1. current process when leader fail, a new leader will be elected, followers will sync with the new leader. After synced, leader send UPTODATE to follower.
2. a corner case but there is a corner case, things will go wrong. suppose message M only exists on leader, after a follower synced with leader, the client connected to the follower will see M. but it only exists on two servers, not on a quorum of servers. If the new leader and the follower failed, message M is lost, but M is already seen by client. 3. one solution So I think UPTODATE can be sent to follower only when a quorum of server synced with the leader. Sincerely
