diff --git a/vendor/google.golang.org/grpc/resolver_conn_wrapper.go b/vendor/google.golang.org/grpc/resolver_conn_wrapper.go
new file mode 100644
index 0000000..7dcefcf
--- /dev/null
+++ b/vendor/google.golang.org/grpc/resolver_conn_wrapper.go
@@ -0,0 +1,265 @@
+/*
+ *
+ * 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 (
+	"fmt"
+	"strings"
+	"sync"
+	"time"
+
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal/channelz"
+	"google.golang.org/grpc/internal/grpcsync"
+	"google.golang.org/grpc/resolver"
+	"google.golang.org/grpc/serviceconfig"
+)
+
+// ccResolverWrapper is a wrapper on top of cc for resolvers.
+// It implements resolver.ClientConnection interface.
+type ccResolverWrapper struct {
+	cc         *ClientConn
+	resolverMu sync.Mutex
+	resolver   resolver.Resolver
+	done       *grpcsync.Event
+	curState   resolver.State
+
+	pollingMu sync.Mutex
+	polling   chan struct{}
+}
+
+// split2 returns the values from strings.SplitN(s, sep, 2).
+// If sep is not found, it returns ("", "", false) instead.
+func split2(s, sep string) (string, string, bool) {
+	spl := strings.SplitN(s, sep, 2)
+	if len(spl) < 2 {
+		return "", "", false
+	}
+	return spl[0], spl[1], true
+}
+
+// parseTarget splits target into a struct containing scheme, authority and
+// endpoint.
+//
+// If target is not a valid scheme://authority/endpoint, it returns {Endpoint:
+// target}.
+func parseTarget(target string) (ret resolver.Target) {
+	var ok bool
+	ret.Scheme, ret.Endpoint, ok = split2(target, "://")
+	if !ok {
+		return resolver.Target{Endpoint: target}
+	}
+	ret.Authority, ret.Endpoint, ok = split2(ret.Endpoint, "/")
+	if !ok {
+		return resolver.Target{Endpoint: target}
+	}
+	return ret
+}
+
+// newCCResolverWrapper uses the resolver.Builder stored in the ClientConn to
+// build a Resolver and returns a ccResolverWrapper object which wraps the
+// newly built resolver.
+func newCCResolverWrapper(cc *ClientConn) (*ccResolverWrapper, error) {
+	rb := cc.dopts.resolverBuilder
+	if rb == nil {
+		return nil, fmt.Errorf("could not get resolver for scheme: %q", cc.parsedTarget.Scheme)
+	}
+
+	ccr := &ccResolverWrapper{
+		cc:   cc,
+		done: grpcsync.NewEvent(),
+	}
+
+	var credsClone credentials.TransportCredentials
+	if creds := cc.dopts.copts.TransportCredentials; creds != nil {
+		credsClone = creds.Clone()
+	}
+	rbo := resolver.BuildOption{
+		DisableServiceConfig: cc.dopts.disableServiceConfig,
+		DialCreds:            credsClone,
+		CredsBundle:          cc.dopts.copts.CredsBundle,
+		Dialer:               cc.dopts.copts.Dialer,
+	}
+
+	var err error
+	// We need to hold the lock here while we assign to the ccr.resolver field
+	// to guard against a data race caused by the following code path,
+	// rb.Build-->ccr.ReportError-->ccr.poll-->ccr.resolveNow, would end up
+	// accessing ccr.resolver which is being assigned here.
+	ccr.resolverMu.Lock()
+	ccr.resolver, err = rb.Build(cc.parsedTarget, ccr, rbo)
+	if err != nil {
+		return nil, err
+	}
+	ccr.resolverMu.Unlock()
+	return ccr, nil
+}
+
+func (ccr *ccResolverWrapper) resolveNow(o resolver.ResolveNowOption) {
+	ccr.resolverMu.Lock()
+	if !ccr.done.HasFired() {
+		ccr.resolver.ResolveNow(o)
+	}
+	ccr.resolverMu.Unlock()
+}
+
+func (ccr *ccResolverWrapper) close() {
+	ccr.resolverMu.Lock()
+	ccr.resolver.Close()
+	ccr.done.Fire()
+	ccr.resolverMu.Unlock()
+}
+
+// poll begins or ends asynchronous polling of the resolver based on whether
+// err is ErrBadResolverState.
+func (ccr *ccResolverWrapper) poll(err error) {
+	ccr.pollingMu.Lock()
+	defer ccr.pollingMu.Unlock()
+	if err != balancer.ErrBadResolverState {
+		// stop polling
+		if ccr.polling != nil {
+			close(ccr.polling)
+			ccr.polling = nil
+		}
+		return
+	}
+	if ccr.polling != nil {
+		// already polling
+		return
+	}
+	p := make(chan struct{})
+	ccr.polling = p
+	go func() {
+		for i := 0; ; i++ {
+			ccr.resolveNow(resolver.ResolveNowOption{})
+			t := time.NewTimer(ccr.cc.dopts.resolveNowBackoff(i))
+			select {
+			case <-p:
+				t.Stop()
+				return
+			case <-ccr.done.Done():
+				// Resolver has been closed.
+				t.Stop()
+				return
+			case <-t.C:
+				select {
+				case <-p:
+					return
+				default:
+				}
+				// Timer expired; re-resolve.
+			}
+		}
+	}()
+}
+
+func (ccr *ccResolverWrapper) UpdateState(s resolver.State) {
+	if ccr.done.HasFired() {
+		return
+	}
+	grpclog.Infof("ccResolverWrapper: sending update to cc: %v", s)
+	if channelz.IsOn() {
+		ccr.addChannelzTraceEvent(s)
+	}
+	ccr.curState = s
+	ccr.poll(ccr.cc.updateResolverState(ccr.curState, nil))
+}
+
+func (ccr *ccResolverWrapper) ReportError(err error) {
+	if ccr.done.HasFired() {
+		return
+	}
+	grpclog.Warningf("ccResolverWrapper: reporting error to cc: %v", err)
+	if channelz.IsOn() {
+		channelz.AddTraceEvent(ccr.cc.channelzID, &channelz.TraceEventDesc{
+			Desc:     fmt.Sprintf("Resolver reported error: %v", err),
+			Severity: channelz.CtWarning,
+		})
+	}
+	ccr.poll(ccr.cc.updateResolverState(resolver.State{}, err))
+}
+
+// NewAddress is called by the resolver implementation to send addresses to gRPC.
+func (ccr *ccResolverWrapper) NewAddress(addrs []resolver.Address) {
+	if ccr.done.HasFired() {
+		return
+	}
+	grpclog.Infof("ccResolverWrapper: sending new addresses to cc: %v", addrs)
+	if channelz.IsOn() {
+		ccr.addChannelzTraceEvent(resolver.State{Addresses: addrs, ServiceConfig: ccr.curState.ServiceConfig})
+	}
+	ccr.curState.Addresses = addrs
+	ccr.poll(ccr.cc.updateResolverState(ccr.curState, nil))
+}
+
+// NewServiceConfig is called by the resolver implementation to send service
+// configs to gRPC.
+func (ccr *ccResolverWrapper) NewServiceConfig(sc string) {
+	if ccr.done.HasFired() {
+		return
+	}
+	grpclog.Infof("ccResolverWrapper: got new service config: %v", sc)
+	scpr := parseServiceConfig(sc)
+	if scpr.Err != nil {
+		grpclog.Warningf("ccResolverWrapper: error parsing service config: %v", scpr.Err)
+		if channelz.IsOn() {
+			channelz.AddTraceEvent(ccr.cc.channelzID, &channelz.TraceEventDesc{
+				Desc:     fmt.Sprintf("Error parsing service config: %v", scpr.Err),
+				Severity: channelz.CtWarning,
+			})
+		}
+		ccr.poll(balancer.ErrBadResolverState)
+		return
+	}
+	if channelz.IsOn() {
+		ccr.addChannelzTraceEvent(resolver.State{Addresses: ccr.curState.Addresses, ServiceConfig: scpr})
+	}
+	ccr.curState.ServiceConfig = scpr
+	ccr.poll(ccr.cc.updateResolverState(ccr.curState, nil))
+}
+
+func (ccr *ccResolverWrapper) ParseServiceConfig(scJSON string) *serviceconfig.ParseResult {
+	return parseServiceConfig(scJSON)
+}
+
+func (ccr *ccResolverWrapper) addChannelzTraceEvent(s resolver.State) {
+	var updates []string
+	var oldSC, newSC *ServiceConfig
+	var oldOK, newOK bool
+	if ccr.curState.ServiceConfig != nil {
+		oldSC, oldOK = ccr.curState.ServiceConfig.Config.(*ServiceConfig)
+	}
+	if s.ServiceConfig != nil {
+		newSC, newOK = s.ServiceConfig.Config.(*ServiceConfig)
+	}
+	if oldOK != newOK || (oldOK && newOK && oldSC.rawJSONString != newSC.rawJSONString) {
+		updates = append(updates, "service config updated")
+	}
+	if len(ccr.curState.Addresses) > 0 && len(s.Addresses) == 0 {
+		updates = append(updates, "resolver returned an empty address list")
+	} else if len(ccr.curState.Addresses) == 0 && len(s.Addresses) > 0 {
+		updates = append(updates, "resolver returned new addresses")
+	}
+	channelz.AddTraceEvent(ccr.cc.channelzID, &channelz.TraceEventDesc{
+		Desc:     fmt.Sprintf("Resolver state updated: %+v (%v)", s, strings.Join(updates, "; ")),
+		Severity: channelz.CtINFO,
+	})
+}