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

2. 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:

4. 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

6. 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

7. 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::Lwrpdemo
resources/directory.rb lwrpdemo_directory Chef::Resource::LwrpdemoDirectory
providers/directory.rb lwrpdemo_directory Chef::Provider::LwrpdemoDirectory

8. LIGHTWEIGHT RESOURCES
The same directory resource if it were using the resource DSL

9. • 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

10. LIGHTWEIGHT PROVIDERS
The same provider if it were using the Provider DSL

11. 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

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

13. 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

15. 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

16. 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