Refactor the (*raft)Step for the case m.Term > r.Term

Signed-off-by: Benjamin Wang <[email protected]>

raft.go

@@ -1075,17 +1075,22 @@ func (r *raft) Step(m pb.Message) error {
 					r.id, last.term, last.index, r.Vote, m.Type, m.From, m.LogTerm, m.Index, r.Term, r.electionTimeout-r.electionElapsed)
 				return nil
 			}
-		}
-		switch {
-		case m.Type == pb.MsgPreVote:
-			// Never change our term in response to a PreVote
-		case m.Type == pb.MsgPreVoteResp && !m.Reject:
+
+			if m.Type == pb.MsgPreVote {
+				// Never change our term in response to a PreVote
+			} else {
+				// m.Type == pb.MsgVote
+				r.logger.Infof("%x [term: %d] received a pb.MsgVote message with higher term from %x [term: %d]",
+					r.id, r.Term, m.From, m.Term)
+				r.becomeFollower(m.Term, None)
+			}
+		} else if m.Type == pb.MsgPreVoteResp && !m.Reject {
 			// We send pre-vote requests with a term in our future. If the
 			// pre-vote is granted, we will increment our term when we get a
 			// quorum. If it is not, the term comes from the node that
 			// rejected our vote so we should become a follower at the new
 			// term.
-		default:
+		} else {
 			r.logger.Infof("%x [term: %d] received a %s message with higher term from %x [term: %d]",
 				r.id, r.Term, m.Type, m.From, m.Term)
 			if m.Type == pb.MsgApp || m.Type == pb.MsgHeartbeat || m.Type == pb.MsgSnap {