Lightweight resource provider (LWRP) provides an option of extending the list of available resources by extending it features and allows Chef user to create custom resources.
By creating custom resources one can simply write cookbooks because one can own enriched custom resources using Chef DSL which helps in making the recipe code more expressive.
In Chef community, many of the custom resources are implemented using LWRPs. There are many working examples of LWRP such as iptables_rules and apt_repository.
Working Method
Make sure one has cookbook name Testing_resource and a run_list of node which contains Testing_resource cookbook.
Building LWRP
Step1 − Create a custom resource in Testing_resource cookbook.
vipin@laptop:~/chef-repo $ subl cookbooks/Testing_resource/resources/default.rb actions :create, :remove attribute :title, kind_of: String, default: "World" attribute :path, kind_of: String, default: "/tmp/greeting.txt"
Step2 − Create a provider for resources in Tesing_resource cookbook.
vipin@laptop:~/chef-repo $ subl cookbooks/Testing_resource/provider/default.rb
action :create do
log "Adding '#{new_resource.name}' greeting as #{new_resource.
path}"
file new_resource.path do
content "#{new_resource.name}, #{new_resource.title}!"
action :create
end
action :remove do
Chef::Log.info "Removing '#{new_resource.name}' greeting #{new_resource.path}"
file new_resource.path do
action :delete
end
end
Step3 − Use a new resource by editing Testing_resource default recipe.
vipin@laptop:~/chef-repo $ subl cookbooks/Tesing_resource/recipes/default.rb greeting "Ohai" do title "Chef" action :create end
Step4 − Upload the modified cookbook to Chef server.
vipin@laptop:~/chef-repo $ knife cookbook upload greeting Uploading greeting [0.1.0]
Step5 − Run Chef-Client on the node.
vipin@server:~$ sudo chef-client ...TRUNCATED OUTPUT... 2013-06-28T21:32:54+00:00] INFO: Processing greeting[Ohai] action create (greeting::default line 9) [2013-06-28T21:32:54+00:00] INFO: Adding 'Ohai' greeting as /tmp/ greeting.txt [2013-06-28T21:32:54+00:00] INFO: Processing file[/tmp/greeting. txt] action create (/srv/chef/file_store/cookbooks/greeting/ providers/default.rb line 7) [2013-06-28T21:32:54+00:00] INFO: entered create [2013-06-28T21:32:54+00:00] INFO: file[/tmp/greeting.txt] created file /tmp/greeting.txt ...TRUNCATED OUTPUT...
Step6 − Validate the content of the generated file.
user@server:~$ cat /tmp/greeting.txt Ohai, Chef!
Workflow Scripts
LWRPs live in cookbooks. A custom resource lives inside the cookbooks, and will be available under the cookbook name. In the workflow, first we define the definitions and then pass the attributes to the resources which is going to be used in the cookbook. Finally, we use those actions and attributes in our recipe.