Kiến trúc phần mềm cho các site chịu tải lớn – Software architecture for high traffic Website Case study giới thiệu về kiến trúc của một site traffic lớn đó là stackoverflow.com - trang hỏi đáp về lập trình rất nổi tiếng Bài trình bày của bạn Ngô Xuân Hòa tại Meetup 4 của Ha Noi .NET Group. Chi tiết vui lòng xem tại: http://tungnt.net

1. Software architecture for high
traffic website
Case study - Stack Overflow
Presenter: Ngô Xuân Hòa (Novaon Adnetwork - Novanet)
Hanoi .Net Meetup

2. Contents
About Stack Overflow
● Beginning
● Restructure #1
● Restructure # 2
● Founders
● Principles
SO architecture
● StackExchange.Redis
● Dapper
● Jil
Open-source Libs

3. About Stack Overflow

4. Founders
Jeff Atwood
Joel Spolsky

5. 2008
Stack Overflow
2009 2010 2011
Server Fault
Stack Exchange 1.0
Stack Exchange 2.0
Stack Overflow Carees
Rome wasn’t build in a day!

6. ● 100+ Q&A Sites
● 600+ million pageviews a month
● 3000+ requests per second
● 16+ million users
● 8+ million question
● 40+ million answers

7. Principles
Perfomance Is a Feature
Cache All The Thing!
Reinvention is OK

8. Stack Overflow Architecture

9. 2 times restructuring
Stack Exchange 1.0
● ASP.NET MVC
● SQL Server
● LINQ to SQL
● Wikipedia DB
Design
Stack Exchange Network
LINQ to SQL
HAProxy
Redis
Lucene.NET
Scale Up
● Cache every things
● Elastic Search
● Reinvention

10. Stack Exchange 1.0 Structure
Windows NLBLoad balancing
IIS Server IIS ServerWeb server
SQL ServerDatabase

11. Window NLB
● Cons:
○ Limit to 8
Nodes
○ Cannot detect
service failed
Web-tier
ASP.NET MVC
LINQ to SQL
SQL Server
● All-in-memory
● Full text search

12. ● 16 million pageviews a month
● 3 million unique visitors a month
● 6 million visits a month

13. Follow none but learn from everyone!

14. Pros
● Bottleneck: Database SQL Server
● High cost to scale up
● Simple
Cons

15. Restructure #1 - Stack Exchange Network
HAProxy
Redis Cache
Lucene.NET
Tag Engine

16. Stack Exchange Network Structure
HAProxy
Redis
IIS Servers
Database
protobuf
sqlhttp http

17. Load Balancing
● HAProxy:
○ Run in Linux
○ Free
Web-tier
ASP.NET MVC 3
LINQ to SQL
jQuery 1.4.5
Lucene.Net
Redis
● In-memory cache
● Master-slave
● Messaging notification

18. 3 Type Cache
Local Cache Site Cache
● Use Redis
● Cache Site’s data:
- Q&As
- Acceptance rates
- ...
Global Cache
● Use Redis
● Cache System Data:
- User info
- Inbox
- ...
● Use
HttpRunTime.Cache
● Cache:
- User Session
- View Count
- ...

19. Update cache flow - Local cache
Local Cache
Redis
DB
Other sites
1 3
2.1
2.2
4
1 - OnStartup - Subcribe invalidation message
to Redis
2.1 - Data changed (by other sites, apps…)
2.2 - Send message to Redis
3 - Redis send Notification to Subscribers
4 - Get data from DB - update Local cache

20. Deployment flow with HAProxy
● Tell HAProxy to take the server out of rotation via a POST
● Delay to let IIS finish current requests (~5 sec)
● Stop the website
● Copy files
● Start the website
● Local testing, update local cache, etc…
● Re-enable HAProxy via another POST

21. ● High performance
● Low-cost Load Balancing
(use HAProxy)
● Use Messaging của Redis
for cache invalidation
Pros
● Too many SQL query
Cons

22. ● 95 million pageviews a month
● 800 requests per second
● 16 million users

23. Restructure #2 - Scale Up
Cache All the Thing
Elastic Search
Reinvention

24. Stack Exchange Network Structure
Elastic Search
Tag Engine
Databases
Redis
HAProxy

25. 5 Level cache
Network Level Local Cache Redis Cache SQL SV Cache SSD
● Network Level: Browser cache…
● Local Cache: HttpRuntime.Cache - Cache all data in memory
● Redis Cache: Cache all data
● SQL Server Cache: Cache all data in memory (the database servers have 384GB of RAM)

26. Cache Flow
● Check Local Cache
● Else, check Redis Cache and update Local Cache
● If Cache Redis doesn’t have data, fetch from databases, then update Redis Cache
and Local Cache

27. Cache All the Things!

28. Pros
● Data has latency
● Very, Very Fast (<400ms)
● Low servers load:
○ IIS: 10-15% CPU usage
○ DB: 10% CPU usage
● 99% request served by cache
Cons

29. ● 95 million pageviews a month
● 800 requests per second
● 16 million users

30. Open-source Libs
• StackExchange.Redis - high perfomance Redis client
• Dapper - a micro ORM - very fast
• Jil - fast JSON Serializer
Reinvention is OK!

31. Reference sources
● http://stackoverflow.com
● http://highscalability.com
● http://codinghorror.com
● http://www.joelonsoftware.com
● http://nickcraver.com
● http://josephwoodward.co.uk/2014/02/the-architecture-of-stackoverflow/

32. Thank you!
Ngô Xuân Hòa
xuanhoa862001@gmail.com