Using a variable inside a Chef recipe

Question

I'm using chef-cookbook-hostname cookbook to setup node's hostname. I don't want my hostname to be hard coded in the attribute file (default['set_fqdn']).

Instead the hostname will be read from a VM definition XML file. I come up with the following default recipe but apparently the variable fqdn is not given value. Is there any idea why this happens or any better to achieve my task?

ruby_block "Find-VM-Hostname" do
   block do
     require 'rexml/document'
     require 'net/http'
     url = 'http://chef-workstation/services.xml'
     file = Net::HTTP.get_response(URI.parse(url)).body
     doc = REXML::Document.new(file)
     REXML::XPath.each(doc, "service_parameters/parameter") do |element|
     if element.attributes["name"].include?"Hostname"
        fqdn = element.attributes["value"]  #this statement does not give value to fqdn
     end
     end
    end
    action :nothing
end
if fqdn
  fqdn = fqdn.sub('*', node.name)
  fqdn =~ /^([^.]+)/
  hostname = Regexp.last_match[1]

  case node['platform']
   when 'freebsd'
    directory '/etc/rc.conf.d' do
      mode '0755'
    end

    file '/etc/rc.conf.d/hostname' do
      content "hostname=#{fqdn}\n"
      mode '0644'
      notifies :reload, 'ohai[reload]'
     end
   else
    file '/etc/hostname' do
       content "#{hostname}\n"
       mode '0644'
       notifies :reload, 'ohai[reload]', :immediately
    end
   end

Answer 1

The source of the problem here is that you are setting the variable fqdn inside the scope of a ruby_block and are attempting to make reference to that variable at the compilation phase. The ruby_block resources allows the ability to run ruby code during the convergence phase.

Given that you appear to be using the fqdn to setup the resource set, it looks as though you can remove the ruby block from around the ruby code. e.g.

fqdn = // logic to get fqdn

file '/tmp/file' do
  content "fqdn=#{fqdn}"
end