Hand Crafted Artisinal Chef Resources

Transcript

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   Hand Crafted Artisanal Chef Resources

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   Config Management Camp Ghent, Belgium February 2016

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   Sean OMeara sean@chef.io @someara

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   whoami

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   Part 1

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   Writing library cookbooks An opinionated workflow Step by step

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

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

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   Contrived examples are the best examples

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    None
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    Place this off to the side, we will come back

    for it later.
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    Step 3 - Create a cookbook By hand. Be a

    wizard. https://flic.kr/p/3mMW6e
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    mkdir -p ~/src/custom-resources-tutorial cd ~/src/custom-resources-tutorial emacs metadata.rb

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    None
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    Step 4 - Embed a test cookbook. By hand. Be

    a wizard. Again. https://flic.kr/p/ai36NG
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    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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    None
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    Step 5 - Tell Berkshelf about it https://flic.kr/p/k5jmja

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

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    None
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    Step 6 - Configure Test Kitchen https://flic.kr/p/r38F5c

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    emacs .kitchen.yml

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    None
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    kitchen test ; echo $?

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

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

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

    -m 'v0.0.1 - cookbook skeleton' git tag v0.0.1
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    Step 8 - Use resource in test recipe https://flic.kr/p/8MuUAX

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

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    None
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    kitchen converge ; echo $?

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

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

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    None
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    kitchen converge ; echo $? kitchen converge ; echo $?

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

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

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    None
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    kitchen verify ; echo $?

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

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

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    None
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    emacs spec/my_file_spec.rb

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    None
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    rubocop -a rspec ; echo $? git add . git

    commit -a -m “v0.1.0 - my_file resource” git tag v0.1.0
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    stove 0.1.0

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

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    Congratulations, you have now written one software.

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    You must now maintain it forever.

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    muahaha.

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    None
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    Part 2

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    Custom Resources Tips and Tricks

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

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    None
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    None
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    None
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    None
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    Converge twice during development Use markers for “negative” actions https://flic.kr/p/pqwd5U

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    None
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    None
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    Tests let you refactor with confidence https://flic.kr/p/4WnjM4

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    None
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    STAR WIPE

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    None
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    Pure Ruby resources https://flic.kr/p/5km2fM

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    Pure Ruby resources utilize - The Ruby Standard Library -

    Chef helper libs (mixlib-shellout) - Ruby gems
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    None
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    It might make sense to vendor gems

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    load_current_value - Runs at converge time - Just before the

    action body - Loads desired state values
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    None
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    converge_if_changed - Runs if any desired_state: true property differs from

    user input - desired_state: false avoids comparison
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    None
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    coerce transforms values - Called when property is set -

    Called when property is read - Use this to raise errors on bad input
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    The docker_container resource uses coercion heavily https://github.com/chef-cookbooks/ docker/blob/master/libraries/ docker_container.rb

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    lazy defaults - Delays evaluation until used - Useful for

    calculated values
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    None
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    Composite resources https://flic.kr/p/fm58oo

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    Composite resources - Reuse Chef resources - Actions look like

    recipes - Do not use load_current_value
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    etcd_installation_binary :create

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    httpd_config_rhel :create

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

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    Resources should be minimalist

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    Early versions might be simple

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    None
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    They rarely stay that way

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    Iterate and add more features Break down into smaller resources

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    Use naming semantics to describe strategy

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    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

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    Recycle patterns as they emerge

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    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

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    Chef selects defaults with the provider resolution system

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    …

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    …

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    Compose resources Most specific to least specific

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    None
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    Enjoy

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    fin