review comments

balancer/weightedroundrobin/balancer.go

@@ -120,7 +120,7 @@ func (b *wrrBalancer) UpdateClientConnState(ccs balancer.ClientConnState) error
 	b.resolverErr = nil
 	cfg, ok := ccs.BalancerConfig.(*lbConfig)
 	if !ok {
-		return fmt.Errorf("wrr: received nil or illegal BalancerConfig: %v", ccs.BalancerConfig)
+		return fmt.Errorf("wrr: received nil or illegal BalancerConfig (type %T): %v", ccs.BalancerConfig, ccs.BalancerConfig)
 	}
 
 	b.cfg = cfg
@@ -206,7 +206,7 @@ func (b *wrrBalancer) ResolverError(err error) {
 func (b *wrrBalancer) UpdateSubConnState(sc balancer.SubConn, state balancer.SubConnState) {
 	wsc := b.scMap[sc]
 	if wsc == nil {
-		b.logger.Errorf("UpdateSubConnStateChange called with an unknown SubConn: %p, %v", sc, state)
+		b.logger.Errorf("UpdateSubConnState called with an unknown SubConn: %p, %v", sc, state)
 		return
 	}
 	if b.logger.V(2) {

balancer/weightedroundrobin/balancer_test.go

@@ -388,8 +388,10 @@ func (s) TestBalancer_TwoAddresses_ErrorPenalty(t *testing.T) {
 	srv2 := startServer(t, reportOOB)
 
 	// srv1 starts loaded and srv2 starts without load; ensure RPCs are routed
-	// disproportionately to srv2 (10:1).  Errors are set (but ignored
-	// initially) such that RPCs will be routed 50/50.
+	// disproportionately to srv2 (10:1).  EPS values are set (but ignored
+	// initially due to ErrorUtilizationPenalty=0).  Later EUP will be updated
+	// to 0.9 which will cause the weights to be equal and RPCs to be routed
+	// 50/50.
 	srv1.oobMetrics.SetQPS(10.0)
 	srv1.oobMetrics.SetCPUUtilization(1.0)
 	srv1.oobMetrics.SetEPS(0)
@@ -432,7 +434,7 @@ func (s) TestBalancer_TwoAddresses_ErrorPenalty(t *testing.T) {
 }
 
 // Tests that the blackout period causes backends to use 0 as their weight
-// until the backout period elapses.
+// (meaning to use the average weight) until the blackout period elapses.
 func (s) TestBalancer_TwoAddresses_BlackoutPeriod(t *testing.T) {
 	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
 	defer cancel()
@@ -509,7 +511,8 @@ func (s) TestBalancer_TwoAddresses_BlackoutPeriod(t *testing.T) {
 }
 
 // Tests that the weight expiration period causes backends to use 0 as their
-// weight once the expiration period elapses.
+// weight (meaning to use the average weight) once the expiration period
+// elapses.
 func (s) TestBalancer_TwoAddresses_WeightExpiration(t *testing.T) {
 	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
 	defer cancel()