instance_check.rb

#!/usr/bin/env ruby
require 'resolv'
require 'httparty'
require 'timeout'

File.read('./instances.txt').each_line(chomp: true) do |domain|
  Timeout.timeout(10) do
    Resolv::DNS.new.getaddress(domain)
    code = HTTParty.get("https://#{domain}/about").code
    raise '404' if code == 404
    raise '410' if code == 410
  end
rescue => e
  puts "#{domain} (#{e.message})"
end