Lessons learned while building Omroep.nl

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

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

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

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

Requirements

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

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

Moar numbers

• 410 Cucumber scenarios, 600 step deﬁnitions
• 2235 RSpec speciﬁcations

so it must be bug-free, right? ;-)

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

Tools: app monitoring

Hoptoad New Relic RPM

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 %

Servers

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

Architecture
Front proxy Front proxy

Application Application Application Application
server server server server

Database memcache

Workﬂow

• BDD
• Shared behaviours
• Performance testing
• Staging and production environment

BDD

• RSpec
• Cucumber
• (Webrat)

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

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

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

Shared behaviours

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

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

Workﬂow: performance testing

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

Challenges

• Content Management System
• Loads and loads and loads of external data

CMS

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

CMS: Articles
Subsite

Thema Page Special

Article

Link Feed Image

Media DB

• Implemented as REST app
• To be used as REST service
• Files, folders, crops

External data
• RSS feeds

• EPG data

• Zelda

• Babel

• News/sport/teletekst

• Twitter

• Lots of custom XML formats

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

External data: EPG data

Zelda

don’t sue us Nintendo... please? :)

External data

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

<!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?
)>

<!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)>

Lessons learned

• Cache the crap out of everything
• Rescue everything
• Test everything (frontend and backend)

Caching

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

Case: article views

• Article is page cached
• Update the number of views in realtime?

Use AJAX!

<% javascript_tag do %>
<%= remote_function :url =>
update_views_article_path(@article) %>
<% end %>

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!

Caching external data

• Don’t expire cache (preferrably)
• Explicitly overwrite
• Update in background (feeeeeeeds)
• memcache FTW!

memcache

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

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...

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

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

Conclusions

• Test
• Optimize
• Monitor

What’s next for us?

• Building a high-performance backend
• Uitzending Gemist statistics API
• 250+ reqs/s at minimum

Lessons learned while building Omroep.nl

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