(Note that messages that are no longer being stored are not necessarily immediately deleted, and may still be accessible until the next ledger rollover. Because clients cannot predict when rollovers may happen, it is not wise to rely on a rollover not happening at an inconvenient point in time.)
由于不太知道bookkeeper的内部原理，也没有使用过它，所以上面这段文字不太理解是什么意思，能指点一下吗，感谢。
