As shown below:
rocket-02: LEADER
rocket-01: FOLLOWER
rocket-03: CANDIDATE
In rocket-03, the waterMark is empty, indicating that the node has changed from FOLLOWER to CANDIDATE.
But the term of 03 is 75, the term of 01 and 02 is 74, and the ledgerEndIndex of 01 and 02 is greater than 03, so 03 cannot be used as CANDIDATE.