{
  ## main loop

  if (cache_is_good()) {
    show_cache_and_exit("current");
  }
  if (cache_is_stale()) {
    if (i_am_the_writer()) {
      if (i_can_fork()) {
        if (i_am_the_parent()) {
          show_cache_and_exit("stale");
        }
        ## child does:
        be_a_child();
        update_cache();
        exit 0;
      }
      ## cannot fork, so it's up to me
      update_cache();
      show_cache_and_exit("current");
    }
    ## I'm not the writer, so show old cache
    show_cache_and_exit("stale");
  }
  ## cache is dead
  if (i_am_the_writer()) {
    update_cache();
    show_cache_and_exit("current");
  }
  ## we cannot do anything about a bad cache, so retry
  close_cache();
  sleep 5;
  redo;
}