Make it SOLID Software Architecture for System Administrators

Gave this talk at the International PHP Conference on October 30th, 2013
Follow me on Twitter: @CodeStars

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.

Transcript

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

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

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

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4. Jimdo
   

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

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

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7. View Slide

8. S O L I D
   

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

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10. the basics
    

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11. software architecture
    VS.
    36 years
    >2000 years
    

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12. configuration management
    Idempotent
    Declarative
    Convergent
    Abstract
    

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13. View Slide

14. 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
    

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15. 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
    

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16. 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]
    }
    }
    

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17. 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!
    

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

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19. View Slide

20. 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]
    }
    }
    }
    

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

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22. 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'] }
    }
    

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24. ?
    

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26. rspec-puppet
    test-kitchen
    

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28. 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
    ?
    

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29. 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 }
    }
    

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

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31. 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
    

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

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35. 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
    }
    

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36. View Slide

37. View Slide

38. 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!
    

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39. >
    

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40. View Slide

41. ?
    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]
    }
    }
    }
    

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

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43. 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.
    

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44. 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.
    

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45. 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.
    

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46. View Slide

47. 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'
    }
    }
    ?
    

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

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50. ?
    

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

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52. # /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
    

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53. 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
    }
    

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54. hiera
    AWS/Cloudformation LDAP
    DNS
    your selfwritten
    stuff
    

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58. What about
    I and L
    in SOLID?
    

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

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

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61. S O L I D
    

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62. View Slide

63. Structure your code!
    Node
    Profile
    Profiles
    Role Profile
    Modules
    Resources
    

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64. Puppet forge
    puppet module registry
    

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65. Dependency Management
    Librarian Puppet
    Berkshelf (chef)
    

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

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67. server spec
    http://serverspec.org/
    

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68. sandboxed
    development
    https://github.com/mlafeldt/skeleton-cookbook
    https://github.com/Jimdo/puppet-skeleton
    

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69. Thank you!
    Rate this talk!
    https://joind.in/9578
    

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

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71. *I ’m just a blank slide*
    

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72. 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
    •
    

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