diff --git a/vendor/go.etcd.io/etcd/etcdserver/api/rafthttp/pipeline.go b/vendor/go.etcd.io/etcd/etcdserver/api/rafthttp/pipeline.go
new file mode 100644
index 0000000..70f9257
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/etcdserver/api/rafthttp/pipeline.go
@@ -0,0 +1,180 @@
+// 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 (
+	"bytes"
+	"context"
+	"errors"
+	"io/ioutil"
+	"sync"
+	"time"
+
+	stats "go.etcd.io/etcd/etcdserver/api/v2stats"
+	"go.etcd.io/etcd/pkg/pbutil"
+	"go.etcd.io/etcd/pkg/types"
+	"go.etcd.io/etcd/raft"
+	"go.etcd.io/etcd/raft/raftpb"
+
+	"go.uber.org/zap"
+)
+
+const (
+	connPerPipeline = 4
+	// pipelineBufSize is the size of pipeline buffer, which helps hold the
+	// temporary network latency.
+	// The size ensures that pipeline does not drop messages when the network
+	// is out of work for less than 1 second in good path.
+	pipelineBufSize = 64
+)
+
+var errStopped = errors.New("stopped")
+
+type pipeline struct {
+	peerID types.ID
+
+	tr     *Transport
+	picker *urlPicker
+	status *peerStatus
+	raft   Raft
+	errorc chan error
+	// deprecate when we depercate v2 API
+	followerStats *stats.FollowerStats
+
+	msgc chan raftpb.Message
+	// wait for the handling routines
+	wg    sync.WaitGroup
+	stopc chan struct{}
+}
+
+func (p *pipeline) start() {
+	p.stopc = make(chan struct{})
+	p.msgc = make(chan raftpb.Message, pipelineBufSize)
+	p.wg.Add(connPerPipeline)
+	for i := 0; i < connPerPipeline; i++ {
+		go p.handle()
+	}
+
+	if p.tr != nil && p.tr.Logger != nil {
+		p.tr.Logger.Info(
+			"started HTTP pipelining with remote peer",
+			zap.String("local-member-id", p.tr.ID.String()),
+			zap.String("remote-peer-id", p.peerID.String()),
+		)
+	} else {
+		plog.Infof("started HTTP pipelining with peer %s", p.peerID)
+	}
+}
+
+func (p *pipeline) stop() {
+	close(p.stopc)
+	p.wg.Wait()
+
+	if p.tr != nil && p.tr.Logger != nil {
+		p.tr.Logger.Info(
+			"stopped HTTP pipelining with remote peer",
+			zap.String("local-member-id", p.tr.ID.String()),
+			zap.String("remote-peer-id", p.peerID.String()),
+		)
+	} else {
+		plog.Infof("stopped HTTP pipelining with peer %s", p.peerID)
+	}
+}
+
+func (p *pipeline) handle() {
+	defer p.wg.Done()
+
+	for {
+		select {
+		case m := <-p.msgc:
+			start := time.Now()
+			err := p.post(pbutil.MustMarshal(&m))
+			end := time.Now()
+
+			if err != nil {
+				p.status.deactivate(failureType{source: pipelineMsg, action: "write"}, err.Error())
+
+				if m.Type == raftpb.MsgApp && p.followerStats != nil {
+					p.followerStats.Fail()
+				}
+				p.raft.ReportUnreachable(m.To)
+				if isMsgSnap(m) {
+					p.raft.ReportSnapshot(m.To, raft.SnapshotFailure)
+				}
+				sentFailures.WithLabelValues(types.ID(m.To).String()).Inc()
+				continue
+			}
+
+			p.status.activate()
+			if m.Type == raftpb.MsgApp && p.followerStats != nil {
+				p.followerStats.Succ(end.Sub(start))
+			}
+			if isMsgSnap(m) {
+				p.raft.ReportSnapshot(m.To, raft.SnapshotFinish)
+			}
+			sentBytes.WithLabelValues(types.ID(m.To).String()).Add(float64(m.Size()))
+		case <-p.stopc:
+			return
+		}
+	}
+}
+
+// post POSTs a data payload to a url. Returns nil if the POST succeeds,
+// error on any failure.
+func (p *pipeline) post(data []byte) (err error) {
+	u := p.picker.pick()
+	req := createPostRequest(u, RaftPrefix, bytes.NewBuffer(data), "application/protobuf", p.tr.URLs, p.tr.ID, p.tr.ClusterID)
+
+	done := make(chan struct{}, 1)
+	ctx, cancel := context.WithCancel(context.Background())
+	req = req.WithContext(ctx)
+	go func() {
+		select {
+		case <-done:
+		case <-p.stopc:
+			waitSchedule()
+			cancel()
+		}
+	}()
+
+	resp, err := p.tr.pipelineRt.RoundTrip(req)
+	done <- struct{}{}
+	if err != nil {
+		p.picker.unreachable(u)
+		return err
+	}
+	defer resp.Body.Close()
+	b, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		p.picker.unreachable(u)
+		return err
+	}
+
+	err = checkPostResponse(resp, b, req, p.peerID)
+	if err != nil {
+		p.picker.unreachable(u)
+		// errMemberRemoved is a critical error since a removed member should
+		// always be stopped. So we use reportCriticalError to report it to errorc.
+		if err == errMemberRemoved {
+			reportCriticalError(err, p.errorc)
+		}
+		return err
+	}
+
+	return nil
+}
+
+// waitSchedule waits other goroutines to be scheduled for a while
+func waitSchedule() { time.Sleep(time.Millisecond) }