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Hand Crafted Artisinal Chef Resources
someara
February 02, 2016
Technology
0
170
Hand Crafted Artisinal Chef Resources
Configuration Management Camp
Ghent Belgium
February 2016
someara
February 02, 2016
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Transcript
Hand Crafted Artisanal Chef Resources
Config Management Camp Ghent, Belgium February 2016
Sean OMeara sean@chef.io @someara
whoami
Part 1
Writing library cookbooks An opinionated workflow Step by step
Step 1 - Disregard dogma “Unit tests first” is a
dirty lie https://flic.kr/p/aTSiXF
Step 2 - Make things up Then work backwards https://flic.kr/p/dXkQ5s
Contrived examples are the best examples
None
Place this off to the side, we will come back
for it later.
Step 3 - Create a cookbook By hand. Be a
wizard. https://flic.kr/p/3mMW6e
mkdir -p ~/src/custom-resources-tutorial cd ~/src/custom-resources-tutorial emacs metadata.rb
None
Step 4 - Embed a test cookbook. By hand. Be
a wizard. Again. https://flic.kr/p/ai36NG
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
None
Step 5 - Tell Berkshelf about it https://flic.kr/p/k5jmja
cd ~/src/custom-resources-tutorial emacs Berksfile
None
Step 6 - Configure Test Kitchen https://flic.kr/p/r38F5c
emacs .kitchen.yml
None
kitchen test ; echo $?
Step 7 - Save game https://flic.kr/p/6ZJ4G7
cd ~/src/custom-resources-tutorial cp ~/src/chef-cookbooks/docker/.gitignore . cp ~/src/chef-cookbooks/docker/.rubocop.yml .
rubocop -a git init git add . git commit -a
-m 'v0.0.1 - cookbook skeleton' git tag v0.0.1
Step 8 - Use resource in test recipe https://flic.kr/p/8MuUAX
emacs test/cookbooks/my_file_test/recipes/ default.rb
None
kitchen converge ; echo $?
Step 9 - Implement resource https://flic.kr/p/bkVKRb
cd ~/src/custom-resources-tutorial mkdir libraries emacs libraries/my_file.rb
None
kitchen converge ; echo $? kitchen converge ; echo $?
Step 10 - Test for behavior https://i.ytimg.com/vi/1y8Rqvz-Jcg/ maxresdefault.jpgz
mkdir -p test/integration/my_file/inspec emacs -p test/integration/my_file/inspec/ run_spec.rb
None
kitchen verify ; echo $?
Step 11 - Add specs and commit https://flic.kr/p/rrgfZh
cd ~/src/custom-resources-tutorial mkdir spec emacs spec/spec_helper.rb
None
emacs spec/my_file_spec.rb
None
rubocop -a rspec ; echo $? git add . git
commit -a -m “v0.1.0 - my_file resource” git tag v0.1.0
stove 0.1.0
Step 12 - Iterate indefinitely https://flic.kr/p/8Ny8Jt
Congratulations, you have now written one software.
You must now maintain it forever.
muahaha.
None
Part 2
Custom Resources Tips and Tricks
Be explicit https://flic.kr/p/pz1JAo
None
None
None
None
Converge twice during development Use markers for “negative” actions https://flic.kr/p/pqwd5U
None
None
Tests let you refactor with confidence https://flic.kr/p/4WnjM4
None
STAR WIPE
None
Pure Ruby resources https://flic.kr/p/5km2fM
Pure Ruby resources utilize - The Ruby Standard Library -
Chef helper libs (mixlib-shellout) - Ruby gems
None
It might make sense to vendor gems
load_current_value - Runs at converge time - Just before the
action body - Loads desired state values
None
converge_if_changed - Runs if any desired_state: true property differs from
user input - desired_state: false avoids comparison
None
coerce transforms values - Called when property is set -
Called when property is read - Use this to raise errors on bad input
The docker_container resource uses coercion heavily https://github.com/chef-cookbooks/ docker/blob/master/libraries/ docker_container.rb
lazy defaults - Delays evaluation until used - Useful for
calculated values
None
Composite resources https://flic.kr/p/fm58oo
Composite resources - Reuse Chef resources - Actions look like
recipes - Do not use load_current_value
etcd_installation_binary :create
httpd_config_rhel :create
Avoid leaky abstractions https://flic.kr/p/7d1kDc
Resources should be minimalist
Early versions might be simple
None
They rarely stay that way
Iterate and add more features Break down into smaller resources
Use naming semantics to describe strategy
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
Recycle patterns as they emerge
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
Chef selects defaults with the provider resolution system
…
…
Compose resources Most specific to least specific
None
Enjoy
fin