diff --git a/vendor/github.com/coreos/etcd/clientv3/balancer/balancer.go b/vendor/github.com/coreos/etcd/clientv3/balancer/balancer.go
new file mode 100644
index 0000000..9306385
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/clientv3/balancer/balancer.go
@@ -0,0 +1,293 @@
+// Copyright 2018 The etcd 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 balancer implements client balancer.
+package balancer
+
+import (
+	"strconv"
+	"sync"
+	"time"
+
+	"github.com/coreos/etcd/clientv3/balancer/connectivity"
+	"github.com/coreos/etcd/clientv3/balancer/picker"
+
+	"go.uber.org/zap"
+	"google.golang.org/grpc/balancer"
+	grpcconnectivity "google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/resolver"
+	_ "google.golang.org/grpc/resolver/dns"         // register DNS resolver
+	_ "google.golang.org/grpc/resolver/passthrough" // register passthrough resolver
+)
+
+// Config defines balancer configurations.
+type Config struct {
+	// Policy configures balancer policy.
+	Policy picker.Policy
+
+	// Picker implements gRPC picker.
+	// Leave empty if "Policy" field is not custom.
+	// TODO: currently custom policy is not supported.
+	// Picker picker.Picker
+
+	// Name defines an additional name for balancer.
+	// Useful for balancer testing to avoid register conflicts.
+	// If empty, defaults to policy name.
+	Name string
+
+	// Logger configures balancer logging.
+	// If nil, logs are discarded.
+	Logger *zap.Logger
+}
+
+// RegisterBuilder creates and registers a builder. Since this function calls balancer.Register, it
+// must be invoked at initialization time.
+func RegisterBuilder(cfg Config) {
+	bb := &builder{cfg}
+	balancer.Register(bb)
+
+	bb.cfg.Logger.Debug(
+		"registered balancer",
+		zap.String("policy", bb.cfg.Policy.String()),
+		zap.String("name", bb.cfg.Name),
+	)
+}
+
+type builder struct {
+	cfg Config
+}
+
+// Build is called initially when creating "ccBalancerWrapper".
+// "grpc.Dial" is called to this client connection.
+// Then, resolved addresses will be handled via "HandleResolvedAddrs".
+func (b *builder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer {
+	bb := &baseBalancer{
+		id:     strconv.FormatInt(time.Now().UnixNano(), 36),
+		policy: b.cfg.Policy,
+		name:   b.cfg.Name,
+		lg:     b.cfg.Logger,
+
+		addrToSc: make(map[resolver.Address]balancer.SubConn),
+		scToAddr: make(map[balancer.SubConn]resolver.Address),
+		scToSt:   make(map[balancer.SubConn]grpcconnectivity.State),
+
+		currentConn:          nil,
+		connectivityRecorder: connectivity.New(b.cfg.Logger),
+
+		// initialize picker always returns "ErrNoSubConnAvailable"
+		picker: picker.NewErr(balancer.ErrNoSubConnAvailable),
+	}
+
+	// TODO: support multiple connections
+	bb.mu.Lock()
+	bb.currentConn = cc
+	bb.mu.Unlock()
+
+	bb.lg.Info(
+		"built balancer",
+		zap.String("balancer-id", bb.id),
+		zap.String("policy", bb.policy.String()),
+		zap.String("resolver-target", cc.Target()),
+	)
+	return bb
+}
+
+// Name implements "grpc/balancer.Builder" interface.
+func (b *builder) Name() string { return b.cfg.Name }
+
+// Balancer defines client balancer interface.
+type Balancer interface {
+	// Balancer is called on specified client connection. Client initiates gRPC
+	// connection with "grpc.Dial(addr, grpc.WithBalancerName)", and then those resolved
+	// addresses are passed to "grpc/balancer.Balancer.HandleResolvedAddrs".
+	// For each resolved address, balancer calls "balancer.ClientConn.NewSubConn".
+	// "grpc/balancer.Balancer.HandleSubConnStateChange" is called when connectivity state
+	// changes, thus requires failover logic in this method.
+	balancer.Balancer
+
+	// Picker calls "Pick" for every client request.
+	picker.Picker
+}
+
+type baseBalancer struct {
+	id     string
+	policy picker.Policy
+	name   string
+	lg     *zap.Logger
+
+	mu sync.RWMutex
+
+	addrToSc map[resolver.Address]balancer.SubConn
+	scToAddr map[balancer.SubConn]resolver.Address
+	scToSt   map[balancer.SubConn]grpcconnectivity.State
+
+	currentConn          balancer.ClientConn
+	connectivityRecorder connectivity.Recorder
+
+	picker picker.Picker
+}
+
+// HandleResolvedAddrs implements "grpc/balancer.Balancer" interface.
+// gRPC sends initial or updated resolved addresses from "Build".
+func (bb *baseBalancer) HandleResolvedAddrs(addrs []resolver.Address, err error) {
+	if err != nil {
+		bb.lg.Warn("HandleResolvedAddrs called with error", zap.String("balancer-id", bb.id), zap.Error(err))
+		return
+	}
+	bb.lg.Info("resolved",
+		zap.String("picker", bb.picker.String()),
+		zap.String("balancer-id", bb.id),
+		zap.Strings("addresses", addrsToStrings(addrs)),
+	)
+
+	bb.mu.Lock()
+	defer bb.mu.Unlock()
+
+	resolved := make(map[resolver.Address]struct{})
+	for _, addr := range addrs {
+		resolved[addr] = struct{}{}
+		if _, ok := bb.addrToSc[addr]; !ok {
+			sc, err := bb.currentConn.NewSubConn([]resolver.Address{addr}, balancer.NewSubConnOptions{})
+			if err != nil {
+				bb.lg.Warn("NewSubConn failed", zap.String("picker", bb.picker.String()), zap.String("balancer-id", bb.id), zap.Error(err), zap.String("address", addr.Addr))
+				continue
+			}
+			bb.lg.Info("created subconn", zap.String("address", addr.Addr))
+			bb.addrToSc[addr] = sc
+			bb.scToAddr[sc] = addr
+			bb.scToSt[sc] = grpcconnectivity.Idle
+			sc.Connect()
+		}
+	}
+
+	for addr, sc := range bb.addrToSc {
+		if _, ok := resolved[addr]; !ok {
+			// was removed by resolver or failed to create subconn
+			bb.currentConn.RemoveSubConn(sc)
+			delete(bb.addrToSc, addr)
+
+			bb.lg.Info(
+				"removed subconn",
+				zap.String("picker", bb.picker.String()),
+				zap.String("balancer-id", bb.id),
+				zap.String("address", addr.Addr),
+				zap.String("subconn", scToString(sc)),
+			)
+
+			// Keep the state of this sc in bb.scToSt until sc's state becomes Shutdown.
+			// The entry will be deleted in HandleSubConnStateChange.
+			// (DO NOT) delete(bb.scToAddr, sc)
+			// (DO NOT) delete(bb.scToSt, sc)
+		}
+	}
+}
+
+// HandleSubConnStateChange implements "grpc/balancer.Balancer" interface.
+func (bb *baseBalancer) HandleSubConnStateChange(sc balancer.SubConn, s grpcconnectivity.State) {
+	bb.mu.Lock()
+	defer bb.mu.Unlock()
+
+	old, ok := bb.scToSt[sc]
+	if !ok {
+		bb.lg.Warn(
+			"state change for an unknown subconn",
+			zap.String("picker", bb.picker.String()),
+			zap.String("balancer-id", bb.id),
+			zap.String("subconn", scToString(sc)),
+			zap.Int("subconn-size", len(bb.scToAddr)),
+			zap.String("state", s.String()),
+		)
+		return
+	}
+
+	bb.lg.Info(
+		"state changed",
+		zap.String("picker", bb.picker.String()),
+		zap.String("balancer-id", bb.id),
+		zap.Bool("connected", s == grpcconnectivity.Ready),
+		zap.String("subconn", scToString(sc)),
+		zap.Int("subconn-size", len(bb.scToAddr)),
+		zap.String("address", bb.scToAddr[sc].Addr),
+		zap.String("old-state", old.String()),
+		zap.String("new-state", s.String()),
+	)
+
+	bb.scToSt[sc] = s
+	switch s {
+	case grpcconnectivity.Idle:
+		sc.Connect()
+	case grpcconnectivity.Shutdown:
+		// When an address was removed by resolver, b called RemoveSubConn but
+		// kept the sc's state in scToSt. Remove state for this sc here.
+		delete(bb.scToAddr, sc)
+		delete(bb.scToSt, sc)
+	}
+
+	oldAggrState := bb.connectivityRecorder.GetCurrentState()
+	bb.connectivityRecorder.RecordTransition(old, s)
+
+	// Update balancer picker when one of the following happens:
+	//  - this sc became ready from not-ready
+	//  - this sc became not-ready from ready
+	//  - the aggregated state of balancer became TransientFailure from non-TransientFailure
+	//  - the aggregated state of balancer became non-TransientFailure from TransientFailure
+	if (s == grpcconnectivity.Ready) != (old == grpcconnectivity.Ready) ||
+		(bb.connectivityRecorder.GetCurrentState() == grpcconnectivity.TransientFailure) != (oldAggrState == grpcconnectivity.TransientFailure) {
+		bb.updatePicker()
+	}
+
+	bb.currentConn.UpdateBalancerState(bb.connectivityRecorder.GetCurrentState(), bb.picker)
+}
+
+func (bb *baseBalancer) updatePicker() {
+	if bb.connectivityRecorder.GetCurrentState() == grpcconnectivity.TransientFailure {
+		bb.picker = picker.NewErr(balancer.ErrTransientFailure)
+		bb.lg.Info(
+			"updated picker to transient error picker",
+			zap.String("picker", bb.picker.String()),
+			zap.String("balancer-id", bb.id),
+			zap.String("policy", bb.policy.String()),
+		)
+		return
+	}
+
+	// only pass ready subconns to picker
+	scToAddr := make(map[balancer.SubConn]resolver.Address)
+	for addr, sc := range bb.addrToSc {
+		if st, ok := bb.scToSt[sc]; ok && st == grpcconnectivity.Ready {
+			scToAddr[sc] = addr
+		}
+	}
+
+	bb.picker = picker.New(picker.Config{
+		Policy:                   bb.policy,
+		Logger:                   bb.lg,
+		SubConnToResolverAddress: scToAddr,
+	})
+	bb.lg.Info(
+		"updated picker",
+		zap.String("picker", bb.picker.String()),
+		zap.String("balancer-id", bb.id),
+		zap.String("policy", bb.policy.String()),
+		zap.Strings("subconn-ready", scsToStrings(scToAddr)),
+		zap.Int("subconn-size", len(scToAddr)),
+	)
+}
+
+// Close implements "grpc/balancer.Balancer" interface.
+// Close is a nop because base balancer doesn't have internal state to clean up,
+// and it doesn't need to call RemoveSubConn for the SubConns.
+func (bb *baseBalancer) Close() {
+	// TODO
+}
diff --git a/vendor/github.com/coreos/etcd/clientv3/balancer/connectivity/connectivity.go b/vendor/github.com/coreos/etcd/clientv3/balancer/connectivity/connectivity.go
new file mode 100644
index 0000000..4c4ad36
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/clientv3/balancer/connectivity/connectivity.go
@@ -0,0 +1,93 @@
+// Copyright 2019 The etcd 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 connectivity implements client connectivity operations.
+package connectivity
+
+import (
+	"sync"
+
+	"go.uber.org/zap"
+	"google.golang.org/grpc/connectivity"
+)
+
+// Recorder records gRPC connectivity.
+type Recorder interface {
+	GetCurrentState() connectivity.State
+	RecordTransition(oldState, newState connectivity.State)
+}
+
+// New returns a new Recorder.
+func New(lg *zap.Logger) Recorder {
+	return &recorder{lg: lg}
+}
+
+// recorder takes the connectivity states of multiple SubConns
+// and returns one aggregated connectivity state.
+// ref. https://github.com/grpc/grpc-go/blob/master/balancer/balancer.go
+type recorder struct {
+	lg *zap.Logger
+
+	mu sync.RWMutex
+
+	cur connectivity.State
+
+	numReady            uint64 // Number of addrConns in ready state.
+	numConnecting       uint64 // Number of addrConns in connecting state.
+	numTransientFailure uint64 // Number of addrConns in transientFailure.
+}
+
+func (rc *recorder) GetCurrentState() (state connectivity.State) {
+	rc.mu.RLock()
+	defer rc.mu.RUnlock()
+	return rc.cur
+}
+
+// RecordTransition records state change happening in subConn and based on that
+// it evaluates what aggregated state should be.
+//
+//  - If at least one SubConn in Ready, the aggregated state is Ready;
+//  - Else if at least one SubConn in Connecting, the aggregated state is Connecting;
+//  - Else the aggregated state is TransientFailure.
+//
+// Idle and Shutdown are not considered.
+//
+// ref. https://github.com/grpc/grpc-go/blob/master/balancer/balancer.go
+func (rc *recorder) RecordTransition(oldState, newState connectivity.State) {
+	rc.mu.Lock()
+	defer rc.mu.Unlock()
+
+	for idx, state := range []connectivity.State{oldState, newState} {
+		updateVal := 2*uint64(idx) - 1 // -1 for oldState and +1 for new.
+		switch state {
+		case connectivity.Ready:
+			rc.numReady += updateVal
+		case connectivity.Connecting:
+			rc.numConnecting += updateVal
+		case connectivity.TransientFailure:
+			rc.numTransientFailure += updateVal
+		default:
+			rc.lg.Warn("connectivity recorder received unknown state", zap.String("connectivity-state", state.String()))
+		}
+	}
+
+	switch { // must be exclusive, no overlap
+	case rc.numReady > 0:
+		rc.cur = connectivity.Ready
+	case rc.numConnecting > 0:
+		rc.cur = connectivity.Connecting
+	default:
+		rc.cur = connectivity.TransientFailure
+	}
+}
diff --git a/vendor/github.com/coreos/etcd/clientv3/balancer/picker/doc.go b/vendor/github.com/coreos/etcd/clientv3/balancer/picker/doc.go
new file mode 100644
index 0000000..35dabf5
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/clientv3/balancer/picker/doc.go
@@ -0,0 +1,16 @@
+// Copyright 2018 The etcd 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 picker defines/implements client balancer picker policy.
+package picker
diff --git a/vendor/github.com/coreos/etcd/clientv3/balancer/picker/err.go b/vendor/github.com/coreos/etcd/clientv3/balancer/picker/err.go
new file mode 100644
index 0000000..9e04378
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/clientv3/balancer/picker/err.go
@@ -0,0 +1,39 @@
+// Copyright 2018 The etcd 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 picker
+
+import (
+	"context"
+
+	"google.golang.org/grpc/balancer"
+)
+
+// NewErr returns a picker that always returns err on "Pick".
+func NewErr(err error) Picker {
+	return &errPicker{p: Error, err: err}
+}
+
+type errPicker struct {
+	p   Policy
+	err error
+}
+
+func (ep *errPicker) String() string {
+	return ep.p.String()
+}
+
+func (ep *errPicker) Pick(context.Context, balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
+	return nil, nil, ep.err
+}
diff --git a/vendor/github.com/coreos/etcd/clientv3/balancer/picker/picker.go b/vendor/github.com/coreos/etcd/clientv3/balancer/picker/picker.go
new file mode 100644
index 0000000..bd1a5d2
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/clientv3/balancer/picker/picker.go
@@ -0,0 +1,91 @@
+// Copyright 2018 The etcd 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 picker
+
+import (
+	"fmt"
+
+	"go.uber.org/zap"
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/resolver"
+)
+
+// Picker defines balancer Picker methods.
+type Picker interface {
+	balancer.Picker
+	String() string
+}
+
+// Config defines picker configuration.
+type Config struct {
+	// Policy specifies etcd clientv3's built in balancer policy.
+	Policy Policy
+
+	// Logger defines picker logging object.
+	Logger *zap.Logger
+
+	// SubConnToResolverAddress maps each gRPC sub-connection to an address.
+	// Basically, it is a list of addresses that the Picker can pick from.
+	SubConnToResolverAddress map[balancer.SubConn]resolver.Address
+}
+
+// Policy defines balancer picker policy.
+type Policy uint8
+
+const (
+	// Error is error picker policy.
+	Error Policy = iota
+
+	// RoundrobinBalanced balances loads over multiple endpoints
+	// and implements failover in roundrobin fashion.
+	RoundrobinBalanced
+
+	// Custom defines custom balancer picker.
+	// TODO: custom picker is not supported yet.
+	Custom
+)
+
+func (p Policy) String() string {
+	switch p {
+	case Error:
+		return "picker-error"
+
+	case RoundrobinBalanced:
+		return "picker-roundrobin-balanced"
+
+	case Custom:
+		panic("'custom' picker policy is not supported yet")
+
+	default:
+		panic(fmt.Errorf("invalid balancer picker policy (%d)", p))
+	}
+}
+
+// New creates a new Picker.
+func New(cfg Config) Picker {
+	switch cfg.Policy {
+	case Error:
+		panic("'error' picker policy is not supported here; use 'picker.NewErr'")
+
+	case RoundrobinBalanced:
+		return newRoundrobinBalanced(cfg)
+
+	case Custom:
+		panic("'custom' picker policy is not supported yet")
+
+	default:
+		panic(fmt.Errorf("invalid balancer picker policy (%d)", cfg.Policy))
+	}
+}
diff --git a/vendor/github.com/coreos/etcd/clientv3/balancer/picker/roundrobin_balanced.go b/vendor/github.com/coreos/etcd/clientv3/balancer/picker/roundrobin_balanced.go
new file mode 100644
index 0000000..1b8b285
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/clientv3/balancer/picker/roundrobin_balanced.go
@@ -0,0 +1,95 @@
+// Copyright 2018 The etcd 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 picker
+
+import (
+	"context"
+	"sync"
+
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/resolver"
+)
+
+// newRoundrobinBalanced returns a new roundrobin balanced picker.
+func newRoundrobinBalanced(cfg Config) Picker {
+	scs := make([]balancer.SubConn, 0, len(cfg.SubConnToResolverAddress))
+	for sc := range cfg.SubConnToResolverAddress {
+		scs = append(scs, sc)
+	}
+	return &rrBalanced{
+		p:        RoundrobinBalanced,
+		lg:       cfg.Logger,
+		scs:      scs,
+		scToAddr: cfg.SubConnToResolverAddress,
+	}
+}
+
+type rrBalanced struct {
+	p Policy
+
+	lg *zap.Logger
+
+	mu       sync.RWMutex
+	next     int
+	scs      []balancer.SubConn
+	scToAddr map[balancer.SubConn]resolver.Address
+}
+
+func (rb *rrBalanced) String() string { return rb.p.String() }
+
+// Pick is called for every client request.
+func (rb *rrBalanced) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
+	rb.mu.RLock()
+	n := len(rb.scs)
+	rb.mu.RUnlock()
+	if n == 0 {
+		return nil, nil, balancer.ErrNoSubConnAvailable
+	}
+
+	rb.mu.Lock()
+	cur := rb.next
+	sc := rb.scs[cur]
+	picked := rb.scToAddr[sc].Addr
+	rb.next = (rb.next + 1) % len(rb.scs)
+	rb.mu.Unlock()
+
+	rb.lg.Debug(
+		"picked",
+		zap.String("picker", rb.p.String()),
+		zap.String("address", picked),
+		zap.Int("subconn-index", cur),
+		zap.Int("subconn-size", n),
+	)
+
+	doneFunc := func(info balancer.DoneInfo) {
+		// TODO: error handling?
+		fss := []zapcore.Field{
+			zap.Error(info.Err),
+			zap.String("picker", rb.p.String()),
+			zap.String("address", picked),
+			zap.Bool("success", info.Err == nil),
+			zap.Bool("bytes-sent", info.BytesSent),
+			zap.Bool("bytes-received", info.BytesReceived),
+		}
+		if info.Err == nil {
+			rb.lg.Debug("balancer done", fss...)
+		} else {
+			rb.lg.Warn("balancer failed", fss...)
+		}
+	}
+	return sc, doneFunc, nil
+}
diff --git a/vendor/github.com/coreos/etcd/clientv3/balancer/resolver/endpoint/endpoint.go b/vendor/github.com/coreos/etcd/clientv3/balancer/resolver/endpoint/endpoint.go
new file mode 100644
index 0000000..864b5df
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/clientv3/balancer/resolver/endpoint/endpoint.go
@@ -0,0 +1,247 @@
+// Copyright 2018 The etcd 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 endpoint resolves etcd entpoints using grpc targets of the form 'endpoint://<id>/<endpoint>'.
+package endpoint
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/url"
+	"strings"
+	"sync"
+
+	"google.golang.org/grpc/resolver"
+)
+
+const scheme = "endpoint"
+
+var (
+	targetPrefix = fmt.Sprintf("%s://", scheme)
+
+	bldr *builder
+)
+
+func init() {
+	bldr = &builder{
+		resolverGroups: make(map[string]*ResolverGroup),
+	}
+	resolver.Register(bldr)
+}
+
+type builder struct {
+	mu             sync.RWMutex
+	resolverGroups map[string]*ResolverGroup
+}
+
+// NewResolverGroup creates a new ResolverGroup with the given id.
+func NewResolverGroup(id string) (*ResolverGroup, error) {
+	return bldr.newResolverGroup(id)
+}
+
+// ResolverGroup keeps all endpoints of resolvers using a common endpoint://<id>/ target
+// up-to-date.
+type ResolverGroup struct {
+	mu        sync.RWMutex
+	id        string
+	endpoints []string
+	resolvers []*Resolver
+}
+
+func (e *ResolverGroup) addResolver(r *Resolver) {
+	e.mu.Lock()
+	addrs := epsToAddrs(e.endpoints...)
+	e.resolvers = append(e.resolvers, r)
+	e.mu.Unlock()
+	r.cc.NewAddress(addrs)
+}
+
+func (e *ResolverGroup) removeResolver(r *Resolver) {
+	e.mu.Lock()
+	for i, er := range e.resolvers {
+		if er == r {
+			e.resolvers = append(e.resolvers[:i], e.resolvers[i+1:]...)
+			break
+		}
+	}
+	e.mu.Unlock()
+}
+
+// SetEndpoints updates the endpoints for ResolverGroup. All registered resolver are updated
+// immediately with the new endpoints.
+func (e *ResolverGroup) SetEndpoints(endpoints []string) {
+	addrs := epsToAddrs(endpoints...)
+	e.mu.Lock()
+	e.endpoints = endpoints
+	for _, r := range e.resolvers {
+		r.cc.NewAddress(addrs)
+	}
+	e.mu.Unlock()
+}
+
+// Target constructs a endpoint target using the endpoint id of the ResolverGroup.
+func (e *ResolverGroup) Target(endpoint string) string {
+	return Target(e.id, endpoint)
+}
+
+// Target constructs a endpoint resolver target.
+func Target(id, endpoint string) string {
+	return fmt.Sprintf("%s://%s/%s", scheme, id, endpoint)
+}
+
+// IsTarget checks if a given target string in an endpoint resolver target.
+func IsTarget(target string) bool {
+	return strings.HasPrefix(target, "endpoint://")
+}
+
+func (e *ResolverGroup) Close() {
+	bldr.close(e.id)
+}
+
+// Build creates or reuses an etcd resolver for the etcd cluster name identified by the authority part of the target.
+func (b *builder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOption) (resolver.Resolver, error) {
+	if len(target.Authority) < 1 {
+		return nil, fmt.Errorf("'etcd' target scheme requires non-empty authority identifying etcd cluster being routed to")
+	}
+	id := target.Authority
+	es, err := b.getResolverGroup(id)
+	if err != nil {
+		return nil, fmt.Errorf("failed to build resolver: %v", err)
+	}
+	r := &Resolver{
+		endpointID: id,
+		cc:         cc,
+	}
+	es.addResolver(r)
+	return r, nil
+}
+
+func (b *builder) newResolverGroup(id string) (*ResolverGroup, error) {
+	b.mu.RLock()
+	_, ok := b.resolverGroups[id]
+	b.mu.RUnlock()
+	if ok {
+		return nil, fmt.Errorf("Endpoint already exists for id: %s", id)
+	}
+
+	es := &ResolverGroup{id: id}
+	b.mu.Lock()
+	b.resolverGroups[id] = es
+	b.mu.Unlock()
+	return es, nil
+}
+
+func (b *builder) getResolverGroup(id string) (*ResolverGroup, error) {
+	b.mu.RLock()
+	es, ok := b.resolverGroups[id]
+	b.mu.RUnlock()
+	if !ok {
+		return nil, fmt.Errorf("ResolverGroup not found for id: %s", id)
+	}
+	return es, nil
+}
+
+func (b *builder) close(id string) {
+	b.mu.Lock()
+	delete(b.resolverGroups, id)
+	b.mu.Unlock()
+}
+
+func (b *builder) Scheme() string {
+	return scheme
+}
+
+// Resolver provides a resolver for a single etcd cluster, identified by name.
+type Resolver struct {
+	endpointID string
+	cc         resolver.ClientConn
+	sync.RWMutex
+}
+
+// TODO: use balancer.epsToAddrs
+func epsToAddrs(eps ...string) (addrs []resolver.Address) {
+	addrs = make([]resolver.Address, 0, len(eps))
+	for _, ep := range eps {
+		addrs = append(addrs, resolver.Address{Addr: ep})
+	}
+	return addrs
+}
+
+func (*Resolver) ResolveNow(o resolver.ResolveNowOption) {}
+
+func (r *Resolver) Close() {
+	es, err := bldr.getResolverGroup(r.endpointID)
+	if err != nil {
+		return
+	}
+	es.removeResolver(r)
+}
+
+// ParseEndpoint endpoint parses an endpoint of the form
+// (http|https)://<host>*|(unix|unixs)://<path>)
+// and returns a protocol ('tcp' or 'unix'),
+// host (or filepath if a unix socket),
+// scheme (http, https, unix, unixs).
+func ParseEndpoint(endpoint string) (proto string, host string, scheme string) {
+	proto = "tcp"
+	host = endpoint
+	url, uerr := url.Parse(endpoint)
+	if uerr != nil || !strings.Contains(endpoint, "://") {
+		return proto, host, scheme
+	}
+	scheme = url.Scheme
+
+	// strip scheme:// prefix since grpc dials by host
+	host = url.Host
+	switch url.Scheme {
+	case "http", "https":
+	case "unix", "unixs":
+		proto = "unix"
+		host = url.Host + url.Path
+	default:
+		proto, host = "", ""
+	}
+	return proto, host, scheme
+}
+
+// ParseTarget parses a endpoint://<id>/<endpoint> string and returns the parsed id and endpoint.
+// If the target is malformed, an error is returned.
+func ParseTarget(target string) (string, string, error) {
+	noPrefix := strings.TrimPrefix(target, targetPrefix)
+	if noPrefix == target {
+		return "", "", fmt.Errorf("malformed target, %s prefix is required: %s", targetPrefix, target)
+	}
+	parts := strings.SplitN(noPrefix, "/", 2)
+	if len(parts) != 2 {
+		return "", "", fmt.Errorf("malformed target, expected %s://<id>/<endpoint>, but got %s", scheme, target)
+	}
+	return parts[0], parts[1], nil
+}
+
+// Dialer dials a endpoint using net.Dialer.
+// Context cancelation and timeout are supported.
+func Dialer(ctx context.Context, dialEp string) (net.Conn, error) {
+	proto, host, _ := ParseEndpoint(dialEp)
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	default:
+	}
+	dialer := &net.Dialer{}
+	if deadline, ok := ctx.Deadline(); ok {
+		dialer.Deadline = deadline
+	}
+	return dialer.DialContext(ctx, proto, host)
+}
diff --git a/vendor/github.com/coreos/etcd/clientv3/balancer/utils.go b/vendor/github.com/coreos/etcd/clientv3/balancer/utils.go
new file mode 100644
index 0000000..48eb8750
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/clientv3/balancer/utils.go
@@ -0,0 +1,68 @@
+// Copyright 2018 The etcd 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 balancer
+
+import (
+	"fmt"
+	"net/url"
+	"sort"
+	"sync/atomic"
+	"time"
+
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/resolver"
+)
+
+func scToString(sc balancer.SubConn) string {
+	return fmt.Sprintf("%p", sc)
+}
+
+func scsToStrings(scs map[balancer.SubConn]resolver.Address) (ss []string) {
+	ss = make([]string, 0, len(scs))
+	for sc, a := range scs {
+		ss = append(ss, fmt.Sprintf("%s (%s)", a.Addr, scToString(sc)))
+	}
+	sort.Strings(ss)
+	return ss
+}
+
+func addrsToStrings(addrs []resolver.Address) (ss []string) {
+	ss = make([]string, len(addrs))
+	for i := range addrs {
+		ss[i] = addrs[i].Addr
+	}
+	sort.Strings(ss)
+	return ss
+}
+
+func epsToAddrs(eps ...string) (addrs []resolver.Address) {
+	addrs = make([]resolver.Address, 0, len(eps))
+	for _, ep := range eps {
+		u, err := url.Parse(ep)
+		if err != nil {
+			addrs = append(addrs, resolver.Address{Addr: ep, Type: resolver.Backend})
+			continue
+		}
+		addrs = append(addrs, resolver.Address{Addr: u.Host, Type: resolver.Backend})
+	}
+	return addrs
+}
+
+var genN = new(uint32)
+
+func genName() string {
+	now := time.Now().UnixNano()
+	return fmt.Sprintf("%X%X", now, atomic.AddUint32(genN, 1))
+}