Recursively extract the hostnames from an ansible inventory file and construct as prometheus sd file.

inv_to_file_sd.rb

#!/bin/env ruby

require 'yaml'
require 'json'

inv = YAML.load_file('auto_inventory.yml')

def find_hosts(parent, h, output)
  h.each {|k, v|
    if v.is_a?(Hash)
      find_hosts(k, v, output)
    elsif k == 'ansible_host'
      return output[parent] = v
    end
  }
  return output
end

hosts = find_hosts(nil, inv, {})

file_sd_config = []

hosts.each {|k, v|
  file_sd_config << {
    'labels' => {
      '__meta_hostname' => k,
      '__meta_network_function' => '',
    },
    'targets' => [v],
  }
}

puts JSON.pretty_generate(file_sd_config)