This document provides lessons learned from building the Dutch public broadcasting company's website omroep.nl. Key points include using Ruby on Rails, BDD with RSpec and Cucumber, caching everything possible, rescuing errors, testing extensively, and handling large amounts of external data from various XML/RSS feeds and APIs. Performance was optimized through techniques like moving static assets to a front proxy, page caching, fragment caching, and using Memcache. The team of 6 people built the CMS from scratch over 6 months.

1. Lessons learned while
building omroep.nl
Bart Zonneveld (@bartzon)
Sjoerd Tieleman (@tieleman)

2. Nederlandse Publieke Omroep
Dutch Public broadcasting Company
AVRO Joodse Omroep NMO Teleac
BNN KRO NOS TROS
BOS LLiNK NPS VARA
EO MAX OHM VPRO
HUMAN NCRV RKK ZvK
IKON NIO RVU

3. Rails sites
• Beetlejuice • Radio 1
• Centrale • Z@PP
navigatie
• Omroep.nl • Z@ppelin
• Nederland 1 • Zelda
• Nederland 3 • Various tools

5. Team
• 2 coders
• 1 designer
• 1 editor
• 1 project manager
6 months, CMS built from scratch

6. Requirements
• Handle 30.000-40.000 pageviews per day
• Handle traffic spikes
• Flexible, multi user CMS
• Loads of external data

7. Daily spread

8. Some numbers
+----------------------+-------+-------+---------+---------+-----+-------+
| Name | Lines | LOC | Classes | Methods | M/C | LOC/M |
+----------------------+-------+-------+---------+---------+-----+-------+
| Controllers | 1864 | 1535 | 41 | 185 | 4 | 6 |
| Helpers | 797 | 631 | 1 | 75 | 75 | 6 |
| Models | 1303 | 1055 | 40 | 153 | 3 | 4 |
| Libraries | 814 | 620 | 15 | 79 | 5 | 5 |
| Integration tests | 0 | 0 | 0 | 0 | 0 | 0 |
| Functional tests | 0 | 0 | 0 | 0 | 0 | 0 |
| Unit tests | 0 | 0 | 0 | 0 | 0 | 0 |
| Model specs | 1932 | 1573 | 0 | 9 | 0 | 172 |
| View specs | 7322 | 5950 | 0 | 153 | 0 | 36 |
| Controller specs | 7292 | 5846 | 0 | 175 | 0 | 31 |
| Helper specs | 900 | 676 | 0 | 2 | 0 | 336 |
| Library specs | 56 | 45 | 2 | 12 | 6 | 1 |
+----------------------+-------+-------+---------+---------+-----+-------+
| Total | 22280 | 17931 | 99 | 843 | 8 | 19 |
+----------------------+-------+-------+---------+---------+-----+-------+
Code LOC: 3841 Test LOC: 14090 Code to Test Ratio: 1:3.7

9. Moar numbers
• 410 Cucumber scenarios, 600 step definitions
• 2235 RSpec specifications
so it must be bug-free, right? ;-)

10. Tools
Ruby on Rails 2.3.4 Rspec + Webrat + Cucumber
Apache 2.2 Paperclip
SVN App monitoring: RPM, Hoptoad
MySQL 5 Service monitoring: Nagios
Memcache

11. Tools: app monitoring
Hoptoad New Relic RPM

12. Architecture
• Apache 2.2 with mod_proxy
• Rails 2.3.4 running on Phusion Passenger
2.2.5 with REE
• 4 hosts, each running 4 instances (per app)
Appdex: 1.0, avg. response time 40ms, 130 rpm, db load 0.6 %

13. Servers
• Quadcore Intel Xeon E542, 32 GB Ram
• Fedora 8
• Other mumbojumbo

14. Architecture
Front proxy Front proxy
Application Application Application Application
server server server server
Database memcache

15. Workflow
• BDD
• Shared behaviours
• Performance testing
• Staging and production environment

16. BDD
• RSpec
• Cucumber
• (Webrat)

17. 3 slide intro to BDD:
RSpec
describe Article do
it_should_behave_like "all objects with userstamps"
it_should_behave_like "all objects than can be published"
it_should_behave_like "all objects that have an url"
it_should_behave_like "all objects that can be searched"
it_should_behave_like "all objects with related articles"
it "should not be valid without a name" do
@article.attributes = @valid_attributes.except(:name)
@article.should_not be_valid
end
it "should not be valid without contents" do
@article.attributes = @valid_attributes.except(:contents)
@article.should_not be_valid
end
end

18. 3 slide intro to BDD:
Cucumber features
Feature: Articles on the homepage
As a visitor
I want to view articles on the homepage
So that I can see the latest content
Scenario: 5 most recent articles
Given there are 8 articles
When I visit the homepage
Then I should see the 5 last published articles

19. 3 slide intro to BDD:
Cucumber steps
Given "there are $num articles" do |num|
num.to_i.times { create_article }
end
When "I visit the homepage" do
visit root_path
end
Then "I should see the $num last published articles" do |num|
Article.last_published(num).each do |article|
response.should contain(article.title)
end
end

20. Shared behaviours
• Tags
• User stamps (created by, updated by)
• Searching
• “Related” articles
• Publication timestamps (on/offline at)

21. Shared behaviours
module UserStamps
def self.included(klass)
class Article < ActiveRecord::Base
klass.instance_eval do
include Shared::UserStamps
include InstanceMethods
end include Shared::Published
end include Shared::Url
include Shared::Search
module InstanceMethods include Shared::RelatedArticles
def created_by
User.find_by_id(creator_id) # stuff
end end
def updated_by
User.find_by_id(updater_id)
end
end
end

22. Workflow: performance testing
• ab, httperf, autobench, cURL
• NewRelic RPM
• Safari Web Inspector
• http://railslab.newrelic.com/scaling-rails

23. Autobench

24. Challenges
• Content Management System
• Loads and loads and loads of external data

25. CMS
• Articles, Themas, Specials, Subsites
• Multiple feeds, images, links
• Version control
• Media database

26. CMS: Articles
Subsite
Thema Page Special
Article
Link Feed Image

27. CMS:Version control

28. Media DB
• Implemented as REST app
• To be used as REST service
• Files, folders, crops

29. External data
• RSS feeds
• EPG data
• Zelda
• Babel
• News/sport/teletekst
• Twitter
• Lots of custom XML formats

30. External data: XML/RSS
• Empty feeds
• Encodings are off (Windows-1252,
ISO-8859-1, UTF-8)
• “Custom” fields
• Incorrect fields (dates, unescaped HTML)
• Timeouts
• Everything that can go wrong, will go wrong

31. External data: Twitter

32. External data: EPG data
Zelda
don’t sue us Nintendo... please? :)

33. External data
• Empty feeds
• Retrieving the feed while someone is
updating it
• Required fields that are empty
• DTD?

34. <!ELEMENT aflevering (
prid?, tite?, medium?,
icon?, aankondiging?, inkl?,
ingl?, infi?, inak?, inds?, inbb?,
kykw?, orti?, aant?, land?, lcod?,
psrt?, prem?, inh1?, afle?, atit?,
inh2?, bron?, prij?, inh3?, mail?,
webs?, inhk?, gids_tekst?,
omroepen?, genres?, personen?,
streams?, fragmenten?, serie?
)>

35. <!ELEMENT inkl (#PCDATA)>
<!ELEMENT ingl (#PCDATA)>
<!ELEMENT intt (#PCDATA)>
<!ELEMENT inhh (#PCDATA)>
<!ELEMENT omro (#PCDATA)>
<!ELEMENT lcod (#PCDATA)>
<!ELEMENT herh (#PCDATA)>
<!ELEMENT inds (#PCDATA)>
<!ELEMENT infi (#PCDATA)>
<!ELEMENT inbb (#PCDATA)>
<!ELEMENT genr (#PCDATA)>
<!ELEMENT kykw (#PCDATA)>
<!ELEMENT afle (#PCDATA)>

36. Lessons learned
• Cache the crap out of everything
• Rescue everything
• Test everything (frontend and backend)

37. Caching
• Cache the homepage
• Page cache → Fragment cache
• Don’t cache forms
• Cache as much as possible

38. Case: article views
• Article is page cached
• Update the number of views in realtime?

39. Use AJAX!
<% javascript_tag do %>
<%= remote_function :url =>
update_views_article_path(@article) %>
<% end %>

40. Case: banner items

41. Case: banner items
• Fast requests (<10ms)
• ETags (304 Not Modified)
• Static resource → page cache
• Move to front proxy, frees up Rails cluster
• 1100rpm → 130rpm
• 20ms → 40ms
• Average response time going up? Oh nooooes!

42. Caching external data
• Don’t expire cache (preferrably)
• Explicitly overwrite
• Update in background (feeeeeeeds)
• memcache FTW!

43. memcache
• Escape your keys using CGI::escape
• Max keylength is 250
• Max value size is 1MB

44. Rescueing
def self.get_feed_contents(url)
content = ""
open(url) { |s| content = s.read }
RSS::Parser.parse(content, false).items
rescue => e
logger.warn "Feed #{url} raised error: #{e.message}"
[]
rescue Timeout::Error => e
logger.warn "Feed #{url} timed out: #{e.message}"
[]
end
Timeout::Error is an interrupt...

45. Testing
• rcov
• Refactor your tests
• Peer reviews, external audits
• Run specs/features
(continuously) in parallel
(your Cucumber is too slooooow!)

46. Cucumber salad
num_of_processes.times do |count|
pids << Process.fork do
setup_database(conn, count)
Cucumber::Cli::Main.execute(
["-f", "progress", "-l", "nl", "-r", "features"] +
feature_sets[count]
)
end
end
MacBook Pro
“Regular” Mac Pro (8)
(4)
12:12 4:34 2:12

47. Conclusions
• Test
• Optimize
• Monitor

48. What’s next for us?
• Building a high-performance backend
• Uitzending Gemist statistics API
• 250+ reqs/s at minimum

49. @questions.any?