send previndex in heartbeat, all part2b test passed (testbackup ocass…

…ionally run out of time)

src/raft/config.go

@@ -452,7 +452,7 @@ func (cfg *config) one(cmd int, expectedServers int, retry bool) int {
 			t1 := time.Now()
 			for time.Since(t1).Seconds() < 2 {
 				nd, cmd1 := cfg.nCommitted(index)
-				//DPrintf("%v servers think %v is committed\n",nd,index)
+				DPrintf("%v servers think %v is committed\n",nd,index)
 				if nd > 0 && nd >= expectedServers {
 					// committed
 					if cmd2, ok := cmd1.(int); ok && cmd2 == cmd {

src/raft/raft.go

@@ -204,6 +204,7 @@ func (rf *Raft) RequestVote(args *RequestVoteArgs, reply *RequestVoteReply) {
 		return
 	}
 
+	// if candidate's log is more up-to-date
 	var upToDate bool
 	lastIndex := len(rf.log)-1
 	if rf.log[lastIndex].Term < args.LastLogTerm {
@@ -215,10 +216,11 @@ func (rf *Raft) RequestVote(args *RequestVoteArgs, reply *RequestVoteReply) {
 	}
 
 	if !upToDate {
-		DPrintf("%v reject %v because log is not up-to-date\n",rf.me,args.CandidateID)
+		DPrintf("server %v reject grant candidate %v in term % v because log is not up-to-date\n",rf.me,args.CandidateID,args.Term)
 		return
 	}
 
+	// if candidate's term is greater, grant
 	if args.Term > rf.currentTerm {
 		rf.votedFor = args.CandidateID
 		rf.currentTerm = args.Term
@@ -237,11 +239,11 @@ func (rf *Raft) RequestVote(args *RequestVoteArgs, reply *RequestVoteReply) {
 func (rf *Raft) AppendEntries(args *AppendEntriesArgs, reply *AppendEntriesReply) {
 	rf.mu.Lock()
 	defer rf.mu.Unlock()
-	reply.Success = true
+	// success only if leader is valid and prevEntry matched
+	reply.Success = false
 
 	if args.Term<rf.currentTerm {
 		reply.Term = rf.currentTerm
-		reply.Success = false
 		return
 	}
 	rf.resetTimerCH <- struct{}{}
@@ -255,20 +257,23 @@ func (rf *Raft) AppendEntries(args *AppendEntriesArgs, reply *AppendEntriesReply
 	}
 
 	reply.Term = rf.currentTerm
-	if args.Entries!=nil {
-		// check prev
-		if args.PrevLogIndex<len(rf.log) && rf.log[args.PrevLogIndex].Term == args.PrevLogTerm {
+
+	last:=0  // last entry matched
+	prevEntryMatch := args.PrevLogIndex<len(rf.log) && rf.log[args.PrevLogIndex].Term == args.PrevLogTerm
+
+	if prevEntryMatch {
+		last = args.PrevLogIndex
+		reply.Success = true
+		if args.Entries!=nil {
 			rf.log = rf.log[0:args.PrevLogIndex+1]  // delete conflict entries
 			rf.log = append(rf.log, args.Entries[0])
-			DPrintf("%v receive %v, at: %v\n", rf.me, args.Term, len(rf.log)-1)
-		} else {
-			reply.Success = false      // not match
+			last+=1
+			DPrintf("server %v receive entry term %v, at index: %v\n", rf.me, args.Term, len(rf.log)-1)
 		}
 	}
 
-	if args.LeaderCommit > rf.commitIndex {
-		rf.commitToIndex(min(args.LeaderCommit, len(rf.log)-1))
-		DPrintf("%v set commit to %v", rf.me, rf.commitIndex)
+	if args.LeaderCommit > rf.commitIndex && prevEntryMatch {
+		rf.commitToIndex(min(args.LeaderCommit, last))
 	}
 }
 
@@ -450,6 +455,7 @@ func (rf *Raft) startElection() {
 						if rf.votedCnt == len(rf.peers)/2 { // already vote for itself
 							//fmt.Printf("%v became leader for term %v\n",rf.me, rf.currentTerm)
 							rf.electionTimer.Stop()                // stop timer until expired
+							DPrintf("server %v become leader\n",rf.me)
 							rf.setRole(Leader)
 							rf.leaderInit()
 							go rf.broadcast() // broadcast as leader
@@ -507,21 +513,23 @@ func (rf *Raft) broadcast() {
 				continue
 			}
 
+			preIndex := rf.nextIndex[i] - 1
+
 			args := AppendEntriesArgs{
 				rf.currentTerm,
 				nil,
 				rf.commitIndex,
-				0,
-				0,
+				preIndex,
+				rf.log[preIndex].Term,
 			}
 
 			if rf.nextIndex[i] < len(rf.log) {
 				// Todo: append more entries
 				args.Entries = append(args.Entries, rf.log[rf.nextIndex[i]])
-				preIndex := rf.nextIndex[i] - 1
-				args.PrevLogIndex = preIndex
-				args.PrevLogTerm = rf.log[preIndex].Term
-				DPrintf("leader %v to send in term %v, pre index %v, to %v\n", rf.me, args.Entries[0].Term,preIndex, i)
+				//preIndex := rf.nextIndex[i] - 1
+				//args.PrevLogIndex = preIndex
+				//args.PrevLogTerm = rf.log[preIndex].Term
+				DPrintf("leader %v to send in term %v, pre index %v, to server %v\n", rf.me, args.Entries[0].Term,preIndex, i)
 			}
 
 			go rf.startAppendEntries(i, args)
@@ -547,14 +555,15 @@ func (rf *Raft) tryCommit() {
 // commit index and all indices preceding index
 func (rf *Raft) commitToIndex(index int) {
 	if rf.commitIndex<index {
-		for i:=rf.commitIndex+1;i<=index;i++ {
+		for i:=rf.commitIndex+1;i<=index&&i<len(rf.log);i++ {
 			rf.commitIndex = i
 			msg:=ApplyMsg{
 				true,
 				rf.log[i].Command,
 				i,
 			}
 			rf.applyCh<-msg
+			DPrintf("server %v set commit to index %v", rf.me, rf.commitIndex)
 		}
 	}
 }