Simple script to audit AWS EC2 Availability Zone usage, to spot imbalances

azaudit.rb

#!/usr/bin/env ruby

# Audits the AZs your instances are running in, and reports back. 
# If you want to run this from an AWS instance without keys, 
# its IAM Role must be granted at least the following:
#
#{
# "Statement": [
# {
# "Action": [
# "ec2:DescribeInstances",
# ],
# "Effect": "Allow",
# "Resource": "*"
# }
# ]
# }

require 'rubygems'
require 'trollop' # Option parsing made stupid easy
require 'aws-sdk'
require 'json'
require 'net/http'
  
class AZ
  attr_accessor :name, :instances, :count

  def initialize(name)
    @name = name
    @instances = Hash.new
    @count = 0
  end

  # Add a running instance (I)
  def add_instance(entry)
    @instances[entry] = @instances.has_key?(entry) ? @instances[entry] + 1 : 1
    @count += 1
  end
  
end


opts = Trollop::options do
  opt :region, "AWS Region",
    :type => String,
    :default => 'us-east-1'
  opt :localkeys, "Use local AWS credentials"
  opt :csvreport, "Output report in CSV (TSV, actually)"
  opt :verbose, "Spell out the variables"
  opt :debug, "Be noisy"
end

# If you need to deal with keys/credentials, do that here.
ec2 = AWS::EC2.new(:region => opts[:region])
AZs = Hash.new

# Collect running instances, add them to the appropriate AZ object
ec2.instances.each {|i|
  next unless i.status.to_s == 'running'
  puts "[d] I id: #{i.id} #{i.availability_zone} #{i.instance_type}" if opts[:debug]
    
  unless AZs.has_key?(i.availability_zone)
    AZs[i.availability_zone] = AZ.new(i.availability_zone)
  end
    
  AZs[i.availability_zone].add_instance(i.instance_type)
    
}

AZs.each_pair {|name, az|
  puts "#{name}: #{az.count}"
}