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backup.go
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backup.go
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// MIT License
//
// Copyright (c) 2021-2023 TTBT Enterprises LLC
// Copyright (c) 2021-2023 Robin Thellend <rthellend@rthellend.com>
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
package storage
import (
"errors"
"fmt"
"io"
"os"
"path/filepath"
"time"
)
func (s *Storage) createBackup(files []string) (*backup, error) {
b := &backup{dir: s.dir, TS: time.Now(), Files: files}
if err := b.backup(); err != nil {
return nil, err
}
b.pending = filepath.Join("pending", fmt.Sprintf("%d", b.TS.UnixNano()))
if err := s.SaveDataFile(b.pending, b); err != nil {
return nil, err
}
return b, nil
}
func (s *Storage) rollbackPendingOps() error {
m, err := filepath.Glob(filepath.Join(s.dir, "pending", "*"))
if err != nil {
return err
}
for _, f := range m {
rel, err := filepath.Rel(s.dir, f)
if err != nil {
return err
}
var b backup
if err := s.ReadDataFile(rel, &b); err != nil {
return err
}
b.dir = s.dir
b.pending = rel
// Make sure pending is this backup is really abandoned.
time.Sleep(time.Until(b.TS.Add(5 * time.Second)))
if err := b.restore(); err != nil {
return err
}
s.Logger().Infof("Rolled back pending operation %d [%v]", b.TS.UnixNano(), b.Files)
// The abandoned files were most likely locked.
s.UnlockMany(b.Files)
}
return nil
}
type backup struct {
// The timestamp of the backup.
TS time.Time `json:"ts"`
// Relative file names.
Files []string `json:"files"`
// The root of the data directory.
dir string
// The relative file name of the pending ops file.
pending string
}
func (b *backup) backup() error {
ch := make(chan error)
for _, f := range b.Files {
go func(fn string) { ch <- copyFile(b.backupFileName(fn), fn) }(filepath.Join(b.dir, f))
}
var errList []error
for _ = range b.Files {
if err := <-ch; err != nil && !errors.Is(err, os.ErrNotExist) {
errList = append(errList, err)
}
}
if errList != nil {
return fmt.Errorf("%w %v", errList[0], errList[1:])
}
return nil
}
func (b *backup) restore() error {
ch := make(chan error)
for _, f := range b.Files {
go func(fn string) { ch <- os.Rename(b.backupFileName(fn), fn) }(filepath.Join(b.dir, f))
}
var errList []error
for _ = range b.Files {
if err := <-ch; err != nil && !errors.Is(err, os.ErrNotExist) {
errList = append(errList, err)
}
}
if errList != nil {
return fmt.Errorf("%w %v", errList[0], errList[1:])
}
if err := os.Remove(filepath.Join(b.dir, b.pending)); err != nil && !errors.Is(err, os.ErrNotExist) {
return err
}
return nil
}
func (b *backup) delete() error {
ch := make(chan error)
for _, f := range b.Files {
go func(fn string) { ch <- os.Remove(b.backupFileName(fn)) }(filepath.Join(b.dir, f))
}
var errList []error
for _ = range b.Files {
if err := <-ch; err != nil && !errors.Is(err, os.ErrNotExist) {
errList = append(errList, err)
}
}
if errList != nil {
return fmt.Errorf("%w %v", errList[0], errList[1:])
}
if err := os.Remove(filepath.Join(b.dir, b.pending)); err != nil && !errors.Is(err, os.ErrNotExist) {
return err
}
return nil
}
func (b *backup) backupFileName(f string) string {
return fmt.Sprintf("%s.bck-%d", f, b.TS.UnixNano())
}
func copyFile(dst, src string) error {
if err := os.Link(src, dst); err == nil {
return nil
}
in, err := os.Open(src)
if err != nil {
return err
}
out, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0600)
if err != nil {
in.Close()
return err
}
if _, err := io.Copy(out, in); err != nil {
in.Close()
out.Close()
return err
}
if err := out.Close(); err != nil {
in.Close()
return err
}
return in.Close()
}