问我们如何在Memcached读操作中阻塞Ruby on Rails，这样它就不会占用CPU？

EN

   loop do # daemon
     until Rails.cache.fetch("have_dirty_rows") do end
     page = 1
     loop do # paginate dirty rows
       dirty_batch = paginate(#:select     => "*",
                           :order      => "id",
                           :per_page   => DIRTY_GET_BATCH_SIZE,
                           :conditions => {:dirty => 1},
                           :page       => page)
       if dirty_batch.empty?
         Rails.cache.write("have_dirty_rows",false)
         break
       end
       ...
       page = page.next
     end
   end