restic/internal/restorer/filerestorer.go

344 lines
9.2 KiB
Go

package restorer
import (
"bufio"
"context"
"io"
"math"
"path/filepath"
"sort"
"sync"
"golang.org/x/sync/errgroup"
"github.com/restic/restic/internal/crypto"
"github.com/restic/restic/internal/debug"
"github.com/restic/restic/internal/errors"
"github.com/restic/restic/internal/restic"
)
// TODO if a blob is corrupt, there may be good blob copies in other packs
// TODO evaluate if it makes sense to split download and processing workers
// pro: can (slowly) read network and decrypt/write files concurrently
// con: each worker needs to keep one pack in memory
const (
workerCount = 8
largeFileBlobCount = 25
)
// information about regular file being restored
type fileInfo struct {
lock sync.Mutex
inProgress bool
size int64
location string // file on local filesystem relative to restorer basedir
blobs interface{} // blobs of the file
}
type fileBlobInfo struct {
id restic.ID // the blob id
offset int64 // blob offset in the file
}
// information about a data pack required to restore one or more files
type packInfo struct {
id restic.ID // the pack id
files map[*fileInfo]struct{} // set of files that use blobs from this pack
}
// fileRestorer restores set of files
type fileRestorer struct {
key *crypto.Key
idx func(restic.BlobHandle) []restic.PackedBlob
packLoader func(ctx context.Context, h restic.Handle, length int, offset int64, fn func(rd io.Reader) error) error
filesWriter *filesWriter
dst string
files []*fileInfo
Error func(string, error) error
}
func newFileRestorer(dst string,
packLoader func(ctx context.Context, h restic.Handle, length int, offset int64, fn func(rd io.Reader) error) error,
key *crypto.Key,
idx func(restic.BlobHandle) []restic.PackedBlob) *fileRestorer {
return &fileRestorer{
key: key,
idx: idx,
packLoader: packLoader,
filesWriter: newFilesWriter(workerCount),
dst: dst,
Error: restorerAbortOnAllErrors,
}
}
func (r *fileRestorer) addFile(location string, content restic.IDs, size int64) {
r.files = append(r.files, &fileInfo{location: location, blobs: content, size: size})
}
func (r *fileRestorer) targetPath(location string) string {
return filepath.Join(r.dst, location)
}
func (r *fileRestorer) forEachBlob(blobIDs []restic.ID, fn func(packID restic.ID, packBlob restic.Blob)) error {
if len(blobIDs) == 0 {
return nil
}
for _, blobID := range blobIDs {
packs := r.idx(restic.BlobHandle{ID: blobID, Type: restic.DataBlob})
if len(packs) == 0 {
return errors.Errorf("Unknown blob %s", blobID.String())
}
fn(packs[0].PackID, packs[0].Blob)
}
return nil
}
func (r *fileRestorer) restoreFiles(ctx context.Context) error {
packs := make(map[restic.ID]*packInfo) // all packs
// Process packs in order of first access. While this cannot guarantee
// that file chunks are restored sequentially, it offers a good enough
// approximation to shorten restore times by up to 19% in some test.
var packOrder restic.IDs
// create packInfo from fileInfo
for _, file := range r.files {
fileBlobs := file.blobs.(restic.IDs)
largeFile := len(fileBlobs) > largeFileBlobCount
var packsMap map[restic.ID][]fileBlobInfo
if largeFile {
packsMap = make(map[restic.ID][]fileBlobInfo)
}
fileOffset := int64(0)
err := r.forEachBlob(fileBlobs, func(packID restic.ID, blob restic.Blob) {
if largeFile {
packsMap[packID] = append(packsMap[packID], fileBlobInfo{id: blob.ID, offset: fileOffset})
fileOffset += int64(blob.Length) - crypto.Extension
}
pack, ok := packs[packID]
if !ok {
pack = &packInfo{
id: packID,
files: make(map[*fileInfo]struct{}),
}
packs[packID] = pack
packOrder = append(packOrder, packID)
}
pack.files[file] = struct{}{}
})
if err != nil {
// repository index is messed up, can't do anything
return err
}
if largeFile {
file.blobs = packsMap
}
}
wg, ctx := errgroup.WithContext(ctx)
downloadCh := make(chan *packInfo)
worker := func() error {
for pack := range downloadCh {
if err := r.downloadPack(ctx, pack); err != nil {
return err
}
}
return nil
}
for i := 0; i < workerCount; i++ {
wg.Go(worker)
}
// the main restore loop
wg.Go(func() error {
for _, id := range packOrder {
pack := packs[id]
select {
case <-ctx.Done():
return ctx.Err()
case downloadCh <- pack:
debug.Log("Scheduled download pack %s", pack.id.Str())
}
}
close(downloadCh)
return nil
})
return wg.Wait()
}
const maxBufferSize = 4 * 1024 * 1024
func (r *fileRestorer) downloadPack(ctx context.Context, pack *packInfo) error {
// calculate pack byte range and blob->[]files->[]offsets mappings
start, end := int64(math.MaxInt64), int64(0)
blobs := make(map[restic.ID]struct {
offset int64 // offset of the blob in the pack
length int // length of the blob
files map[*fileInfo][]int64 // file -> offsets (plural!) of the blob in the file
})
for file := range pack.files {
addBlob := func(blob restic.Blob, fileOffset int64) {
if start > int64(blob.Offset) {
start = int64(blob.Offset)
}
if end < int64(blob.Offset+blob.Length) {
end = int64(blob.Offset + blob.Length)
}
blobInfo, ok := blobs[blob.ID]
if !ok {
blobInfo.offset = int64(blob.Offset)
blobInfo.length = int(blob.Length)
blobInfo.files = make(map[*fileInfo][]int64)
blobs[blob.ID] = blobInfo
}
blobInfo.files[file] = append(blobInfo.files[file], fileOffset)
}
if fileBlobs, ok := file.blobs.(restic.IDs); ok {
fileOffset := int64(0)
err := r.forEachBlob(fileBlobs, func(packID restic.ID, blob restic.Blob) {
if packID.Equal(pack.id) {
addBlob(blob, fileOffset)
}
fileOffset += int64(blob.Length) - crypto.Extension
})
if err != nil {
// restoreFiles should have caught this error before
panic(err)
}
} else if packsMap, ok := file.blobs.(map[restic.ID][]fileBlobInfo); ok {
for _, blob := range packsMap[pack.id] {
idxPacks := r.idx(restic.BlobHandle{ID: blob.id, Type: restic.DataBlob})
for _, idxPack := range idxPacks {
if idxPack.PackID.Equal(pack.id) {
addBlob(idxPack.Blob, blob.offset)
break
}
}
}
}
}
sortedBlobs := make([]restic.ID, 0, len(blobs))
for blobID := range blobs {
sortedBlobs = append(sortedBlobs, blobID)
}
sort.Slice(sortedBlobs, func(i, j int) bool {
return blobs[sortedBlobs[i]].offset < blobs[sortedBlobs[j]].offset
})
sanitizeError := func(file *fileInfo, err error) error {
if err != nil {
err = r.Error(file.location, err)
}
return err
}
h := restic.Handle{Type: restic.PackFile, Name: pack.id.String()}
err := r.packLoader(ctx, h, int(end-start), start, func(rd io.Reader) error {
bufferSize := int(end - start)
if bufferSize > maxBufferSize {
bufferSize = maxBufferSize
}
bufRd := bufio.NewReaderSize(rd, bufferSize)
currentBlobEnd := start
var blobData, buf []byte
for _, blobID := range sortedBlobs {
blob := blobs[blobID]
_, err := bufRd.Discard(int(blob.offset - currentBlobEnd))
if err != nil {
return err
}
blobData, buf, err = r.loadBlob(bufRd, blobID, blob.length, buf)
if err != nil {
for file := range blob.files {
if errFile := sanitizeError(file, err); errFile != nil {
return errFile
}
}
continue
}
currentBlobEnd = blob.offset + int64(blob.length)
for file, offsets := range blob.files {
for _, offset := range offsets {
writeToFile := func() error {
// this looks overly complicated and needs explanation
// two competing requirements:
// - must create the file once and only once
// - should allow concurrent writes to the file
// so write the first blob while holding file lock
// write other blobs after releasing the lock
createSize := int64(-1)
file.lock.Lock()
if file.inProgress {
file.lock.Unlock()
} else {
defer file.lock.Unlock()
file.inProgress = true
createSize = file.size
}
return r.filesWriter.writeToFile(r.targetPath(file.location), blobData, offset, createSize)
}
err := sanitizeError(file, writeToFile())
if err != nil {
return err
}
}
}
}
return nil
})
if err != nil {
for file := range pack.files {
if errFile := sanitizeError(file, err); errFile != nil {
return errFile
}
}
}
return nil
}
func (r *fileRestorer) loadBlob(rd io.Reader, blobID restic.ID, length int, buf []byte) ([]byte, []byte, error) {
// TODO reconcile with Repository#loadBlob implementation
if cap(buf) < length {
buf = make([]byte, length)
} else {
buf = buf[:length]
}
n, err := io.ReadFull(rd, buf)
if err != nil {
return nil, nil, err
}
if n != length {
return nil, nil, errors.Errorf("error loading blob %v: wrong length returned, want %d, got %d", blobID.Str(), length, n)
}
// decrypt
nonce, ciphertext := buf[:r.key.NonceSize()], buf[r.key.NonceSize():]
plaintext, err := r.key.Open(ciphertext[:0], nonce, ciphertext, nil)
if err != nil {
return nil, nil, errors.Errorf("decrypting blob %v failed: %v", blobID, err)
}
// check hash
if !restic.Hash(plaintext).Equal(blobID) {
return nil, nil, errors.Errorf("blob %v returned invalid hash", blobID)
}
return plaintext, buf, nil
}