How is it that participant A would have a later zxid than the leader? In particular, it seems to me that it should be impossible to have these two facts be true:
1) a transaction has been committed with zxid = z_0. This implies that a quorum of the cluster has accepted this transaction and it has been committed. 2) a new leader election nominates a leader with latest zxid < z_0. My reasoning is that any new leader election has to involve a quorum and at least a sufficient number of that quorum must have accepted zxid >= z_0 and therefore would refuse to be part of the quorum (this is a contradiction). Thus, no leader could be elected with zxid < z_0 if fact (1) is true. What you are describing seems to require both of these facts. Perhaps I am missing something about your suggested scenario. Could you describe what you are thinking in more detail? On Thu, Aug 27, 2020 at 2:08 AM 李珣 <274952...@qq.com> wrote: > version 3.6.1 > org.apache.zookeeper.server.quorum.Learner.java line:605 > Suppose there is a situation > zxid_n is the largest zxid of Participant A (the leader has just resumed > from downtime). Zxid_n has not been recognized by the quorum. Assuming > Participant A is elected as the Leader, then if a follower appears to use > DIFF to synchronize data with the Leader, Leader After sending the > UPTODATE, the leader can already provide external access, but at this time, > the latest zxid_n of the leader has not been supported by the quorum of the > follower. At this time, if a client connects to the leader and sees zxid_n, > then at this time both the leader and the follower are down. For some > reason, the leader cannot be started, and the follower can start normally. > At this time, a new leader can only be elected from the follower. Since the > data of the follower when the follower uses the DIFF method to synchronize > with the leader is still in the memory, it has not had time to persist, > then this The newly elected leader does not have the data of zxid_n, but > before zxid_n has been seen by the client on the old leader, there will be > inconsistencies in the data view. > Is the above situation possible?
