[VOL-4291] Rw-core updates for gRPC migration

Change-Id: I8d5a554409115b29318089671ca4e1ab3fa98810
diff --git a/vendor/github.com/coreos/etcd/etcdserver/membership/cluster.go b/vendor/github.com/coreos/etcd/etcdserver/membership/cluster.go
new file mode 100644
index 0000000..ba5c541
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/etcdserver/membership/cluster.go
@@ -0,0 +1,518 @@
+// 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 membership
+
+import (
+	"bytes"
+	"context"
+	"crypto/sha1"
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"path"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/coreos/etcd/mvcc/backend"
+	"github.com/coreos/etcd/pkg/netutil"
+	"github.com/coreos/etcd/pkg/types"
+	"github.com/coreos/etcd/raft"
+	"github.com/coreos/etcd/raft/raftpb"
+	"github.com/coreos/etcd/store"
+	"github.com/coreos/etcd/version"
+
+	"github.com/coreos/go-semver/semver"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+// RaftCluster is a list of Members that belong to the same raft cluster
+type RaftCluster struct {
+	id    types.ID
+	token string
+
+	store store.Store
+	be    backend.Backend
+
+	sync.Mutex // guards the fields below
+	version    *semver.Version
+	members    map[types.ID]*Member
+	// removed contains the ids of removed members in the cluster.
+	// removed id cannot be reused.
+	removed map[types.ID]bool
+}
+
+func NewClusterFromURLsMap(token string, urlsmap types.URLsMap) (*RaftCluster, error) {
+	c := NewCluster(token)
+	for name, urls := range urlsmap {
+		m := NewMember(name, urls, token, nil)
+		if _, ok := c.members[m.ID]; ok {
+			return nil, fmt.Errorf("member exists with identical ID %v", m)
+		}
+		if uint64(m.ID) == raft.None {
+			return nil, fmt.Errorf("cannot use %x as member id", raft.None)
+		}
+		c.members[m.ID] = m
+	}
+	c.genID()
+	return c, nil
+}
+
+func NewClusterFromMembers(token string, id types.ID, membs []*Member) *RaftCluster {
+	c := NewCluster(token)
+	c.id = id
+	for _, m := range membs {
+		c.members[m.ID] = m
+	}
+	return c
+}
+
+func NewCluster(token string) *RaftCluster {
+	return &RaftCluster{
+		token:   token,
+		members: make(map[types.ID]*Member),
+		removed: make(map[types.ID]bool),
+	}
+}
+
+func (c *RaftCluster) ID() types.ID { return c.id }
+
+func (c *RaftCluster) Members() []*Member {
+	c.Lock()
+	defer c.Unlock()
+	var ms MembersByID
+	for _, m := range c.members {
+		ms = append(ms, m.Clone())
+	}
+	sort.Sort(ms)
+	return []*Member(ms)
+}
+
+func (c *RaftCluster) Member(id types.ID) *Member {
+	c.Lock()
+	defer c.Unlock()
+	return c.members[id].Clone()
+}
+
+// MemberByName returns a Member with the given name if exists.
+// If more than one member has the given name, it will panic.
+func (c *RaftCluster) MemberByName(name string) *Member {
+	c.Lock()
+	defer c.Unlock()
+	var memb *Member
+	for _, m := range c.members {
+		if m.Name == name {
+			if memb != nil {
+				plog.Panicf("two members with the given name %q exist", name)
+			}
+			memb = m
+		}
+	}
+	return memb.Clone()
+}
+
+func (c *RaftCluster) MemberIDs() []types.ID {
+	c.Lock()
+	defer c.Unlock()
+	var ids []types.ID
+	for _, m := range c.members {
+		ids = append(ids, m.ID)
+	}
+	sort.Sort(types.IDSlice(ids))
+	return ids
+}
+
+func (c *RaftCluster) IsIDRemoved(id types.ID) bool {
+	c.Lock()
+	defer c.Unlock()
+	return c.removed[id]
+}
+
+// PeerURLs returns a list of all peer addresses.
+// The returned list is sorted in ascending lexicographical order.
+func (c *RaftCluster) PeerURLs() []string {
+	c.Lock()
+	defer c.Unlock()
+	urls := make([]string, 0)
+	for _, p := range c.members {
+		urls = append(urls, p.PeerURLs...)
+	}
+	sort.Strings(urls)
+	return urls
+}
+
+// ClientURLs returns a list of all client addresses.
+// The returned list is sorted in ascending lexicographical order.
+func (c *RaftCluster) ClientURLs() []string {
+	c.Lock()
+	defer c.Unlock()
+	urls := make([]string, 0)
+	for _, p := range c.members {
+		urls = append(urls, p.ClientURLs...)
+	}
+	sort.Strings(urls)
+	return urls
+}
+
+func (c *RaftCluster) String() string {
+	c.Lock()
+	defer c.Unlock()
+	b := &bytes.Buffer{}
+	fmt.Fprintf(b, "{ClusterID:%s ", c.id)
+	var ms []string
+	for _, m := range c.members {
+		ms = append(ms, fmt.Sprintf("%+v", m))
+	}
+	fmt.Fprintf(b, "Members:[%s] ", strings.Join(ms, " "))
+	var ids []string
+	for id := range c.removed {
+		ids = append(ids, id.String())
+	}
+	fmt.Fprintf(b, "RemovedMemberIDs:[%s]}", strings.Join(ids, " "))
+	return b.String()
+}
+
+func (c *RaftCluster) genID() {
+	mIDs := c.MemberIDs()
+	b := make([]byte, 8*len(mIDs))
+	for i, id := range mIDs {
+		binary.BigEndian.PutUint64(b[8*i:], uint64(id))
+	}
+	hash := sha1.Sum(b)
+	c.id = types.ID(binary.BigEndian.Uint64(hash[:8]))
+}
+
+func (c *RaftCluster) SetID(id types.ID) { c.id = id }
+
+func (c *RaftCluster) SetStore(st store.Store) { c.store = st }
+
+func (c *RaftCluster) SetBackend(be backend.Backend) {
+	c.be = be
+	mustCreateBackendBuckets(c.be)
+}
+
+func (c *RaftCluster) Recover(onSet func(*semver.Version)) {
+	c.Lock()
+	defer c.Unlock()
+
+	c.members, c.removed = membersFromStore(c.store)
+	c.version = clusterVersionFromStore(c.store)
+	mustDetectDowngrade(c.version)
+	onSet(c.version)
+
+	for _, m := range c.members {
+		plog.Infof("added member %s %v to cluster %s from store", m.ID, m.PeerURLs, c.id)
+	}
+	if c.version != nil {
+		plog.Infof("set the cluster version to %v from store", version.Cluster(c.version.String()))
+	}
+}
+
+// ValidateConfigurationChange takes a proposed ConfChange and
+// ensures that it is still valid.
+func (c *RaftCluster) ValidateConfigurationChange(cc raftpb.ConfChange) error {
+	members, removed := membersFromStore(c.store)
+	id := types.ID(cc.NodeID)
+	if removed[id] {
+		return ErrIDRemoved
+	}
+	switch cc.Type {
+	case raftpb.ConfChangeAddNode:
+		if members[id] != nil {
+			return ErrIDExists
+		}
+		urls := make(map[string]bool)
+		for _, m := range members {
+			for _, u := range m.PeerURLs {
+				urls[u] = true
+			}
+		}
+		m := new(Member)
+		if err := json.Unmarshal(cc.Context, m); err != nil {
+			plog.Panicf("unmarshal member should never fail: %v", err)
+		}
+		for _, u := range m.PeerURLs {
+			if urls[u] {
+				return ErrPeerURLexists
+			}
+		}
+	case raftpb.ConfChangeRemoveNode:
+		if members[id] == nil {
+			return ErrIDNotFound
+		}
+	case raftpb.ConfChangeUpdateNode:
+		if members[id] == nil {
+			return ErrIDNotFound
+		}
+		urls := make(map[string]bool)
+		for _, m := range members {
+			if m.ID == id {
+				continue
+			}
+			for _, u := range m.PeerURLs {
+				urls[u] = true
+			}
+		}
+		m := new(Member)
+		if err := json.Unmarshal(cc.Context, m); err != nil {
+			plog.Panicf("unmarshal member should never fail: %v", err)
+		}
+		for _, u := range m.PeerURLs {
+			if urls[u] {
+				return ErrPeerURLexists
+			}
+		}
+	default:
+		plog.Panicf("ConfChange type should be either AddNode, RemoveNode or UpdateNode")
+	}
+	return nil
+}
+
+// AddMember adds a new Member into the cluster, and saves the given member's
+// raftAttributes into the store. The given member should have empty attributes.
+// A Member with a matching id must not exist.
+func (c *RaftCluster) AddMember(m *Member) {
+	c.Lock()
+	defer c.Unlock()
+	if c.store != nil {
+		mustSaveMemberToStore(c.store, m)
+	}
+	if c.be != nil {
+		mustSaveMemberToBackend(c.be, m)
+	}
+
+	c.members[m.ID] = m
+
+	plog.Infof("added member %s %v to cluster %s", m.ID, m.PeerURLs, c.id)
+}
+
+// RemoveMember removes a member from the store.
+// The given id MUST exist, or the function panics.
+func (c *RaftCluster) RemoveMember(id types.ID) {
+	c.Lock()
+	defer c.Unlock()
+	if c.store != nil {
+		mustDeleteMemberFromStore(c.store, id)
+	}
+	if c.be != nil {
+		mustDeleteMemberFromBackend(c.be, id)
+	}
+
+	delete(c.members, id)
+	c.removed[id] = true
+
+	plog.Infof("removed member %s from cluster %s", id, c.id)
+}
+
+func (c *RaftCluster) UpdateAttributes(id types.ID, attr Attributes) {
+	c.Lock()
+	defer c.Unlock()
+	if m, ok := c.members[id]; ok {
+		m.Attributes = attr
+		if c.store != nil {
+			mustUpdateMemberAttrInStore(c.store, m)
+		}
+		if c.be != nil {
+			mustSaveMemberToBackend(c.be, m)
+		}
+		return
+	}
+	_, ok := c.removed[id]
+	if !ok {
+		plog.Panicf("error updating attributes of unknown member %s", id)
+	}
+	plog.Warningf("skipped updating attributes of removed member %s", id)
+}
+
+func (c *RaftCluster) UpdateRaftAttributes(id types.ID, raftAttr RaftAttributes) {
+	c.Lock()
+	defer c.Unlock()
+
+	c.members[id].RaftAttributes = raftAttr
+	if c.store != nil {
+		mustUpdateMemberInStore(c.store, c.members[id])
+	}
+	if c.be != nil {
+		mustSaveMemberToBackend(c.be, c.members[id])
+	}
+
+	plog.Noticef("updated member %s %v in cluster %s", id, raftAttr.PeerURLs, c.id)
+}
+
+func (c *RaftCluster) Version() *semver.Version {
+	c.Lock()
+	defer c.Unlock()
+	if c.version == nil {
+		return nil
+	}
+	return semver.Must(semver.NewVersion(c.version.String()))
+}
+
+func (c *RaftCluster) SetVersion(ver *semver.Version, onSet func(*semver.Version)) {
+	c.Lock()
+	defer c.Unlock()
+	if c.version != nil {
+		plog.Noticef("updated the cluster version from %v to %v", version.Cluster(c.version.String()), version.Cluster(ver.String()))
+	} else {
+		plog.Noticef("set the initial cluster version to %v", version.Cluster(ver.String()))
+	}
+	oldVer := c.version
+	c.version = ver
+	mustDetectDowngrade(c.version)
+	if c.store != nil {
+		mustSaveClusterVersionToStore(c.store, ver)
+	}
+	if c.be != nil {
+		mustSaveClusterVersionToBackend(c.be, ver)
+	}
+	if oldVer != nil {
+		ClusterVersionMetrics.With(prometheus.Labels{"cluster_version": version.Cluster(oldVer.String())}).Set(0)
+	}
+	ClusterVersionMetrics.With(prometheus.Labels{"cluster_version": version.Cluster(ver.String())}).Set(1)
+	onSet(ver)
+}
+
+func (c *RaftCluster) IsReadyToAddNewMember() bool {
+	nmembers := 1
+	nstarted := 0
+
+	for _, member := range c.members {
+		if member.IsStarted() {
+			nstarted++
+		}
+		nmembers++
+	}
+
+	if nstarted == 1 && nmembers == 2 {
+		// a case of adding a new node to 1-member cluster for restoring cluster data
+		// https://github.com/coreos/etcd/blob/master/Documentation/v2/admin_guide.md#restoring-the-cluster
+
+		plog.Debugf("The number of started member is 1. This cluster can accept add member request.")
+		return true
+	}
+
+	nquorum := nmembers/2 + 1
+	if nstarted < nquorum {
+		plog.Warningf("Reject add member request: the number of started member (%d) will be less than the quorum number of the cluster (%d)", nstarted, nquorum)
+		return false
+	}
+
+	return true
+}
+
+func (c *RaftCluster) IsReadyToRemoveMember(id uint64) bool {
+	nmembers := 0
+	nstarted := 0
+
+	for _, member := range c.members {
+		if uint64(member.ID) == id {
+			continue
+		}
+
+		if member.IsStarted() {
+			nstarted++
+		}
+		nmembers++
+	}
+
+	nquorum := nmembers/2 + 1
+	if nstarted < nquorum {
+		plog.Warningf("Reject remove member request: the number of started member (%d) will be less than the quorum number of the cluster (%d)", nstarted, nquorum)
+		return false
+	}
+
+	return true
+}
+
+func membersFromStore(st store.Store) (map[types.ID]*Member, map[types.ID]bool) {
+	members := make(map[types.ID]*Member)
+	removed := make(map[types.ID]bool)
+	e, err := st.Get(StoreMembersPrefix, true, true)
+	if err != nil {
+		if isKeyNotFound(err) {
+			return members, removed
+		}
+		plog.Panicf("get storeMembers should never fail: %v", err)
+	}
+	for _, n := range e.Node.Nodes {
+		var m *Member
+		m, err = nodeToMember(n)
+		if err != nil {
+			plog.Panicf("nodeToMember should never fail: %v", err)
+		}
+		members[m.ID] = m
+	}
+
+	e, err = st.Get(storeRemovedMembersPrefix, true, true)
+	if err != nil {
+		if isKeyNotFound(err) {
+			return members, removed
+		}
+		plog.Panicf("get storeRemovedMembers should never fail: %v", err)
+	}
+	for _, n := range e.Node.Nodes {
+		removed[MustParseMemberIDFromKey(n.Key)] = true
+	}
+	return members, removed
+}
+
+func clusterVersionFromStore(st store.Store) *semver.Version {
+	e, err := st.Get(path.Join(storePrefix, "version"), false, false)
+	if err != nil {
+		if isKeyNotFound(err) {
+			return nil
+		}
+		plog.Panicf("unexpected error (%v) when getting cluster version from store", err)
+	}
+	return semver.Must(semver.NewVersion(*e.Node.Value))
+}
+
+// ValidateClusterAndAssignIDs validates the local cluster by matching the PeerURLs
+// with the existing cluster. If the validation succeeds, it assigns the IDs
+// from the existing cluster to the local cluster.
+// If the validation fails, an error will be returned.
+func ValidateClusterAndAssignIDs(local *RaftCluster, existing *RaftCluster) error {
+	ems := existing.Members()
+	lms := local.Members()
+	if len(ems) != len(lms) {
+		return fmt.Errorf("member count is unequal")
+	}
+	sort.Sort(MembersByPeerURLs(ems))
+	sort.Sort(MembersByPeerURLs(lms))
+
+	ctx, cancel := context.WithTimeout(context.TODO(), 30*time.Second)
+	defer cancel()
+	for i := range ems {
+		if ok, err := netutil.URLStringsEqual(ctx, ems[i].PeerURLs, lms[i].PeerURLs); !ok {
+			return fmt.Errorf("unmatched member while checking PeerURLs (%v)", err)
+		}
+		lms[i].ID = ems[i].ID
+	}
+	local.members = make(map[types.ID]*Member)
+	for _, m := range lms {
+		local.members[m.ID] = m
+	}
+	return nil
+}
+
+func mustDetectDowngrade(cv *semver.Version) {
+	lv := semver.Must(semver.NewVersion(version.Version))
+	// only keep major.minor version for comparison against cluster version
+	lv = &semver.Version{Major: lv.Major, Minor: lv.Minor}
+	if cv != nil && lv.LessThan(*cv) {
+		plog.Fatalf("cluster cannot be downgraded (current version: %s is lower than determined cluster version: %s).", version.Version, version.Cluster(cv.String()))
+	}
+}
diff --git a/vendor/github.com/coreos/etcd/etcdserver/membership/doc.go b/vendor/github.com/coreos/etcd/etcdserver/membership/doc.go
new file mode 100644
index 0000000..b07fb2d
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/etcdserver/membership/doc.go
@@ -0,0 +1,16 @@
+// Copyright 2017 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 membership describes individual etcd members and clusters of members.
+package membership
diff --git a/vendor/github.com/coreos/etcd/etcdserver/membership/errors.go b/vendor/github.com/coreos/etcd/etcdserver/membership/errors.go
new file mode 100644
index 0000000..e4d36af
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/etcdserver/membership/errors.go
@@ -0,0 +1,33 @@
+// Copyright 2016 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 membership
+
+import (
+	"errors"
+
+	etcdErr "github.com/coreos/etcd/error"
+)
+
+var (
+	ErrIDRemoved     = errors.New("membership: ID removed")
+	ErrIDExists      = errors.New("membership: ID exists")
+	ErrIDNotFound    = errors.New("membership: ID not found")
+	ErrPeerURLexists = errors.New("membership: peerURL exists")
+)
+
+func isKeyNotFound(err error) bool {
+	e, ok := err.(*etcdErr.Error)
+	return ok && e.ErrorCode == etcdErr.EcodeKeyNotFound
+}
diff --git a/vendor/github.com/coreos/etcd/etcdserver/membership/member.go b/vendor/github.com/coreos/etcd/etcdserver/membership/member.go
new file mode 100644
index 0000000..6de74d2
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/etcdserver/membership/member.go
@@ -0,0 +1,124 @@
+// 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 membership
+
+import (
+	"crypto/sha1"
+	"encoding/binary"
+	"fmt"
+	"math/rand"
+	"sort"
+	"time"
+
+	"github.com/coreos/etcd/pkg/types"
+	"github.com/coreos/pkg/capnslog"
+)
+
+var (
+	plog = capnslog.NewPackageLogger("github.com/coreos/etcd", "etcdserver/membership")
+)
+
+// RaftAttributes represents the raft related attributes of an etcd member.
+type RaftAttributes struct {
+	// PeerURLs is the list of peers in the raft cluster.
+	// TODO(philips): ensure these are URLs
+	PeerURLs []string `json:"peerURLs"`
+}
+
+// Attributes represents all the non-raft related attributes of an etcd member.
+type Attributes struct {
+	Name       string   `json:"name,omitempty"`
+	ClientURLs []string `json:"clientURLs,omitempty"`
+}
+
+type Member struct {
+	ID types.ID `json:"id"`
+	RaftAttributes
+	Attributes
+}
+
+// NewMember creates a Member without an ID and generates one based on the
+// cluster name, peer URLs, and time. This is used for bootstrapping/adding new member.
+func NewMember(name string, peerURLs types.URLs, clusterName string, now *time.Time) *Member {
+	m := &Member{
+		RaftAttributes: RaftAttributes{PeerURLs: peerURLs.StringSlice()},
+		Attributes:     Attributes{Name: name},
+	}
+
+	var b []byte
+	sort.Strings(m.PeerURLs)
+	for _, p := range m.PeerURLs {
+		b = append(b, []byte(p)...)
+	}
+
+	b = append(b, []byte(clusterName)...)
+	if now != nil {
+		b = append(b, []byte(fmt.Sprintf("%d", now.Unix()))...)
+	}
+
+	hash := sha1.Sum(b)
+	m.ID = types.ID(binary.BigEndian.Uint64(hash[:8]))
+	return m
+}
+
+// PickPeerURL chooses a random address from a given Member's PeerURLs.
+// It will panic if there is no PeerURLs available in Member.
+func (m *Member) PickPeerURL() string {
+	if len(m.PeerURLs) == 0 {
+		plog.Panicf("member should always have some peer url")
+	}
+	return m.PeerURLs[rand.Intn(len(m.PeerURLs))]
+}
+
+func (m *Member) Clone() *Member {
+	if m == nil {
+		return nil
+	}
+	mm := &Member{
+		ID: m.ID,
+		Attributes: Attributes{
+			Name: m.Name,
+		},
+	}
+	if m.PeerURLs != nil {
+		mm.PeerURLs = make([]string, len(m.PeerURLs))
+		copy(mm.PeerURLs, m.PeerURLs)
+	}
+	if m.ClientURLs != nil {
+		mm.ClientURLs = make([]string, len(m.ClientURLs))
+		copy(mm.ClientURLs, m.ClientURLs)
+	}
+	return mm
+}
+
+func (m *Member) IsStarted() bool {
+	return len(m.Name) != 0
+}
+
+// MembersByID implements sort by ID interface
+type MembersByID []*Member
+
+func (ms MembersByID) Len() int           { return len(ms) }
+func (ms MembersByID) Less(i, j int) bool { return ms[i].ID < ms[j].ID }
+func (ms MembersByID) Swap(i, j int)      { ms[i], ms[j] = ms[j], ms[i] }
+
+// MembersByPeerURLs implements sort by peer urls interface
+type MembersByPeerURLs []*Member
+
+func (ms MembersByPeerURLs) Len() int { return len(ms) }
+func (ms MembersByPeerURLs) Less(i, j int) bool {
+	return ms[i].PeerURLs[0] < ms[j].PeerURLs[0]
+}
+func (ms MembersByPeerURLs) Swap(i, j int) { ms[i], ms[j] = ms[j], ms[i] }
diff --git a/vendor/github.com/coreos/etcd/etcdserver/membership/metrics.go b/vendor/github.com/coreos/etcd/etcdserver/membership/metrics.go
new file mode 100644
index 0000000..b3212bc
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/etcdserver/membership/metrics.go
@@ -0,0 +1,31 @@
+// 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 membership
+
+import "github.com/prometheus/client_golang/prometheus"
+
+var (
+	ClusterVersionMetrics = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace: "etcd",
+		Subsystem: "cluster",
+		Name:      "version",
+		Help:      "Which version is running. 1 for 'cluster_version' label with current cluster version",
+	},
+		[]string{"cluster_version"})
+)
+
+func init() {
+	prometheus.MustRegister(ClusterVersionMetrics)
+}
diff --git a/vendor/github.com/coreos/etcd/etcdserver/membership/store.go b/vendor/github.com/coreos/etcd/etcdserver/membership/store.go
new file mode 100644
index 0000000..d3f8f24
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/etcdserver/membership/store.go
@@ -0,0 +1,193 @@
+// Copyright 2016 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 membership
+
+import (
+	"encoding/json"
+	"fmt"
+	"path"
+
+	"github.com/coreos/etcd/mvcc/backend"
+	"github.com/coreos/etcd/pkg/types"
+	"github.com/coreos/etcd/store"
+
+	"github.com/coreos/go-semver/semver"
+)
+
+const (
+	attributesSuffix     = "attributes"
+	raftAttributesSuffix = "raftAttributes"
+
+	// the prefix for stroing membership related information in store provided by store pkg.
+	storePrefix = "/0"
+)
+
+var (
+	membersBucketName        = []byte("members")
+	membersRemovedBucketName = []byte("members_removed")
+	clusterBucketName        = []byte("cluster")
+
+	StoreMembersPrefix        = path.Join(storePrefix, "members")
+	storeRemovedMembersPrefix = path.Join(storePrefix, "removed_members")
+)
+
+func mustSaveMemberToBackend(be backend.Backend, m *Member) {
+	mkey := backendMemberKey(m.ID)
+	mvalue, err := json.Marshal(m)
+	if err != nil {
+		plog.Panicf("marshal raftAttributes should never fail: %v", err)
+	}
+
+	tx := be.BatchTx()
+	tx.Lock()
+	tx.UnsafePut(membersBucketName, mkey, mvalue)
+	tx.Unlock()
+}
+
+func mustDeleteMemberFromBackend(be backend.Backend, id types.ID) {
+	mkey := backendMemberKey(id)
+
+	tx := be.BatchTx()
+	tx.Lock()
+	tx.UnsafeDelete(membersBucketName, mkey)
+	tx.UnsafePut(membersRemovedBucketName, mkey, []byte("removed"))
+	tx.Unlock()
+}
+
+func mustSaveClusterVersionToBackend(be backend.Backend, ver *semver.Version) {
+	ckey := backendClusterVersionKey()
+
+	tx := be.BatchTx()
+	tx.Lock()
+	defer tx.Unlock()
+	tx.UnsafePut(clusterBucketName, ckey, []byte(ver.String()))
+}
+
+func mustSaveMemberToStore(s store.Store, m *Member) {
+	b, err := json.Marshal(m.RaftAttributes)
+	if err != nil {
+		plog.Panicf("marshal raftAttributes should never fail: %v", err)
+	}
+	p := path.Join(MemberStoreKey(m.ID), raftAttributesSuffix)
+	if _, err := s.Create(p, false, string(b), false, store.TTLOptionSet{ExpireTime: store.Permanent}); err != nil {
+		plog.Panicf("create raftAttributes should never fail: %v", err)
+	}
+}
+
+func mustDeleteMemberFromStore(s store.Store, id types.ID) {
+	if _, err := s.Delete(MemberStoreKey(id), true, true); err != nil {
+		plog.Panicf("delete member should never fail: %v", err)
+	}
+	if _, err := s.Create(RemovedMemberStoreKey(id), false, "", false, store.TTLOptionSet{ExpireTime: store.Permanent}); err != nil {
+		plog.Panicf("create removedMember should never fail: %v", err)
+	}
+}
+
+func mustUpdateMemberInStore(s store.Store, m *Member) {
+	b, err := json.Marshal(m.RaftAttributes)
+	if err != nil {
+		plog.Panicf("marshal raftAttributes should never fail: %v", err)
+	}
+	p := path.Join(MemberStoreKey(m.ID), raftAttributesSuffix)
+	if _, err := s.Update(p, string(b), store.TTLOptionSet{ExpireTime: store.Permanent}); err != nil {
+		plog.Panicf("update raftAttributes should never fail: %v", err)
+	}
+}
+
+func mustUpdateMemberAttrInStore(s store.Store, m *Member) {
+	b, err := json.Marshal(m.Attributes)
+	if err != nil {
+		plog.Panicf("marshal raftAttributes should never fail: %v", err)
+	}
+	p := path.Join(MemberStoreKey(m.ID), attributesSuffix)
+	if _, err := s.Set(p, false, string(b), store.TTLOptionSet{ExpireTime: store.Permanent}); err != nil {
+		plog.Panicf("update raftAttributes should never fail: %v", err)
+	}
+}
+
+func mustSaveClusterVersionToStore(s store.Store, ver *semver.Version) {
+	if _, err := s.Set(StoreClusterVersionKey(), false, ver.String(), store.TTLOptionSet{ExpireTime: store.Permanent}); err != nil {
+		plog.Panicf("save cluster version should never fail: %v", err)
+	}
+}
+
+// nodeToMember builds member from a key value node.
+// the child nodes of the given node MUST be sorted by key.
+func nodeToMember(n *store.NodeExtern) (*Member, error) {
+	m := &Member{ID: MustParseMemberIDFromKey(n.Key)}
+	attrs := make(map[string][]byte)
+	raftAttrKey := path.Join(n.Key, raftAttributesSuffix)
+	attrKey := path.Join(n.Key, attributesSuffix)
+	for _, nn := range n.Nodes {
+		if nn.Key != raftAttrKey && nn.Key != attrKey {
+			return nil, fmt.Errorf("unknown key %q", nn.Key)
+		}
+		attrs[nn.Key] = []byte(*nn.Value)
+	}
+	if data := attrs[raftAttrKey]; data != nil {
+		if err := json.Unmarshal(data, &m.RaftAttributes); err != nil {
+			return nil, fmt.Errorf("unmarshal raftAttributes error: %v", err)
+		}
+	} else {
+		return nil, fmt.Errorf("raftAttributes key doesn't exist")
+	}
+	if data := attrs[attrKey]; data != nil {
+		if err := json.Unmarshal(data, &m.Attributes); err != nil {
+			return m, fmt.Errorf("unmarshal attributes error: %v", err)
+		}
+	}
+	return m, nil
+}
+
+func backendMemberKey(id types.ID) []byte {
+	return []byte(id.String())
+}
+
+func backendClusterVersionKey() []byte {
+	return []byte("clusterVersion")
+}
+
+func mustCreateBackendBuckets(be backend.Backend) {
+	tx := be.BatchTx()
+	tx.Lock()
+	defer tx.Unlock()
+	tx.UnsafeCreateBucket(membersBucketName)
+	tx.UnsafeCreateBucket(membersRemovedBucketName)
+	tx.UnsafeCreateBucket(clusterBucketName)
+}
+
+func MemberStoreKey(id types.ID) string {
+	return path.Join(StoreMembersPrefix, id.String())
+}
+
+func StoreClusterVersionKey() string {
+	return path.Join(storePrefix, "version")
+}
+
+func MemberAttributesStorePath(id types.ID) string {
+	return path.Join(MemberStoreKey(id), attributesSuffix)
+}
+
+func MustParseMemberIDFromKey(key string) types.ID {
+	id, err := types.IDFromString(path.Base(key))
+	if err != nil {
+		plog.Panicf("unexpected parse member id error: %v", err)
+	}
+	return id
+}
+
+func RemovedMemberStoreKey(id types.ID) string {
+	return path.Join(storeRemovedMembersPrefix, id.String())
+}