Ruby on Rails
Performance
Tips
Barcamp Coimbra
2008 Pedro Sousa

Your application is
slow

Caching in RoR

Before you begin
You need to define where to place your cache
(db, memory, file)
You need to tweak you development
environment to test caching

Setup up your
environment
> Rails 2.1
<= Rails 2.0

Types of
Cache Store

Setup up your
environment
development.rb

3 Types of Caching
Page Caching
will always use File Store
Action Caching & Fragment Caching
Will use the cache store you defined

Page Caching
Transforms your views into pure HTML
Best for pages with common content for all
your users or very static pages

Example

Action Caching
Works the same as way as page caching ...
but goes through dispatcher to run filters and
callbacks
For example you can use it with pages that
require authentication

Example

More options

Fragment Caching
More flexible
Great for dynamic content directed at specific
users or conditions (ex: your friends latest blog
posts)
Transforms portions of your views into rendered
HTML

Examples of Caching

Example No caching

Fragment Caching

Oops, I forgot about
the controller

the fragment

Cleaning up
individual cache files

Cleaning up
(brute force)

Cleaning up
with memcached
soon...

DB Model Cache
It’s built into Rails, you don’t have to do
nothing
good for not making the same query twice
limited... only works on the same request

DB Cache
(stupid) example

Memcached
New in Rails 2.0
Simple to use
It’s like a Hash in memory, has a key/value
way of working

Methods
Rails.cache.read
Rails.cache.write
Rails.cache.fetch
Rails.cache.delete
Rails.cache.exist?
Rails.cache.increment
Rails.cache.decrement

example

example with data
Model
Controller

example with data
View (first time)
View (second time, it’s read from the cache)

More info on caching
http://www.railsenvy.com/2007/2/28/rails-caching-
tutorial
http://railscasts.com/episodes/115
http://www.thewebfellas.com/blog/2008/6/9/rails-2-1-
now-with-better-integrated-caching
http://www.akitaonrails.com/2008/5/25/rolling-with-
rails-2-1-the-first-full-tutorial-part-1

Tips for
Optimization

Write Eficient
SQL Queries
Bring only what you need

Eager Loading
Sometimes it’s best to bring all data at once
Prevents N+1 problem
Optimized Eager Loading in Rails 2.1

Create indexes on DB
It really makes a difference
Don’t exagerate

Use Transactions
Group Transactions when possible
Minimizes errors
Less effort on the Database

Reduce http requests
Too many javascript and css files makes your
page slow
You can package all you files into only one

Solutions
Built-in mechanism in Rails 2.0 but without js
minification
Alternative plugin - Bundle-FU
http://code.google.com/p/bundle-fu/

Bundling Example
Before/After

Too many images?
Use CSS Sprites Technique
Less http requests
More hard to manage

References about
CSS Sprites
http://css-tricks.com/css-sprites-what-they-are-why-
theyre-cool-and-how-to-use-them/
http://www.alistapart.com/articles/sprites

Tools

Firebug & Yslow
Track your page performance
Easy to install and run
Download from
http://developer.yahoo.com/yslow/

Examples

More examples

TextMate Footnotes
Useful plugin for Rails
Download from
http://github.com/drnic/rails-footnotes/
tree/master

Other Small Tips
Use LibXML-Ruby for processing XML:
http://libxml.rubyforge.org/
Log only what you need
Use a CDN (ex: Amazon CloudFront)
Patch the RUBY GC:
http://rubyforge.org/projects/railsbench/

That’s it!
Have fun!
Don’t be afraid to
experiment!
Tweak until your
satisfied!
If all fails, invest in
hardware. :)

The End

Thank you
Pedro Sousa
[blog] http://www.reinventar.com
[work] http://www.thinkorange.pt
[linkedin] http://www.linkedin.com/psousa