raft: Add applied index as an argument to newRaft and RestartNode.

etcdserver/raft.go

@@ -116,7 +116,7 @@ func restartNode(cfg *ServerConfig, snapshot *raftpb.Snapshot) (types.ID, raft.N
 	}
 	s.SetHardState(st)
 	s.Append(ents)
-	n := raft.RestartNode(uint64(id), cfg.ElectionTicks, 1, s)
+	n := raft.RestartNode(uint64(id), cfg.ElectionTicks, 1, s, 0)
 	return id, n, s, w
 }
 
@@ -157,7 +157,7 @@ func restartAsStandaloneNode(cfg *ServerConfig, snapshot *raftpb.Snapshot) (type
 	}
 	s.SetHardState(st)
 	s.Append(ents)
-	n := raft.RestartNode(uint64(id), cfg.ElectionTicks, 1, s)
+	n := raft.RestartNode(uint64(id), cfg.ElectionTicks, 1, s, 0)
 	return id, n, s, w
 }
 

raft/node.go

@@ -135,7 +135,7 @@ type Peer struct {
 // It appends a ConfChangeAddNode entry for each given peer to the initial log.
 func StartNode(id uint64, peers []Peer, election, heartbeat int, storage Storage) Node {
 	n := newNode()
-	r := newRaft(id, nil, election, heartbeat, storage)
+	r := newRaft(id, nil, election, heartbeat, storage, 0)
 
 	// become the follower at term 1 and apply initial configuration
 	// entires of term 1
@@ -171,11 +171,13 @@ func StartNode(id uint64, peers []Peer, election, heartbeat int, storage Storage
 	return &n
 }
 
-// RestartNode is identical to StartNode but does not take a list of peers.
+// RestartNode is similar to StartNode but does not take a list of peers.
 // The current membership of the cluster will be restored from the Storage.
-func RestartNode(id uint64, election, heartbeat int, storage Storage) Node {
+// If the caller has an existing state machine, pass in the last log index that
+// has been applied to it; otherwise use zero.
+func RestartNode(id uint64, election, heartbeat int, storage Storage, applied uint64) Node {
 	n := newNode()
-	r := newRaft(id, nil, election, heartbeat, storage)
+	r := newRaft(id, nil, election, heartbeat, storage, applied)
 
 	go n.run(r)
 	return &n

raft/node_bench_test.go

@@ -28,7 +28,7 @@ func BenchmarkOneNode(b *testing.B) {
 
 	n := newNode()
 	s := NewMemoryStorage()
-	r := newRaft(1, []uint64{1}, 10, 1, s)
+	r := newRaft(1, []uint64{1}, 10, 1, s, 0)
 	go n.run(r)
 
 	defer n.Stop()

raft/node_test.go

@@ -116,7 +116,7 @@ func TestNodePropose(t *testing.T) {
 
 	n := newNode()
 	s := NewMemoryStorage()
-	r := newRaft(1, []uint64{1}, 10, 1, s)
+	r := newRaft(1, []uint64{1}, 10, 1, s, 0)
 	go n.run(r)
 	n.Campaign(context.TODO())
 	for {
@@ -154,7 +154,7 @@ func TestNodeProposeConfig(t *testing.T) {
 
 	n := newNode()
 	s := NewMemoryStorage()
-	r := newRaft(1, []uint64{1}, 10, 1, s)
+	r := newRaft(1, []uint64{1}, 10, 1, s, 0)
 	go n.run(r)
 	n.Campaign(context.TODO())
 	for {
@@ -192,7 +192,7 @@ func TestNodeProposeConfig(t *testing.T) {
 // who is the current leader.
 func TestBlockProposal(t *testing.T) {
 	n := newNode()
-	r := newRaft(1, []uint64{1}, 10, 1, NewMemoryStorage())
+	r := newRaft(1, []uint64{1}, 10, 1, NewMemoryStorage(), 0)
 	go n.run(r)
 	defer n.Stop()
 
@@ -225,7 +225,7 @@ func TestBlockProposal(t *testing.T) {
 func TestNodeTick(t *testing.T) {
 	n := newNode()
 	s := NewMemoryStorage()
-	r := newRaft(1, []uint64{1}, 10, 1, s)
+	r := newRaft(1, []uint64{1}, 10, 1, s, 0)
 	go n.run(r)
 	elapsed := r.elapsed
 	n.Tick()
@@ -240,7 +240,7 @@ func TestNodeTick(t *testing.T) {
 func TestNodeStop(t *testing.T) {
 	n := newNode()
 	s := NewMemoryStorage()
-	r := newRaft(1, []uint64{1}, 10, 1, s)
+	r := newRaft(1, []uint64{1}, 10, 1, s, 0)
 	donec := make(chan struct{})
 
 	go func() {
@@ -364,7 +364,7 @@ func TestNodeRestart(t *testing.T) {
 	storage := NewMemoryStorage()
 	storage.SetHardState(st)
 	storage.Append(entries)
-	n := RestartNode(1, 10, 1, storage)
+	n := RestartNode(1, 10, 1, storage, 0)
 	if g := <-n.Ready(); !reflect.DeepEqual(g, want) {
 		t.Errorf("g = %+v,\n             w   %+v", g, want)
 	}
@@ -400,7 +400,7 @@ func TestNodeRestartFromSnapshot(t *testing.T) {
 	s.SetHardState(st)
 	s.ApplySnapshot(snap)
 	s.Append(entries)
-	n := RestartNode(1, 10, 1, s)
+	n := RestartNode(1, 10, 1, s, 0)
 	if g := <-n.Ready(); !reflect.DeepEqual(g, want) {
 		t.Errorf("g = %+v,\n             w   %+v", g, want)
 	} else {

raft/raft.go

@@ -139,7 +139,8 @@ type raft struct {
 	step             stepFunc
 }
 
-func newRaft(id uint64, peers []uint64, election, heartbeat int, storage Storage) *raft {
+func newRaft(id uint64, peers []uint64, election, heartbeat int, storage Storage,
+	applied uint64) *raft {
 	if id == None {
 		panic("cannot use none id")
 	}
@@ -172,6 +173,9 @@ func newRaft(id uint64, peers []uint64, election, heartbeat int, storage Storage
 	if !isHardStateEqual(hs, emptyState) {
 		r.loadState(hs)
 	}
+	if applied > 0 {
+		raftlog.appliedTo(applied)
+	}
 	r.becomeFollower(r.Term, None)
 
 	nodesStrs := make([]string, 0)

raft/raft_paper_test.go

@@ -56,7 +56,7 @@ func TestLeaderUpdateTermFromMessage(t *testing.T) {
 // it immediately reverts to follower state.
 // Reference: section 5.1
 func testUpdateTermFromMessage(t *testing.T, state StateType) {
-	r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage())
+	r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage(), 0)
 	switch state {
 	case StateFollower:
 		r.becomeFollower(1, 2)
@@ -86,7 +86,7 @@ func TestRejectStaleTermMessage(t *testing.T) {
 	fakeStep := func(r *raft, m pb.Message) {
 		called = true
 	}
-	r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage())
+	r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage(), 0)
 	r.step = fakeStep
 	r.loadState(pb.HardState{Term: 2})
 
@@ -100,7 +100,7 @@ func TestRejectStaleTermMessage(t *testing.T) {
 // TestStartAsFollower tests that when servers start up, they begin as followers.
 // Reference: section 5.2
 func TestStartAsFollower(t *testing.T) {
-	r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage())
+	r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage(), 0)
 	if r.state != StateFollower {
 		t.Errorf("state = %s, want %s", r.state, StateFollower)
 	}
@@ -113,7 +113,7 @@ func TestStartAsFollower(t *testing.T) {
 func TestLeaderBcastBeat(t *testing.T) {
 	// heartbeat interval
 	hi := 1
-	r := newRaft(1, []uint64{1, 2, 3}, 10, hi, NewMemoryStorage())
+	r := newRaft(1, []uint64{1, 2, 3}, 10, hi, NewMemoryStorage(), 0)
 	r.becomeCandidate()
 	r.becomeLeader()
 	for i := 0; i < 10; i++ {
@@ -155,7 +155,7 @@ func TestCandidateStartNewElection(t *testing.T) {
 func testNonleaderStartElection(t *testing.T, state StateType) {
 	// election timeout
 	et := 10
-	r := newRaft(1, []uint64{1, 2, 3}, et, 1, NewMemoryStorage())
+	r := newRaft(1, []uint64{1, 2, 3}, et, 1, NewMemoryStorage(), 0)
 	switch state {
 	case StateFollower:
 		r.becomeFollower(1, 2)
@@ -219,7 +219,7 @@ func TestLeaderElectionInOneRoundRPC(t *testing.T) {
 		{5, map[uint64]bool{}, StateCandidate},
 	}
 	for i, tt := range tests {
-		r := newRaft(1, idsBySize(tt.size), 10, 1, NewMemoryStorage())
+		r := newRaft(1, idsBySize(tt.size), 10, 1, NewMemoryStorage(), 0)
 
 		r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgHup})
 		for id, vote := range tt.votes {
@@ -252,7 +252,7 @@ func TestFollowerVote(t *testing.T) {
 		{2, 1, true},
 	}
 	for i, tt := range tests {
-		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage())
+		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage(), 0)
 		r.loadState(pb.HardState{Term: 1, Vote: tt.vote})
 
 		r.Step(pb.Message{From: tt.nvote, To: 1, Term: 1, Type: pb.MsgVote})
@@ -278,7 +278,7 @@ func TestCandidateFallback(t *testing.T) {
 		{From: 2, To: 1, Term: 2, Type: pb.MsgApp},
 	}
 	for i, tt := range tests {
-		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage())
+		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage(), 0)
 		r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgHup})
 		if r.state != StateCandidate {
 			t.Fatalf("unexpected state = %s, want %s", r.state, StateCandidate)
@@ -311,7 +311,7 @@ func TestCandidateElectionTimeoutRandomized(t *testing.T) {
 // Reference: section 5.2
 func testNonleaderElectionTimeoutRandomized(t *testing.T, state StateType) {
 	et := 10
-	r := newRaft(1, []uint64{1, 2, 3}, et, 1, NewMemoryStorage())
+	r := newRaft(1, []uint64{1, 2, 3}, et, 1, NewMemoryStorage(), 0)
 	timeouts := make(map[int]bool)
 	for round := 0; round < 50*et; round++ {
 		switch state {
@@ -357,7 +357,7 @@ func testNonleadersElectionTimeoutNonconflict(t *testing.T, state StateType) {
 	rs := make([]*raft, size)
 	ids := idsBySize(size)
 	for k := range rs {
-		rs[k] = newRaft(ids[k], ids, et, 1, NewMemoryStorage())
+		rs[k] = newRaft(ids[k], ids, et, 1, NewMemoryStorage(), 0)
 	}
 	conflicts := 0
 	for round := 0; round < 1000; round++ {
@@ -400,7 +400,7 @@ func testNonleadersElectionTimeoutNonconflict(t *testing.T, state StateType) {
 // Reference: section 5.3
 func TestLeaderStartReplication(t *testing.T) {
 	s := NewMemoryStorage()
-	r := newRaft(1, []uint64{1, 2, 3}, 10, 1, s)
+	r := newRaft(1, []uint64{1, 2, 3}, 10, 1, s, 0)
 	r.becomeCandidate()
 	r.becomeLeader()
 	commitNoopEntry(r, s)
@@ -439,7 +439,7 @@ func TestLeaderStartReplication(t *testing.T) {
 // Reference: section 5.3
 func TestLeaderCommitEntry(t *testing.T) {
 	s := NewMemoryStorage()
-	r := newRaft(1, []uint64{1, 2, 3}, 10, 1, s)
+	r := newRaft(1, []uint64{1, 2, 3}, 10, 1, s, 0)
 	r.becomeCandidate()
 	r.becomeLeader()
 	commitNoopEntry(r, s)
@@ -493,7 +493,7 @@ func TestLeaderAcknowledgeCommit(t *testing.T) {
 	}
 	for i, tt := range tests {
 		s := NewMemoryStorage()
-		r := newRaft(1, idsBySize(tt.size), 10, 1, s)
+		r := newRaft(1, idsBySize(tt.size), 10, 1, s, 0)
 		r.becomeCandidate()
 		r.becomeLeader()
 		commitNoopEntry(r, s)
@@ -527,7 +527,7 @@ func TestLeaderCommitPrecedingEntries(t *testing.T) {
 	for i, tt := range tests {
 		storage := NewMemoryStorage()
 		storage.Append(tt)
-		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, storage)
+		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, storage, 0)
 		r.loadState(pb.HardState{Term: 2})
 		r.becomeCandidate()
 		r.becomeLeader()
@@ -582,7 +582,7 @@ func TestFollowerCommitEntry(t *testing.T) {
 		},
 	}
 	for i, tt := range tests {
-		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage())
+		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage(), 0)
 		r.becomeFollower(1, 2)
 
 		r.Step(pb.Message{From: 2, To: 1, Type: pb.MsgApp, Term: 1, Entries: tt.ents, Commit: tt.commit})
@@ -619,7 +619,7 @@ func TestFollowerCheckMsgApp(t *testing.T) {
 	for i, tt := range tests {
 		storage := NewMemoryStorage()
 		storage.Append(ents)
-		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, storage)
+		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, storage, 0)
 		r.loadState(pb.HardState{Commit: 2})
 		r.becomeFollower(2, 2)
 
@@ -675,7 +675,7 @@ func TestFollowerAppendEntries(t *testing.T) {
 	for i, tt := range tests {
 		storage := NewMemoryStorage()
 		storage.Append([]pb.Entry{{Term: 1, Index: 1}, {Term: 2, Index: 2}})
-		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, storage)
+		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, storage, 0)
 		r.becomeFollower(2, 2)
 
 		r.Step(pb.Message{From: 2, To: 1, Type: pb.MsgApp, Term: 2, LogTerm: tt.term, Index: tt.index, Entries: tt.ents})
@@ -744,11 +744,11 @@ func TestLeaderSyncFollowerLog(t *testing.T) {
 	for i, tt := range tests {
 		leadStorage := NewMemoryStorage()
 		leadStorage.Append(ents)
-		lead := newRaft(1, []uint64{1, 2, 3}, 10, 1, leadStorage)
+		lead := newRaft(1, []uint64{1, 2, 3}, 10, 1, leadStorage, 0)
 		lead.loadState(pb.HardState{Commit: lead.raftLog.lastIndex(), Term: term})
 		followerStorage := NewMemoryStorage()
 		followerStorage.Append(tt)
-		follower := newRaft(2, []uint64{1, 2, 3}, 10, 1, followerStorage)
+		follower := newRaft(2, []uint64{1, 2, 3}, 10, 1, followerStorage, 0)
 		follower.loadState(pb.HardState{Term: term - 1})
 		// It is necessary to have a three-node cluster.
 		// The second may have more up-to-date log than the first one, so the
@@ -777,7 +777,7 @@ func TestVoteRequest(t *testing.T) {
 		{[]pb.Entry{{Term: 1, Index: 1}, {Term: 2, Index: 2}}, 3},
 	}
 	for i, tt := range tests {
-		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage())
+		r := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage(), 0)
 		r.Step(pb.Message{
 			From: 2, To: 1, Type: pb.MsgApp, Term: tt.wterm - 1, LogTerm: 0, Index: 0, Entries: tt.ents,
 		})
@@ -840,7 +840,7 @@ func TestVoter(t *testing.T) {
 	for i, tt := range tests {
 		storage := NewMemoryStorage()
 		storage.Append(tt.ents)
-		r := newRaft(1, []uint64{1, 2}, 10, 1, storage)
+		r := newRaft(1, []uint64{1, 2}, 10, 1, storage, 0)
 
 		r.Step(pb.Message{From: 2, To: 1, Type: pb.MsgVote, Term: 3, LogTerm: tt.logterm, Index: tt.index})
 
@@ -876,7 +876,7 @@ func TestLeaderOnlyCommitsLogFromCurrentTerm(t *testing.T) {
 	for i, tt := range tests {
 		storage := NewMemoryStorage()
 		storage.Append(ents)
-		r := newRaft(1, []uint64{1, 2}, 10, 1, storage)
+		r := newRaft(1, []uint64{1, 2}, 10, 1, storage, 0)
 		r.loadState(pb.HardState{Term: 2})
 		// become leader at term 3
 		r.becomeCandidate()

raft/raft_test.go

@@ -195,7 +195,7 @@ func TestProgressWaitReset(t *testing.T) {
 
 // TestProgressDecr ensures raft.heartbeat decreases progress.wait by heartbeat.
 func TestProgressDecr(t *testing.T) {
-	r := newRaft(1, []uint64{1, 2}, 5, 1, NewMemoryStorage())
+	r := newRaft(1, []uint64{1, 2}, 5, 1, NewMemoryStorage(), 0)
 	r.becomeCandidate()
 	r.becomeLeader()
 	r.prs[2].Wait = r.heartbeatTimeout * 2
@@ -207,7 +207,7 @@ func TestProgressDecr(t *testing.T) {
 }
 
 func TestProgressWait(t *testing.T) {
-	r := newRaft(1, []uint64{1, 2}, 5, 1, NewMemoryStorage())
+	r := newRaft(1, []uint64{1, 2}, 5, 1, NewMemoryStorage(), 0)
 	r.becomeCandidate()
 	r.becomeLeader()
 	r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
@@ -399,9 +399,9 @@ func TestCommitWithoutNewTermEntry(t *testing.T) {
 }
 
 func TestDuelingCandidates(t *testing.T) {
-	a := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage())
-	b := newRaft(2, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage())
-	c := newRaft(3, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage())
+	a := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage(), 0)
+	b := newRaft(2, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage(), 0)
+	c := newRaft(3, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage(), 0)
 
 	nt := newNetwork(a, b, c)
 	nt.cut(1, 3)
@@ -669,7 +669,7 @@ func TestCommit(t *testing.T) {
 		storage.Append(tt.logs)
 		storage.hardState = pb.HardState{Term: tt.smTerm}
 
-		sm := newRaft(1, []uint64{1}, 5, 1, storage)
+		sm := newRaft(1, []uint64{1}, 5, 1, storage, 0)
 		for j := 0; j < len(tt.matches); j++ {
 			sm.setProgress(uint64(j)+1, tt.matches[j], tt.matches[j]+1)
 		}
@@ -694,7 +694,7 @@ func TestIsElectionTimeout(t *testing.T) {
 	}
 
 	for i, tt := range tests {
-		sm := newRaft(1, []uint64{1}, 10, 1, NewMemoryStorage())
+		sm := newRaft(1, []uint64{1}, 10, 1, NewMemoryStorage(), 0)
 		sm.elapsed = tt.elapse
 		c := 0
 		for j := 0; j < 10000; j++ {
@@ -719,7 +719,7 @@ func TestStepIgnoreOldTermMsg(t *testing.T) {
 	fakeStep := func(r *raft, m pb.Message) {
 		called = true
 	}
-	sm := newRaft(1, []uint64{1}, 10, 1, NewMemoryStorage())
+	sm := newRaft(1, []uint64{1}, 10, 1, NewMemoryStorage(), 0)
 	sm.step = fakeStep
 	sm.Term = 2
 	sm.Step(pb.Message{Type: pb.MsgApp, Term: sm.Term - 1})
@@ -761,7 +761,7 @@ func TestHandleMsgApp(t *testing.T) {
 	for i, tt := range tests {
 		storage := NewMemoryStorage()
 		storage.Append([]pb.Entry{{Index: 1, Term: 1}, {Index: 2, Term: 2}})
-		sm := newRaft(1, []uint64{1}, 10, 1, storage)
+		sm := newRaft(1, []uint64{1}, 10, 1, storage, 0)
 		sm.becomeFollower(2, None)
 
 		sm.handleAppendEntries(tt.m)
@@ -795,7 +795,7 @@ func TestHandleHeartbeat(t *testing.T) {
 	for i, tt := range tests {
 		storage := NewMemoryStorage()
 		storage.Append([]pb.Entry{{Index: 1, Term: 1}, {Index: 2, Term: 2}, {Index: 3, Term: 3}})
-		sm := newRaft(1, []uint64{1, 2}, 5, 1, storage)
+		sm := newRaft(1, []uint64{1, 2}, 5, 1, storage, 0)
 		sm.becomeFollower(2, 2)
 		sm.raftLog.commitTo(commit)
 		sm.handleHeartbeat(tt.m)
@@ -816,7 +816,7 @@ func TestHandleHeartbeat(t *testing.T) {
 func TestHandleHeartbeatResp(t *testing.T) {
 	storage := NewMemoryStorage()
 	storage.Append([]pb.Entry{{Index: 1, Term: 1}, {Index: 2, Term: 2}, {Index: 3, Term: 3}})
-	sm := newRaft(1, []uint64{1, 2}, 5, 1, storage)
+	sm := newRaft(1, []uint64{1, 2}, 5, 1, storage, 0)
 	sm.becomeCandidate()
 	sm.becomeLeader()
 	sm.raftLog.commitTo(sm.raftLog.lastIndex())
@@ -904,7 +904,7 @@ func TestRecvMsgVote(t *testing.T) {
 	}
 
 	for i, tt := range tests {
-		sm := newRaft(1, []uint64{1}, 10, 1, NewMemoryStorage())
+		sm := newRaft(1, []uint64{1}, 10, 1, NewMemoryStorage(), 0)
 		sm.state = tt.state
 		switch tt.state {
 		case StateFollower:
@@ -964,7 +964,7 @@ func TestStateTransition(t *testing.T) {
 				}
 			}()
 
-			sm := newRaft(1, []uint64{1}, 10, 1, NewMemoryStorage())
+			sm := newRaft(1, []uint64{1}, 10, 1, NewMemoryStorage(), 0)
 			sm.state = tt.from
 
 			switch tt.to {
@@ -1003,7 +1003,7 @@ func TestAllServerStepdown(t *testing.T) {
 	tterm := uint64(3)
 
 	for i, tt := range tests {
-		sm := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage())
+		sm := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage(), 0)
 		switch tt.state {
 		case StateFollower:
 			sm.becomeFollower(1, None)
@@ -1062,7 +1062,7 @@ func TestLeaderAppResp(t *testing.T) {
 	for i, tt := range tests {
 		// sm term is 1 after it becomes the leader.
 		// thus the last log term must be 1 to be committed.
-		sm := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage())
+		sm := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage(), 0)
 		sm.raftLog = &raftLog{
 			storage:  &MemoryStorage{ents: []pb.Entry{{}, {Index: 1, Term: 0}, {Index: 2, Term: 1}}},
 			unstable: unstable{offset: 3},
@@ -1110,7 +1110,7 @@ func TestBcastBeat(t *testing.T) {
 	}
 	storage := NewMemoryStorage()
 	storage.ApplySnapshot(s)
-	sm := newRaft(1, nil, 10, 1, storage)
+	sm := newRaft(1, nil, 10, 1, storage, 0)
 	sm.Term = 1
 
 	sm.becomeCandidate()
@@ -1169,7 +1169,7 @@ func TestRecvMsgBeat(t *testing.T) {
 	}
 
 	for i, tt := range tests {
-		sm := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage())
+		sm := newRaft(1, []uint64{1, 2, 3}, 10, 1, NewMemoryStorage(), 0)
 		sm.raftLog = &raftLog{storage: &MemoryStorage{ents: []pb.Entry{{}, {Index: 1, Term: 0}, {Index: 2, Term: 1}}}}
 		sm.Term = 1
 		sm.state = tt.state
@@ -1212,7 +1212,7 @@ func TestLeaderIncreaseNext(t *testing.T) {
 	}
 
 	for i, tt := range tests {
-		sm := newRaft(1, []uint64{1, 2}, 10, 1, NewMemoryStorage())
+		sm := newRaft(1, []uint64{1, 2}, 10, 1, NewMemoryStorage(), 0)
 		sm.raftLog.append(previousEnts...)
 		sm.becomeCandidate()
 		sm.becomeLeader()
@@ -1236,7 +1236,7 @@ func TestRestore(t *testing.T) {
 	}
 
 	storage := NewMemoryStorage()
-	sm := newRaft(1, []uint64{1, 2}, 10, 1, storage)
+	sm := newRaft(1, []uint64{1, 2}, 10, 1, storage, 0)
 	if ok := sm.restore(s); !ok {
 		t.Fatal("restore fail, want succeed")
 	}
@@ -1261,7 +1261,7 @@ func TestRestoreIgnoreSnapshot(t *testing.T) {
 	previousEnts := []pb.Entry{{Term: 1, Index: 1}, {Term: 1, Index: 2}, {Term: 1, Index: 3}}
 	commit := uint64(1)
 	storage := NewMemoryStorage()
-	sm := newRaft(1, []uint64{1, 2}, 10, 1, storage)
+	sm := newRaft(1, []uint64{1, 2}, 10, 1, storage, 0)
 	sm.raftLog.append(previousEnts...)
 	sm.raftLog.commitTo(commit)
 
@@ -1302,7 +1302,7 @@ func TestProvideSnap(t *testing.T) {
 		},
 	}
 	storage := NewMemoryStorage()
-	sm := newRaft(1, []uint64{1}, 10, 1, storage)
+	sm := newRaft(1, []uint64{1}, 10, 1, storage, 0)
 	sm.restore(s)
 
 	sm.becomeCandidate()
@@ -1333,7 +1333,7 @@ func TestRestoreFromSnapMsg(t *testing.T) {
 	}
 	m := pb.Message{Type: pb.MsgSnap, From: 1, Term: 2, Snapshot: s}
 
-	sm := newRaft(2, []uint64{1, 2}, 10, 1, NewMemoryStorage())
+	sm := newRaft(2, []uint64{1, 2}, 10, 1, NewMemoryStorage(), 0)
 	sm.Step(m)
 
 	// TODO(bdarnell): what should this test?
@@ -1367,7 +1367,7 @@ func TestSlowNodeRestore(t *testing.T) {
 // it appends the entry to log and sets pendingConf to be true.
 func TestStepConfig(t *testing.T) {
 	// a raft that cannot make progress
-	r := newRaft(1, []uint64{1, 2}, 10, 1, NewMemoryStorage())
+	r := newRaft(1, []uint64{1, 2}, 10, 1, NewMemoryStorage(), 0)
 	r.becomeCandidate()
 	r.becomeLeader()
 	index := r.raftLog.lastIndex()
@@ -1385,7 +1385,7 @@ func TestStepConfig(t *testing.T) {
 // the proposal to noop and keep its original state.
 func TestStepIgnoreConfig(t *testing.T) {
 	// a raft that cannot make progress
-	r := newRaft(1, []uint64{1, 2}, 10, 1, NewMemoryStorage())
+	r := newRaft(1, []uint64{1, 2}, 10, 1, NewMemoryStorage(), 0)
 	r.becomeCandidate()
 	r.becomeLeader()
 	r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Type: pb.EntryConfChange}}})
@@ -1412,7 +1412,7 @@ func TestRecoverPendingConfig(t *testing.T) {
 		{pb.EntryConfChange, true},
 	}
 	for i, tt := range tests {
-		r := newRaft(1, []uint64{1, 2}, 10, 1, NewMemoryStorage())
+		r := newRaft(1, []uint64{1, 2}, 10, 1, NewMemoryStorage(), 0)
 		r.appendEntry(pb.Entry{Type: tt.entType})
 		r.becomeCandidate()
 		r.becomeLeader()
@@ -1431,7 +1431,7 @@ func TestRecoverDoublePendingConfig(t *testing.T) {
 				t.Errorf("expect panic, but nothing happens")
 			}
 		}()
-		r := newRaft(1, []uint64{1, 2}, 10, 1, NewMemoryStorage())
+		r := newRaft(1, []uint64{1, 2}, 10, 1, NewMemoryStorage(), 0)
 		r.appendEntry(pb.Entry{Type: pb.EntryConfChange})
 		r.appendEntry(pb.Entry{Type: pb.EntryConfChange})
 		r.becomeCandidate()
@@ -1441,7 +1441,7 @@ func TestRecoverDoublePendingConfig(t *testing.T) {
 
 // TestAddNode tests that addNode could update pendingConf and nodes correctly.
 func TestAddNode(t *testing.T) {
-	r := newRaft(1, []uint64{1}, 10, 1, NewMemoryStorage())
+	r := newRaft(1, []uint64{1}, 10, 1, NewMemoryStorage(), 0)
 	r.pendingConf = true
 	r.addNode(2)
 	if r.pendingConf != false {
@@ -1457,7 +1457,7 @@ func TestAddNode(t *testing.T) {
 // TestRemoveNode tests that removeNode could update pendingConf, nodes and
 // and removed list correctly.
 func TestRemoveNode(t *testing.T) {
-	r := newRaft(1, []uint64{1, 2}, 10, 1, NewMemoryStorage())
+	r := newRaft(1, []uint64{1, 2}, 10, 1, NewMemoryStorage(), 0)
 	r.pendingConf = true
 	r.removeNode(2)
 	if r.pendingConf != false {
@@ -1481,7 +1481,7 @@ func TestPromotable(t *testing.T) {
 		{[]uint64{2, 3}, false},
 	}
 	for i, tt := range tests {
-		r := newRaft(id, tt.peers, 5, 1, NewMemoryStorage())
+		r := newRaft(id, tt.peers, 5, 1, NewMemoryStorage(), 0)
 		if g := r.promotable(); g != tt.wp {
 			t.Errorf("#%d: promotable = %v, want %v", i, g, tt.wp)
 		}
@@ -1503,7 +1503,7 @@ func TestRaftNodes(t *testing.T) {
 		},
 	}
 	for i, tt := range tests {
-		r := newRaft(1, tt.ids, 10, 1, NewMemoryStorage())
+		r := newRaft(1, tt.ids, 10, 1, NewMemoryStorage(), 0)
 		if !reflect.DeepEqual(r.nodes(), tt.wids) {
 			t.Errorf("#%d: nodes = %+v, want %+v", i, r.nodes(), tt.wids)
 		}
@@ -1515,7 +1515,7 @@ func ents(terms ...uint64) *raft {
 	for i, term := range terms {
 		storage.Append([]pb.Entry{{Index: uint64(i + 1), Term: term}})
 	}
-	sm := newRaft(1, []uint64{}, 5, 1, storage)
+	sm := newRaft(1, []uint64{}, 5, 1, storage, 0)
 	sm.reset(0)
 	return sm
 }
@@ -1543,7 +1543,7 @@ func newNetwork(peers ...Interface) *network {
 		switch v := p.(type) {
 		case nil:
 			nstorage[id] = NewMemoryStorage()
-			sm := newRaft(id, peerAddrs, 10, 1, nstorage[id])
+			sm := newRaft(id, peerAddrs, 10, 1, nstorage[id], 0)
 			npeers[id] = sm
 		case *raft:
 			v.id = id