A script (should be added to cron) to dynamically update munin hosts

updatemunin.rb

require 'rubygems'
require 'AWS'

ACCESS_KEY_ID = ""
SECRET_KEY = ""
NODEGROUP = ""

@ec2 = AWS::EC2::Base.new(:secret_access_key => SECRET_KEY, :access_key_id => ACCESS_KEY_ID)

output = ""

for reservation in @ec2.describe_instances.reservationSet.item do
	if reservation.groupSet.item.first.groupId == NODEGROUP		
		for instance in reservation.instancesSet.item do
			output += "[appservers;#{instance.privateDnsName}]\n"
			output += "    address #{instance.ipAddress}\n\n"
		end
	end
end

File.open("/etc/munin/munin-conf.d/hosts.conf", 'w+') {|f| f.write(output) }