Hand Crafted Artisinal Chef Resources

Transcript

1. Hand Crafted Artisanal Chef Resources

2. Config Management Camp Ghent, Belgium February 2016

3. Sean OMeara sean@chef.io @someara

4. whoami

5. Part 1

6. Writing library cookbooks An opinionated workflow Step by step

7. Step 1 - Disregard dogma “Unit tests first” is a

   dirty lie https://flic.kr/p/aTSiXF

8. Step 2 - Make things up Then work backwards https://flic.kr/p/dXkQ5s

9. Contrived examples are the best examples

10. None

11. Place this off to the side, we will come back

    for it later.

12. Step 3 - Create a cookbook By hand. Be a

    wizard. https://flic.kr/p/3mMW6e

13. mkdir -p ~/src/custom-resources-tutorial cd ~/src/custom-resources-tutorial emacs metadata.rb

14. None

15. Step 4 - Embed a test cookbook. By hand. Be

    a wizard. Again. https://flic.kr/p/ai36NG

16. mkdir -p test/cookbooks/my_file_test cd test/cookbooks/my_file_test echo “test cookbook” > README.md

    mkdir recipes touch recipes/default.rb emacs metadata.rb
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18. Step 5 - Tell Berkshelf about it https://flic.kr/p/k5jmja

19. cd ~/src/custom-resources-tutorial emacs Berksfile

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21. Step 6 - Configure Test Kitchen https://flic.kr/p/r38F5c

22. emacs .kitchen.yml

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24. kitchen test ; echo $?

25. Step 7 - Save game https://flic.kr/p/6ZJ4G7

26. cd ~/src/custom-resources-tutorial cp ~/src/chef-cookbooks/docker/.gitignore . cp ~/src/chef-cookbooks/docker/.rubocop.yml .

27. rubocop -a git init git add . git commit -a

    -m 'v0.0.1 - cookbook skeleton' git tag v0.0.1

28. Step 8 - Use resource in test recipe https://flic.kr/p/8MuUAX

29. emacs test/cookbooks/my_file_test/recipes/ default.rb

30. None

31. kitchen converge ; echo $?

32. Step 9 - Implement resource https://flic.kr/p/bkVKRb

33. cd ~/src/custom-resources-tutorial mkdir libraries emacs libraries/my_file.rb

34. None

35. kitchen converge ; echo $? kitchen converge ; echo $?

36. Step 10 - Test for behavior https://i.ytimg.com/vi/1y8Rqvz-Jcg/ maxresdefault.jpgz

37. mkdir -p test/integration/my_file/inspec emacs -p test/integration/my_file/inspec/ run_spec.rb

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39. kitchen verify ; echo $?

40. Step 11 - Add specs and commit https://flic.kr/p/rrgfZh

41. cd ~/src/custom-resources-tutorial mkdir spec emacs spec/spec_helper.rb

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43. emacs spec/my_file_spec.rb

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45. rubocop -a rspec ; echo $? git add . git

    commit -a -m “v0.1.0 - my_file resource” git tag v0.1.0

46. stove 0.1.0

47. Step 12 - Iterate indefinitely https://flic.kr/p/8Ny8Jt

48. Congratulations, you have now written one software.

49. You must now maintain it forever.

50. muahaha.

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52. Part 2

53. Custom Resources Tips and Tricks

54. Be explicit https://flic.kr/p/pz1JAo

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59. Converge twice during development Use markers for “negative” actions https://flic.kr/p/pqwd5U

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62. Tests let you refactor with confidence https://flic.kr/p/4WnjM4

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64. STAR WIPE

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66. Pure Ruby resources https://flic.kr/p/5km2fM

67. Pure Ruby resources utilize - The Ruby Standard Library -

    Chef helper libs (mixlib-shellout) - Ruby gems
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69. It might make sense to vendor gems

70. load_current_value - Runs at converge time - Just before the

    action body - Loads desired state values
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72. converge_if_changed - Runs if any desired_state: true property differs from

    user input - desired_state: false avoids comparison
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74. coerce transforms values - Called when property is set -

    Called when property is read - Use this to raise errors on bad input

75. The docker_container resource uses coercion heavily https://github.com/chef-cookbooks/ docker/blob/master/libraries/ docker_container.rb

76. lazy defaults - Delays evaluation until used - Useful for

    calculated values
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78. Composite resources https://flic.kr/p/fm58oo

79. Composite resources - Reuse Chef resources - Actions look like

    recipes - Do not use load_current_value

80. etcd_installation_binary :create

81. httpd_config_rhel :create

82. Avoid leaky abstractions https://flic.kr/p/7d1kDc

83. Resources should be minimalist

84. Early versions might be simple

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86. They rarely stay that way

87. Iterate and add more features Break down into smaller resources

88. Use naming semantics to describe strategy

89. etcd_installation_binary etcd_installation_docker etcd_installation_package etcd_service_manager_docker etcd_service_manager_execute etcd_service_manager_systemd etcd_service_manager_sysvinit etcd_service_manager_upstart

90. Recycle patterns as they emerge

91. docker_installation_binary docker_installation_package docker_installation_script docker_service_manager_execute docker_service_manager_systemd docker_service_manager_sysvinit docker_service_manager_upstart

92. Chef selects defaults with the provider resolution system

93. …

94. …

95. Compose resources Most specific to least specific

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97. Enjoy

98. fin