Lwrp presentation

LWRP DEVELOPMENT Speaker: Brian Bianco Email: brian.bianco@gmail.com Twitter: @brianwbianco http://github.com/brianbianco

RESOURCES• Resources represent a piece of system state• We supply resources with data• Ordering of resources is important• Chef ’s Recipe DSL creates resources• During the compile phase these resources are added to the resource collection Example of a resource in a recipe:

PROVIDERS•Providers are the underlying implementation of a resource•They are loaded by Chef::RunContext before Resources• Node attributes are NOT available to them (they can however be passed in via resource attributes)• Normal providers are selected by Chef::Platform

WHAT ARE LWRPS• A DSL provided to make writing resources and providers easier• Useful for creating your own resources and providers without having to implement the actual ruby classes• LWRP has two components: Resource & Provider• Great way to abstract some repeated pattern

FILE STRUCTURE Filename paths are relative to: /cookbooks/lwrpdemo Filename Resource / Provider Generated Class Name resources/default.rb lwrpdemo Chef::Resource::Lwrpdemo providers/default.rb lwrpdemo Chef::Provider::Lwrpdemoresources/directory.rb lwrpdemo_directory Chef::Resource::LwrpdemoDirectoryproviders/directory.rb lwrpdemo_directory Chef::Provider::LwrpdemoDirectory

LIGHTWEIGHT RESOURCESThe same directory resource if it were using the resource DSL

• Resources will look for providers by the same name (you can specify one with the provider resource attribute)• Actions deﬁned in the resource correspond to action methods in the provider• Attributes correspond to methods for the resource (These are called parameters)• Validation parameters: :default :kind_of :required :regex :equal_to :name_attribute :callbacks :respond_to

LIGHTWEIGHT PROVIDERSThe same provider if it were using the Provider DSL

load_current_resource•This method is responsible for loading the current state of the resource into @current_resource• @current_resource = Chef::Resource::LwrpdemoDirectory.new(new_resource.name) updated_by_last_action •Call this method when the provider changes something • When called with true, will ﬁre off notiﬁcations

ANOTHER PROVIDER EXAMPLE Python VirtualEnv Create Action Checking to see if the virtual env exists already

NESTED RESOURCES• Resources can be nested inside of light weight providers• If those resources call updated_by_last action your provider will not inherit that• Luckily there is a pattern you can use to solve this!• You can use the updated? method on any resource in the Chef::ResourceCollection

TIPS • Check out others cookbooks, especially the opscode teams• The default recipe should just make the resource available and setup any necessary ﬁles and conﬁgurations• The #chef channel on irc.freenode.org is full of helpful people • The mailing list is a great place to ask questions http://lists.opscode.com

CONTRIBUTING BACK• http://wiki.opscode.com/display/chef/How+to+Contribute • Create a jira account • Sign the CLA • Submit pull requests• Share you cookbooks on Github and community.opscode.com• Even the smallest bug ﬁxes help

Lwrp presentation

by geekbri on Jul 18, 2012

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