7 Stages of Scaling Web Applications

The 7 Stages of Scaling Web Apps: Strategies for Architects John Engates CTO, Rackspace Presented: LinuxWorld Conference & Expo, San Francisco August 6, 2008

Agenda
Desirable Properties in a Web App
Typical Growth Scenario
Best practices
Q & A

Desirable Properties of a Web App
Scalability
High Availability
Performance
Manageability
Low Cost
Feature Rich
Generates $$$

High Availability Defined
High Availability (HA) is a design and implementation that ensures a certain degree of operational continuity.
In other words…
The site is up
The users are happy
The business is not losing money due to outages
(And the system doesn’t cost more than it’s worth)

Scalability Defined
What scalability is:
Scalability is a desirable property of a system which indicates its ability to either handle growing amounts of work in a graceful manner, or to be readily enlarged as demands increase.
What scalability is not :
Raw speed or performance (2 GHz vs. 3 Ghz)
About the operating system (Solaris vs. Linux)
About a particular software technology (Java vs. Python vs. Rails)
About a particular hardware platform (AMD vs. Intel)
About optimized code (10 lines of code vs. 1000)
About storage technology (SAN vs. NAS)

PERFORMANCE AND SCALABILITY ARE NOT THE SAME…

Performance

Scalability

Performance

Scalability

More Scalability

Truth #1
It won’t scale if it’s not designed to scale.

Truth #2
Even if it’s designed to scale, there’s going to be pain!

Pain Scale Back

Stage 1 – The Beginning
Simple architecture
Firewall and load balancer
A pair of web servers
Database server
Internal storage
Low complexity and overhead means quick development and lots of features, fast
No redundancy, low operational cost – great for startups

Stage 2 – More of the same, just bigger
Business is becoming successful – risk tolerance low
Add redundant firewalls, load balancers
Add more web servers for performance
Scale up the database and optimize with DBA help
Add database redundancy
Database storage moves to SAN or DAS
Still relatively simple from an application perspective

Stage 3 – The Pain Begins
Publicity hits (Digg, Slashdot)
Squid or Varnish reverse proxy, or high end load balancers – to cache static content
Add even more web servers
Managing content becomes painful
Single database can’t cut it anymore
Split reads and writes - all writes go to a single master server with read-only slaves
May require some re-coding of the app

Scaling Through Database Replication

Stage 4 – The Pain Intensifies
Caching with memcached
Replication doesn’t work for everything
Single “writes” database - Too many writes - Replication takes too long
Database partitioning starts to make sense
Certain features get their own database
Shared storage makes sense for content
Requires significant re-architecting of the app and DB
Devs may not have done this stuff before

Stage 5 – This Really Hurts!
Panic sets in. Hasn’t anyone done this before?
Re-thinking entire application / business model
Why didn’t we architect this thing for scale?
Can’t just partition on features – what else can we use?
Partitioning based on geography, last name, user ID, etc
Create user-clusters
All features available on each user-cluster
Use a hashing scheme or master DB for locating which user belongs to which cluster

Stage 6 – Getting (a little) less painful
Scalable application and database architecture
Acceptable performance
Starting to add new features again
Optimizing some of the code
Still growing, but it’s manageable

Stage 7 – Entering the unknown…
Where are the remaining bottlenecks?
Power, Space
Bandwidth, CDN, Hosting provider big enough?
Firewall, Load balancer bottlenecks
Storage
People and process
Database technology limits – scalable, key-value store anyone?
All eggs in one basket?
Single datacenter
Single instance of the data
Difficult to replicate data and load balance geographically

Good Practices
Don’t re-invent the wheel, copy someone else
Think Simplicity
Everything should be made as simple as possible -- but not simpler. A. Einstein
Think horizontal…not vertical…on everything
“ How many?” vs. “how fast?”
Use commodity equipment
Make troubleshooting easy
Design for operation
Isolate services
Don’t change lots of things at once

More good practices…
Don’t spend your time over-optimizing
Get your architecture right, adjust often, optimize later (or never)
Test your ability to scale with appropriate load testing
Get a baseline before you think you need it
Use caching wherever it makes sense
Lots of memory and 64-bit architecture helps
Evaluate every feature vs. performance/scalability impact
Nice to have vs. have to have

Managing Change Protects Availability
Don’t underestimate the need for process and documentation
Release Management
Develop – Test – Release
Procedures in place to support these activities
Source Control
RCS, CVS, Subversion
Issue Tracking
Coding Standards
Change Management
Plan – Test – Implement
Critical for high availability infrastructure

Cloud Computing …
The Future?

Questions?
jengates “at” rackspace.com

http://racklabs.com

Help Wanted!

http://www.rackspace.com	872
http://local.sf2excedesoft.dev	305
http://ithelp.ithome.com.tw	300
http://www.webyantra.net	260
http://www.excedesoft.com	252
http://www.profyclub.org	243
http://hi-load.php.com.ua	232
http://www.slideshare.net	163
http://webcrunch.ru	163
http://local.excedesoft2.com	82
http://wiki	77
http://www.hasanozgan.com	68
http://www.saasburst.com	41
http://www.i-knowledge.ru	41
http://hi-load.social.php.com.ua	38
http://blog.ultrainno.com	27
http://yekmer.posterous.com	27
http://www.cnblogs.com	25
http://yekmer.blogspot.com	17
http://swdevlittleinfos.blogspot.com	14
http://feeds.feedburner.com	10
http://php.com.ua	10
http://boand.ru	10
http://www.techiegyan.com	10
http://207.97.206.44	9
http://www.schoox.com	9
http://ord.wip.rackspace.com	8
http://social.php.com.ua	8
http://www.excedesoft.com.ar	8
http://www.brijj.com	7
http://www.jasonslater.co.uk	7
http://ipv6.excedesoft.com	6
http://profyclub.org	6
http://www.mentormob.com	6
http://excedesoft.com	6
http://localhost	5
http://local.excedesoft.symf2.com	5
http://yok.to	5
http://wiki.body.local	4
https://twitter.com	4
http://www.ipv6.excedesoft.com	4
http://tms.ivmx.pl:8080	4
http://grumpy.junta.com.au	4
http://www.devbrijj1.infoedge.com	3
http://kowidi.com	3
http://swdevlittleinfos.blogspot.gr	2
https://twimg0-a.akamaihd.net	2
https://bmx.updatelog.com	2
http://www.wip.rackspacecloud.com	2
http://www.webcrunch.ru	2
http://swdevlittleinfos.blogspot.kr	2

7 Stages of Scaling Web Applications

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