diff --git a/vendor/go.etcd.io/etcd/etcdserver/backend.go b/vendor/go.etcd.io/etcd/etcdserver/backend.go
new file mode 100644
index 0000000..01ba192
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/etcdserver/backend.go
@@ -0,0 +1,112 @@
+// 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 etcdserver
+
+import (
+	"fmt"
+	"os"
+	"time"
+
+	"go.etcd.io/etcd/etcdserver/api/snap"
+	"go.etcd.io/etcd/lease"
+	"go.etcd.io/etcd/mvcc"
+	"go.etcd.io/etcd/mvcc/backend"
+	"go.etcd.io/etcd/raft/raftpb"
+
+	"go.uber.org/zap"
+)
+
+func newBackend(cfg ServerConfig) backend.Backend {
+	bcfg := backend.DefaultBackendConfig()
+	bcfg.Path = cfg.backendPath()
+	if cfg.BackendBatchLimit != 0 {
+		bcfg.BatchLimit = cfg.BackendBatchLimit
+		if cfg.Logger != nil {
+			cfg.Logger.Info("setting backend batch limit", zap.Int("batch limit", cfg.BackendBatchLimit))
+		}
+	}
+	if cfg.BackendBatchInterval != 0 {
+		bcfg.BatchInterval = cfg.BackendBatchInterval
+		if cfg.Logger != nil {
+			cfg.Logger.Info("setting backend batch interval", zap.Duration("batch interval", cfg.BackendBatchInterval))
+		}
+	}
+	bcfg.BackendFreelistType = cfg.BackendFreelistType
+	bcfg.Logger = cfg.Logger
+	if cfg.QuotaBackendBytes > 0 && cfg.QuotaBackendBytes != DefaultQuotaBytes {
+		// permit 10% excess over quota for disarm
+		bcfg.MmapSize = uint64(cfg.QuotaBackendBytes + cfg.QuotaBackendBytes/10)
+	}
+	return backend.New(bcfg)
+}
+
+// openSnapshotBackend renames a snapshot db to the current etcd db and opens it.
+func openSnapshotBackend(cfg ServerConfig, ss *snap.Snapshotter, snapshot raftpb.Snapshot) (backend.Backend, error) {
+	snapPath, err := ss.DBFilePath(snapshot.Metadata.Index)
+	if err != nil {
+		return nil, fmt.Errorf("failed to find database snapshot file (%v)", err)
+	}
+	if err := os.Rename(snapPath, cfg.backendPath()); err != nil {
+		return nil, fmt.Errorf("failed to rename database snapshot file (%v)", err)
+	}
+	return openBackend(cfg), nil
+}
+
+// openBackend returns a backend using the current etcd db.
+func openBackend(cfg ServerConfig) backend.Backend {
+	fn := cfg.backendPath()
+
+	now, beOpened := time.Now(), make(chan backend.Backend)
+	go func() {
+		beOpened <- newBackend(cfg)
+	}()
+
+	select {
+	case be := <-beOpened:
+		if cfg.Logger != nil {
+			cfg.Logger.Info("opened backend db", zap.String("path", fn), zap.Duration("took", time.Since(now)))
+		}
+		return be
+
+	case <-time.After(10 * time.Second):
+		if cfg.Logger != nil {
+			cfg.Logger.Info(
+				"db file is flocked by another process, or taking too long",
+				zap.String("path", fn),
+				zap.Duration("took", time.Since(now)),
+			)
+		} else {
+			plog.Warningf("another etcd process is using %q and holds the file lock, or loading backend file is taking >10 seconds", fn)
+			plog.Warningf("waiting for it to exit before starting...")
+		}
+	}
+
+	return <-beOpened
+}
+
+// recoverBackendSnapshot recovers the DB from a snapshot in case etcd crashes
+// before updating the backend db after persisting raft snapshot to disk,
+// violating the invariant snapshot.Metadata.Index < db.consistentIndex. In this
+// case, replace the db with the snapshot db sent by the leader.
+func recoverSnapshotBackend(cfg ServerConfig, oldbe backend.Backend, snapshot raftpb.Snapshot) (backend.Backend, error) {
+	var cIndex consistentIndex
+	kv := mvcc.New(cfg.Logger, oldbe, &lease.FakeLessor{}, &cIndex, mvcc.StoreConfig{CompactionBatchLimit: cfg.CompactionBatchLimit})
+	defer kv.Close()
+	if snapshot.Metadata.Index <= kv.ConsistentIndex() {
+		return oldbe, nil
+	}
+	oldbe.Close()
+	return openSnapshotBackend(cfg, snap.New(cfg.Logger, cfg.SnapDir()), snapshot)
+}