並列に実行して最初に返ってきた結果を得るやつ

duel.rb

class Duel
  def initialize(*jobs)
    @lock = Mutex.new
    @done = false
    make_thread(jobs)
  end

  def join
    return if @done
    @threads.first.join
  end

  def done?
    lock {
      @done
    }
  end

  def kill
    lock {
      _kill
    }
  end

  def result
    raise 'running' unless done?
    @result
  end

  protected

  def make_thread(jobs)
    @threads = jobs.map{|job|
      Thread.new {
        result = job.call
        kill
        @result = result
      }
    }
  end

  def lock(&block)
    res = nil
    @lock.synchronize {
      res = block.call
    }
    res
  end

  def _kill
    @threads.select{ |t|
      t != Thread.current
    }.each{ |t|
      t.kill
    }
    @done = true
  end
end

require 'open-uri'
require 'nokogiri'

duel = Duel.new(lambda{
    (Nokogiri open 'http://hitode909.hatenablog.com').at('title').content
  },
  lambda {
    (Nokogiri open 'http://hatenablog.com').at('title').content
  }
  )

duel.join
puts duel.result