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snapshotter.go
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/
snapshotter.go
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// Copyright 2015 CoreOS, Inc.
//
// 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 snap
import (
"errors"
"fmt"
"hash/crc32"
"io/ioutil"
"log"
"os"
"path"
"sort"
"strings"
"github.com/coreos/etcd/pkg/pbutil"
"github.com/coreos/etcd/raft"
"github.com/coreos/etcd/raft/raftpb"
"github.com/coreos/etcd/snap/snappb"
)
const (
snapSuffix = ".snap"
)
var (
ErrNoSnapshot = errors.New("snap: no available snapshot")
ErrEmptySnapshot = errors.New("snap: empty snapshot")
ErrCRCMismatch = errors.New("snap: crc mismatch")
crcTable = crc32.MakeTable(crc32.Castagnoli)
)
type Snapshotter struct {
dir string
}
func New(dir string) *Snapshotter {
return &Snapshotter{
dir: dir,
}
}
func (s *Snapshotter) SaveSnap(snapshot raftpb.Snapshot) error {
if raft.IsEmptySnap(snapshot) {
return nil
}
return s.save(&snapshot)
}
func (s *Snapshotter) save(snapshot *raftpb.Snapshot) error {
fname := fmt.Sprintf("%016x-%016x%s", snapshot.Metadata.Term, snapshot.Metadata.Index, snapSuffix)
b := pbutil.MustMarshal(snapshot)
crc := crc32.Update(0, crcTable, b)
snap := snappb.Snapshot{Crc: crc, Data: b}
d, err := snap.Marshal()
if err != nil {
return err
}
return ioutil.WriteFile(path.Join(s.dir, fname), d, 0666)
}
func (s *Snapshotter) Load() (*raftpb.Snapshot, error) {
names, err := s.snapNames()
if err != nil {
return nil, err
}
var snap *raftpb.Snapshot
for _, name := range names {
if snap, err = loadSnap(s.dir, name); err == nil {
break
}
}
return snap, err
}
func loadSnap(dir, name string) (*raftpb.Snapshot, error) {
fpath := path.Join(dir, name)
snap, err := Read(fpath)
if err != nil {
renameBroken(fpath)
}
return snap, err
}
// Read reads the snapshot named by snapname and returns the snapshot.
func Read(snapname string) (*raftpb.Snapshot, error) {
b, err := ioutil.ReadFile(snapname)
if err != nil {
log.Printf("snap: snapshotter cannot read file %v: %v", snapname, err)
return nil, err
}
var serializedSnap snappb.Snapshot
if err = serializedSnap.Unmarshal(b); err != nil {
log.Printf("snap: corrupted snapshot file %v: %v", snapname, err)
return nil, err
}
if len(serializedSnap.Data) == 0 || serializedSnap.Crc == 0 {
log.Printf("snap: unexpected empty snapshot")
return nil, ErrEmptySnapshot
}
crc := crc32.Update(0, crcTable, serializedSnap.Data)
if crc != serializedSnap.Crc {
log.Printf("snap: corrupted snapshot file %v: crc mismatch", snapname)
return nil, ErrCRCMismatch
}
var snap raftpb.Snapshot
if err = snap.Unmarshal(serializedSnap.Data); err != nil {
log.Printf("snap: corrupted snapshot file %v: %v", snapname, err)
return nil, err
}
return &snap, nil
}
// snapNames returns the filename of the snapshots in logical time order (from newest to oldest).
// If there is no available snapshots, an ErrNoSnapshot will be returned.
func (s *Snapshotter) snapNames() ([]string, error) {
dir, err := os.Open(s.dir)
if err != nil {
return nil, err
}
defer dir.Close()
names, err := dir.Readdirnames(-1)
if err != nil {
return nil, err
}
snaps := checkSuffix(names)
if len(snaps) == 0 {
return nil, ErrNoSnapshot
}
sort.Sort(sort.Reverse(sort.StringSlice(snaps)))
return snaps, nil
}
func checkSuffix(names []string) []string {
snaps := []string{}
for i := range names {
if strings.HasSuffix(names[i], snapSuffix) {
snaps = append(snaps, names[i])
} else {
log.Printf("snap: unexpected non-snap file %v", names[i])
}
}
return snaps
}
func renameBroken(path string) {
brokenPath := path + ".broken"
if err := os.Rename(path, brokenPath); err != nil {
log.Printf("snap: cannot rename broken snapshot file %v to %v: %v", path, brokenPath, err)
}
}