mirror of
https://github.com/restic/restic.git
synced 2024-12-24 16:54:00 +00:00
324 lines
9 KiB
Go
324 lines
9 KiB
Go
package restorer
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import (
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"context"
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"io"
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"path/filepath"
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"github.com/restic/restic/internal/crypto"
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"github.com/restic/restic/internal/debug"
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"github.com/restic/restic/internal/errors"
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"github.com/restic/restic/internal/restic"
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)
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// TODO if a blob is corrupt, there may be good blob copies in other packs
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// TODO evaluate if it makes sense to split download and processing workers
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// pro: can (slowly) read network and decrypt/write files concurrently
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// con: each worker needs to keep one pack in memory
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// TODO evaluate memory footprint for larger repositories, say 10M packs/10M files
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// TODO consider replacing pack file cache with blob cache
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// TODO avoid decrypting the same blob multiple times
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// TODO evaluate disabled debug logging overhead for large repositories
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const (
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workerCount = 8
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// max number of cached open output file handles
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filesWriterCacheCap = 32
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// estimated average pack size used to calculate pack cache capacity
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averagePackSize = 5 * 1024 * 1024
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// pack cache capacity should support at least one cached pack per worker
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// allow space for extra 5 packs for actual caching
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packCacheCapacity = (workerCount + 5) * averagePackSize
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)
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// information about regular file being restored
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type fileInfo struct {
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location string // file on local filesystem relative to restorer basedir
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blobs []restic.ID // remaining blobs of the file
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}
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// information about a data pack required to restore one or more files
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type packInfo struct {
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// the pack id
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id restic.ID
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// set of files that use blobs from this pack
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files map[*fileInfo]struct{}
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// number of other packs that must be downloaded before all blobs in this pack can be used
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cost int
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// used by packHeap
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index int
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}
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// fileRestorer restores set of files
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type fileRestorer struct {
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key *crypto.Key
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idx filePackTraverser
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packLoader func(ctx context.Context, h restic.Handle, length int, offset int64, fn func(rd io.Reader) error) error
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packCache *packCache // pack cache
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filesWriter *filesWriter // file write
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dst string
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files []*fileInfo
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}
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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 filePackTraverser) *fileRestorer {
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return &fileRestorer{
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packLoader: packLoader,
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key: key,
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idx: idx,
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filesWriter: newFilesWriter(filesWriterCacheCap),
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packCache: newPackCache(packCacheCapacity),
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dst: dst,
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}
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}
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func (r *fileRestorer) addFile(location string, content restic.IDs) {
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r.files = append(r.files, &fileInfo{location: location, blobs: content})
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}
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func (r *fileRestorer) targetPath(location string) string {
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return filepath.Join(r.dst, location)
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}
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// used to pass information among workers (wish golang channels allowed multivalues)
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type processingInfo struct {
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pack *packInfo
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files map[*fileInfo]error
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}
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func (r *fileRestorer) restoreFiles(ctx context.Context, onError func(path string, err error)) error {
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// TODO conditionally enable when debug log is on
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// for _, file := range r.files {
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// dbgmsg := file.location + ": "
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// r.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, packBlobs []restic.Blob) bool {
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// if packIdx > 0 {
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// dbgmsg += ", "
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// }
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// dbgmsg += "pack{id=" + packID.Str() + ", blobs: "
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// for blobIdx, blob := range packBlobs {
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// if blobIdx > 0 {
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// dbgmsg += ", "
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// }
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// dbgmsg += blob.ID.Str()
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// }
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// dbgmsg += "}"
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// return true // keep going
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// })
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// debug.Log(dbgmsg)
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// }
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inprogress := make(map[*fileInfo]struct{})
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queue, err := newPackQueue(r.idx, r.files, func(files map[*fileInfo]struct{}) bool {
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for file := range files {
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if _, found := inprogress[file]; found {
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return true
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}
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}
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return false
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})
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if err != nil {
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return err
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}
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// workers
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downloadCh := make(chan processingInfo)
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feedbackCh := make(chan processingInfo)
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defer close(downloadCh)
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defer close(feedbackCh)
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worker := func() {
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for {
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select {
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case <-ctx.Done():
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return
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case request, ok := <-downloadCh:
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if !ok {
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return // channel closed
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}
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rd, err := r.downloadPack(ctx, request.pack)
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if err == nil {
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r.processPack(ctx, request, rd)
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} else {
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// mark all files as failed
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for file := range request.files {
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request.files[file] = err
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}
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}
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feedbackCh <- request
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}
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}
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}
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for i := 0; i < workerCount; i++ {
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go worker()
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}
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processFeedback := func(pack *packInfo, ferrors map[*fileInfo]error) {
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// update files blobIdx
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// must do it here to avoid race among worker and processing feedback threads
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var success []*fileInfo
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var failure []*fileInfo
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for file, ferr := range ferrors {
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target := r.targetPath(file.location)
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if ferr != nil {
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onError(file.location, ferr)
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r.filesWriter.close(target)
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delete(inprogress, file)
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failure = append(failure, file)
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} else {
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r.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, packBlobs []restic.Blob) bool {
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file.blobs = file.blobs[len(packBlobs):]
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return false // only interesed in the first pack
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})
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if len(file.blobs) == 0 {
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r.filesWriter.close(target)
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delete(inprogress, file)
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}
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success = append(success, file)
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}
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}
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// update the queue and requeueu the pack as necessary
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if !queue.requeuePack(pack, success, failure) {
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r.packCache.remove(pack.id)
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debug.Log("Purged used up pack %s from pack cache", pack.id.Str())
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}
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}
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// the main restore loop
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for !queue.isEmpty() {
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debug.Log("-----------------------------------")
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pack, files := queue.nextPack()
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if pack != nil {
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ferrors := make(map[*fileInfo]error)
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for _, file := range files {
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ferrors[file] = nil
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inprogress[file] = struct{}{}
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}
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select {
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case <-ctx.Done():
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return ctx.Err()
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case downloadCh <- processingInfo{pack: pack, files: ferrors}:
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debug.Log("Scheduled download pack %s (%d files)", pack.id.Str(), len(files))
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case feedback := <-feedbackCh:
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queue.requeuePack(pack, []*fileInfo{}, []*fileInfo{}) // didn't use the pack during this iteration
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processFeedback(feedback.pack, feedback.files)
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}
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} else {
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select {
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case <-ctx.Done():
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return ctx.Err()
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case feedback := <-feedbackCh:
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processFeedback(feedback.pack, feedback.files)
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}
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}
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}
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return nil
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}
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func (r *fileRestorer) downloadPack(ctx context.Context, pack *packInfo) (readerAtCloser, error) {
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const MaxInt64 = 1<<63 - 1 // odd Go does not have this predefined somewhere
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// calculate pack byte range
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start, end := int64(MaxInt64), int64(0)
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for file := range pack.files {
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r.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, packBlobs []restic.Blob) bool {
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if packID.Equal(pack.id) {
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for _, blob := range packBlobs {
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if start > int64(blob.Offset) {
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start = int64(blob.Offset)
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}
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if end < int64(blob.Offset+blob.Length) {
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end = int64(blob.Offset + blob.Length)
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}
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}
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}
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return true // keep going
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})
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}
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packReader, err := r.packCache.get(pack.id, start, int(end-start), func(offset int64, length int, wr io.WriteSeeker) error {
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h := restic.Handle{Type: restic.DataFile, Name: pack.id.String()}
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return r.packLoader(ctx, h, length, offset, func(rd io.Reader) error {
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// reset the file in case of a download retry
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_, err := wr.Seek(0, io.SeekStart)
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if err != nil {
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return err
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}
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len, err := io.Copy(wr, rd)
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if err != nil {
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return err
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}
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if len != int64(length) {
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return errors.Errorf("unexpected pack size: expected %d but got %d", length, len)
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}
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return nil
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})
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})
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if err != nil {
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return nil, err
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}
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return packReader, nil
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}
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func (r *fileRestorer) processPack(ctx context.Context, request processingInfo, rd readerAtCloser) {
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defer rd.Close()
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for file := range request.files {
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target := r.targetPath(file.location)
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r.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, packBlobs []restic.Blob) bool {
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for _, blob := range packBlobs {
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debug.Log("Writing blob %s (%d bytes) from pack %s to %s", blob.ID.Str(), blob.Length, packID.Str(), file.location)
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buf, err := r.loadBlob(rd, blob)
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if err == nil {
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err = r.filesWriter.writeToFile(target, buf)
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}
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if err != nil {
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request.files[file] = err
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break // could not restore the file
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}
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}
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return false
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})
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}
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}
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func (r *fileRestorer) loadBlob(rd io.ReaderAt, blob restic.Blob) ([]byte, error) {
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// TODO reconcile with Repository#loadBlob implementation
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buf := make([]byte, blob.Length)
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n, err := rd.ReadAt(buf, int64(blob.Offset))
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if err != nil {
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return nil, err
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}
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if n != int(blob.Length) {
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return nil, errors.Errorf("error loading blob %v: wrong length returned, want %d, got %d", blob.ID.Str(), blob.Length, n)
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}
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// decrypt
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nonce, ciphertext := buf[:r.key.NonceSize()], buf[r.key.NonceSize():]
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plaintext, err := r.key.Open(ciphertext[:0], nonce, ciphertext, nil)
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if err != nil {
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return nil, errors.Errorf("decrypting blob %v failed: %v", blob.ID, err)
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}
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// check hash
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if !restic.Hash(plaintext).Equal(blob.ID) {
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return nil, errors.Errorf("blob %v returned invalid hash", blob.ID)
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}
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return plaintext, nil
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}
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