address the comments

grpclb/grpclb.go

@@ -70,6 +70,7 @@ type addrInfo struct {
 type balancer struct {
 	r      naming.Resolver
 	mu     sync.Mutex
+	seq    int // a sequence number to make sure addrCh does not get stale addresses.
 	w      naming.Watcher
 	addrCh chan []grpc.Address
 	rbs    []remoteBalancerInfo
@@ -84,12 +85,12 @@ func (b *balancer) watchAddrUpdates(w naming.Watcher, ch chan remoteBalancerInfo
 	if err != nil {
 		return err
 	}
-	var bAddr remoteBalancerInfo
 	b.mu.Lock()
 	defer b.mu.Unlock()
 	if b.done {
 		return grpc.ErrClientConnClosing
 	}
+	var bAddr remoteBalancerInfo
 	if len(b.rbs) > 0 {
 		bAddr = b.rbs[0]
 	}
@@ -102,7 +103,7 @@ func (b *balancer) watchAddrUpdates(w naming.Watcher, ch chan remoteBalancerInfo
 		case naming.Add:
 			var exist bool
 			for _, v := range b.rbs {
-				// TODO: Is the same addr with different different server name a different balancer?
+				// TODO: Is the same addr with different server name a different balancer?
 				if addr == v.addr {
 					exist = true
 					break
@@ -139,7 +140,7 @@ func (b *balancer) watchAddrUpdates(w naming.Watcher, ch chan remoteBalancerInfo
 	return nil
 }
 
-func (b *balancer) processServerList(l *lbpb.ServerList) {
+func (b *balancer) processServerList(l *lbpb.ServerList, seq int) {
 	servers := l.GetServers()
 	var (
 		sl    []addrInfo
@@ -159,7 +160,7 @@ func (b *balancer) processServerList(l *lbpb.ServerList) {
 	}
 	b.mu.Lock()
 	defer b.mu.Unlock()
-	if b.done {
+	if b.done || seq < b.seq {
 		return
 	}
 	if len(sl) > 0 {
@@ -172,12 +173,6 @@ func (b *balancer) processServerList(l *lbpb.ServerList) {
 }
 
 func (b *balancer) callRemoteBalancer(lbc lbpb.LoadBalancerClient) (retry bool) {
-	b.mu.Lock()
-	if b.done {
-		b.mu.Unlock()
-		return
-	}
-	b.mu.Unlock()
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 	stream, err := lbc.BalanceLoad(ctx, grpc.FailFast(false))
@@ -185,6 +180,14 @@ func (b *balancer) callRemoteBalancer(lbc lbpb.LoadBalancerClient) (retry bool)
 		grpclog.Printf("Failed to perform RPC to the remote balancer %v", err)
 		return
 	}
+	b.mu.Lock()
+	if b.done {
+		b.mu.Unlock()
+		return
+	}
+	b.seq++
+	seq := b.seq
+	b.mu.Unlock()
 	initReq := &lbpb.LoadBalanceRequest{
 		LoadBalanceRequestType: &lbpb.LoadBalanceRequest_InitialRequest{
 			InitialRequest: new(lbpb.InitialLoadBalanceRequest),
@@ -217,7 +220,7 @@ func (b *balancer) callRemoteBalancer(lbc lbpb.LoadBalancerClient) (retry bool)
 			break
 		}
 		if serverList := reply.GetServerList(); serverList != nil {
-			b.processServerList(serverList)
+			b.processServerList(serverList, seq)
 		}
 	}
 	return true
@@ -307,6 +310,9 @@ func (b *balancer) down(addr grpc.Address, err error) {
 func (b *balancer) Up(addr grpc.Address) func(error) {
 	b.mu.Lock()
 	defer b.mu.Unlock()
+	if b.done {
+		return nil
+	}
 	var cnt int
 	for _, a := range b.addrs {
 		if a.addr == addr {

grpclb/grpclb_test.go

@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2014, Google Inc.
+ * Copyright 2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -57,12 +57,15 @@ type testWatcher struct {
 }
 
 func (w *testWatcher) Next() (updates []*naming.Update, err error) {
-	n := <-w.side
-	if n == 0 {
+	n, ok := <-w.side
+	if !ok {
 		return nil, fmt.Errorf("w.side is closed")
 	}
 	for i := 0; i < n; i++ {
-		u := <-w.update
+		u, ok := <-w.update
+		if !ok {
+			break
+		}
 		if u != nil {
 			updates = append(updates, u)
 		}
@@ -158,11 +161,11 @@ func stopBackends(servers []*grpc.Server) {
 	}
 }
 
-func TestGrpcLB(t *testing.T) {
+func TestGRPCLB(t *testing.T) {
 	// Start a backend.
 	beLis, err := net.Listen("tcp", "localhost:0")
 	if err != nil {
-		t.Fatalf("fadjf")
+		t.Fatalf("Failed to listen %v", err)
 	}
 	backends := startBackends(beLis)
 	defer stopBackends(backends)