless, redundant architecture that can scale horizontally across multiple servers and avoid single points of failure.

1. Scaling Out Yii2
App
@petrabarus
YiiConf Indonesia
26 Ags 2017

2. Hi Everyone!
I am Petra Novandi
Now serves as
Chief Technology Officer at
UrbanIndo.com
-
Contact me at
Email:
petra.barus@gmail.com
Twitter:
@petrabarus

3. UrbanIndo & Yii
- Use Yii 1.1 at 2011
- Migrate to Yii 2.0 at 2015
- Contribute to Yii core
- #7435 #8933 #9249 #9277
- Contribute to Yii2 plugins
- yii2-queue, yii2-s3-cache, yii2-dynamodb

4. WHAT’S
THIS ABOUT?

5. Let me tell you a common story...
Dewi is a software engineer.
She had a great idea for app!
So Dewi build a new app from scratch.

6. MySQL
Yii App
PHP
Apache
Pictures
Assets
Libraries
Logs
Scripts
Files
Like a lot other
engineers, Dewi
put all the stuffs
in one server.

7. AND THE
TRAFFIC
GOES UP
UP UP!
AWESOME!!

8. BUT ALL HELL BREAK LOOSE!
SOUNDS FAMILIAR?

9. This is story
about Scaling

10. Scale Up
(Vertical)
Scale Out
(Horizontal)

11. Continuous
Availability/Redundancy
No single point of failure
Cost/Performance
Flexibility
Not being locked by the
hardware
WHY SCALE OUT?
Continuous Upgrade
Without downtime
Geographical
Distribution
Access to nearest node

12. Multi-servers environment concerns in Yii2
Database
Assets
Load Balancing
File System
Session
Deployment
And many more… Logging, Cache, Queue,
Batch Processings.
Let’s discuss that on another occasion..
I don’t have enough time.. :(

13. LOAD
BALANCING
DATABASE SESSION
FILE SYSTEM ASSETS DEPLOYMENT

14. Yii2
Apache
Yii2
Apache
Yii2
Apache
Yii2
Apache
Yii2
Apache
Yii2
Apache
Yii2
Apache
Yii2
Apache
Load
Balancer
Load balancer will forward
requests to instances

15. Sticky Sessions
Requests from same client
will be forwarded to same
instance
Load Balancer Session Types
Non-Sticky Sessions
Requests from same client
can be forwarded to
different instances.

16. Open Source Load Balancer
Technologies

17. Example Config in
NGINX

18. » No need a lot of configuration in the Yii side
» Although you might want to have concerns in
⋄ hostInfo in the yiiwebUrlManager
⋄ ipHeaders in yiiwebRequest (upcoming Yii
2.0.13), different proxies can have different headers

19. LOAD
BALANCING DATABASE SESSION
FILE SYSTEM ASSETS DEPLOYMENT

20. Yii2
Apache
Yii2
Apache
Yii2
Apache
Yii2
Apache
Yii2
Apache
Yii2
Apache
Yii2
Apache
Yii2
Apache
Database
All instances access the
same database instance(s).
Make them more stateless

21. Simple Change in Configuration

22. DATABASE CAN BE
SCALED TOO!

23. Master-Master
Master-Slave
or both

24. Yii2 Natively Support Db
Replication
Or use other tech like
ProxySQL

25. LOAD
BALANCING
DATABASE SESSION
FILE SYSTEM ASSETS DEPLOYMENT

26. ❏ Since PHP stores session in file system
we need to store it outside the instance
❏ Similar like database
❏ Use classes like yiimongodbSession,
yiiredisSession,
yiiwebDbSession,
yiiwebCacheSession,

27. Sample Config

28. Some Considerations
» Better use key-value storage type that stores in
memory instead of files
⋄ E.g. Redis, memcached
⋄ Or SQL that support memory storage
⋄ MySQL’s MEMORY storage engine
» Execute Session::gcSession() using cron.

29. LOAD
BALANCING
DATABASE SESSION
FILE SYSTEM ASSETS DEPLOYMENT

30. Avoid writing and
storing data to local file
systems
Every app instance has
to identical

31. file_put_contents(‘/tmp/text1.txt’,
‘blablabla’)
Instance A
Instance B
file_get_contents(‘/tmp/text1.txt’)

32. Write file to centralized storage
» FTP
» Amazon S3
» Azure
» DropBox
Use filesystem abstraction!
» GridFs
» Rackspace
» Copy.com
Recommended library:
league/flysystem
⇨ creocoder/yii2-flysystem

33. Sample Config

34. Yii::$app->fs->write(‘text1.txt’,
blablabla’)
Instance A
Instance B
Yii::$app->fs->read(‘text1.txt’)
Central Storage

35. LOAD
BALANCING
DATABASE SESSION
FILE SYSTEM ASSETS DEPLOYMENT

36. Asset Management in Single Server
» Hash is not deterministic due to filemtime()
(yiiwebAssetManager::hash)
» Different server can have different filemtime()

37. Multiple Server
/var/www/web/assets/1234567890/script.js
/var/www/web/assets/ABCDEFGHIJ/script.js

38. Configuring
Asset Hash
Generation

39. Multiple Server With Consistent Hash
/var/www/web/assets/1234567890/script.js
/var/www/web/assets/1234567890/script.js

40. A Much Better Way
1. Build and compress the assets in build
server
2. Upload assets to central storage (e.g. S3)
3. Put a CDN in front of the storage

41. BUILD COMPR
ESS
UPLOA
D
DEPLO
Y
SOURCE REPO
BUILD SERVER
CENTRAL
STORAGE (S3)
APP SERVERS
HTML
Requests
JS/CSS Requests
CDN

42. Pros
1. No need additional
local process to
generate assets
(Reduced request
time)
2. Optimized assets
3. Served through CDN
Cons
1. Need build server
2. Need central storage
3. Need CDN
4. Build can be slow

43. LOAD
BALANCING
DATABASE SESSION
FILE SYSTEM ASSETS DEPLOYMENT

44. Deployment Can Be As Simple As
BUT a lot of things can go wrong with this

45. Deploy Command
Things can go wrong,
e.g. failure on deploy or
bug after deploying,
need rollback

46. Deployment & Automation
Technologies

47. Some Considerations
» Composer installation after code pull
» Asset installation, build, compress after code pull
» Load balancer request draining before code
symlink
» Local cache clean up
» JIT warming up (if using HHVM)
» Health check for load balancer
» Blue-green deployment

48. NOW FOR
CONCLUSION!

49. ❏ Scaling Out has more better
merits in common use cases
❏ App has to be Stateless for
scaling out
❏ Data storages has to be
Centralized

50. THANKS!
You can find me at
» @petrabarus
» petra.barus@gmail.com