Starting with Chef or Puppet as a System Administrator will lead you to a problem where you are not sure what’s the best solution of a problem in terms of software architecture. We will give you a brief overview of general well known and battle tested software patterns, which also applies to infrastructure management code. In addition, we‘ll also show Antipatterns, and best practices.

1. Ole Michaelis & Sönke Ruempler | Jimdo
Make it SOLID
Software Architecture for System
Administrators

2. OSDC 2014
Ole Michaelis
“Open Source Rockstar”
@CodeStars
github.com/nesQuick
codestars.eu

3. OSDC 2014
Sönke
Ruempler
“Chief Trolling Officer”
@s0enke
github.com/s0enke
ruempler.eu

4. OSDC 2014
Jimdo

5. OSDC 2014
because infrastructure development is
neither a Jenga game!
S.O.L.I.D

6. OSDC 2014
a little poll!
http://images.fineartamerica.com/images-medium-large/live-long-mr-spock-tobias-woelki.jpg

7. OSDC 2014

8. OSDC 2014
S O L I D

9. OSDC 2014
A
dev/ops
story
Ole
as
Junior Admin
Sönke
as
Dr. Software

10. OSDC 2014
the basics

11. OSDC 2014
configuration management
Idempotent
Declarative
Convergent
Abstract

12. OSDC 2014
software architecture
VS.
36 years
>2000 years

13. OSDC 2014

14. OSDC 2014
node web-1 {
$role = 'web-app-a'
$has_apache = true;
include php5
}
node web-2 {
$role = 'web-app-b'
$has_fcgi=true
include php5
}
# has both enabled, but needs a special config
node web-3 {
$role = 'web-app-c'
$has_fcgi=true
$has_apache=true
include php5
}
Web
App 1
Web
App 2
Web
App 3

15. OSDC 2014
class php5 {
if ($::has_fcgi)
package { 'php5-cli' : ensure => installed }
}
if ($::has_apache) {
package { 'php5-apache' : ensure => installed }
}
if ($::role == 'web-app-c')
package { 'php5-web-app-c-special-module' }
file { '/etc/php5/php.ini' :
source => 'puppet:///modules/php5/php.ini-web-app-c'
}
}
}
Global variable!
Out of Context!
No abstraction

16. OSDC 2014
class php5(
$has_fcgi = false,
$has_apache = false,
$role = undef
) {
if ($has_fcgi)
package { 'php5-cli' : ensure => installed }
}
if ($has_apache) {
package { 'php5-apache' : ensure => installed }
}
if ($role == 'web-app-c') {
package { 'php5-web-app-c-special-module' }
file { '/etc/php5/php.ini' :
source => 'puppet:///modules/php5/php.ini-web-app-c',
require => Package[php-fcgi]
}
}

17. OSDC 2014
node 'web-1' {
$role = 'web-app-a'
$has_apache = true
class { 'php5' :
has_apache => true,
role => 'web-app-a'
}
}
node 'web-2' {
$role = 'web-app-b'
$has_fcgi = true
class { 'php5' :
has_fcgi => true,
role => 'web-app-b'
}
}
Injection!
Injection!

18. OSDC 2014
Would you solder a
lamp directly to the
electrical wiring in a
wall?
Dependency
Inversion

19. OSDC 2014

20. OSDC 2014
class php5(
$has_fcgi = false,
$has_apache = false,
$role = undef
) {
if ($has_fcgi)
package { 'php5-cli' : ensure => installed }
}
if ($has_apache) {
package { 'php5-apache' : ensure => installed }
}
if ($role == 'web-app-c') {
package { 'php5-web-app-c-special-module' }
file { '/etc/php5/php.ini' :
source => 'puppet:///modules/php5/php.ini-web-app-c'
require => Package[php-fcgi]
}
}
}

21. OSDC 2014
Stuff tends to
get big
Beware of god classes!

22. OSDC 2014
if ($lighttpd) {
package { 'php5-cgi': }
configdir { '/etc/php5/cgi': require => Package['php5-cgi'] }
configdir { '/etc/php5/cgi/conf.d': require => Package['php5-cgi'] }
if ($testserver) {
configfile { '/etc/php5/cgi/php.ini': sourcename => 'php5/cgi/php.ini-testserver',
require => Package['php5-cgi'] }
} else {
if ($cms ) {
configfile { '/etc/php5/cgi/php.ini': sourcename => 'php5/cgi/php.ini-cms',
require => Package['php5-cgi'] }
} else {
if ($mgmt ) {
configfile { '/etc/php5/cgi/php.ini': sourcename => 'php5/cgi/php.ini-mgmt',
require => Package['php5-cgi'] }
} else {
if ($lc ) {
configfile { '/etc/php5/cgi/php.ini': sourcename => 'php5/cgi/php.ini-lc.
jimdo.com', require => Package['php5-cgi'] }
} else {
configfile { '/etc/php5/cgi/php.ini': sourcename => 'php5/cgi/php.ini',
require => Package['php5-cgi'] }
}
}
}
}
configfile { '/etc/php5/cgi/conf.d/pdo.ini': sourcename => 'php5/cgi/conf.d/pdo.ini',
require => Package['php5-cgi'] }
}

23. OSDC 2014

24. OSDC 2014
?

25. OSDC 2014

26. OSDC 2014
rspec-puppet
test-kitchen

27. OSDC 2014

28. OSDC 2014
describe :node => 'web-1' do
it { should contain_package ('php5-fcgi') }
end
describe :node => 'web-2' do
it { should contain_package ('php5-apache2' ) }
end
describe :node => 'web-3' do
it { should contain_package ('php5-fcgi') }
it { should contain_package ('php5-apache2' ) }
end
Test php5 class:
Install Package
?

29. OSDC 2014
describe :class => 'php5::fcgi' do
it { should contain_package('php5-cli') }
end
describe :class => 'php5::apache' do
it { should contain_package('php5-apache2') }
end
class php5::fgci {
package { 'php5-cgi' : ensure => installed }
}
class php5::apache {
package { 'php5-apache' : ensure => installed }
}

30. OSDC 2014
Just because you can,
doesn’t mean you
should!
Single
Responsibility

31. OSDC 2014
describe :node => 'web-1' do
it { should include_class('php5::fcgi') }
it { should contain_package('php5-fcgi') }
end
describe :node => 'web-2' do
it { should include_class('php5::apache') }
it { should contain_package('php5-apache2') }
end
node web-1 {
include php5::apache
}
node web-2 {
include php5::fcgi
}
Tests
Code

32. OSDC 2014

33. OSDC 2014
“programs […] are changed by adding
new code, rather than by changing
existing code”
Open Close
Principle

34. OSDC 2014

35. OSDC 2014
new
requirements...
now web app 1 needs a second
node
node web-1 {
$role = 'web-app-a'
include php5::apache
}
node web-1a {
$role = 'web-app-a'
include php5::apache
}

36. OSDC 2014

37. OSDC 2014

38. OSDC 2014
class role::web-app-a {
include php5::apache
}
node web-1 {
include role::web-app-
a
}
node web-1a {
include role::web-app-
a
}
Our new role!
And nodes just
include it!

39. OSDC 2014
>

40. OSDC 2014

41. OSDC 2014
?
class php5::fcgi($role = undef) {
if ($role == 'web-app-c') {
package { 'php5-web-app-c-special-module' }
file { '/etc/php5/php.ini' :
source =>
'puppet:///modules/php5/php.ini-web-app-c',
require => Package[php-fcgi]
}
}
}

42. OSDC 2014
Don’t call us,
we call you!
Hollywood
Principle

43. OSDC 2014
class role::web-app-c::special-php-stuff {
package { 'php5-web-app-c-special-module' }
file { '/etc/php5/php.ini' :
source => 'puppet:///modules/php5/php.ini-web-app-c'
}
}
1. Split out the special case into its own class.

44. OSDC 2014
class php5::fcgi($include_after_package_install = undef) {
package { 'php5-fcgi' : ensure => installed }
if ($include_after_package_install)
include $include_after_package_install
Package['php5-fcgi'] -> Class[$include_after_package_install]
}
}
2. Make the special case pluggable and
reusable.
2a. And name it abstract.

45. OSDC 2014
class role::web-app-c {
include php5::apache
class { 'php5::fcgi' :
include_after_package_install => 'profile::web-app-c::special-php-stuff'
}
}
3. Pass the special case as dependency in our
web-app-c.

46. OSDC 2014

47. OSDC 2014
class profile::web-app-c::special-php-stuff {
package { 'php5-web-app-c-special-module' }
file { '/etc/php5/php.ini' :
source => 'puppet:///modules/php5/php.ini-web-app-c'
}
}
?

48. OSDC 2014
define php5::specialconfig(
$ensure = present,
$sapi,
$module,
$key,
$value,
$section = undef,
$path = '/etc/php5/%s/conf.d/%s.ini'
) {
ini_setting { $title:
ensure => $ensure,
path => sprintf($path, $sapi, $module),
section => $section,
setting => $key,
value => $value,
require => Package["php5-${sapi}"]
}
}

49. OSDC 2014

50. OSDC 2014
?

51. OSDC 2014
“puppet separate code and data”
I’m feeling lucky

52. OSDC 2014
# /etc/puppet/hieradata/web1.yaml
---
classes:
- profile::web-app-a
# /etc/puppet/hieradata/web1a.yaml
---
classes:
- profile::web-app-a
# /etc/puppet/hieradata/web2.yaml
---
classes:
- profile::web-app-c
# /etc/puppet/hieradata/web3.yaml
---
classes:
- profile::web-app-c
puppet-hiera
example in YAML

53. OSDC 2014
node default {
hiera_include('classes')
}
node web-1 {
include role::web-app-a
}
node web-1a {
include role::web-app-a
}
node web-2 {
include role::web-app-b
}
node web-3 {
include role::web-app-c
}

54. OSDC 2014
hiera
AWS/Cloudformation LDAP
DNS
your selfwritten
stuff

55. OSDC 2014

56. OSDC 2014

57. OSDC 2014

58. OSDC 2014
What about
I and L
in SOLID?

59. OSDC 2014
You want me to plug
this in, where?
Interface
Segregation

60. OSDC 2014
If it looks like a duck,
quacks like a duck, but
need batteries - you
probably have the
wrong abstraction!
Liskov
Substitution

61. OSDC 2014
S O L I D

62. OSDC 2014

63. OSDC 2014
Structure your code!Node
ProfileProfilesRole ProfileModules
Resources

64. OSDC 2014
Puppet forge
puppet module registry

65. OSDC 2014
Librarian Puppet
r10k
Berkshelf (chef)

66. OSDC 2014
stdmod
https://github.com/stdmod

67. OSDC 2014
sandboxed
development
https://github.com/mlafeldt/skeleton-cookbook
https://github.com/Jimdo/puppet-skeleton

68. OSDC 2014
server spec
http://serverspec.org/
beaker
(puppet)
https://github.com/puppetlabs/beaker

69. OSDC 2014
Thank you!

70. OSDC 2014
@CodeStars
ole@jimdo.com
@s0enke
soenke@jimdo.com
Questions?

71. OSDC 2014
*I ’m just a blank slide*

72. OSDC 2014
Sources
• http://www.slideshare.net/PuppetLabs/garethrushgrove-puppetconf
• http://www.slideshare.net/PuppetLabs/alessandro-franceschi-new
• https://github.com/jedi4ever/stop-the-fork
• http://lostechies.com/derickbailey/2009/02/11/solid-development-principles-in-motivational-
pictures/
• https://speakerdeck.com/jfryman/refactoring-puppet
• http://www.clker.com/cliparts/e/2/a/d/1206574733930851359Ryan_Taylor_Green_Tick.svg.med.
png
• http://www.craigdunn.org/2012/05/239/
• http://cdn.slashgear.com/wp-content/uploads/2012/10/google-datacenter-tech-13.jpg
• http://deviq.com/Media/Default/Article/Dont-Call-Us-Well-Call-You-Jun-2013.png
• http://www.timeshighereducation.co.uk/Pictures/web/g/q/g/copy_paste_keyboard_button_450.jpg
• http://sanremo.com.au/wp-content/uploads/2013/05/lasagna.jpg
• http://4.bp.blogspot.
com/_9kQQgQD35rY/SaV5p8YBGhI/AAAAAAAAAkg/HOvlhIo7yGI/s400/06_Red_Green_Refactor.
JPG
• http://www.thelolshop.com/wp-content/uploads/2012/11/20121126-101937.jpg
•