介绍 lock-sequencer 这种方案时作者似乎漏了一种子方案？即在应用侧收到请求时拿着 sequencer 去 consistent cache 中校验一把锁是否还有效，这个子方案相比应用侧只校验 lock generation number 单增适用范围更广（比方说支持多对象的资源锁），缺点是要维护 session（其中含有 cache）。不知道这种子方案在业界是否有实践应用呢？ 对应原文： The recipient server is expected to test whether the sequencer is still valid and has the appropriate mode; if not, it should reject the request. The validity of a sequencer can be checked against the server’s Chubby cache or, if the server does not wish to maintain a session with Chubby, against the most recent sequencer that the server has observed.