The document outlines the use of Ruby in DevOps, including its features, libraries, and applications in automation, server management, and configuration. It covers various tools such as Chef, Vagrant, and testing frameworks like RSpec, along with code examples for automation scripts, database interactions, and monitoring systems. Additionally, it provides insights into Ruby's syntax, object-oriented programming concepts, and practical usage scenarios for managing services and system configurations.

1. Ruby
for devops
Adam Klein

2. Questions
Ask at any time

3. Why!?

4. Ruby for automation scripts
easy & intuitive
rich libraries and open source

5. DevOps tools
Chef
Capistrano
Server Spec
Vagrant
God

6. Better understanding
of Ruby-based systems

7. About me
Adam Klein
Co-Founder of 500Tech.com
@500TechIL

8. Some stuff to know about Ruby
Interpreted language
It's fun
Rich built-in libraries
Garbage collection
Great open-source

9. Non-devops usages
Mainly used in web server frameworks:
Rails
Sinatra
Grape
Padrino

10. Supports
Mac
Linux
"Windows"

11. Interpreters
Ruby = YARV (>= 1.9)
Latest version = 2.1.1
Other:
MRI (< 1.9)
JRuby
Rubinius
IronRuby

12. Threading
(YARV)
native threads - only one at a time

13. JRuby
Allows Java code integration
Allows parallel multi-threading (JVM threads)

14. Memory
Lazy Garbage Collection
Ruby hardly frees up memory to user space
Ruby on Rails processes consume much memory
JRuby is a memory hog

15. Installation
Install RVM - manages installed ruby versions
rvm use 2.0.0
rvm install ruby-2.1.2
rvm list

16. GEMs
Open source libraries (MIT)
They are just ruby code
Some require native code compilation (C compiler)
Some include an executable
Manage using a Powerful CLI
$ gem install pry
$ gem list aws
$ gem search debugger
$ gem dependency rails -v '4.0.0'

17. Running code
ruby test.rb (run code from file)
irb (interactive)
pry (irb with color)

18. Basic syntax

19. Dynamic vars
num = 5
numbers = [1,2,3]
title = "hello world"
details = {name: 'Adam', company: '500Tech'}
now = Time.new

20. methods
> arr = ["one", "two", "three"]
> csv = arr.join ", "
=> "one, two, three"
> 4.to_f
=> 4.0
> Time.now
=> 2014-07-13 19:23:09 +0300

21. defining methods
def greet(first, last)
"Hello #{first} #{last}"
end

22. Loops & blocks
websites = %w(yad2.co.il
homeless.co.il
winwin.co.il)
websites.each do |website|
scrape(website)
end

23. More block examples
5.times do
putc "."
sleep 1
end
hezkot = (1..10).map {|num| 2 ** num}

24. GEMs
packaged code
online repositories (rubygems.org)
easily managed in terminal
dependency management

25. GEMs
$ gem install nokogiri
> require 'nokogiri'
> path = 'www.google.co.il/search?q=ruby'
> doc = Nokogiri.HTML(open(path))
> doc.css('#ires a').first.text
=> "Ruby Programming Language"

26. Object Oriented
Classes
class Cow
def initialize # constructor
@litres = 10 # instance variable
end
def milk # instance method
@litres -= 1
end
attr_reader :litres # getter method
end

27. Object Oriented
Instances
daisy = Cow.new
daisy.milk
daisy.milk
daisy.litres
=> 8
betty = Cow.new
betty.litres
=> 10

28. Modules / namespaces
module Animal
class Cow
..
end
end
betty = Animal::Cow.new

29. Concrete example
Given:
heroku application
daily backups
maximum 7 backups
Needed:
script to upload backups to S3
Solution:
Ruby!

30. The GEMs
open-uri
aws-sdk

31. The code
require 'open-uri'
require 'aws'
AWS.config(access_key_id: 'XXX', secret_access_key: 'YYY')
bucket = AWS::S3.new.buckets['my_project']
data = open(`heroku pgbackups:url`)
bucket.objects["backups/#{Time.now.to_i}"].write(data)

32. Directories and Files
Dir.pwd
Dir['**.txt']
Dir.open('.').each {|f| ... }
Dir.mkdir('tmp/files')
File.exist?('docs/words.txt')
File.basename?('docs/words.txt')
f = File.open('docs/words.txt')
f.size
f.path

33. DB
client = Mysql2::Client.new
host: 'localhost',
username: 'root'
client.query('select * from users')
.each do |user|
puts user[:name]
end

34. ActiveRecord

35. Migrations
Change DB Schema with ruby code
Keep several branches in sync

36. Example
class CreateProducts < ActiveRecord::Migration
def change
create_table :products do |t|
t.string :name
t.text :description
t.float :price
end
end
end

37. Usage
rake db:migrate
rake db:rollback
rake db:migrate:status
* Note - non rails projects will need custom setup

38. Abstraction of the DB
connection.rb
require 'active_record'
ActiveRecord::Base.establish_connection(
database: 'my_db',
adapter: 'postgresql',
host: '...',
port: ...,
username: '.....'
)

39. Simple Example
Assume we have an 'orders' table
require 'connection'
class Order < ActiveRecord::Base
end
> Order.count
=> 1403
> Order.create price: 1005, title: 'PC'

40. * Note: you can override conventions
Relations
models.rb
class Order < ActiveRecord::Base
has_many :items
end
class Item < ActiveRecord::Base
belongs_to :order
end

41. Relations usage
Order.first.items.sum(:price)
Underlying SQL:
Select sum(price) from items where order_id = (select

42. God
monitoring framework
config files in ruby

43. Simple config file
God.watch do |w|
w.name = "simple"
w.start = "ruby /full/path/to/simple.rb"
w.keepalive
end

44. Complex config files
God.watch do |w|
w.name = "gravatar2-mongrel-#{port}"
w.start = "mongrel_rails start -c #{RAILS_ROOT} -p #{port}
-P #{RAILS_ROOT}/log/mongrel.#{port}.pid -d"
w.stop = "mongrel_rails stop -P #{RAILS_ROOT}/log/mongrel.#{port}.pid"
w.restart = "mongrel_rails restart -P #{RAILS_ROOT}/log/mongrel.#{port}.pid"
w.pid_file = File.join(RAILS_ROOT, "log/mongrel.#{port}.pid")
w.behavior(:clean_pid_file)
w.start_if do |start|
start.condition(:process_running) do |c|
c.interval = 5.seconds
c.running = false
end
end
w.restart_if do |restart|
restart.condition(:memory_usage) do |c|
c.above = 150.megabytes
c.times = [3, 5] # 3 out of 5 intervals

45. end
restart.condition(:cpu_usage) do |c|
c.above = 50.percent
c.times = 5
end
end
# lifecycle
w.lifecycle do |on|
on.condition(:flapping) do |c|
c.to_state = [:start, :restart]
c.times = 5
c.within = 5.minute
c.transition = :unmonitored
c.retry_in = 10.minutes
c.retry_times = 5
c.retry_within = 2.hours
end
end
end
Features
Alert contacts (email, webhooks, campfire, etc.)
Memory / CPU thresholds
Restart logic (retries, intervals)
Modify STOP signal
Grouping processes
Etc.
e.g:
If process goes over 95% CPU 5 times in 1 minutes, restart it. If
this condition was met more than 5 times within 20 minutes,
shutdown the process and alert the admin.

46. Reuse code
def cpu(w, percent = 95, times = 5)
w.restart_if do |restart|
restart.condition(:cpu_usage) do |c|
c.above = percent.percent
c.times = times
end
end
end
def memory(w, limit = 100, times = 5)
...
end

47. Reuse code
God.load('common.god')
God.watch do |w|
w.name = "simple"
w.start = "ruby /full/path/to/simple.rb"
w.keepalive
cpu(w)
memory(w, 150, 3)
flapping
end

48. Use loops
{first: '/first/path/to/file',
second: '/second/path/to/file',
third: '/usr/bin/third'}
.each do |name, path|
God.watch do |w|
w.name = name.gsub('/', '_')
w.start = "ruby #{path}.rb"
...
end
end

49. Debug!
$ gem install pry-debugger
require 'pry'
God.watch do |w|
w.name = "simple"
w.start = "ruby #{ENV['ROOT_DIR']}/simple.rb"
binding.pry
w.keepalive
end

50. Ruby DSLs
Domain Specific Language

51. Chef
"Chef delivers fast, scalable, flexible IT
automation"
All in Ruby:
config files
recipes

52. Chef DSL
file 'foo' do
content 'hello world'
end

53. Without DSL
require 'chef'
Chef.file 'foo' do |f|
f.content 'hello world'
end

54. Vagrant
Create and share development environments easily
develop normally on local filesystem + GIT
run & test on virtual machine (box)
Saves installation & configuration time

55. Vagrantfile
The config file is written in.....
Ruby

56. Share code
common.rb:
RAILS_ROOT = '/my/project'
AWS_KEY = 'XXX'
NODES = 4
...
def timestamp
Time.now.strftime("%Y%m%d%H%M%S")
end
...

57. Reuse code
Vagrantfile:
chef_recipe.rb:
config.god:
require 'common'
...
require 'common'
...
require 'common'
...

58. server spec
Testing server configuration with RSpec

59. Example
describe package('httpd') do
it { should be_installed }
end
describe port(80) do
it { should be_listening }
end
describe file('/etc/httpd/conf/httpd.conf') do
it { should be_file }

60. its(:content) { should match /ServerName www.example.jp/ }
end
Output
package httpd
is installed
service httpd
is enabled
is running (FAILED - 1)
port 80
is listening
file httpd.conf
is a file
has content '...'

61. Output
Failures:
1) service httpd is running
Failure/Error: it('is running') { should be_running}
expected `service("httpd").running?` to return true, got false
# ./test.rb:13:in `block (2 levels) in <top (required)>'

62. Output
Finished in 0.003 seconds (files took 0.18 seconds to load)
6 examples, 1 failure
Failed examples:
rspec ./test.rb:13 # service httpd is running

63. RSpec DSL
describe file('/etc/httpd/conf/httpd.conf') do
before(:each) do ... end
it { should be_file }
its(:content) { should match /ServerName www.example.jp/ }
end

64. Server Spec Methods
describe service('httpd') do
it { should be_enabled }
it { should be_running }
end
describe port(80) do
it { should be_listening }
end

65. describe file('/etc/httpd/conf/httpd.conf') do
it { should be_file }
its(:content) { should match /ServerName www.example.jp/ }
end
Ruby goodness
services = %w(httpd stunnel mysql redis)
services.each do |name|
describe service(name) do
it { should be_enabled }
it { should be_running }
end
end

66. Resources
www.ruby-doc.org
ruby-toolbox.com

67. Questions?
adam@500tech.com
@500TechIL
500tech.com
hackademy.co.il
angular.co.il