diff --git a/vendor/go.etcd.io/etcd/mvcc/kvstore_txn.go b/vendor/go.etcd.io/etcd/mvcc/kvstore_txn.go
new file mode 100644
index 0000000..9698254
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/mvcc/kvstore_txn.go
@@ -0,0 +1,313 @@
+// 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 mvcc
+
+import (
+	"go.etcd.io/etcd/lease"
+	"go.etcd.io/etcd/mvcc/backend"
+	"go.etcd.io/etcd/mvcc/mvccpb"
+	"go.uber.org/zap"
+)
+
+type storeTxnRead struct {
+	s  *store
+	tx backend.ReadTx
+
+	firstRev int64
+	rev      int64
+}
+
+func (s *store) Read() TxnRead {
+	s.mu.RLock()
+	s.revMu.RLock()
+	// backend holds b.readTx.RLock() only when creating the concurrentReadTx. After
+	// ConcurrentReadTx is created, it will not block write transaction.
+	tx := s.b.ConcurrentReadTx()
+	tx.RLock() // RLock is no-op. concurrentReadTx does not need to be locked after it is created.
+	firstRev, rev := s.compactMainRev, s.currentRev
+	s.revMu.RUnlock()
+	return newMetricsTxnRead(&storeTxnRead{s, tx, firstRev, rev})
+}
+
+func (tr *storeTxnRead) FirstRev() int64 { return tr.firstRev }
+func (tr *storeTxnRead) Rev() int64      { return tr.rev }
+
+func (tr *storeTxnRead) Range(key, end []byte, ro RangeOptions) (r *RangeResult, err error) {
+	return tr.rangeKeys(key, end, tr.Rev(), ro)
+}
+
+func (tr *storeTxnRead) End() {
+	tr.tx.RUnlock() // RUnlock signals the end of concurrentReadTx.
+	tr.s.mu.RUnlock()
+}
+
+type storeTxnWrite struct {
+	storeTxnRead
+	tx backend.BatchTx
+	// beginRev is the revision where the txn begins; it will write to the next revision.
+	beginRev int64
+	changes  []mvccpb.KeyValue
+}
+
+func (s *store) Write() TxnWrite {
+	s.mu.RLock()
+	tx := s.b.BatchTx()
+	tx.Lock()
+	tw := &storeTxnWrite{
+		storeTxnRead: storeTxnRead{s, tx, 0, 0},
+		tx:           tx,
+		beginRev:     s.currentRev,
+		changes:      make([]mvccpb.KeyValue, 0, 4),
+	}
+	return newMetricsTxnWrite(tw)
+}
+
+func (tw *storeTxnWrite) Rev() int64 { return tw.beginRev }
+
+func (tw *storeTxnWrite) Range(key, end []byte, ro RangeOptions) (r *RangeResult, err error) {
+	rev := tw.beginRev
+	if len(tw.changes) > 0 {
+		rev++
+	}
+	return tw.rangeKeys(key, end, rev, ro)
+}
+
+func (tw *storeTxnWrite) DeleteRange(key, end []byte) (int64, int64) {
+	if n := tw.deleteRange(key, end); n != 0 || len(tw.changes) > 0 {
+		return n, tw.beginRev + 1
+	}
+	return 0, tw.beginRev
+}
+
+func (tw *storeTxnWrite) Put(key, value []byte, lease lease.LeaseID) int64 {
+	tw.put(key, value, lease)
+	return tw.beginRev + 1
+}
+
+func (tw *storeTxnWrite) End() {
+	// only update index if the txn modifies the mvcc state.
+	if len(tw.changes) != 0 {
+		tw.s.saveIndex(tw.tx)
+		// hold revMu lock to prevent new read txns from opening until writeback.
+		tw.s.revMu.Lock()
+		tw.s.currentRev++
+	}
+	tw.tx.Unlock()
+	if len(tw.changes) != 0 {
+		tw.s.revMu.Unlock()
+	}
+	tw.s.mu.RUnlock()
+}
+
+func (tr *storeTxnRead) rangeKeys(key, end []byte, curRev int64, ro RangeOptions) (*RangeResult, error) {
+	rev := ro.Rev
+	if rev > curRev {
+		return &RangeResult{KVs: nil, Count: -1, Rev: curRev}, ErrFutureRev
+	}
+	if rev <= 0 {
+		rev = curRev
+	}
+	if rev < tr.s.compactMainRev {
+		return &RangeResult{KVs: nil, Count: -1, Rev: 0}, ErrCompacted
+	}
+
+	revpairs := tr.s.kvindex.Revisions(key, end, rev)
+	if len(revpairs) == 0 {
+		return &RangeResult{KVs: nil, Count: 0, Rev: curRev}, nil
+	}
+	if ro.Count {
+		return &RangeResult{KVs: nil, Count: len(revpairs), Rev: curRev}, nil
+	}
+
+	limit := int(ro.Limit)
+	if limit <= 0 || limit > len(revpairs) {
+		limit = len(revpairs)
+	}
+
+	kvs := make([]mvccpb.KeyValue, limit)
+	revBytes := newRevBytes()
+	for i, revpair := range revpairs[:len(kvs)] {
+		revToBytes(revpair, revBytes)
+		_, vs := tr.tx.UnsafeRange(keyBucketName, revBytes, nil, 0)
+		if len(vs) != 1 {
+			if tr.s.lg != nil {
+				tr.s.lg.Fatal(
+					"range failed to find revision pair",
+					zap.Int64("revision-main", revpair.main),
+					zap.Int64("revision-sub", revpair.sub),
+				)
+			} else {
+				plog.Fatalf("range cannot find rev (%d,%d)", revpair.main, revpair.sub)
+			}
+		}
+		if err := kvs[i].Unmarshal(vs[0]); err != nil {
+			if tr.s.lg != nil {
+				tr.s.lg.Fatal(
+					"failed to unmarshal mvccpb.KeyValue",
+					zap.Error(err),
+				)
+			} else {
+				plog.Fatalf("cannot unmarshal event: %v", err)
+			}
+		}
+	}
+	return &RangeResult{KVs: kvs, Count: len(revpairs), Rev: curRev}, nil
+}
+
+func (tw *storeTxnWrite) put(key, value []byte, leaseID lease.LeaseID) {
+	rev := tw.beginRev + 1
+	c := rev
+	oldLease := lease.NoLease
+
+	// if the key exists before, use its previous created and
+	// get its previous leaseID
+	_, created, ver, err := tw.s.kvindex.Get(key, rev)
+	if err == nil {
+		c = created.main
+		oldLease = tw.s.le.GetLease(lease.LeaseItem{Key: string(key)})
+	}
+
+	ibytes := newRevBytes()
+	idxRev := revision{main: rev, sub: int64(len(tw.changes))}
+	revToBytes(idxRev, ibytes)
+
+	ver = ver + 1
+	kv := mvccpb.KeyValue{
+		Key:            key,
+		Value:          value,
+		CreateRevision: c,
+		ModRevision:    rev,
+		Version:        ver,
+		Lease:          int64(leaseID),
+	}
+
+	d, err := kv.Marshal()
+	if err != nil {
+		if tw.storeTxnRead.s.lg != nil {
+			tw.storeTxnRead.s.lg.Fatal(
+				"failed to marshal mvccpb.KeyValue",
+				zap.Error(err),
+			)
+		} else {
+			plog.Fatalf("cannot marshal event: %v", err)
+		}
+	}
+
+	tw.tx.UnsafeSeqPut(keyBucketName, ibytes, d)
+	tw.s.kvindex.Put(key, idxRev)
+	tw.changes = append(tw.changes, kv)
+
+	if oldLease != lease.NoLease {
+		if tw.s.le == nil {
+			panic("no lessor to detach lease")
+		}
+		err = tw.s.le.Detach(oldLease, []lease.LeaseItem{{Key: string(key)}})
+		if err != nil {
+			if tw.storeTxnRead.s.lg != nil {
+				tw.storeTxnRead.s.lg.Fatal(
+					"failed to detach old lease from a key",
+					zap.Error(err),
+				)
+			} else {
+				plog.Errorf("unexpected error from lease detach: %v", err)
+			}
+		}
+	}
+	if leaseID != lease.NoLease {
+		if tw.s.le == nil {
+			panic("no lessor to attach lease")
+		}
+		err = tw.s.le.Attach(leaseID, []lease.LeaseItem{{Key: string(key)}})
+		if err != nil {
+			panic("unexpected error from lease Attach")
+		}
+	}
+}
+
+func (tw *storeTxnWrite) deleteRange(key, end []byte) int64 {
+	rrev := tw.beginRev
+	if len(tw.changes) > 0 {
+		rrev++
+	}
+	keys, _ := tw.s.kvindex.Range(key, end, rrev)
+	if len(keys) == 0 {
+		return 0
+	}
+	for _, key := range keys {
+		tw.delete(key)
+	}
+	return int64(len(keys))
+}
+
+func (tw *storeTxnWrite) delete(key []byte) {
+	ibytes := newRevBytes()
+	idxRev := revision{main: tw.beginRev + 1, sub: int64(len(tw.changes))}
+	revToBytes(idxRev, ibytes)
+
+	if tw.storeTxnRead.s != nil && tw.storeTxnRead.s.lg != nil {
+		ibytes = appendMarkTombstone(tw.storeTxnRead.s.lg, ibytes)
+	} else {
+		// TODO: remove this in v3.5
+		ibytes = appendMarkTombstone(nil, ibytes)
+	}
+
+	kv := mvccpb.KeyValue{Key: key}
+
+	d, err := kv.Marshal()
+	if err != nil {
+		if tw.storeTxnRead.s.lg != nil {
+			tw.storeTxnRead.s.lg.Fatal(
+				"failed to marshal mvccpb.KeyValue",
+				zap.Error(err),
+			)
+		} else {
+			plog.Fatalf("cannot marshal event: %v", err)
+		}
+	}
+
+	tw.tx.UnsafeSeqPut(keyBucketName, ibytes, d)
+	err = tw.s.kvindex.Tombstone(key, idxRev)
+	if err != nil {
+		if tw.storeTxnRead.s.lg != nil {
+			tw.storeTxnRead.s.lg.Fatal(
+				"failed to tombstone an existing key",
+				zap.String("key", string(key)),
+				zap.Error(err),
+			)
+		} else {
+			plog.Fatalf("cannot tombstone an existing key (%s): %v", string(key), err)
+		}
+	}
+	tw.changes = append(tw.changes, kv)
+
+	item := lease.LeaseItem{Key: string(key)}
+	leaseID := tw.s.le.GetLease(item)
+
+	if leaseID != lease.NoLease {
+		err = tw.s.le.Detach(leaseID, []lease.LeaseItem{item})
+		if err != nil {
+			if tw.storeTxnRead.s.lg != nil {
+				tw.storeTxnRead.s.lg.Fatal(
+					"failed to detach old lease from a key",
+					zap.Error(err),
+				)
+			} else {
+				plog.Errorf("cannot detach %v", err)
+			}
+		}
+	}
+}
+
+func (tw *storeTxnWrite) Changes() []mvccpb.KeyValue { return tw.changes }