Hand Crafted Artisinal Chef Resources

Configuration Management Camp
Ghent Belgium
February 2016

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
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
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
18. Step 5 - Tell Berkshelf about it https://flic.kr/p/k5jmja
19. cd ~/src/custom-resources-tutorial emacs Berksfile
21. Step 6 - Configure Test Kitchen https://flic.kr/p/r38F5c
22. emacs .kitchen.yml
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
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
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
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
43. emacs spec/my_file_spec.rb
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.
52. Part 2
53. Custom Resources Tips and Tricks
54. Be explicit https://flic.kr/p/pz1JAo
59. Converge twice during development Use markers for “negative” actions https://flic.kr/p/pqwd5U
62. Tests let you refactor with confidence https://flic.kr/p/4WnjM4
64. STAR WIPE
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
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
72. converge_if_changed - Runs if any desired_state: true property differs from user input - desired_state: false avoids comparison
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
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
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
97. Enjoy
98. fin