Logic for simple Auto Scale setup

Auto Scale API Mashup.rb

require 'rubygems'; require 'active_resource'; require 'new_relic_api'

servers = File.open("server_count.txt", "r").first.to_i
instances_per_server = 6
cpu_burn_for_system = 1000.0 * 0.20

NewRelicApi.api_key = "<Your API Key>"

account             = NewRelicApi::Account.find(:first);
application         = account.applications[3];
metrics             = application.threshold_values;
response_time       = metrics.select{|m| m.name == "Response Time" }.first.metric_value
throughput          = metrics.select{|m| m.name == "Throughput" }.first.metric_value
rps                 = throughput / 60 
instances           = servers * instances_per_server
rps_per_instance    = rps / instances
cpu_burn_per_second = rps_per_instance * response_time

if cpu_burn_per_second > 1.0 - cpu_burn_for_system
	puts "Need More Power."
	puts "Start up a block with Fog!"
	
	servers += 1
else
	puts "At or Over Capacity"
	puts "Shut down the block."
	
	servers -= 1
end

# Save servers to a persistent store
File.open("server_count.txt", 'w') { |f| f.write( servers ) }