ec2tags.rb

require 'facter'
require 'time'
require 'yaml'
require 'json'

if Facter.value("ec2_instance_id") != nil
  # Inspired by: http://puppetlabs.com/blog/facter-part-3-caching-and-ttl
  #
  # facts cache directory/file on puppet agent:
  facts_cache_dir='/etc/puppet/facts.d'
  ec2_cache_file=facts_cache_dir+'/ec2.yaml'
  # facts cache time to live in seconds (1 hour)
  facts_cache_ttl=3600

  if File::exist?(ec2_cache_file) and YAML.load_file(ec2_cache_file) then
    ec2_cache=YAML.load_file(ec2_cache_file)
    ec2_data=ec2_cache
    cache_time=File.mtime(ec2_cache_file)
  else
    Facter.debug("Debug: no ec2.yaml local cache. Generating...")
    ec2_cache={}
    cache_time=Time.at(0)
  end

  # retrieve new ec2 data if no local cache, or fact exceeds TTL
  if ec2_cache.empty? || (Time.now - cache_time) > facts_cache_ttl
    begin
      require 'aws'
      instance_id = Facter.value("ec2_instance_id")
      region = Facter.value("ec2_placement_availability_zone")[0..-2]
      # IAM User 'ec2reader', read-only EC2 credentials, until we move to IAM Roles
      AWS.config(
        "access_key_id" => "XXXXXXXXX",
        "secret_access_key" => "XXXXXXXXXXXX",
        "region" => region
      )

      ec2 = AWS.ec2
      ec2_data = ec2.instances[instance_id].tags.to_h
      raise "No EC2 tags found for #{instance_id}" if ec2_data.empty?
      # Prepend "ec2_tag_" to each tag name
      ec2_data = Hash[ec2_data.map { |k, v| ["ec2_tag_#{k.downcase}", v] }]

      begin
        Dir.mkdir(facts_cache_dir) if !File::exists?(facts_cache_dir)
        File.open(ec2_cache_file, 'w') do |out|
          YAML.dump(ec2_data, out)
        end
      rescue
        Facter.warn("Err: failed to write ec2.yaml cache file.")
      end
    rescue => e
      Facter.warn("Err: failed to obtain ec2 data from api. #{e}")
      ec2_data=ec2_cache
    end
  end

  # add facts to Facter
  ec2_data.each_pair do |name, value|
    # This allows us to push arrays up as tags, since tags only support strings
    # Could just use eval here...security?
    #
    # Does it look like an array, e.g "['foo', 'bar']"
    if /\[(?:[^,]+,)*[^,]+\]/ =~ value
      value.gsub!("'", '"')
      value = JSON.parse(value)
    end
    Facter.add(name) { setcode { value } }
  end
end