diff --git a/vendor/google.golang.org/grpc/pickfirst.go b/vendor/google.golang.org/grpc/pickfirst.go
new file mode 100644
index 0000000..ed05b02
--- /dev/null
+++ b/vendor/google.golang.org/grpc/pickfirst.go
@@ -0,0 +1,118 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"context"
+
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/resolver"
+)
+
+// PickFirstBalancerName is the name of the pick_first balancer.
+const PickFirstBalancerName = "pick_first"
+
+func newPickfirstBuilder() balancer.Builder {
+	return &pickfirstBuilder{}
+}
+
+type pickfirstBuilder struct{}
+
+func (*pickfirstBuilder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer {
+	return &pickfirstBalancer{cc: cc}
+}
+
+func (*pickfirstBuilder) Name() string {
+	return PickFirstBalancerName
+}
+
+type pickfirstBalancer struct {
+	cc balancer.ClientConn
+	sc balancer.SubConn
+}
+
+func (b *pickfirstBalancer) HandleResolvedAddrs(addrs []resolver.Address, err error) {
+	if err != nil {
+		if grpclog.V(2) {
+			grpclog.Infof("pickfirstBalancer: HandleResolvedAddrs called with error %v", err)
+		}
+		return
+	}
+	if b.sc == nil {
+		b.sc, err = b.cc.NewSubConn(addrs, balancer.NewSubConnOptions{})
+		if err != nil {
+			//TODO(yuxuanli): why not change the cc state to Idle?
+			if grpclog.V(2) {
+				grpclog.Errorf("pickfirstBalancer: failed to NewSubConn: %v", err)
+			}
+			return
+		}
+		b.cc.UpdateBalancerState(connectivity.Idle, &picker{sc: b.sc})
+		b.sc.Connect()
+	} else {
+		b.sc.UpdateAddresses(addrs)
+		b.sc.Connect()
+	}
+}
+
+func (b *pickfirstBalancer) HandleSubConnStateChange(sc balancer.SubConn, s connectivity.State) {
+	if grpclog.V(2) {
+		grpclog.Infof("pickfirstBalancer: HandleSubConnStateChange: %p, %v", sc, s)
+	}
+	if b.sc != sc {
+		if grpclog.V(2) {
+			grpclog.Infof("pickfirstBalancer: ignored state change because sc is not recognized")
+		}
+		return
+	}
+	if s == connectivity.Shutdown {
+		b.sc = nil
+		return
+	}
+
+	switch s {
+	case connectivity.Ready, connectivity.Idle:
+		b.cc.UpdateBalancerState(s, &picker{sc: sc})
+	case connectivity.Connecting:
+		b.cc.UpdateBalancerState(s, &picker{err: balancer.ErrNoSubConnAvailable})
+	case connectivity.TransientFailure:
+		b.cc.UpdateBalancerState(s, &picker{err: balancer.ErrTransientFailure})
+	}
+}
+
+func (b *pickfirstBalancer) Close() {
+}
+
+type picker struct {
+	err error
+	sc  balancer.SubConn
+}
+
+func (p *picker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
+	if p.err != nil {
+		return nil, nil, p.err
+	}
+	return p.sc, nil, nil
+}
+
+func init() {
+	balancer.Register(newPickfirstBuilder())
+}