inventory.rb

require 'json'
require 'csv'
require 'puppet/face'
# Requires installation of https://forge.puppetlabs.com/dalen/puppetdbquery

# comma separated list of fact names you care about
whitelist = File.open('whitelist.csv').read.chomp
headers = whitelist.split(',')

# get yo data
Puppet.initialize_settings
nodes = Puppet::Face[:query, :current].facts('hostname~".*"', :facts => whitelist)

out_csv = CSV.open('inventory.csv', 'wb') do |csv|

  #create header row
  csv << ['node'] + headers

  # get row data
  nodes.each do |node_name, facts|
    values = Array.new
    values.push(node_name)

    headers.each do |header|
      if facts.has_key?(header)
        values.push(facts.fetch(header))
      else
        values.push('')
      end
    end
    csv  << values
  end
end

puts "CSV output to inventory.csv"