ContactRocket/engine/app/models/resolver.rb

require 'rubydns'
require 'rubydns/system'
class Resolver

  def resolve(domains=[])

    return false if domains.empty?

    resolver = RubyDNS::Resolver.new(RubyDNS::System::nameservers)
    dead = []
    alive = []

    EventMachine::run do

     domains.each do |domain|
          resolver.query(domain) do |response|
            if response.answer.blank?
              dead << domain
            else
              alive << domain
            end
          end
     end

     EventMachine::stop

    end

    results = {}
    results[:dead] = dead
    results[:alive] = alive
    results

  end
end