Auto scalling dynos on heroku using NewRelic

heroku_autoscalling.rb

=begin
Need to install gems heroku, newrelic_rpm
 $ gem install heroku newrelic_rpm

Set your apps setting
 app_name    : heroku's app_name of auto scaling
 license_key : NewRelic api key. You can get heroku's NewRelic admin console. "App setting" and "Agent configuration"

execute with cron every minutes
 $ ruby ./adjust_dynos_with_newrelic.rb
=end

require "rubygems"
require 'heroku'
require "heroku/command"

require "newrelic_rpm"
require "new_relic_api"

# setup config
app_name = "app_name"
license_key = "license_key"

# get NewRelic data
NewRelicApi.license_key = license_key
puts values = NewRelicApi::Account.find(:first).applications.first.threshold_values
threshold_value = values.detect{ |v| v.name == "Apdex" }.threshold_value
puts "threshould_value: #{threshold_value}"

# get Heroku data
heroku = Heroku::Command::Auth.new({}).client

current = heroku.info(app_name)[:dynos].to_i
puts "current: #{current}"

# set Heroku dyno
next_dynos = case threshold_value
             when 0
               1
             when 1
               if current > 1
                 (current.to_i - 1)
               else
                 1
               end
             else
               (current + threshold_value)
             end
puts "set: #{heroku.set_dynos(app_name, next_dynos)}"