class Rufus::Scheduler

def shutdown(opt=nil)
  @started_at = nil
  jobs.each { |j| j.unschedule }
  @work_queue.clear
  if opt == :wait
    join_all_work_threads
  elsif opt == :kill
    kill_all_work_threads
  end
  @lockfile.flock(File::LOCK_UN) if @lockfile
end