package restorer import ( "context" "path/filepath" "sync" "golang.org/x/sync/errgroup" "github.com/restic/restic/internal/debug" "github.com/restic/restic/internal/errors" "github.com/restic/restic/internal/repository" "github.com/restic/restic/internal/restic" "github.com/restic/restic/internal/ui/restore" ) // 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 ( largeFileBlobCount = 25 ) // information about regular file being restored type fileInfo struct { lock sync.Mutex inProgress bool sparse 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 } type blobsLoaderFn func(ctx context.Context, packID restic.ID, blobs []restic.Blob, handleBlobFn func(blob restic.BlobHandle, buf []byte, err error) error) error // fileRestorer restores set of files type fileRestorer struct { idx func(restic.BlobType, restic.ID) []restic.PackedBlob blobsLoader blobsLoaderFn workerCount int filesWriter *filesWriter zeroChunk restic.ID sparse bool progress *restore.Progress dst string files []*fileInfo Error func(string, error) error } func newFileRestorer(dst string, blobsLoader blobsLoaderFn, idx func(restic.BlobType, restic.ID) []restic.PackedBlob, connections uint, sparse bool, progress *restore.Progress) *fileRestorer { // as packs are streamed the concurrency is limited by IO workerCount := int(connections) return &fileRestorer{ idx: idx, blobsLoader: blobsLoader, filesWriter: newFilesWriter(workerCount), zeroChunk: repository.ZeroChunk(), sparse: sparse, progress: progress, workerCount: 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.DataBlob, blobID) 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.DataLength()) } 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 blob.ID.Equal(r.zeroChunk) { file.sparse = r.sparse } }) if len(fileBlobs) == 1 { // no need to preallocate files with a single block, thus we can always consider them to be sparse // in addition, a short chunk will never match r.zeroChunk which would prevent sparseness for short files file.sparse = r.sparse } 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 < r.workerCount; i++ { wg.Go(worker) } // the main restore loop wg.Go(func() error { for _, id := range packOrder { pack := packs[id] // allow garbage collection of packInfo delete(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() } type blobToFileOffsetsMapping map[restic.ID]struct { files map[*fileInfo][]int64 // file -> offsets (plural!) of the blob in the file blob restic.Blob } func (r *fileRestorer) downloadPack(ctx context.Context, pack *packInfo) error { // calculate blob->[]files->[]offsets mappings blobs := make(blobToFileOffsetsMapping) for file := range pack.files { addBlob := func(blob restic.Blob, fileOffset int64) { blobInfo, ok := blobs[blob.ID] if !ok { blobInfo.files = make(map[*fileInfo][]int64) blobInfo.blob = blob 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.DataLength()) }) 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.DataBlob, blob.id) for _, idxPack := range idxPacks { if idxPack.PackID.Equal(pack.id) { addBlob(idxPack.Blob, blob.offset) break } } } } } // track already processed blobs for precise error reporting processedBlobs := restic.NewBlobSet() for _, entry := range blobs { occurrences := 0 for _, offsets := range entry.files { occurrences += len(offsets) } // With a maximum blob size of 8MB, the normal blob streaming has to write // at most 800MB for a single blob. This should be short enough to avoid // network connection timeouts. Based on a quick test, a limit of 100 only // selects a very small number of blobs (the number of references per blob // - aka. `count` - seem to follow a expontential distribution) if occurrences > 100 { // process frequently referenced blobs first as these can take a long time to write // which can cause backend connections to time out delete(blobs, entry.blob.ID) partialBlobs := blobToFileOffsetsMapping{entry.blob.ID: entry} err := r.downloadBlobs(ctx, pack.id, partialBlobs, processedBlobs) if err := r.reportError(blobs, processedBlobs, err); err != nil { return err } } } if len(blobs) == 0 { return nil } err := r.downloadBlobs(ctx, pack.id, blobs, processedBlobs) return r.reportError(blobs, processedBlobs, err) } func (r *fileRestorer) sanitizeError(file *fileInfo, err error) error { if err != nil { err = r.Error(file.location, err) } return err } func (r *fileRestorer) reportError(blobs blobToFileOffsetsMapping, processedBlobs restic.BlobSet, err error) error { if err == nil { return nil } // only report error for not yet processed blobs affectedFiles := make(map[*fileInfo]struct{}) for _, entry := range blobs { if processedBlobs.Has(entry.blob.BlobHandle) { continue } for file := range entry.files { affectedFiles[file] = struct{}{} } } for file := range affectedFiles { if errFile := r.sanitizeError(file, err); errFile != nil { return errFile } } return nil } func (r *fileRestorer) downloadBlobs(ctx context.Context, packID restic.ID, blobs blobToFileOffsetsMapping, processedBlobs restic.BlobSet) error { blobList := make([]restic.Blob, 0, len(blobs)) for _, entry := range blobs { blobList = append(blobList, entry.blob) } return r.blobsLoader(ctx, packID, blobList, func(h restic.BlobHandle, blobData []byte, err error) error { processedBlobs.Insert(h) blob := blobs[h.ID] if err != nil { for file := range blob.files { if errFile := r.sanitizeError(file, err); errFile != nil { return errFile } } return nil } 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 } writeErr := r.filesWriter.writeToFile(r.targetPath(file.location), blobData, offset, createSize, file.sparse) if r.progress != nil { r.progress.AddProgress(file.location, uint64(len(blobData)), uint64(file.size)) } return writeErr } err := r.sanitizeError(file, writeToFile()) if err != nil { return err } } } return nil }) }