vendor/go.etcd.io/etcd/etcdserver/cluster_util.go - voltha-go - Gitiles

 // 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 etcdserver

 import (
 	"context"
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
 	"net/http"
 	"sort"
 	"strings"
 	"time"

 	"go.etcd.io/etcd/etcdserver/api/membership"
 	"go.etcd.io/etcd/pkg/types"
 	"go.etcd.io/etcd/version"

 	"github.com/coreos/go-semver/semver"
 	"go.uber.org/zap"
 )

 // isMemberBootstrapped tries to check if the given member has been bootstrapped
 // in the given cluster.
 func isMemberBootstrapped(lg *zap.Logger, cl *membership.RaftCluster, member string, rt http.RoundTripper, timeout time.Duration) bool {
 	rcl, err := getClusterFromRemotePeers(lg, getRemotePeerURLs(cl, member), timeout, false, rt)
 	if err != nil {
 		return false
 	}
 	id := cl.MemberByName(member).ID
 	m := rcl.Member(id)
 	if m == nil {
 		return false
 	}
 	if len(m.ClientURLs) > 0 {
 		return true
 	}
 	return false
 }

 // GetClusterFromRemotePeers takes a set of URLs representing etcd peers, and
 // attempts to construct a Cluster by accessing the members endpoint on one of
 // these URLs. The first URL to provide a response is used. If no URLs provide
 // a response, or a Cluster cannot be successfully created from a received
 // response, an error is returned.
 // Each request has a 10-second timeout. Because the upper limit of TTL is 5s,
 // 10 second is enough for building connection and finishing request.
 func GetClusterFromRemotePeers(lg *zap.Logger, urls []string, rt http.RoundTripper) (*membership.RaftCluster, error) {
 	return getClusterFromRemotePeers(lg, urls, 10*time.Second, true, rt)
 }

 // If logerr is true, it prints out more error messages.
 func getClusterFromRemotePeers(lg *zap.Logger, urls []string, timeout time.Duration, logerr bool, rt http.RoundTripper) (*membership.RaftCluster, error) {
 	cc := &http.Client{
 		Transport: rt,
 		Timeout:   timeout,
 	}
 	for _, u := range urls {
 		addr := u + "/members"
 		resp, err := cc.Get(addr)
 		if err != nil {
 			if logerr {
 				if lg != nil {
 					lg.Warn("failed to get cluster response", zap.String("address", addr), zap.Error(err))
 				} else {
 					plog.Warningf("could not get cluster response from %s: %v", u, err)
 				}
 			}
 			continue
 		}
 		b, err := ioutil.ReadAll(resp.Body)
 		resp.Body.Close()
 		if err != nil {
 			if logerr {
 				if lg != nil {
 					lg.Warn("failed to read body of cluster response", zap.String("address", addr), zap.Error(err))
 				} else {
 					plog.Warningf("could not read the body of cluster response: %v", err)
 				}
 			}
 			continue
 		}
 		var membs []*membership.Member
 		if err = json.Unmarshal(b, &membs); err != nil {
 			if logerr {
 				if lg != nil {
 					lg.Warn("failed to unmarshal cluster response", zap.String("address", addr), zap.Error(err))
 				} else {
 					plog.Warningf("could not unmarshal cluster response: %v", err)
 				}
 			}
 			continue
 		}
 		id, err := types.IDFromString(resp.Header.Get("X-Etcd-Cluster-ID"))
 		if err != nil {
 			if logerr {
 				if lg != nil {
 					lg.Warn(
 						"failed to parse cluster ID",
 						zap.String("address", addr),
 						zap.String("header", resp.Header.Get("X-Etcd-Cluster-ID")),
 						zap.Error(err),
 					)
 				} else {
 					plog.Warningf("could not parse the cluster ID from cluster res: %v", err)
 				}
 			}
 			continue
 		}

 		// check the length of membership members
 		// if the membership members are present then prepare and return raft cluster
 		// if membership members are not present then the raft cluster formed will be
 		// an invalid empty cluster hence return failed to get raft cluster member(s) from the given urls error
 		if len(membs) > 0 {
 			return membership.NewClusterFromMembers(lg, "", id, membs), nil
 		}
 		return nil, fmt.Errorf("failed to get raft cluster member(s) from the given URLs")
 	}
 	return nil, fmt.Errorf("could not retrieve cluster information from the given URLs")
 }

 // getRemotePeerURLs returns peer urls of remote members in the cluster. The
 // returned list is sorted in ascending lexicographical order.
 func getRemotePeerURLs(cl *membership.RaftCluster, local string) []string {
 	us := make([]string, 0)
 	for _, m := range cl.Members() {
 		if m.Name == local {
 			continue
 		}
 		us = append(us, m.PeerURLs...)
 	}
 	sort.Strings(us)
 	return us
 }

 // getVersions returns the versions of the members in the given cluster.
 // The key of the returned map is the member's ID. The value of the returned map
 // is the semver versions string, including server and cluster.
 // If it fails to get the version of a member, the key will be nil.
 func getVersions(lg *zap.Logger, cl *membership.RaftCluster, local types.ID, rt http.RoundTripper) map[string]*version.Versions {
 	members := cl.Members()
 	vers := make(map[string]*version.Versions)
 	for _, m := range members {
 		if m.ID == local {
 			cv := "not_decided"
 			if cl.Version() != nil {
 				cv = cl.Version().String()
 			}
 			vers[m.ID.String()] = &version.Versions{Server: version.Version, Cluster: cv}
 			continue
 		}
 		ver, err := getVersion(lg, m, rt)
 		if err != nil {
 			if lg != nil {
 				lg.Warn("failed to get version", zap.String("remote-member-id", m.ID.String()), zap.Error(err))
 			} else {
 				plog.Warningf("cannot get the version of member %s (%v)", m.ID, err)
 			}
 			vers[m.ID.String()] = nil
 		} else {
 			vers[m.ID.String()] = ver
 		}
 	}
 	return vers
 }

 // decideClusterVersion decides the cluster version based on the versions map.
 // The returned version is the min server version in the map, or nil if the min
 // version in unknown.
 func decideClusterVersion(lg *zap.Logger, vers map[string]*version.Versions) *semver.Version {
 	var cv *semver.Version
 	lv := semver.Must(semver.NewVersion(version.Version))

 	for mid, ver := range vers {
 		if ver == nil {
 			return nil
 		}
 		v, err := semver.NewVersion(ver.Server)
 		if err != nil {
 			if lg != nil {
 				lg.Warn(
 					"failed to parse server version of remote member",
 					zap.String("remote-member-id", mid),
 					zap.String("remote-member-version", ver.Server),
 					zap.Error(err),
 				)
 			} else {
 				plog.Errorf("cannot understand the version of member %s (%v)", mid, err)
 			}
 			return nil
 		}
 		if lv.LessThan(*v) {
 			if lg != nil {
 				lg.Warn(
 					"leader found higher-versioned member",
 					zap.String("local-member-version", lv.String()),
 					zap.String("remote-member-id", mid),
 					zap.String("remote-member-version", ver.Server),
 				)
 			} else {
 				plog.Warningf("the local etcd version %s is not up-to-date", lv.String())
 				plog.Warningf("member %s has a higher version %s", mid, ver.Server)
 			}
 		}
 		if cv == nil {
 			cv = v
 		} else if v.LessThan(*cv) {
 			cv = v
 		}
 	}
 	return cv
 }

 // isCompatibleWithCluster return true if the local member has a compatible version with
 // the current running cluster.
 // The version is considered as compatible when at least one of the other members in the cluster has a
 // cluster version in the range of [MinClusterVersion, Version] and no known members has a cluster version
 // out of the range.
 // We set this rule since when the local member joins, another member might be offline.
 func isCompatibleWithCluster(lg *zap.Logger, cl *membership.RaftCluster, local types.ID, rt http.RoundTripper) bool {
 	vers := getVersions(lg, cl, local, rt)
 	minV := semver.Must(semver.NewVersion(version.MinClusterVersion))
 	maxV := semver.Must(semver.NewVersion(version.Version))
 	maxV = &semver.Version{
 		Major: maxV.Major,
 		Minor: maxV.Minor,
 	}
 	return isCompatibleWithVers(lg, vers, local, minV, maxV)
 }

 func isCompatibleWithVers(lg *zap.Logger, vers map[string]*version.Versions, local types.ID, minV, maxV *semver.Version) bool {
 	var ok bool
 	for id, v := range vers {
 		// ignore comparison with local version
 		if id == local.String() {
 			continue
 		}
 		if v == nil {
 			continue
 		}
 		clusterv, err := semver.NewVersion(v.Cluster)
 		if err != nil {
 			if lg != nil {
 				lg.Warn(
 					"failed to parse cluster version of remote member",
 					zap.String("remote-member-id", id),
 					zap.String("remote-member-cluster-version", v.Cluster),
 					zap.Error(err),
 				)
 			} else {
 				plog.Errorf("cannot understand the cluster version of member %s (%v)", id, err)
 			}
 			continue
 		}
 		if clusterv.LessThan(*minV) {
 			if lg != nil {
 				lg.Warn(
 					"cluster version of remote member is not compatible; too low",
 					zap.String("remote-member-id", id),
 					zap.String("remote-member-cluster-version", clusterv.String()),
 					zap.String("minimum-cluster-version-supported", minV.String()),
 				)
 			} else {
 				plog.Warningf("the running cluster version(%v) is lower than the minimal cluster version(%v) supported", clusterv.String(), minV.String())
 			}
 			return false
 		}
 		if maxV.LessThan(*clusterv) {
 			if lg != nil {
 				lg.Warn(
 					"cluster version of remote member is not compatible; too high",
 					zap.String("remote-member-id", id),
 					zap.String("remote-member-cluster-version", clusterv.String()),
 					zap.String("minimum-cluster-version-supported", minV.String()),
 				)
 			} else {
 				plog.Warningf("the running cluster version(%v) is higher than the maximum cluster version(%v) supported", clusterv.String(), maxV.String())
 			}
 			return false
 		}
 		ok = true
 	}
 	return ok
 }

 // getVersion returns the Versions of the given member via its
 // peerURLs. Returns the last error if it fails to get the version.
 func getVersion(lg *zap.Logger, m *membership.Member, rt http.RoundTripper) (*version.Versions, error) {
 	cc := &http.Client{
 		Transport: rt,
 	}
 	var (
 		err  error
 		resp *http.Response
 	)

 	for _, u := range m.PeerURLs {
 		addr := u + "/version"
 		resp, err = cc.Get(addr)
 		if err != nil {
 			if lg != nil {
 				lg.Warn(
 					"failed to reach the peer URL",
 					zap.String("address", addr),
 					zap.String("remote-member-id", m.ID.String()),
 					zap.Error(err),
 				)
 			} else {
 				plog.Warningf("failed to reach the peerURL(%s) of member %s (%v)", u, m.ID, err)
 			}
 			continue
 		}
 		var b []byte
 		b, err = ioutil.ReadAll(resp.Body)
 		resp.Body.Close()
 		if err != nil {
 			if lg != nil {
 				lg.Warn(
 					"failed to read body of response",
 					zap.String("address", addr),
 					zap.String("remote-member-id", m.ID.String()),
 					zap.Error(err),
 				)
 			} else {
 				plog.Warningf("failed to read out the response body from the peerURL(%s) of member %s (%v)", u, m.ID, err)
 			}
 			continue
 		}
 		var vers version.Versions
 		if err = json.Unmarshal(b, &vers); err != nil {
 			if lg != nil {
 				lg.Warn(
 					"failed to unmarshal response",
 					zap.String("address", addr),
 					zap.String("remote-member-id", m.ID.String()),
 					zap.Error(err),
 				)
 			} else {
 				plog.Warningf("failed to unmarshal the response body got from the peerURL(%s) of member %s (%v)", u, m.ID, err)
 			}
 			continue
 		}
 		return &vers, nil
 	}
 	return nil, err
 }

 func promoteMemberHTTP(ctx context.Context, url string, id uint64, peerRt http.RoundTripper) ([]*membership.Member, error) {
 	cc := &http.Client{Transport: peerRt}
 	// TODO: refactor member http handler code
 	// cannot import etcdhttp, so manually construct url
 	requestUrl := url + "/members/promote/" + fmt.Sprintf("%d", id)
 	req, err := http.NewRequest("POST", requestUrl, nil)
 	if err != nil {
 		return nil, err
 	}
 	req = req.WithContext(ctx)
 	resp, err := cc.Do(req)
 	if err != nil {
 		return nil, err
 	}
 	defer resp.Body.Close()
 	b, err := ioutil.ReadAll(resp.Body)
 	if err != nil {
 		return nil, err
 	}

 	if resp.StatusCode == http.StatusRequestTimeout {
 		return nil, ErrTimeout
 	}
 	if resp.StatusCode == http.StatusPreconditionFailed {
 		// both ErrMemberNotLearner and ErrLearnerNotReady have same http status code
 		if strings.Contains(string(b), ErrLearnerNotReady.Error()) {
 			return nil, ErrLearnerNotReady
 		}
 		if strings.Contains(string(b), membership.ErrMemberNotLearner.Error()) {
 			return nil, membership.ErrMemberNotLearner
 		}
 		return nil, fmt.Errorf("member promote: unknown error(%s)", string(b))
 	}
 	if resp.StatusCode == http.StatusNotFound {
 		return nil, membership.ErrIDNotFound
 	}

 	if resp.StatusCode != http.StatusOK { // all other types of errors
 		return nil, fmt.Errorf("member promote: unknown error(%s)", string(b))
 	}

 	var membs []*membership.Member
 	if err := json.Unmarshal(b, &membs); err != nil {
 		return nil, err
 	}
 	return membs, nil
 }
	// 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 etcdserver

	import (
	"context"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"sort"
	"strings"
	"time"

	"go.etcd.io/etcd/etcdserver/api/membership"
	"go.etcd.io/etcd/pkg/types"
	"go.etcd.io/etcd/version"

	"github.com/coreos/go-semver/semver"
	"go.uber.org/zap"
	)

	// isMemberBootstrapped tries to check if the given member has been bootstrapped
	// in the given cluster.
	func isMemberBootstrapped(lg zap.Logger, cl membership.RaftCluster, member string, rt http.RoundTripper, timeout time.Duration) bool {
	rcl, err := getClusterFromRemotePeers(lg, getRemotePeerURLs(cl, member), timeout, false, rt)
	if err != nil {
	return false
	}
	id := cl.MemberByName(member).ID
	m := rcl.Member(id)
	if m == nil {
	return false
	}
	if len(m.ClientURLs) > 0 {
	return true
	}
	return false
	}

	// GetClusterFromRemotePeers takes a set of URLs representing etcd peers, and
	// attempts to construct a Cluster by accessing the members endpoint on one of
	// these URLs. The first URL to provide a response is used. If no URLs provide
	// a response, or a Cluster cannot be successfully created from a received
	// response, an error is returned.
	// Each request has a 10-second timeout. Because the upper limit of TTL is 5s,
	// 10 second is enough for building connection and finishing request.
	func GetClusterFromRemotePeers(lg zap.Logger, urls []string, rt http.RoundTripper) (membership.RaftCluster, error) {
	return getClusterFromRemotePeers(lg, urls, 10*time.Second, true, rt)
	}

	// If logerr is true, it prints out more error messages.
	func getClusterFromRemotePeers(lg zap.Logger, urls []string, timeout time.Duration, logerr bool, rt http.RoundTripper) (membership.RaftCluster, error) {
	cc := &http.Client{
	Transport: rt,
	Timeout: timeout,
	}
	for _, u := range urls {
	addr := u + "/members"
	resp, err := cc.Get(addr)
	if err != nil {
	if logerr {
	if lg != nil {
	lg.Warn("failed to get cluster response", zap.String("address", addr), zap.Error(err))
	} else {
	plog.Warningf("could not get cluster response from %s: %v", u, err)
	}
	}
	continue
	}
	b, err := ioutil.ReadAll(resp.Body)
	resp.Body.Close()
	if err != nil {
	if logerr {
	if lg != nil {
	lg.Warn("failed to read body of cluster response", zap.String("address", addr), zap.Error(err))
	} else {
	plog.Warningf("could not read the body of cluster response: %v", err)
	}
	}
	continue
	}
	var membs []*membership.Member
	if err = json.Unmarshal(b, &membs); err != nil {
	if logerr {
	if lg != nil {
	lg.Warn("failed to unmarshal cluster response", zap.String("address", addr), zap.Error(err))
	} else {
	plog.Warningf("could not unmarshal cluster response: %v", err)
	}
	}
	continue
	}
	id, err := types.IDFromString(resp.Header.Get("X-Etcd-Cluster-ID"))
	if err != nil {
	if logerr {
	if lg != nil {
	lg.Warn(
	"failed to parse cluster ID",
	zap.String("address", addr),
	zap.String("header", resp.Header.Get("X-Etcd-Cluster-ID")),
	zap.Error(err),
	)
	} else {
	plog.Warningf("could not parse the cluster ID from cluster res: %v", err)
	}
	}
	continue
	}

	// check the length of membership members
	// if the membership members are present then prepare and return raft cluster
	// if membership members are not present then the raft cluster formed will be
	// an invalid empty cluster hence return failed to get raft cluster member(s) from the given urls error
	if len(membs) > 0 {
	return membership.NewClusterFromMembers(lg, "", id, membs), nil
	}
	return nil, fmt.Errorf("failed to get raft cluster member(s) from the given URLs")
	}
	return nil, fmt.Errorf("could not retrieve cluster information from the given URLs")
	}

	// getRemotePeerURLs returns peer urls of remote members in the cluster. The
	// returned list is sorted in ascending lexicographical order.
	func getRemotePeerURLs(cl *membership.RaftCluster, local string) []string {
	us := make([]string, 0)
	for _, m := range cl.Members() {
	if m.Name == local {
	continue
	}
	us = append(us, m.PeerURLs...)
	}
	sort.Strings(us)
	return us
	}

	// getVersions returns the versions of the members in the given cluster.
	// The key of the returned map is the member's ID. The value of the returned map
	// is the semver versions string, including server and cluster.
	// If it fails to get the version of a member, the key will be nil.
	func getVersions(lg zap.Logger, cl membership.RaftCluster, local types.ID, rt http.RoundTripper) map[string]*version.Versions {
	members := cl.Members()
	vers := make(map[string]*version.Versions)
	for _, m := range members {
	if m.ID == local {
	cv := "not_decided"
	if cl.Version() != nil {
	cv = cl.Version().String()
	}
	vers[m.ID.String()] = &version.Versions{Server: version.Version, Cluster: cv}
	continue
	}
	ver, err := getVersion(lg, m, rt)
	if err != nil {
	if lg != nil {
	lg.Warn("failed to get version", zap.String("remote-member-id", m.ID.String()), zap.Error(err))
	} else {
	plog.Warningf("cannot get the version of member %s (%v)", m.ID, err)
	}
	vers[m.ID.String()] = nil
	} else {
	vers[m.ID.String()] = ver
	}
	}
	return vers
	}

	// decideClusterVersion decides the cluster version based on the versions map.
	// The returned version is the min server version in the map, or nil if the min
	// version in unknown.
	func decideClusterVersion(lg zap.Logger, vers map[string]version.Versions) *semver.Version {
	var cv *semver.Version
	lv := semver.Must(semver.NewVersion(version.Version))

	for mid, ver := range vers {
	if ver == nil {
	return nil
	}
	v, err := semver.NewVersion(ver.Server)
	if err != nil {
	if lg != nil {
	lg.Warn(
	"failed to parse server version of remote member",
	zap.String("remote-member-id", mid),
	zap.String("remote-member-version", ver.Server),
	zap.Error(err),
	)
	} else {
	plog.Errorf("cannot understand the version of member %s (%v)", mid, err)
	}
	return nil
	}
	if lv.LessThan(*v) {
	if lg != nil {
	lg.Warn(
	"leader found higher-versioned member",
	zap.String("local-member-version", lv.String()),
	zap.String("remote-member-id", mid),
	zap.String("remote-member-version", ver.Server),
	)
	} else {
	plog.Warningf("the local etcd version %s is not up-to-date", lv.String())
	plog.Warningf("member %s has a higher version %s", mid, ver.Server)
	}
	}
	if cv == nil {
	cv = v
	} else if v.LessThan(*cv) {
	cv = v
	}
	}
	return cv
	}

	// isCompatibleWithCluster return true if the local member has a compatible version with
	// the current running cluster.
	// The version is considered as compatible when at least one of the other members in the cluster has a
	// cluster version in the range of [MinClusterVersion, Version] and no known members has a cluster version
	// out of the range.
	// We set this rule since when the local member joins, another member might be offline.
	func isCompatibleWithCluster(lg zap.Logger, cl membership.RaftCluster, local types.ID, rt http.RoundTripper) bool {
	vers := getVersions(lg, cl, local, rt)
	minV := semver.Must(semver.NewVersion(version.MinClusterVersion))
	maxV := semver.Must(semver.NewVersion(version.Version))
	maxV = &semver.Version{
	Major: maxV.Major,
	Minor: maxV.Minor,
	}
	return isCompatibleWithVers(lg, vers, local, minV, maxV)
	}

	func isCompatibleWithVers(lg zap.Logger, vers map[string]version.Versions, local types.ID, minV, maxV *semver.Version) bool {
	var ok bool
	for id, v := range vers {
	// ignore comparison with local version
	if id == local.String() {
	continue
	}
	if v == nil {
	continue
	}
	clusterv, err := semver.NewVersion(v.Cluster)
	if err != nil {
	if lg != nil {
	lg.Warn(
	"failed to parse cluster version of remote member",
	zap.String("remote-member-id", id),
	zap.String("remote-member-cluster-version", v.Cluster),
	zap.Error(err),
	)
	} else {
	plog.Errorf("cannot understand the cluster version of member %s (%v)", id, err)
	}
	continue
	}
	if clusterv.LessThan(*minV) {
	if lg != nil {
	lg.Warn(
	"cluster version of remote member is not compatible; too low",
	zap.String("remote-member-id", id),
	zap.String("remote-member-cluster-version", clusterv.String()),
	zap.String("minimum-cluster-version-supported", minV.String()),
	)
	} else {
	plog.Warningf("the running cluster version(%v) is lower than the minimal cluster version(%v) supported", clusterv.String(), minV.String())
	}
	return false
	}
	if maxV.LessThan(*clusterv) {
	if lg != nil {
	lg.Warn(
	"cluster version of remote member is not compatible; too high",
	zap.String("remote-member-id", id),
	zap.String("remote-member-cluster-version", clusterv.String()),
	zap.String("minimum-cluster-version-supported", minV.String()),
	)
	} else {
	plog.Warningf("the running cluster version(%v) is higher than the maximum cluster version(%v) supported", clusterv.String(), maxV.String())
	}
	return false
	}
	ok = true
	}
	return ok
	}

	// getVersion returns the Versions of the given member via its
	// peerURLs. Returns the last error if it fails to get the version.
	func getVersion(lg zap.Logger, m membership.Member, rt http.RoundTripper) (*version.Versions, error) {
	cc := &http.Client{
	Transport: rt,
	}
	var (
	err error
	resp *http.Response
	)

	for _, u := range m.PeerURLs {
	addr := u + "/version"
	resp, err = cc.Get(addr)
	if err != nil {
	if lg != nil {
	lg.Warn(
	"failed to reach the peer URL",
	zap.String("address", addr),
	zap.String("remote-member-id", m.ID.String()),
	zap.Error(err),
	)
	} else {
	plog.Warningf("failed to reach the peerURL(%s) of member %s (%v)", u, m.ID, err)
	}
	continue
	}
	var b []byte
	b, err = ioutil.ReadAll(resp.Body)
	resp.Body.Close()
	if err != nil {
	if lg != nil {
	lg.Warn(
	"failed to read body of response",
	zap.String("address", addr),
	zap.String("remote-member-id", m.ID.String()),
	zap.Error(err),
	)
	} else {
	plog.Warningf("failed to read out the response body from the peerURL(%s) of member %s (%v)", u, m.ID, err)
	}
	continue
	}
	var vers version.Versions
	if err = json.Unmarshal(b, &vers); err != nil {
	if lg != nil {
	lg.Warn(
	"failed to unmarshal response",
	zap.String("address", addr),
	zap.String("remote-member-id", m.ID.String()),
	zap.Error(err),
	)
	} else {
	plog.Warningf("failed to unmarshal the response body got from the peerURL(%s) of member %s (%v)", u, m.ID, err)
	}
	continue
	}
	return &vers, nil
	}
	return nil, err
	}

	func promoteMemberHTTP(ctx context.Context, url string, id uint64, peerRt http.RoundTripper) ([]*membership.Member, error) {
	cc := &http.Client{Transport: peerRt}
	// TODO: refactor member http handler code
	// cannot import etcdhttp, so manually construct url
	requestUrl := url + "/members/promote/" + fmt.Sprintf("%d", id)
	req, err := http.NewRequest("POST", requestUrl, nil)
	if err != nil {
	return nil, err
	}
	req = req.WithContext(ctx)
	resp, err := cc.Do(req)
	if err != nil {
	return nil, err
	}
	defer resp.Body.Close()
	b, err := ioutil.ReadAll(resp.Body)
	if err != nil {
	return nil, err
	}

	if resp.StatusCode == http.StatusRequestTimeout {
	return nil, ErrTimeout
	}
	if resp.StatusCode == http.StatusPreconditionFailed {
	// both ErrMemberNotLearner and ErrLearnerNotReady have same http status code
	if strings.Contains(string(b), ErrLearnerNotReady.Error()) {
	return nil, ErrLearnerNotReady
	}
	if strings.Contains(string(b), membership.ErrMemberNotLearner.Error()) {
	return nil, membership.ErrMemberNotLearner
	}
	return nil, fmt.Errorf("member promote: unknown error(%s)", string(b))
	}
	if resp.StatusCode == http.StatusNotFound {
	return nil, membership.ErrIDNotFound
	}

	if resp.StatusCode != http.StatusOK { // all other types of errors
	return nil, fmt.Errorf("member promote: unknown error(%s)", string(b))
	}

	var membs []*membership.Member
	if err := json.Unmarshal(b, &membs); err != nil {
	return nil, err
	}
	return membs, nil
	}