Hi, I have a question about the leader-based atomic broadcast used in ZooKeeper.
According to the Zab paper "A simple totally ordered broadcast protocol"[1], the protocol has the requirement of reliable delivery: If a message is delivered to one server, it will be eventually delivered by all correct servers. ***My question is: When will the leader delete the message from its FIFO queue? I assume the leader won't delete the message until the message is delivered to all servers? If so, will the leader's FIFO queue keep increasing when there exists a slow follower (or slow connection), where it takes a long time for the slow follower to receive a message? Thank you very much! [1] https://www.datadoghq.com/pdf/zab.totally-ordered-broadcast-protocol.2008.pdf Best, Meng
