read existing broker stats

weed/mq/broker/broker_grpc_balancer.go

@@ -20,11 +20,15 @@ func (broker *MessageQueueBroker) ConnectToBalancer(stream mq_pb.SeaweedMessagin
 
 	// process init message
 	initMessage := req.GetInit()
-	brokerStats := balancer.NewBrokerStats()
+	var brokerStats *balancer.BrokerStats
 	if initMessage != nil {
-		broker.Balancer.Brokers.Set(initMessage.Broker, brokerStats)
+		var found bool
+		brokerStats, found = broker.Balancer.Brokers.Get(initMessage.Broker)
+		if !found {
+			brokerStats = balancer.NewBrokerStats()
+			broker.Balancer.Brokers.Set(initMessage.Broker, brokerStats)
+		}
 	} else {
-		// TODO fix this
 		return status.Errorf(codes.InvalidArgument, "balancer init message is empty")
 	}
 	defer func() {