an example of using rest_graph to query New Relic

newrelic_data.rb

    # returns like this:
    # {"Apdex"=>"0.85 [0.5]", "Error Rate"=>"0.33%",
    #  "Throughput"=>"202 rpm", "CPU"=>"11%", "Response Time"=>"330 ms",
    #  "Errors"=>"0.67 epm", "Memory"=>"135 MB", "DB"=>"4.3%"}

    def newrelic_data
      key = Variant.current.newrelic_api_key
      url = Variant.current.newrelic_data_url
      return {} unless url # not using newrelic

      xml = rest_graph.request({:headers     => {'x-api-key' => key},
                                :expires_in  => 1.minutes,
                                :auto_decode => false},
                               [:get, url])
      doc = Nokogiri::XML.parse(xml)

      return {} unless doc.errors.empty? # parse error
      return {} unless doc.root # empty document (wrong format)

      data = doc.root.xpath('threshold_value')

      return {} if data.empty? # no threshold_value (wrong format)

      return data.inject({}){ |r, i|
        r[i['name']] = i['formatted_metric_value']; r }

    rescue RestClient::Exception, SystemCallError # network error
      {}
    end

Where would you define rest_graph variable?