Migrating from LWRPs to Custom Resources
Overview
It is no longer recommended to write resources in the Light Weight Resource Provider (LWRP) format.
This guide describes how to migrate from an existing LWRP to a Custom Resource.
If you are creating a Custom Resource from scratch please see the Custom Resource Getting Started Guide instead.
Convert files to Custom Resources Layout
LWRPs consist of two library files: a resource and a provider for that resource.
|- libraries
|- provider_rvm_ruby.rb
|- resource_rvm_ruby.rb
These files are merged into one, and moved into the resources directory.
|- resources
|- rvm_ruby.rb
Drop LWRP classes
LWRPs used classes to separate Provider and Resource behaviors, but Custom Resources do not need this distinction. This means that we remove the class definitions in their entirety, as shown in the following example:
#rvm/libraries/resource_rvm_ruby.rb
require 'chef/resource/lwrp_base'
class Chef
class Resource
class RvmRuby < Chef::Resource::LWRPBase
provides :rvm_ruby
self.resource_name = :rvm_ruby
default_action :install
end
end
end
# rvm/libraries/provider_rvm_ruby.rb
require 'chef/provider/lwrp_base'
class Chef
class Provider
class RvmRuby < Chef::Provider::LWRPBase
provides :rvm_ruby
action :install do
remote_file 'rvm_installer' do
path "#{Chef::Config[:file_cache_path]}/rvm_installer.sh"
source node['rvm']['installer_url']
mode '755'
not_if { ::File.exist?("#{Chef::Config[:file_cache_path]}/rvm_installer.sh") }
action :create
end
end
end
end
end
Replace the above files with a singular resource:
#rvm/resources/rvm_ruby.rb
provides :rvm_ruby
default_action :install
action :install do
remote_file 'rvm_installer' do
path "#{Chef::Config[:file_cache_path]}/rvm_installer.sh"
source node['rvm']['installer_url']
mode '755'
not_if { ::File.exist?("#{Chef::Config[:file_cache_path]}/rvm_installer.sh") }
action :create
end
end
Remove Attributes
It is best practice to use properties to change the behavior of resources.
In the previous example example we used an attribute to change the installer_url.
Instead, we should use a property that we can perform checks on. In this case, we can make sure we only accept a String.
#rvm/resources/rvm_ruby.rb
provides :rvm_ruby
default_action :install
property installer_url, String, default: 'https://raw.githubusercontent.com/rvm/rvm/master/binscripts/rvm-installer'
action :install do
remote_file 'rvm_installer' do
path "#{Chef::Config[:file_cache_path]}/rvm_installer.sh"
source new_resource.installer_url
mode '755'
not_if { ::File.exist?("#{Chef::Config[:file_cache_path]}/rvm_installer.sh") }
action :create
end
end