Chef Lazy variables usage

I will provide simple example on how to read content of a file and assign it to chef variable and pass that local variable to the template.

# retrieve the jnlp slave secret
ruby_block  'jnlp_secret'  do
block do
if File.exists?('c:/jenkins/secret')
node.default['secret'] = File.read('c:/jenkins/secret').chomp
end
end
end
# Download Jenkins service installer XML
template 'c:/jenkins/jenkins_slave.xml' do
source 'jenkins.xml.erb'
action :create
variables(jenkins_server: node['windows']['jenkins_server'],
node_name: node['hostname'],
secret_key: lazy { node['secret'] })
end

Explanation: In the above recipe , we read the value inside in the secret file and assigned to node.default['secret'] variable which is local to the recipe and passed that variable to the template and passed as variable secret_key: lazy {node['secret']} so the template will get the value of the local variable. It will specially help in defining local variables when they are completely dynamic and using as part of chef run time variables.