redisstore用来做session持久层 redis-store /http://stackoverflow.com/questions/4221735/rails-and-caching-is-it-easy-to-switch-between-memcache-and-redishttp://stackoverflow.com/questions/4188620/redis-and-memcache-or-just-redishttp://stackoverflow.com/questions/4188620/redis-and-memcache-or-just-redis