diff --git a/vendor/go.etcd.io/etcd/etcdserver/api/v2discovery/discovery.go b/vendor/go.etcd.io/etcd/etcdserver/api/v2discovery/discovery.go
new file mode 100644
index 0000000..cf770b3
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/etcdserver/api/v2discovery/discovery.go
@@ -0,0 +1,440 @@
+// Copyright 2015 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 v2discovery provides an implementation of the cluster discovery that
+// is used by etcd with v2 client.
+package v2discovery
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"math"
+	"net/http"
+	"net/url"
+	"path"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+
+	"go.etcd.io/etcd/client"
+	"go.etcd.io/etcd/pkg/transport"
+	"go.etcd.io/etcd/pkg/types"
+
+	"github.com/coreos/pkg/capnslog"
+	"github.com/jonboulle/clockwork"
+	"go.uber.org/zap"
+)
+
+var (
+	plog = capnslog.NewPackageLogger("go.etcd.io/etcd", "discovery")
+
+	ErrInvalidURL           = errors.New("discovery: invalid URL")
+	ErrBadSizeKey           = errors.New("discovery: size key is bad")
+	ErrSizeNotFound         = errors.New("discovery: size key not found")
+	ErrTokenNotFound        = errors.New("discovery: token not found")
+	ErrDuplicateID          = errors.New("discovery: found duplicate id")
+	ErrDuplicateName        = errors.New("discovery: found duplicate name")
+	ErrFullCluster          = errors.New("discovery: cluster is full")
+	ErrTooManyRetries       = errors.New("discovery: too many retries")
+	ErrBadDiscoveryEndpoint = errors.New("discovery: bad discovery endpoint")
+)
+
+var (
+	// Number of retries discovery will attempt before giving up and erroring out.
+	nRetries             = uint(math.MaxUint32)
+	maxExpoentialRetries = uint(8)
+)
+
+// JoinCluster will connect to the discovery service at the given url, and
+// register the server represented by the given id and config to the cluster
+func JoinCluster(lg *zap.Logger, durl, dproxyurl string, id types.ID, config string) (string, error) {
+	d, err := newDiscovery(lg, durl, dproxyurl, id)
+	if err != nil {
+		return "", err
+	}
+	return d.joinCluster(config)
+}
+
+// GetCluster will connect to the discovery service at the given url and
+// retrieve a string describing the cluster
+func GetCluster(lg *zap.Logger, durl, dproxyurl string) (string, error) {
+	d, err := newDiscovery(lg, durl, dproxyurl, 0)
+	if err != nil {
+		return "", err
+	}
+	return d.getCluster()
+}
+
+type discovery struct {
+	lg      *zap.Logger
+	cluster string
+	id      types.ID
+	c       client.KeysAPI
+	retries uint
+	url     *url.URL
+
+	clock clockwork.Clock
+}
+
+// newProxyFunc builds a proxy function from the given string, which should
+// represent a URL that can be used as a proxy. It performs basic
+// sanitization of the URL and returns any error encountered.
+func newProxyFunc(lg *zap.Logger, proxy string) (func(*http.Request) (*url.URL, error), error) {
+	if proxy == "" {
+		return nil, nil
+	}
+	// Do a small amount of URL sanitization to help the user
+	// Derived from net/http.ProxyFromEnvironment
+	proxyURL, err := url.Parse(proxy)
+	if err != nil || !strings.HasPrefix(proxyURL.Scheme, "http") {
+		// proxy was bogus. Try prepending "http://" to it and
+		// see if that parses correctly. If not, we ignore the
+		// error and complain about the original one
+		var err2 error
+		proxyURL, err2 = url.Parse("http://" + proxy)
+		if err2 == nil {
+			err = nil
+		}
+	}
+	if err != nil {
+		return nil, fmt.Errorf("invalid proxy address %q: %v", proxy, err)
+	}
+
+	if lg != nil {
+		lg.Info("running proxy with discovery", zap.String("proxy-url", proxyURL.String()))
+	} else {
+		plog.Infof("using proxy %q", proxyURL.String())
+	}
+	return http.ProxyURL(proxyURL), nil
+}
+
+func newDiscovery(lg *zap.Logger, durl, dproxyurl string, id types.ID) (*discovery, error) {
+	u, err := url.Parse(durl)
+	if err != nil {
+		return nil, err
+	}
+	token := u.Path
+	u.Path = ""
+	pf, err := newProxyFunc(lg, dproxyurl)
+	if err != nil {
+		return nil, err
+	}
+
+	// TODO: add ResponseHeaderTimeout back when watch on discovery service writes header early
+	tr, err := transport.NewTransport(transport.TLSInfo{}, 30*time.Second)
+	if err != nil {
+		return nil, err
+	}
+	tr.Proxy = pf
+	cfg := client.Config{
+		Transport: tr,
+		Endpoints: []string{u.String()},
+	}
+	c, err := client.New(cfg)
+	if err != nil {
+		return nil, err
+	}
+	dc := client.NewKeysAPIWithPrefix(c, "")
+	return &discovery{
+		lg:      lg,
+		cluster: token,
+		c:       dc,
+		id:      id,
+		url:     u,
+		clock:   clockwork.NewRealClock(),
+	}, nil
+}
+
+func (d *discovery) joinCluster(config string) (string, error) {
+	// fast path: if the cluster is full, return the error
+	// do not need to register to the cluster in this case.
+	if _, _, _, err := d.checkCluster(); err != nil {
+		return "", err
+	}
+
+	if err := d.createSelf(config); err != nil {
+		// Fails, even on a timeout, if createSelf times out.
+		// TODO(barakmich): Retrying the same node might want to succeed here
+		// (ie, createSelf should be idempotent for discovery).
+		return "", err
+	}
+
+	nodes, size, index, err := d.checkCluster()
+	if err != nil {
+		return "", err
+	}
+
+	all, err := d.waitNodes(nodes, size, index)
+	if err != nil {
+		return "", err
+	}
+
+	return nodesToCluster(all, size)
+}
+
+func (d *discovery) getCluster() (string, error) {
+	nodes, size, index, err := d.checkCluster()
+	if err != nil {
+		if err == ErrFullCluster {
+			return nodesToCluster(nodes, size)
+		}
+		return "", err
+	}
+
+	all, err := d.waitNodes(nodes, size, index)
+	if err != nil {
+		return "", err
+	}
+	return nodesToCluster(all, size)
+}
+
+func (d *discovery) createSelf(contents string) error {
+	ctx, cancel := context.WithTimeout(context.Background(), client.DefaultRequestTimeout)
+	resp, err := d.c.Create(ctx, d.selfKey(), contents)
+	cancel()
+	if err != nil {
+		if eerr, ok := err.(client.Error); ok && eerr.Code == client.ErrorCodeNodeExist {
+			return ErrDuplicateID
+		}
+		return err
+	}
+
+	// ensure self appears on the server we connected to
+	w := d.c.Watcher(d.selfKey(), &client.WatcherOptions{AfterIndex: resp.Node.CreatedIndex - 1})
+	_, err = w.Next(context.Background())
+	return err
+}
+
+func (d *discovery) checkCluster() ([]*client.Node, int, uint64, error) {
+	configKey := path.Join("/", d.cluster, "_config")
+	ctx, cancel := context.WithTimeout(context.Background(), client.DefaultRequestTimeout)
+	// find cluster size
+	resp, err := d.c.Get(ctx, path.Join(configKey, "size"), nil)
+	cancel()
+	if err != nil {
+		if eerr, ok := err.(*client.Error); ok && eerr.Code == client.ErrorCodeKeyNotFound {
+			return nil, 0, 0, ErrSizeNotFound
+		}
+		if err == client.ErrInvalidJSON {
+			return nil, 0, 0, ErrBadDiscoveryEndpoint
+		}
+		if ce, ok := err.(*client.ClusterError); ok {
+			if d.lg != nil {
+				d.lg.Warn(
+					"failed to get from discovery server",
+					zap.String("discovery-url", d.url.String()),
+					zap.String("path", path.Join(configKey, "size")),
+					zap.Error(err),
+					zap.String("err-detail", ce.Detail()),
+				)
+			} else {
+				plog.Error(ce.Detail())
+			}
+			return d.checkClusterRetry()
+		}
+		return nil, 0, 0, err
+	}
+	size, err := strconv.Atoi(resp.Node.Value)
+	if err != nil {
+		return nil, 0, 0, ErrBadSizeKey
+	}
+
+	ctx, cancel = context.WithTimeout(context.Background(), client.DefaultRequestTimeout)
+	resp, err = d.c.Get(ctx, d.cluster, nil)
+	cancel()
+	if err != nil {
+		if ce, ok := err.(*client.ClusterError); ok {
+			if d.lg != nil {
+				d.lg.Warn(
+					"failed to get from discovery server",
+					zap.String("discovery-url", d.url.String()),
+					zap.String("path", d.cluster),
+					zap.Error(err),
+					zap.String("err-detail", ce.Detail()),
+				)
+			} else {
+				plog.Error(ce.Detail())
+			}
+			return d.checkClusterRetry()
+		}
+		return nil, 0, 0, err
+	}
+	var nodes []*client.Node
+	// append non-config keys to nodes
+	for _, n := range resp.Node.Nodes {
+		if path.Base(n.Key) != path.Base(configKey) {
+			nodes = append(nodes, n)
+		}
+	}
+
+	snodes := sortableNodes{nodes}
+	sort.Sort(snodes)
+
+	// find self position
+	for i := range nodes {
+		if path.Base(nodes[i].Key) == path.Base(d.selfKey()) {
+			break
+		}
+		if i >= size-1 {
+			return nodes[:size], size, resp.Index, ErrFullCluster
+		}
+	}
+	return nodes, size, resp.Index, nil
+}
+
+func (d *discovery) logAndBackoffForRetry(step string) {
+	d.retries++
+	// logAndBackoffForRetry stops exponential backoff when the retries are more than maxExpoentialRetries and is set to a constant backoff afterward.
+	retries := d.retries
+	if retries > maxExpoentialRetries {
+		retries = maxExpoentialRetries
+	}
+	retryTimeInSecond := time.Duration(0x1<<retries) * time.Second
+	if d.lg != nil {
+		d.lg.Info(
+			"retry connecting to discovery service",
+			zap.String("url", d.url.String()),
+			zap.String("reason", step),
+			zap.Duration("backoff", retryTimeInSecond),
+		)
+	} else {
+		plog.Infof("%s: error connecting to %s, retrying in %s", step, d.url, retryTimeInSecond)
+	}
+	d.clock.Sleep(retryTimeInSecond)
+}
+
+func (d *discovery) checkClusterRetry() ([]*client.Node, int, uint64, error) {
+	if d.retries < nRetries {
+		d.logAndBackoffForRetry("cluster status check")
+		return d.checkCluster()
+	}
+	return nil, 0, 0, ErrTooManyRetries
+}
+
+func (d *discovery) waitNodesRetry() ([]*client.Node, error) {
+	if d.retries < nRetries {
+		d.logAndBackoffForRetry("waiting for other nodes")
+		nodes, n, index, err := d.checkCluster()
+		if err != nil {
+			return nil, err
+		}
+		return d.waitNodes(nodes, n, index)
+	}
+	return nil, ErrTooManyRetries
+}
+
+func (d *discovery) waitNodes(nodes []*client.Node, size int, index uint64) ([]*client.Node, error) {
+	if len(nodes) > size {
+		nodes = nodes[:size]
+	}
+	// watch from the next index
+	w := d.c.Watcher(d.cluster, &client.WatcherOptions{AfterIndex: index, Recursive: true})
+	all := make([]*client.Node, len(nodes))
+	copy(all, nodes)
+	for _, n := range all {
+		if path.Base(n.Key) == path.Base(d.selfKey()) {
+			if d.lg != nil {
+				d.lg.Info(
+					"found self from discovery server",
+					zap.String("discovery-url", d.url.String()),
+					zap.String("self", path.Base(d.selfKey())),
+				)
+			} else {
+				plog.Noticef("found self %s in the cluster", path.Base(d.selfKey()))
+			}
+		} else {
+			if d.lg != nil {
+				d.lg.Info(
+					"found peer from discovery server",
+					zap.String("discovery-url", d.url.String()),
+					zap.String("peer", path.Base(n.Key)),
+				)
+			} else {
+				plog.Noticef("found peer %s in the cluster", path.Base(n.Key))
+			}
+		}
+	}
+
+	// wait for others
+	for len(all) < size {
+		if d.lg != nil {
+			d.lg.Info(
+				"found peers from discovery server; waiting for more",
+				zap.String("discovery-url", d.url.String()),
+				zap.Int("found-peers", len(all)),
+				zap.Int("needed-peers", size-len(all)),
+			)
+		} else {
+			plog.Noticef("found %d peer(s), waiting for %d more", len(all), size-len(all))
+		}
+		resp, err := w.Next(context.Background())
+		if err != nil {
+			if ce, ok := err.(*client.ClusterError); ok {
+				plog.Error(ce.Detail())
+				return d.waitNodesRetry()
+			}
+			return nil, err
+		}
+		if d.lg != nil {
+			d.lg.Info(
+				"found peer from discovery server",
+				zap.String("discovery-url", d.url.String()),
+				zap.String("peer", path.Base(resp.Node.Key)),
+			)
+		} else {
+			plog.Noticef("found peer %s in the cluster", path.Base(resp.Node.Key))
+		}
+		all = append(all, resp.Node)
+	}
+	if d.lg != nil {
+		d.lg.Info(
+			"found all needed peers from discovery server",
+			zap.String("discovery-url", d.url.String()),
+			zap.Int("found-peers", len(all)),
+		)
+	} else {
+		plog.Noticef("found %d needed peer(s)", len(all))
+	}
+	return all, nil
+}
+
+func (d *discovery) selfKey() string {
+	return path.Join("/", d.cluster, d.id.String())
+}
+
+func nodesToCluster(ns []*client.Node, size int) (string, error) {
+	s := make([]string, len(ns))
+	for i, n := range ns {
+		s[i] = n.Value
+	}
+	us := strings.Join(s, ",")
+	m, err := types.NewURLsMap(us)
+	if err != nil {
+		return us, ErrInvalidURL
+	}
+	if m.Len() != size {
+		return us, ErrDuplicateName
+	}
+	return us, nil
+}
+
+type sortableNodes struct{ Nodes []*client.Node }
+
+func (ns sortableNodes) Len() int { return len(ns.Nodes) }
+func (ns sortableNodes) Less(i, j int) bool {
+	return ns.Nodes[i].CreatedIndex < ns.Nodes[j].CreatedIndex
+}
+func (ns sortableNodes) Swap(i, j int) { ns.Nodes[i], ns.Nodes[j] = ns.Nodes[j], ns.Nodes[i] }