thinking through styling and layout of modules, class and defines by tom doran
DESCRIPTION
How do you structure your puppet code? Where do you put the files, how do you name things, how do you structure parameters and hieradata? I’m still stuck on puppet 2.7, how do I write code now to take advantage of puppet 3.0 features when I upgrade? This talk will go through a set of guidelines for writing classes, defines, having defaults and how to use hieradata right. It’ll be focusing on real code with real examples taken from modules I’ve helped write or code review. Whilst suitable for beginners, this talk should hopefully be helpful for more advanced users as whilst most of us have a shared vision of ‘well known’ ways things can be done - we rarely step back and think through exactly why in detail.TRANSCRIPT
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• Still takes effort to understand
•More than one right way to do it
• KISS
• Get data out of manifests
• Follow conventions
Lots of great material
http://www.slideshare.net/PuppetLabs/modern-module-development-ken-barber-2012-edinburgh-puppet-camp http://www.slideshare.net/slideshow/embed_code/25536833 https://speakerdeck.com/player/889a6450ee6b0130026036a0670cc949
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• No manifests except site.pp
• autoload structure
•Modules work with environments
•Well known higher level reuse patterns! (Later)
Modules only!
All code should be in modules, always - with no exceptions except a site.pp
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•Most important for forge modules!
• For your own modules, KISS
• Allow package install to be overridden!
• Allow service to be not managed!
• Don’t manage users!
Be flexible!
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• Puppet 0.x •… upgrade?
• Puppet 2.7 • Parameterized classes • Dynamic scope
• Puppet 3.0 • NO dynamic scope • Data bindings (automatic hiera)
• Puppet 3.3 • Hiera in modules
Version compatibility
http://docs.puppetlabs.com/guides/parameterized_classes.html
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Dynamic scope
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Dynamic scope
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NO Dynamic scope
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Data binding
Puppet 2.7
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Data binding
Puppet 2.7
Puppet 3.x
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ARM9
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ARM9
?????
Eh? Is that a processor type?
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ARM9
Or one of these?
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• In puppet 3.3: modules/foo/data modules/foo/data/common.yaml modules/foo/data/os/Linux.yaml modules/foo/hiera.yaml
• Doesn’t really affect design if you did it right!
ARM9 - hiera in modules
https://github.com/puppetlabs/armatures/blob/master/arm-9.data_in_modules/index.md
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Package / File / Service
Starting at the basics….
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Package / File / Service
Most modules do something like this. Note the ${module_name} variable for DRY http://docs.puppetlabs.com/puppet/3/reference/lang_variables.html#parser-set-variables http://docs.puppetlabs.com/learning/ordering.html#packagefileservice
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Metaparameters
http://docs.puppetlabs.com/learning/ordering.html#packagefileservice
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Package/Config/Service classes
Putting each component in it’s own class makes dependencies simpler / more declarative http://www.devco.net/archives/2009/09/28/simple_puppet_module_structure.php
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• Entry point should always be init.pp: include foo
One entry point
!http://www.devco.net/archives/2009/09/28/simple_puppet_module_structure.php
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• Put inter-class dependencies in init.pp
Externalize dependencies
Some people don’t like this (I do), as it makes the dependencies obvious from the entry point you include. http://www.devco.net/archives/2012/12/13/simple-puppet-module-structure-redux.php
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Separate parameters
This is the traditional method, having a ::params class. This is good when you have conditional logic around parameters. http://docs.puppetlabs.com/puppet/3/reference/lang_classes.html#inheritance http://docs.puppetlabs.com/guides/parameterized_classes.html#appendix-smart-parameter-defaults
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Hiera parameters (2.7)
For simple (non conditional) values, you can just use a hiera lookup. If you’re shipping to the forge you still need params class, if you’re not you can just use hiera.
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Hiera parameters (3.x)
http://docs.puppetlabs.com/puppet/3/reference/lang_classes.html#inheritance http://docs.puppetlabs.com/guides/parameterized_classes.html#appendix-smart-parameter-defaults
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Hiera parameter variance
Data in params.pp is kinda gross. Move it out to common.yaml? Logic for which key to look in can be embedded in the hiera call (instead of params.pp).
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Hiera parameter variance
If your hierarchy includes: os/%{::operatingsystem} common
!You can just use: foo::package_name !
If you have ${::operating_system} in your hierarchy, you can do this simpler thing. Possible to argue this both ways round, but I’d recommend this as it’s more forward compatible (ARM9)
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Hiera parameter variance
If your hierarchy includes: os/%{::operatingsystem} common
!You can just use: foo::package_name !
Unless it’s a forge module :(
If you’re shipping to the forge, you can’t (sanely) rely on puppet 3.3, and you don’t want to force people to add to their hieradata - fallback to params.pp
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Puppet 3.3
Per module hierarchy: foo/data/os/%{::operatingsystem}.yaml foo/data/common.yaml
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• str2bool • any2array • ensure_packages • ensure_resource • get_module_path • getparam • facts.d •many many more!
Use stdlib
https://github.com/puppetlabs/puppetlabs-stdlib
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• ‘true’ vs true • All class parameters • All hiera data
• Other backends may not have booleans!
str2bool
https://github.com/puppetlabs/puppetlabs-stdlib
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• Any time you take an array parameter!
any2array
https://github.com/puppetlabs/puppetlabs-stdlib
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!
• Avoids duplicate resources
!!!
• Same for generic resources
ensure_packages / ensure_resource
https://github.com/puppetlabs/puppetlabs-stdlib
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• nginx::vhost {} • docker::run {}
Toolkits
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• nginx::vhost {} • docker::run {}
• create_resources helper
Toolkits
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Multiple instances
•May have more than one nginx running!
• This is where it gets complex :)
• Class or define params override hiera
• Default params in foo::bar
• Instance params: foo::instance::${instance_name}::bar
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Toolkits + Multiple instances
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getparam (stdlib)
https://github.com/puppetlabs/puppetlabs-stdlib
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Toolkits + Multiple instances
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• Role = node classifier (contains >= 1 profile) • role::webserver
• Profile = use multiple modules + hiera data • profile::apache • profile::tomcat
•Module = Single concern • apache • tomcat
Roles and profiles
http://www.craigdunn.org/2012/05/239/ http://blog.keepingyouhonest.net/?p=443 https://puppetlabs.com/learn/roles-profiles-introduction
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tags for overriding
http://docs.puppetlabs.com/puppet/3/reference/lang_resources.html#amending-attributes-with-a-collector
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Thanks!
$864
http://www.yelp.com/careers?jvi=ogVTXfwL
Questions?
Slides will be up shortly at:
http://slideshare.net/bobtfish/
Mail: [email protected]
Twitter: @bobtfish