// SaveDBFrom saves snapshot of the database from the given reader. It
// guarantees the save operation is atomic.
func (s *Snapshotter) SaveDBFrom(r io.Reader, id uint64) error {
f, err := ioutil.TempFile(s.dir, "tmp")
if err != nil {
return err
}
var n int64
n, err = io.Copy(f, r)
if err == nil {
err = fileutil.Fsync(f)
}
f.Close()
if err != nil {
os.Remove(f.Name())
return err
}
fn := path.Join(s.dir, fmt.Sprintf("%016x.snap.db", id))
if fileutil.Exist(fn) {
os.Remove(f.Name())
return nil
}
err = os.Rename(f.Name(), fn)
if err != nil {
os.Remove(f.Name())
return err
}
plog.Infof("saved database snapshot to disk [total bytes: %d]", n)
return nil
}
func snapshotSaveCommandFunc(cmd *cobra.Command, args []string) {
if len(args) != 1 {
err := fmt.Errorf("snapshot save expects one argument")
ExitWithError(ExitBadArgs, err)
}
path := args[0]
partpath := path + ".part"
f, err := os.Create(partpath)
defer f.Close()
if err != nil {
exiterr := fmt.Errorf("could not open %s (%v)", partpath, err)
ExitWithError(ExitBadArgs, exiterr)
}
c := mustClientFromCmd(cmd)
r, serr := c.Snapshot(context.TODO())
if serr != nil {
os.RemoveAll(partpath)
ExitWithError(ExitInterrupted, serr)
}
if _, rerr := io.Copy(f, r); rerr != nil {
os.RemoveAll(partpath)
ExitWithError(ExitInterrupted, rerr)
}
fileutil.Fsync(f)
if rerr := os.Rename(partpath, path); rerr != nil {
exiterr := fmt.Errorf("could not rename %s to %s (%v)", partpath, path, rerr)
ExitWithError(ExitIO, exiterr)
}
fmt.Printf("Snapshot saved at %s\n", path)
}
// WriteAndSyncFile behaves just like ioutil.WriteFile in the standard library,
// but calls Sync before closing the file. WriteAndSyncFile guarantees the data
// is synced if there is no error returned.
func WriteAndSyncFile(filename string, data []byte, perm os.FileMode) error {
f, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
if err != nil {
return err
}
n, err := f.Write(data)
if err == nil && n < len(data) {
err = io.ErrShortWrite
}
if err == nil {
err = fileutil.Fsync(f)
}
if err1 := f.Close(); err == nil {
err = err1
}
return err
}
// Create creates a WAL ready for appending records. The given metadata is
// recorded at the head of each WAL file, and can be retrieved with ReadAll.
func Create(dirpath string, metadata []byte) (*WAL, error) {
if Exist(dirpath) {
return nil, os.ErrExist
}
// keep temporary wal directory so WAL initialization appears atomic
tmpdirpath := path.Clean(dirpath) + ".tmp"
if fileutil.Exist(tmpdirpath) {
if err := os.RemoveAll(tmpdirpath); err != nil {
return nil, err
}
}
if err := fileutil.CreateDirAll(tmpdirpath); err != nil {
return nil, err
}
p := path.Join(tmpdirpath, walName(0, 0))
f, err := fileutil.LockFile(p, os.O_WRONLY|os.O_CREATE, fileutil.PrivateFileMode)
if err != nil {
return nil, err
}
if _, err = f.Seek(0, os.SEEK_END); err != nil {
return nil, err
}
if err = fileutil.Preallocate(f.File, SegmentSizeBytes, true); err != nil {
return nil, err
}
w := &WAL{
dir: dirpath,
metadata: metadata,
encoder: newEncoder(f, 0),
}
w.locks = append(w.locks, f)
if err = w.saveCrc(0); err != nil {
return nil, err
}
if err = w.encoder.encode(&walpb.Record{Type: metadataType, Data: metadata}); err != nil {
return nil, err
}
if err = w.SaveSnapshot(walpb.Snapshot{}); err != nil {
return nil, err
}
if w, err = w.renameWal(tmpdirpath); err != nil {
return nil, err
}
// directory was renamed; sync parent dir to persist rename
pdir, perr := fileutil.OpenDir(path.Dir(w.dir))
if perr != nil {
return nil, perr
}
if perr = fileutil.Fsync(pdir); perr != nil {
return nil, perr
}
if perr = pdir.Close(); err != nil {
return nil, perr
}
return w, nil
}
// cut closes current file written and creates a new one ready to append.
// cut first creates a temp wal file and writes necessary headers into it.
// Then cut atomically rename temp wal file to a wal file.
func (w *WAL) cut() error {
// close old wal file; truncate to avoid wasting space if an early cut
off, serr := w.tail().Seek(0, os.SEEK_CUR)
if serr != nil {
return serr
}
if err := w.tail().Truncate(off); err != nil {
return err
}
if err := w.sync(); err != nil {
return err
}
fpath := path.Join(w.dir, walName(w.seq()+1, w.enti+1))
// create a temp wal file with name sequence + 1, or truncate the existing one
newTail, err := w.fp.Open()
if err != nil {
return err
}
// update writer and save the previous crc
w.locks = append(w.locks, newTail)
prevCrc := w.encoder.crc.Sum32()
w.encoder = newEncoder(w.tail(), prevCrc)
if err = w.saveCrc(prevCrc); err != nil {
return err
}
if err = w.encoder.encode(&walpb.Record{Type: metadataType, Data: w.metadata}); err != nil {
return err
}
if err = w.saveState(&w.state); err != nil {
return err
}
// atomically move temp wal file to wal file
if err = w.sync(); err != nil {
return err
}
off, err = w.tail().Seek(0, os.SEEK_CUR)
if err != nil {
return err
}
if err = os.Rename(newTail.Name(), fpath); err != nil {
return err
}
if err = fileutil.Fsync(w.dirFile); err != nil {
return err
}
newTail.Close()
if newTail, err = fileutil.LockFile(fpath, os.O_WRONLY, fileutil.PrivateFileMode); err != nil {
return err
}
if _, err = newTail.Seek(off, os.SEEK_SET); err != nil {
return err
}
w.locks[len(w.locks)-1] = newTail
prevCrc = w.encoder.crc.Sum32()
w.encoder = newEncoder(w.tail(), prevCrc)
plog.Infof("segmented wal file %v is created", fpath)
return nil
}
// Repair tries to repair ErrUnexpectedEOF in the
// last wal file by truncating.
func Repair(dirpath string) bool {
f, err := openLast(dirpath)
if err != nil {
return false
}
defer f.Close()
rec := &walpb.Record{}
decoder := newDecoder(f)
for {
lastOffset := decoder.lastOffset()
err := decoder.decode(rec)
switch err {
case nil:
// update crc of the decoder when necessary
switch rec.Type {
case crcType:
crc := decoder.crc.Sum32()
// current crc of decoder must match the crc of the record.
// do no need to match 0 crc, since the decoder is a new one at this case.
if crc != 0 && rec.Validate(crc) != nil {
return false
}
decoder.updateCRC(rec.Crc)
}
continue
case io.EOF:
return true
case io.ErrUnexpectedEOF:
plog.Noticef("repairing %v", f.Name())
bf, bferr := os.Create(f.Name() + ".broken")
if bferr != nil {
plog.Errorf("could not repair %v, failed to create backup file", f.Name())
return false
}
defer bf.Close()
if _, err = f.Seek(0, os.SEEK_SET); err != nil {
plog.Errorf("could not repair %v, failed to read file", f.Name())
return false
}
if _, err = io.Copy(bf, f); err != nil {
plog.Errorf("could not repair %v, failed to copy file", f.Name())
return false
}
if err = f.Truncate(int64(lastOffset)); err != nil {
plog.Errorf("could not repair %v, failed to truncate file", f.Name())
return false
}
if err = fileutil.Fsync(f.File); err != nil {
plog.Errorf("could not repair %v, failed to sync file", f.Name())
return false
}
return true
default:
plog.Errorf("could not repair error (%v)", err)
return false
}
}
}
