diff --git a/vendor/go.etcd.io/etcd/etcdserver/api/rafthttp/http.go b/vendor/go.etcd.io/etcd/etcdserver/api/rafthttp/http.go
new file mode 100644
index 0000000..d0e0c81
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/etcdserver/api/rafthttp/http.go
@@ -0,0 +1,577 @@
+// 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 rafthttp
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"path"
+	"strings"
+	"time"
+
+	"go.etcd.io/etcd/etcdserver/api/snap"
+	pioutil "go.etcd.io/etcd/pkg/ioutil"
+	"go.etcd.io/etcd/pkg/types"
+	"go.etcd.io/etcd/raft/raftpb"
+	"go.etcd.io/etcd/version"
+
+	humanize "github.com/dustin/go-humanize"
+	"go.uber.org/zap"
+)
+
+const (
+	// connReadLimitByte limits the number of bytes
+	// a single read can read out.
+	//
+	// 64KB should be large enough for not causing
+	// throughput bottleneck as well as small enough
+	// for not causing a read timeout.
+	connReadLimitByte = 64 * 1024
+)
+
+var (
+	RaftPrefix         = "/raft"
+	ProbingPrefix      = path.Join(RaftPrefix, "probing")
+	RaftStreamPrefix   = path.Join(RaftPrefix, "stream")
+	RaftSnapshotPrefix = path.Join(RaftPrefix, "snapshot")
+
+	errIncompatibleVersion = errors.New("incompatible version")
+	errClusterIDMismatch   = errors.New("cluster ID mismatch")
+)
+
+type peerGetter interface {
+	Get(id types.ID) Peer
+}
+
+type writerToResponse interface {
+	WriteTo(w http.ResponseWriter)
+}
+
+type pipelineHandler struct {
+	lg      *zap.Logger
+	localID types.ID
+	tr      Transporter
+	r       Raft
+	cid     types.ID
+}
+
+// newPipelineHandler returns a handler for handling raft messages
+// from pipeline for RaftPrefix.
+//
+// The handler reads out the raft message from request body,
+// and forwards it to the given raft state machine for processing.
+func newPipelineHandler(t *Transport, r Raft, cid types.ID) http.Handler {
+	return &pipelineHandler{
+		lg:      t.Logger,
+		localID: t.ID,
+		tr:      t,
+		r:       r,
+		cid:     cid,
+	}
+}
+
+func (h *pipelineHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.Method != "POST" {
+		w.Header().Set("Allow", "POST")
+		http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	w.Header().Set("X-Etcd-Cluster-ID", h.cid.String())
+
+	if err := checkClusterCompatibilityFromHeader(h.lg, h.localID, r.Header, h.cid); err != nil {
+		http.Error(w, err.Error(), http.StatusPreconditionFailed)
+		return
+	}
+
+	addRemoteFromRequest(h.tr, r)
+
+	// Limit the data size that could be read from the request body, which ensures that read from
+	// connection will not time out accidentally due to possible blocking in underlying implementation.
+	limitedr := pioutil.NewLimitedBufferReader(r.Body, connReadLimitByte)
+	b, err := ioutil.ReadAll(limitedr)
+	if err != nil {
+		if h.lg != nil {
+			h.lg.Warn(
+				"failed to read Raft message",
+				zap.String("local-member-id", h.localID.String()),
+				zap.Error(err),
+			)
+		} else {
+			plog.Errorf("failed to read raft message (%v)", err)
+		}
+		http.Error(w, "error reading raft message", http.StatusBadRequest)
+		recvFailures.WithLabelValues(r.RemoteAddr).Inc()
+		return
+	}
+
+	var m raftpb.Message
+	if err := m.Unmarshal(b); err != nil {
+		if h.lg != nil {
+			h.lg.Warn(
+				"failed to unmarshal Raft message",
+				zap.String("local-member-id", h.localID.String()),
+				zap.Error(err),
+			)
+		} else {
+			plog.Errorf("failed to unmarshal raft message (%v)", err)
+		}
+		http.Error(w, "error unmarshalling raft message", http.StatusBadRequest)
+		recvFailures.WithLabelValues(r.RemoteAddr).Inc()
+		return
+	}
+
+	receivedBytes.WithLabelValues(types.ID(m.From).String()).Add(float64(len(b)))
+
+	if err := h.r.Process(context.TODO(), m); err != nil {
+		switch v := err.(type) {
+		case writerToResponse:
+			v.WriteTo(w)
+		default:
+			if h.lg != nil {
+				h.lg.Warn(
+					"failed to process Raft message",
+					zap.String("local-member-id", h.localID.String()),
+					zap.Error(err),
+				)
+			} else {
+				plog.Warningf("failed to process raft message (%v)", err)
+			}
+			http.Error(w, "error processing raft message", http.StatusInternalServerError)
+			w.(http.Flusher).Flush()
+			// disconnect the http stream
+			panic(err)
+		}
+		return
+	}
+
+	// Write StatusNoContent header after the message has been processed by
+	// raft, which facilitates the client to report MsgSnap status.
+	w.WriteHeader(http.StatusNoContent)
+}
+
+type snapshotHandler struct {
+	lg          *zap.Logger
+	tr          Transporter
+	r           Raft
+	snapshotter *snap.Snapshotter
+
+	localID types.ID
+	cid     types.ID
+}
+
+func newSnapshotHandler(t *Transport, r Raft, snapshotter *snap.Snapshotter, cid types.ID) http.Handler {
+	return &snapshotHandler{
+		lg:          t.Logger,
+		tr:          t,
+		r:           r,
+		snapshotter: snapshotter,
+		localID:     t.ID,
+		cid:         cid,
+	}
+}
+
+const unknownSnapshotSender = "UNKNOWN_SNAPSHOT_SENDER"
+
+// ServeHTTP serves HTTP request to receive and process snapshot message.
+//
+// If request sender dies without closing underlying TCP connection,
+// the handler will keep waiting for the request body until TCP keepalive
+// finds out that the connection is broken after several minutes.
+// This is acceptable because
+// 1. snapshot messages sent through other TCP connections could still be
+// received and processed.
+// 2. this case should happen rarely, so no further optimization is done.
+func (h *snapshotHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	start := time.Now()
+
+	if r.Method != "POST" {
+		w.Header().Set("Allow", "POST")
+		http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
+		snapshotReceiveFailures.WithLabelValues(unknownSnapshotSender).Inc()
+		return
+	}
+
+	w.Header().Set("X-Etcd-Cluster-ID", h.cid.String())
+
+	if err := checkClusterCompatibilityFromHeader(h.lg, h.localID, r.Header, h.cid); err != nil {
+		http.Error(w, err.Error(), http.StatusPreconditionFailed)
+		snapshotReceiveFailures.WithLabelValues(unknownSnapshotSender).Inc()
+		return
+	}
+
+	addRemoteFromRequest(h.tr, r)
+
+	dec := &messageDecoder{r: r.Body}
+	// let snapshots be very large since they can exceed 512MB for large installations
+	m, err := dec.decodeLimit(uint64(1 << 63))
+	from := types.ID(m.From).String()
+	if err != nil {
+		msg := fmt.Sprintf("failed to decode raft message (%v)", err)
+		if h.lg != nil {
+			h.lg.Warn(
+				"failed to decode Raft message",
+				zap.String("local-member-id", h.localID.String()),
+				zap.String("remote-snapshot-sender-id", from),
+				zap.Error(err),
+			)
+		} else {
+			plog.Error(msg)
+		}
+		http.Error(w, msg, http.StatusBadRequest)
+		recvFailures.WithLabelValues(r.RemoteAddr).Inc()
+		snapshotReceiveFailures.WithLabelValues(from).Inc()
+		return
+	}
+
+	msgSize := m.Size()
+	receivedBytes.WithLabelValues(from).Add(float64(msgSize))
+
+	if m.Type != raftpb.MsgSnap {
+		if h.lg != nil {
+			h.lg.Warn(
+				"unexpected Raft message type",
+				zap.String("local-member-id", h.localID.String()),
+				zap.String("remote-snapshot-sender-id", from),
+				zap.String("message-type", m.Type.String()),
+			)
+		} else {
+			plog.Errorf("unexpected raft message type %s on snapshot path", m.Type)
+		}
+		http.Error(w, "wrong raft message type", http.StatusBadRequest)
+		snapshotReceiveFailures.WithLabelValues(from).Inc()
+		return
+	}
+
+	snapshotReceiveInflights.WithLabelValues(from).Inc()
+	defer func() {
+		snapshotReceiveInflights.WithLabelValues(from).Dec()
+	}()
+
+	if h.lg != nil {
+		h.lg.Info(
+			"receiving database snapshot",
+			zap.String("local-member-id", h.localID.String()),
+			zap.String("remote-snapshot-sender-id", from),
+			zap.Uint64("incoming-snapshot-index", m.Snapshot.Metadata.Index),
+			zap.Int("incoming-snapshot-message-size-bytes", msgSize),
+			zap.String("incoming-snapshot-message-size", humanize.Bytes(uint64(msgSize))),
+		)
+	} else {
+		plog.Infof("receiving database snapshot [index:%d, from %s] ...", m.Snapshot.Metadata.Index, types.ID(m.From))
+	}
+
+	// save incoming database snapshot.
+	n, err := h.snapshotter.SaveDBFrom(r.Body, m.Snapshot.Metadata.Index)
+	if err != nil {
+		msg := fmt.Sprintf("failed to save KV snapshot (%v)", err)
+		if h.lg != nil {
+			h.lg.Warn(
+				"failed to save incoming database snapshot",
+				zap.String("local-member-id", h.localID.String()),
+				zap.String("remote-snapshot-sender-id", from),
+				zap.Uint64("incoming-snapshot-index", m.Snapshot.Metadata.Index),
+				zap.Error(err),
+			)
+		} else {
+			plog.Error(msg)
+		}
+		http.Error(w, msg, http.StatusInternalServerError)
+		snapshotReceiveFailures.WithLabelValues(from).Inc()
+		return
+	}
+
+	receivedBytes.WithLabelValues(from).Add(float64(n))
+
+	if h.lg != nil {
+		h.lg.Info(
+			"received and saved database snapshot",
+			zap.String("local-member-id", h.localID.String()),
+			zap.String("remote-snapshot-sender-id", from),
+			zap.Uint64("incoming-snapshot-index", m.Snapshot.Metadata.Index),
+			zap.Int64("incoming-snapshot-size-bytes", n),
+			zap.String("incoming-snapshot-size", humanize.Bytes(uint64(n))),
+		)
+	} else {
+		plog.Infof("received and saved database snapshot [index: %d, from: %s] successfully", m.Snapshot.Metadata.Index, types.ID(m.From))
+	}
+
+	if err := h.r.Process(context.TODO(), m); err != nil {
+		switch v := err.(type) {
+		// Process may return writerToResponse error when doing some
+		// additional checks before calling raft.Node.Step.
+		case writerToResponse:
+			v.WriteTo(w)
+		default:
+			msg := fmt.Sprintf("failed to process raft message (%v)", err)
+			if h.lg != nil {
+				h.lg.Warn(
+					"failed to process Raft message",
+					zap.String("local-member-id", h.localID.String()),
+					zap.String("remote-snapshot-sender-id", from),
+					zap.Error(err),
+				)
+			} else {
+				plog.Error(msg)
+			}
+			http.Error(w, msg, http.StatusInternalServerError)
+			snapshotReceiveFailures.WithLabelValues(from).Inc()
+		}
+		return
+	}
+
+	// Write StatusNoContent header after the message has been processed by
+	// raft, which facilitates the client to report MsgSnap status.
+	w.WriteHeader(http.StatusNoContent)
+
+	snapshotReceive.WithLabelValues(from).Inc()
+	snapshotReceiveSeconds.WithLabelValues(from).Observe(time.Since(start).Seconds())
+}
+
+type streamHandler struct {
+	lg         *zap.Logger
+	tr         *Transport
+	peerGetter peerGetter
+	r          Raft
+	id         types.ID
+	cid        types.ID
+}
+
+func newStreamHandler(t *Transport, pg peerGetter, r Raft, id, cid types.ID) http.Handler {
+	return &streamHandler{
+		lg:         t.Logger,
+		tr:         t,
+		peerGetter: pg,
+		r:          r,
+		id:         id,
+		cid:        cid,
+	}
+}
+
+func (h *streamHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.Method != "GET" {
+		w.Header().Set("Allow", "GET")
+		http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	w.Header().Set("X-Server-Version", version.Version)
+	w.Header().Set("X-Etcd-Cluster-ID", h.cid.String())
+
+	if err := checkClusterCompatibilityFromHeader(h.lg, h.tr.ID, r.Header, h.cid); err != nil {
+		http.Error(w, err.Error(), http.StatusPreconditionFailed)
+		return
+	}
+
+	var t streamType
+	switch path.Dir(r.URL.Path) {
+	case streamTypeMsgAppV2.endpoint():
+		t = streamTypeMsgAppV2
+	case streamTypeMessage.endpoint():
+		t = streamTypeMessage
+	default:
+		if h.lg != nil {
+			h.lg.Debug(
+				"ignored unexpected streaming request path",
+				zap.String("local-member-id", h.tr.ID.String()),
+				zap.String("remote-peer-id-stream-handler", h.id.String()),
+				zap.String("path", r.URL.Path),
+			)
+		} else {
+			plog.Debugf("ignored unexpected streaming request path %s", r.URL.Path)
+		}
+		http.Error(w, "invalid path", http.StatusNotFound)
+		return
+	}
+
+	fromStr := path.Base(r.URL.Path)
+	from, err := types.IDFromString(fromStr)
+	if err != nil {
+		if h.lg != nil {
+			h.lg.Warn(
+				"failed to parse path into ID",
+				zap.String("local-member-id", h.tr.ID.String()),
+				zap.String("remote-peer-id-stream-handler", h.id.String()),
+				zap.String("path", fromStr),
+				zap.Error(err),
+			)
+		} else {
+			plog.Errorf("failed to parse from %s into ID (%v)", fromStr, err)
+		}
+		http.Error(w, "invalid from", http.StatusNotFound)
+		return
+	}
+	if h.r.IsIDRemoved(uint64(from)) {
+		if h.lg != nil {
+			h.lg.Warn(
+				"rejected stream from remote peer because it was removed",
+				zap.String("local-member-id", h.tr.ID.String()),
+				zap.String("remote-peer-id-stream-handler", h.id.String()),
+				zap.String("remote-peer-id-from", from.String()),
+			)
+		} else {
+			plog.Warningf("rejected the stream from peer %s since it was removed", from)
+		}
+		http.Error(w, "removed member", http.StatusGone)
+		return
+	}
+	p := h.peerGetter.Get(from)
+	if p == nil {
+		// This may happen in following cases:
+		// 1. user starts a remote peer that belongs to a different cluster
+		// with the same cluster ID.
+		// 2. local etcd falls behind of the cluster, and cannot recognize
+		// the members that joined after its current progress.
+		if urls := r.Header.Get("X-PeerURLs"); urls != "" {
+			h.tr.AddRemote(from, strings.Split(urls, ","))
+		}
+		if h.lg != nil {
+			h.lg.Warn(
+				"failed to find remote peer in cluster",
+				zap.String("local-member-id", h.tr.ID.String()),
+				zap.String("remote-peer-id-stream-handler", h.id.String()),
+				zap.String("remote-peer-id-from", from.String()),
+				zap.String("cluster-id", h.cid.String()),
+			)
+		} else {
+			plog.Errorf("failed to find member %s in cluster %s", from, h.cid)
+		}
+		http.Error(w, "error sender not found", http.StatusNotFound)
+		return
+	}
+
+	wto := h.id.String()
+	if gto := r.Header.Get("X-Raft-To"); gto != wto {
+		if h.lg != nil {
+			h.lg.Warn(
+				"ignored streaming request; ID mismatch",
+				zap.String("local-member-id", h.tr.ID.String()),
+				zap.String("remote-peer-id-stream-handler", h.id.String()),
+				zap.String("remote-peer-id-header", gto),
+				zap.String("remote-peer-id-from", from.String()),
+				zap.String("cluster-id", h.cid.String()),
+			)
+		} else {
+			plog.Errorf("streaming request ignored (ID mismatch got %s want %s)", gto, wto)
+		}
+		http.Error(w, "to field mismatch", http.StatusPreconditionFailed)
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+	w.(http.Flusher).Flush()
+
+	c := newCloseNotifier()
+	conn := &outgoingConn{
+		t:       t,
+		Writer:  w,
+		Flusher: w.(http.Flusher),
+		Closer:  c,
+		localID: h.tr.ID,
+		peerID:  h.id,
+	}
+	p.attachOutgoingConn(conn)
+	<-c.closeNotify()
+}
+
+// checkClusterCompatibilityFromHeader checks the cluster compatibility of
+// the local member from the given header.
+// It checks whether the version of local member is compatible with
+// the versions in the header, and whether the cluster ID of local member
+// matches the one in the header.
+func checkClusterCompatibilityFromHeader(lg *zap.Logger, localID types.ID, header http.Header, cid types.ID) error {
+	remoteName := header.Get("X-Server-From")
+
+	remoteServer := serverVersion(header)
+	remoteVs := ""
+	if remoteServer != nil {
+		remoteVs = remoteServer.String()
+	}
+
+	remoteMinClusterVer := minClusterVersion(header)
+	remoteMinClusterVs := ""
+	if remoteMinClusterVer != nil {
+		remoteMinClusterVs = remoteMinClusterVer.String()
+	}
+
+	localServer, localMinCluster, err := checkVersionCompatibility(remoteName, remoteServer, remoteMinClusterVer)
+
+	localVs := ""
+	if localServer != nil {
+		localVs = localServer.String()
+	}
+	localMinClusterVs := ""
+	if localMinCluster != nil {
+		localMinClusterVs = localMinCluster.String()
+	}
+
+	if err != nil {
+		if lg != nil {
+			lg.Warn(
+				"failed to check version compatibility",
+				zap.String("local-member-id", localID.String()),
+				zap.String("local-member-cluster-id", cid.String()),
+				zap.String("local-member-server-version", localVs),
+				zap.String("local-member-server-minimum-cluster-version", localMinClusterVs),
+				zap.String("remote-peer-server-name", remoteName),
+				zap.String("remote-peer-server-version", remoteVs),
+				zap.String("remote-peer-server-minimum-cluster-version", remoteMinClusterVs),
+				zap.Error(err),
+			)
+		} else {
+			plog.Errorf("request version incompatibility (%v)", err)
+		}
+		return errIncompatibleVersion
+	}
+	if gcid := header.Get("X-Etcd-Cluster-ID"); gcid != cid.String() {
+		if lg != nil {
+			lg.Warn(
+				"request cluster ID mismatch",
+				zap.String("local-member-id", localID.String()),
+				zap.String("local-member-cluster-id", cid.String()),
+				zap.String("local-member-server-version", localVs),
+				zap.String("local-member-server-minimum-cluster-version", localMinClusterVs),
+				zap.String("remote-peer-server-name", remoteName),
+				zap.String("remote-peer-server-version", remoteVs),
+				zap.String("remote-peer-server-minimum-cluster-version", remoteMinClusterVs),
+				zap.String("remote-peer-cluster-id", gcid),
+			)
+		} else {
+			plog.Errorf("request cluster ID mismatch (got %s want %s)", gcid, cid)
+		}
+		return errClusterIDMismatch
+	}
+	return nil
+}
+
+type closeNotifier struct {
+	done chan struct{}
+}
+
+func newCloseNotifier() *closeNotifier {
+	return &closeNotifier{
+		done: make(chan struct{}),
+	}
+}
+
+func (n *closeNotifier) Close() error {
+	close(n.done)
+	return nil
+}
+
+func (n *closeNotifier) closeNotify() <-chan struct{} { return n.done }