update state without proposal when leader changes in zero (#2319)

* update state without proposal when leader changes in zero
* copy key during predicate move

dgraph/cmd/zero/raft.go

@@ -406,8 +406,9 @@ func (n *node) applyConfChange(e raftpb.Entry) {
 
 func (n *node) triggerLeaderChange() {
 	n.server.triggerLeaderChange()
-	m := &intern.Member{Id: n.Id, Addr: n.RaftContext.Addr, Leader: n.AmLeader()}
-	go n.proposeAndWait(context.Background(), &intern.ZeroProposal{Member: m})
+	// We update leader information on each node without proposal. This
+	// function is called on all nodes on leader change.
+	n.server.updateZeroLeader()
 }
 
 func (n *node) initAndStartNode(wal *raftwal.Wal) error {

dgraph/cmd/zero/zero.go

@@ -203,6 +203,19 @@ func (s *Server) storeZero(m *intern.Member) {
 	s.state.Zeros[m.Id] = m
 }
 
+func (s *Server) updateZeroLeader() {
+	s.Lock()
+	defer s.Unlock()
+	leader := s.Node.Raft().Status().Lead
+	for _, m := range s.state.Zeros {
+		if m.Id == leader {
+			m.Leader = true
+		} else {
+			m.Leader = false
+		}
+	}
+}
+
 func (s *Server) removeZero(nodeId uint64) {
 	s.Lock()
 	defer s.Unlock()

worker/groups.go

@@ -247,7 +247,10 @@ func (g *groupi) applyState(state *intern.MembershipState) {
 	x.AssertTrue(state != nil)
 	g.Lock()
 	defer g.Unlock()
-	if g.state != nil && g.state.Counter >= state.Counter {
+	// We don't update state if we get any old state. Counter stores the raftindex of
+	// last update. For leader changes at zero since we don't propose, state can get
+	// updated at same counter value. So ignore only if counter is less.
+	if g.state != nil && g.state.Counter > state.Counter {
 		return
 	}
 

worker/predicate_move.go

@@ -134,7 +134,10 @@ func movePredicateHelper(ctx context.Context, predicate string, gid uint32) erro
 		}
 		prevKey = prevKey[:len(key)]
 		copy(prevKey, key)
-		l, err := posting.ReadPostingList(prevKey, it)
+
+		nkey := make([]byte, len(key))
+		copy(nkey, key)
+		l, err := posting.ReadPostingList(nkey, it)
 		if err != nil {
 			return err
 		}