Merge pull request #14721 from nvanbenschoten/nvanbenschoten/noCommit…

…tedOnSnap

raft: don't apply entries when applying snapshot

raft/log.go

@@ -181,9 +181,13 @@ func (l *raftLog) unstableEntries() []pb.Entry {
 // If applied is smaller than the index of snapshot, it returns all committed
 // entries after the index of snapshot.
 func (l *raftLog) nextCommittedEnts() (ents []pb.Entry) {
-	off := max(l.applied+1, l.firstIndex())
-	if l.committed+1 > off {
-		ents, err := l.slice(off, l.committed+1, l.maxNextCommittedEntsSize)
+	if l.hasPendingSnapshot() {
+		// See comment in hasNextCommittedEnts.
+		return nil
+	}
+	if l.committed > l.applied {
+		lo, hi := l.applied+1, l.committed+1 // [lo, hi)
+		ents, err := l.slice(lo, hi, l.maxNextCommittedEntsSize)
 		if err != nil {
 			l.logger.Panicf("unexpected error when getting unapplied entries (%v)", err)
 		}
@@ -195,13 +199,18 @@ func (l *raftLog) nextCommittedEnts() (ents []pb.Entry) {
 // hasNextCommittedEnts returns if there is any available entries for execution.
 // This is a fast check without heavy raftLog.slice() in nextCommittedEnts().
 func (l *raftLog) hasNextCommittedEnts() bool {
-	off := max(l.applied+1, l.firstIndex())
-	return l.committed+1 > off
+	if l.hasPendingSnapshot() {
+		// If we have a snapshot to apply, don't also return any committed
+		// entries. Doing so raises questions about what should be applied
+		// first.
+		return false
+	}
+	return l.committed > l.applied
 }
 
 // hasPendingSnapshot returns if there is pending snapshot waiting for applying.
 func (l *raftLog) hasPendingSnapshot() bool {
-	return l.unstable.snapshot != nil && !IsEmptySnap(*l.unstable.snapshot)
+	return l.unstable.snapshot != nil
 }
 
 func (l *raftLog) snapshot() (pb.Snapshot, error) {

raft/log_test.go

@@ -349,13 +349,16 @@ func TestHasNextCommittedEnts(t *testing.T) {
 		{Term: 1, Index: 6},
 	}
 	tests := []struct {
-		applied uint64
-		hasNext bool
+		applied  uint64
+		snap     bool
+		whasNext bool
 	}{
-		{0, true},
-		{3, true},
-		{4, true},
-		{5, false},
+		{applied: 0, snap: false, whasNext: true},
+		{applied: 3, snap: false, whasNext: true},
+		{applied: 4, snap: false, whasNext: true},
+		{applied: 5, snap: false, whasNext: false},
+		// With snapshot.
+		{applied: 3, snap: true, whasNext: false},
 	}
 	for i, tt := range tests {
 		storage := NewMemoryStorage()
@@ -364,10 +367,15 @@ func TestHasNextCommittedEnts(t *testing.T) {
 		raftLog.append(ents...)
 		raftLog.maybeCommit(5, 1)
 		raftLog.appliedTo(tt.applied)
+		if tt.snap {
+			newSnap := snap
+			newSnap.Metadata.Index++
+			raftLog.restore(newSnap)
+		}
 
 		hasNext := raftLog.hasNextCommittedEnts()
-		if hasNext != tt.hasNext {
-			t.Errorf("#%d: hasNext = %v, want %v", i, hasNext, tt.hasNext)
+		if hasNext != tt.whasNext {
+			t.Errorf("#%d: hasNext = %v, want %v", i, hasNext, tt.whasNext)
 		}
 	}
 }
@@ -383,12 +391,15 @@ func TestNextCommittedEnts(t *testing.T) {
 	}
 	tests := []struct {
 		applied uint64
+		snap    bool
 		wents   []pb.Entry
 	}{
-		{0, ents[:2]},
-		{3, ents[:2]},
-		{4, ents[1:2]},
-		{5, nil},
+		{applied: 0, snap: false, wents: ents[:2]},
+		{applied: 3, snap: false, wents: ents[:2]},
+		{applied: 4, snap: false, wents: ents[1:2]},
+		{applied: 5, snap: false, wents: nil},
+		// With snapshot.
+		{applied: 3, snap: true, wents: nil},
 	}
 	for i, tt := range tests {
 		storage := NewMemoryStorage()
@@ -397,6 +408,11 @@ func TestNextCommittedEnts(t *testing.T) {
 		raftLog.append(ents...)
 		raftLog.maybeCommit(5, 1)
 		raftLog.appliedTo(tt.applied)
+		if tt.snap {
+			newSnap := snap
+			newSnap.Metadata.Index++
+			raftLog.restore(newSnap)
+		}
 
 		nents := raftLog.nextCommittedEnts()
 		if !reflect.DeepEqual(nents, tt.wents) {