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snapshotter.go
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/
snapshotter.go
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// 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 snap stores raft nodes' states with snapshots.
package snap
import (
"errors"
"fmt"
"hash/crc32"
"io/ioutil"
"os"
"path/filepath"
"sort"
"strconv"
"strings"
"time"
pioutil "github.com/coreos/etcd/pkg/ioutil"
"github.com/coreos/etcd/pkg/pbutil"
"github.com/coreos/etcd/raft"
"github.com/coreos/etcd/raft/raftpb"
"github.com/coreos/etcd/snap/snappb"
"github.com/coreos/etcd/wal/walpb"
"github.com/coreos/pkg/capnslog"
)
const (
snapSuffix = ".snap"
)
var (
plog = capnslog.NewPackageLogger("github.com/coreos/etcd", "snap")
ErrNoSnapshot = errors.New("snap: no available snapshot")
ErrEmptySnapshot = errors.New("snap: empty snapshot")
ErrCRCMismatch = errors.New("snap: crc mismatch")
crcTable = crc32.MakeTable(crc32.Castagnoli)
// A map of valid files that can be present in the snap folder.
validFiles = map[string]bool{
"db": true,
}
)
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 {
start := time.Now()
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
}
marshallingDurations.Observe(float64(time.Since(start)) / float64(time.Second))
err = pioutil.WriteAndSyncFile(filepath.Join(s.dir, fname), d, 0666)
if err == nil {
saveDurations.Observe(float64(time.Since(start)) / float64(time.Second))
} else {
err1 := os.Remove(filepath.Join(s.dir, fname))
if err1 != nil {
plog.Errorf("failed to remove broken snapshot file %s", filepath.Join(s.dir, fname))
}
}
return err
}
func (s *Snapshotter) Load() (*raftpb.Snapshot, error) {
return s.loadMatching(func(*raftpb.Snapshot) bool { return true })
}
// LoadNewestAvailable loads the newest snapshot available that is in walSnaps.
func (s *Snapshotter) LoadNewestAvailable(walSnaps []walpb.Snapshot) (*raftpb.Snapshot, error) {
return s.loadMatching(func(snapshot *raftpb.Snapshot) bool {
m := snapshot.Metadata
for i := len(walSnaps) - 1; i >= 0; i-- {
if m.Term == walSnaps[i].Term && m.Index == walSnaps[i].Index {
return true
}
}
return false
})
}
// loadMatching returns the newest snapshot where matchFn returns true.
func (s *Snapshotter) loadMatching(matchFn func(*raftpb.Snapshot) bool) (*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 && matchFn(snap) {
return snap, nil
}
}
return nil, ErrNoSnapshot
}
func loadSnap(dir, name string) (*raftpb.Snapshot, error) {
fpath := filepath.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 {
plog.Errorf("cannot read file %v: %v", snapname, err)
return nil, err
}
if len(b) == 0 {
plog.Errorf("unexpected empty snapshot")
return nil, ErrEmptySnapshot
}
var serializedSnap snappb.Snapshot
if err = serializedSnap.Unmarshal(b); err != nil {
plog.Errorf("corrupted snapshot file %v: %v", snapname, err)
return nil, err
}
if len(serializedSnap.Data) == 0 || serializedSnap.Crc == 0 {
plog.Errorf("unexpected empty snapshot")
return nil, ErrEmptySnapshot
}
crc := crc32.Update(0, crcTable, serializedSnap.Data)
if crc != serializedSnap.Crc {
plog.Errorf("corrupted snapshot file %v: crc mismatch", snapname)
return nil, ErrCRCMismatch
}
var snap raftpb.Snapshot
if err = snap.Unmarshal(serializedSnap.Data); err != nil {
plog.Errorf("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
}
names, err = s.cleanupSnapdir(names)
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 {
// If we find a file which is not a snapshot then check if it's
// a vaild file. If not throw out a warning.
if _, ok := validFiles[names[i]]; !ok {
plog.Warningf("skipped unexpected non snapshot file %v", names[i])
}
}
}
return snaps
}
func renameBroken(path string) {
brokenPath := path + ".broken"
if err := os.Rename(path, brokenPath); err != nil {
plog.Warningf("cannot rename broken snapshot file %v to %v: %v", path, brokenPath, err)
}
}
// cleanupSnapdir removes any files that should not be in the snapshot directory:
// - db.tmp prefixed files that can be orphaned by defragmentation
func (s *Snapshotter) cleanupSnapdir(filenames []string) (names []string, err error) {
for _, filename := range filenames {
if strings.HasPrefix(filename, "db.tmp") {
plog.Infof("found orphaned defragmentation file; deleting: %s", filename)
if rmErr := os.Remove(filepath.Join(s.dir, filename)); rmErr != nil && !os.IsNotExist(rmErr) {
return nil, fmt.Errorf("failed to remove orphaned defragmentation file %s: %v", filename, rmErr)
}
continue
}
names = append(names, filename)
}
return names, nil
}
func (s *Snapshotter) ReleaseSnapDBs(snap raftpb.Snapshot) error {
dir, err := os.Open(s.dir)
if err != nil {
return err
}
defer dir.Close()
filenames, err := dir.Readdirnames(-1)
if err != nil {
return err
}
for _, filename := range filenames {
if strings.HasSuffix(filename, ".snap.db") {
hexIndex := strings.TrimSuffix(filepath.Base(filename), ".snap.db")
index, err := strconv.ParseUint(hexIndex, 16, 64)
if err != nil {
plog.Warningf("failed to parse index from filename: %s (%v)", filename, err)
continue
}
if index < snap.Metadata.Index {
plog.Infof("found orphaned .snap.db file; deleting %q", filename)
if rmErr := os.Remove(filepath.Join(s.dir, filename)); rmErr != nil && !os.IsNotExist(rmErr) {
plog.Warningf("failed to remove orphaned .snap.db file: %s (%v)", filename, rmErr)
}
}
}
}
return nil
}