restorer: Allow writing target file blobs out of order

Much simpler implementation that guarantees each required pack
is downloaded only once (and hence does not need to manage
pack cache). Also improves large file restore performance.

Signed-off-by: Igor Fedorenko <igor@ifedorenko.com>

changelog/unreleased/pull-2195

@@ -0,0 +1,17 @@
+Enhancement: Simplify and improve restore performance
+
+Significantly improves restore performance of large files (i.e. 50M+):
+https://github.com/restic/restic/issues/2074
+https://forum.restic.net/t/restore-using-rclone-gdrive-backend-is-slow/1112/8
+https://forum.restic.net/t/degraded-restore-performance-s3-backend/1400
+
+Fixes "not enough cache capacity" error during restore:
+https://github.com/restic/restic/issues/2244
+
+NOTE: This new implementation does not guarantee order in which blobs
+are written to the target files and, for example, the last blob of a
+file can be written to the file before any of the preceeding file blobs.
+It is therefore possible to have gaps in the data written to the target
+files if restore fails or interrupted by the user.
+
+https://github.com/restic/restic/pull/2195

internal/restorer/doc.go

@@ -5,29 +5,20 @@
 // request and avoiding repeated downloads of the same pack. In addition,
 // several pack files are fetched concurrently.
 //
-// Here is high-level pseudo-code of the how the Restorer attempts to achieve
+// Here is high-level pseudo-code of how the Restorer attempts to achieve
 // these goals:
 //
 //   while there are packs to process
 //     choose a pack to process                      [1]
-//     get the pack from the backend or cache        [2]
+//     retrieve the pack from the backend            [2]
 //     write pack blobs to the files that need them  [3]
-//     if not all pack blobs were used
-//       cache the pack for future use               [4]
 //
-// Pack download and processing (steps [2] - [4]) runs on multiple concurrent
+// Retrieval of repository packs (step [2]) and writing target files (step [3])
-// Goroutines. The Restorer runs all steps [2]-[4] sequentially on the same
+// are performed concurrently on multiple goroutines.
-// Goroutine.
 //
-// Before a pack is downloaded (step [2]), the required space is "reserved" in
+// Implementation does not guarantee order in which blobs are written to the
-// the pack cache. Actual download uses single backend request to get all
+// target files and, for example, the last blob of a file can be written to the
-// required pack blobs. This may download blobs that are not needed, but we
+// file before any of the preceeding file blobs. It is therefore possible to
-// assume it'll still be faster than getting individual blobs.
+// have gaps in the data written to the target files if restore fails or
-//
+// interrupted by the user.
-// Target files are written (step [3]) in the "right" order, first file blob
-// first, then second, then third and so on. Blob write order implies that some
-// pack blobs may not be immediately used, i.e. they are "out of order" for
-// their respective target files. Packs with unused blobs are cached (step
-// [4]). The cache has capacity limit and may purge packs before they are fully
-// used, in which case the purged packs will need to be re-downloaded.
 package restorer

internal/restorer/filepacktraverser.go

@@ -1,52 +0,0 @@
-package restorer
-
-import (
-	"github.com/restic/restic/internal/errors"
-	"github.com/restic/restic/internal/restic"
-)
-
-type filePackTraverser struct {
-	lookup func(restic.ID, restic.BlobType) ([]restic.PackedBlob, bool)
-}
-
-// iterates over all remaining packs of the file
-func (t *filePackTraverser) forEachFilePack(file *fileInfo, fn func(packIdx int, packID restic.ID, packBlobs []restic.Blob) bool) error {
-	if len(file.blobs) == 0 {
-		return nil
-	}
-
-	getBlobPack := func(blobID restic.ID) (restic.PackedBlob, error) {
-		packs, found := t.lookup(blobID, restic.DataBlob)
-		if !found {
-			return restic.PackedBlob{}, errors.Errorf("Unknown blob %s", blobID.String())
-		}
-		// TODO which pack to use if multiple packs have the blob?
-		// MUST return the same pack for the same blob during the same execution
-		return packs[0], nil
-	}
-
-	var prevPackID restic.ID
-	var prevPackBlobs []restic.Blob
-	packIdx := 0
-	for _, blobID := range file.blobs {
-		packedBlob, err := getBlobPack(blobID)
-		if err != nil {
-			return err
-		}
-		if !prevPackID.IsNull() && prevPackID != packedBlob.PackID {
-			if !fn(packIdx, prevPackID, prevPackBlobs) {
-				return nil
-			}
-			packIdx++
-		}
-		if prevPackID != packedBlob.PackID {
-			prevPackID = packedBlob.PackID
-			prevPackBlobs = make([]restic.Blob, 0)
-		}
-		prevPackBlobs = append(prevPackBlobs, packedBlob.Blob)
-	}
-	if len(prevPackBlobs) > 0 {
-		fn(packIdx, prevPackID, prevPackBlobs)
-	}
-	return nil
-}

internal/restorer/filerestorer.go

@@ -1,9 +1,12 @@
 package restorer
 
 import (
+	"bytes"
 	"context"
 	"io"
+	"math"
 	"path/filepath"
+	"sync"
 
 	"github.com/restic/restic/internal/crypto"
 	"github.com/restic/restic/internal/debug"
@@ -15,66 +18,58 @@ import (
 // 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
-// TODO evaluate memory footprint for larger repositories, say 10M packs/10M files
-// TODO consider replacing pack file cache with blob cache
-// TODO avoid decrypting the same blob multiple times
-// TODO evaluate disabled debug logging overhead for large repositories
 
 const (
 	workerCount = 8
 
-	// max number of cached open output file handles
+	// fileInfo flags
-	filesWriterCacheCap = 32
+	fileProgress = 1
+	fileError    = 2
 
-	// estimated average pack size used to calculate pack cache capacity
+	largeFileBlobCount = 25
-	averagePackSize = 5 * 1024 * 1024
-
-	// pack cache capacity should support at least one cached pack per worker
-	// allow space for extra 5 packs for actual caching
-	packCacheCapacity = (workerCount + 5) * averagePackSize
 )
 
 // information about regular file being restored
 type fileInfo struct {
+	lock     sync.Mutex
+	flags    int
 	location string      // file on local filesystem relative to restorer basedir
-	blobs    []restic.ID // remaining blobs of the file
+	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 {
-	// the pack id
+	id    restic.ID              // the pack id
-	id restic.ID
+	files map[*fileInfo]struct{} // set of files that use blobs from this pack
-
-	// set of files that use blobs from this pack
-	files map[*fileInfo]struct{}
-
-	// number of other packs that must be downloaded before all blobs in this pack can be used
-	cost int
-
-	// used by packHeap
-	index int
 }
 
 // fileRestorer restores set of files
 type fileRestorer struct {
 	key        *crypto.Key
-	idx        filePackTraverser
+	idx        func(restic.ID, restic.BlobType) ([]restic.PackedBlob, bool)
 	packLoader func(ctx context.Context, h restic.Handle, length int, offset int64, fn func(rd io.Reader) error) error
 
-	packCache   *packCache   // pack cache
+	filesWriter *filesWriter
-	filesWriter *filesWriter // file write
 
 	dst   string
 	files []*fileInfo
 }
 
-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 {
+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.ID, restic.BlobType) ([]restic.PackedBlob, bool)) *fileRestorer {
+
 	return &fileRestorer{
-		packLoader:  packLoader,
 		key:         key,
 		idx:         idx,
-		filesWriter: newFilesWriter(filesWriterCacheCap),
+		packLoader:  packLoader,
-		packCache:   newPackCache(packCacheCapacity),
+		filesWriter: newFilesWriter(workerCount),
 		dst:         dst,
 	}
 }
@@ -87,237 +82,237 @@ func (r *fileRestorer) targetPath(location string) string {
 	return filepath.Join(r.dst, location)
 }
 
-// used to pass information among workers (wish golang channels allowed multivalues)
+func (r *fileRestorer) forEachBlob(blobIDs []restic.ID, fn func(packID restic.ID, packBlob restic.Blob)) error {
-type processingInfo struct {
+	if len(blobIDs) == 0 {
-	pack  *packInfo
+		return nil
-	files map[*fileInfo]error
-}
-
-func (r *fileRestorer) restoreFiles(ctx context.Context, onError func(path string, err error)) error {
-	// TODO conditionally enable when debug log is on
-	// for _, file := range r.files {
-	// 	dbgmsg := file.location + ": "
-	// 	r.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, packBlobs []restic.Blob) bool {
-	// 		if packIdx > 0 {
-	// 			dbgmsg += ", "
-	// 		}
-	// 		dbgmsg += "pack{id=" + packID.Str() + ", blobs: "
-	// 		for blobIdx, blob := range packBlobs {
-	// 			if blobIdx > 0 {
-	// 				dbgmsg += ", "
-	// 			}
-	// 			dbgmsg += blob.ID.Str()
-	// 		}
-	// 		dbgmsg += "}"
-	// 		return true // keep going
-	// 	})
-	// 	debug.Log(dbgmsg)
-	// }
-
-	inprogress := make(map[*fileInfo]struct{})
-	queue, err := newPackQueue(r.idx, r.files, func(files map[*fileInfo]struct{}) bool {
-		for file := range files {
-			if _, found := inprogress[file]; found {
-				return true
-			}
-		}
-		return false
-	})
-	if err != nil {
-		return err
 	}
 
-	// workers
+	for _, blobID := range blobIDs {
-	downloadCh := make(chan processingInfo)
+		packs, found := r.idx(blobID, restic.DataBlob)
-	feedbackCh := make(chan processingInfo)
+		if !found {
-
+			return errors.Errorf("Unknown blob %s", blobID.String())
-	defer close(downloadCh)
-	defer close(feedbackCh)
-
-	worker := func() {
-		for {
-			select {
-			case <-ctx.Done():
-				return
-			case request, ok := <-downloadCh:
-				if !ok {
-					return // channel closed
-				}
-				rd, err := r.downloadPack(ctx, request.pack)
-				if err == nil {
-					r.processPack(ctx, request, rd)
-				} else {
-					// mark all files as failed
-					for file := range request.files {
-						request.files[file] = err
-					}
-				}
-				feedbackCh <- request
-			}
-		}
-	}
-	for i := 0; i < workerCount; i++ {
-		go worker()
-	}
-
-	processFeedback := func(pack *packInfo, ferrors map[*fileInfo]error) {
-		// update files blobIdx
-		// must do it here to avoid race among worker and processing feedback threads
-		var success []*fileInfo
-		var failure []*fileInfo
-		for file, ferr := range ferrors {
-			target := r.targetPath(file.location)
-			if ferr != nil {
-				onError(file.location, ferr)
-				r.filesWriter.close(target)
-				delete(inprogress, file)
-				failure = append(failure, file)
-			} else {
-				r.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, packBlobs []restic.Blob) bool {
-					file.blobs = file.blobs[len(packBlobs):]
-					return false // only interesed in the first pack
-				})
-				if len(file.blobs) == 0 {
-					r.filesWriter.close(target)
-					delete(inprogress, file)
-				}
-				success = append(success, file)
-			}
-		}
-		// update the queue and requeueu the pack as necessary
-		if !queue.requeuePack(pack, success, failure) {
-			r.packCache.remove(pack.id)
-			debug.Log("Purged used up pack %s from pack cache", pack.id.Str())
-		}
-	}
-
-	// the main restore loop
-	for !queue.isEmpty() {
-		debug.Log("-----------------------------------")
-		pack, files := queue.nextPack()
-		if pack != nil {
-			ferrors := make(map[*fileInfo]error)
-			for _, file := range files {
-				ferrors[file] = nil
-				inprogress[file] = struct{}{}
-			}
-			select {
-			case <-ctx.Done():
-				return ctx.Err()
-			case downloadCh <- processingInfo{pack: pack, files: ferrors}:
-				debug.Log("Scheduled download pack %s (%d files)", pack.id.Str(), len(files))
-			case feedback := <-feedbackCh:
-				queue.requeuePack(pack, []*fileInfo{}, []*fileInfo{}) // didn't use the pack during this iteration
-				processFeedback(feedback.pack, feedback.files)
-			}
-		} else {
-			select {
-			case <-ctx.Done():
-				return ctx.Err()
-			case feedback := <-feedbackCh:
-				processFeedback(feedback.pack, feedback.files)
-			}
 		}
+		fn(packs[0].PackID, packs[0].Blob)
 	}
 
 	return nil
 }
 
-func (r *fileRestorer) downloadPack(ctx context.Context, pack *packInfo) (readerAtCloser, error) {
+func (r *fileRestorer) restoreFiles(ctx context.Context) error {
-	const MaxInt64 = 1<<63 - 1 // odd Go does not have this predefined somewhere
 
-	// calculate pack byte range
+	packs := make(map[restic.ID]*packInfo) // all packs
-	start, end := int64(MaxInt64), int64(0)
+
-	for file := range pack.files {
+	// create packInfo from fileInfo
-		r.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, packBlobs []restic.Blob) bool {
+	for _, file := range r.files {
-			if packID.Equal(pack.id) {
+		fileBlobs := file.blobs.(restic.IDs)
-				for _, blob := range packBlobs {
+		largeFile := len(fileBlobs) > largeFileBlobCount
-					if start > int64(blob.Offset) {
+		var packsMap map[restic.ID][]fileBlobInfo
-						start = int64(blob.Offset)
+		if largeFile {
-					}
+			packsMap = make(map[restic.ID][]fileBlobInfo)
-					if end < int64(blob.Offset+blob.Length) {
+		}
-						end = int64(blob.Offset + blob.Length)
+		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]
-			return true // keep going
+			if !ok {
+				pack = &packInfo{
+					id:    packID,
+					files: make(map[*fileInfo]struct{}),
+				}
+				packs[packID] = pack
+			}
+			pack.files[file] = struct{}{}
 		})
+		if err != nil {
+			// repository index is messed up, can't do anything
+			return err
+		}
+		if largeFile {
+			file.blobs = packsMap
+		}
 	}
 
-	packReader, err := r.packCache.get(pack.id, start, int(end-start), func(offset int64, length int, wr io.WriteSeeker) error {
+	var wg sync.WaitGroup
-		h := restic.Handle{Type: restic.DataFile, Name: pack.id.String()}
+	downloadCh := make(chan *packInfo)
-		return r.packLoader(ctx, h, length, offset, func(rd io.Reader) error {
+	worker := func() {
-			// reset the file in case of a download retry
+		defer wg.Done()
-			_, err := wr.Seek(0, io.SeekStart)
+		for {
-			if err != nil {
+			select {
-				return err
+			case <-ctx.Done():
+				return // context cancelled
+			case pack, ok := <-downloadCh:
+				if !ok {
+					return // channel closed
+				}
+				r.downloadPack(ctx, pack)
 			}
+		}
+	}
+	for i := 0; i < workerCount; i++ {
+		go worker()
+		wg.Add(1)
+	}
 
-			len, err := io.Copy(wr, rd)
+	// the main restore loop
-			if err != nil {
+	for _, pack := range packs {
-				return err
+		select {
-			}
+		case <-ctx.Done():
-			if len != int64(length) {
+			return ctx.Err()
-				return errors.Errorf("unexpected pack size: expected %d but got %d", length, len)
+		case downloadCh <- pack:
-			}
+			debug.Log("Scheduled download pack %s", pack.id.Str())
+		}
+	}
 
-			return nil
+	close(downloadCh)
-		})
+	wg.Wait()
+
+	return nil
+}
+
+func (r *fileRestorer) downloadPack(ctx context.Context, pack *packInfo) {
+
+	// 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
 	})
-	if err != nil {
+	for file := range pack.files {
-		return nil, err
+		addBlob := func(blob restic.Blob, fileOffset int64) {
-	}
+			if start > int64(blob.Offset) {
-
+				start = int64(blob.Offset)
-	return packReader, nil
+			}
-}
+			if end < int64(blob.Offset+blob.Length) {
-
+				end = int64(blob.Offset + blob.Length)
-func (r *fileRestorer) processPack(ctx context.Context, request processingInfo, rd readerAtCloser) {
+			}
-	defer rd.Close()
+			blobInfo, ok := blobs[blob.ID]
-
+			if !ok {
-	for file := range request.files {
+				blobInfo.offset = int64(blob.Offset)
-		target := r.targetPath(file.location)
+				blobInfo.length = int(blob.Length)
-		r.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, packBlobs []restic.Blob) bool {
+				blobInfo.files = make(map[*fileInfo][]int64)
-			for _, blob := range packBlobs {
+				blobs[blob.ID] = blobInfo
-				debug.Log("Writing blob %s (%d bytes) from pack %s to %s", blob.ID.Str(), blob.Length, packID.Str(), file.location)
+			}
-				buf, err := r.loadBlob(rd, blob)
+			blobInfo.files[file] = append(blobInfo.files[file], fileOffset)
-				if err == nil {
+		}
-					err = r.filesWriter.writeToFile(target, buf)
+		if fileBlobs, ok := file.blobs.(restic.IDs); ok {
+			fileOffset := int64(0)
+			r.forEachBlob(fileBlobs, func(packID restic.ID, blob restic.Blob) {
+				if packID.Equal(pack.id) {
+					addBlob(blob, fileOffset)
 				}
-				if err != nil {
+				fileOffset += int64(blob.Length) - crypto.Extension
-					request.files[file] = err
+			})
-					break // could not restore the file
+		} else if packsMap, ok := file.blobs.(map[restic.ID][]fileBlobInfo); ok {
+			for _, blob := range packsMap[pack.id] {
+				idxPacks, found := r.idx(blob.id, restic.DataBlob)
+				if found {
+					for _, idxPack := range idxPacks {
+						if idxPack.PackID.Equal(pack.id) {
+							addBlob(idxPack.Blob, blob.offset)
+							break
+						}
+					}
 				}
 			}
-			return false
+		}
-		})
+	}
+
+	packData := make([]byte, int(end-start))
+
+	h := restic.Handle{Type: restic.DataFile, Name: pack.id.String()}
+	err := r.packLoader(ctx, h, int(end-start), start, func(rd io.Reader) error {
+		l, err := io.ReadFull(rd, packData)
+		if err != nil {
+			return err
+		}
+		if l != len(packData) {
+			return errors.Errorf("unexpected pack size: expected %d but got %d", len(packData), l)
+		}
+		return nil
+	})
+
+	markFileError := func(file *fileInfo, err error) {
+		file.lock.Lock()
+		defer file.lock.Unlock()
+		if file.flags&fileError == 0 {
+			file.flags |= fileError
+		}
+	}
+
+	if err != nil {
+		for file := range pack.files {
+			markFileError(file, err)
+		}
+		return
+	}
+
+	rd := bytes.NewReader(packData)
+
+	for blobID, blob := range blobs {
+		blobData, err := r.loadBlob(rd, blobID, blob.offset-start, blob.length)
+		if err != nil {
+			for file := range blob.files {
+				markFileError(file, err)
+			}
+			continue
+		}
+		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
+					file.lock.Lock()
+					create := file.flags&fileProgress == 0
+					if create {
+						defer file.lock.Unlock()
+						file.flags |= fileProgress
+					} else {
+						file.lock.Unlock()
+					}
+					return r.filesWriter.writeToFile(r.targetPath(file.location), blobData, offset, create)
+				}
+				err := writeToFile()
+				if err != nil {
+					markFileError(file, err)
+					break
+				}
+			}
+		}
 	}
 }
 
-func (r *fileRestorer) loadBlob(rd io.ReaderAt, blob restic.Blob) ([]byte, error) {
+func (r *fileRestorer) loadBlob(rd io.ReaderAt, blobID restic.ID, offset int64, length int) ([]byte, error) {
 	// TODO reconcile with Repository#loadBlob implementation
 
-	buf := make([]byte, blob.Length)
+	buf := make([]byte, length)
 
-	n, err := rd.ReadAt(buf, int64(blob.Offset))
+	n, err := rd.ReadAt(buf, offset)
 	if err != nil {
 		return nil, err
 	}
 
-	if n != int(blob.Length) {
+	if n != length {
-		return nil, errors.Errorf("error loading blob %v: wrong length returned, want %d, got %d", blob.ID.Str(), blob.Length, n)
+		return 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, errors.Errorf("decrypting blob %v failed: %v", blob.ID, err)
+		return nil, errors.Errorf("decrypting blob %v failed: %v", blobID, err)
 	}
 
 	// check hash
-	if !restic.Hash(plaintext).Equal(blob.ID) {
+	if !restic.Hash(plaintext).Equal(blobID) {
-		return nil, errors.Errorf("blob %v returned invalid hash", blob.ID)
+		return nil, errors.Errorf("blob %v returned invalid hash", blobID)
 	}
 
 	return plaintext, nil

internal/restorer/filerestorer_test.go

@@ -8,7 +8,6 @@ import (
 	"testing"
 
 	"github.com/restic/restic/internal/crypto"
-	"github.com/restic/restic/internal/errors"
 	"github.com/restic/restic/internal/restic"
 	rtest "github.com/restic/restic/internal/test"
 )
@@ -38,9 +37,6 @@ type TestRepo struct {
 
 	//
 	loader func(ctx context.Context, h restic.Handle, length int, offset int64, fn func(rd io.Reader) error) error
-
-	//
-	idx filePackTraverser
 }
 
 func (i *TestRepo) Lookup(blobID restic.ID, _ restic.BlobType) ([]restic.PackedBlob, bool) {
@@ -56,11 +52,6 @@ func (i *TestRepo) packID(name string) restic.ID {
 	return i.packsNameToID[name]
 }
 
-func (i *TestRepo) pack(queue *packQueue, name string) *packInfo {
-	id := i.packsNameToID[name]
-	return queue.packs[id]
-}
-
 func (i *TestRepo) fileContent(file *fileInfo) string {
 	return i.filesPathToContent[file.location]
 }
@@ -147,7 +138,6 @@ func newTestRepo(content []TestFile) *TestRepo {
 		files:              files,
 		filesPathToContent: filesPathToContent,
 	}
-	repo.idx = filePackTraverser{lookup: repo.Lookup}
 	repo.loader = func(ctx context.Context, h restic.Handle, length int, offset int64, fn func(rd io.Reader) error) error {
 		packID, err := restic.ParseID(h.Name)
 		if err != nil {
@@ -163,12 +153,11 @@ func newTestRepo(content []TestFile) *TestRepo {
 func restoreAndVerify(t *testing.T, tempdir string, content []TestFile) {
 	repo := newTestRepo(content)
 
-	r := newFileRestorer(tempdir, repo.loader, repo.key, repo.idx)
+	r := newFileRestorer(tempdir, repo.loader, repo.key, repo.Lookup)
 	r.files = repo.files
 
-	r.restoreFiles(context.TODO(), func(path string, err error) {
+	err := r.restoreFiles(context.TODO())
-		rtest.OK(t, errors.Wrapf(err, "unexpected error"))
+	rtest.OK(t, err)
-	})
 
 	for _, file := range repo.files {
 		target := r.targetPath(file.location)
@@ -178,16 +167,11 @@ func restoreAndVerify(t *testing.T, tempdir string, content []TestFile) {
 			continue
 		}
 
-		_, contains := r.filesWriter.cache[target]
-		rtest.Equals(t, false, contains)
-
 		content := repo.fileContent(file)
 		if !bytes.Equal(data, []byte(content)) {
 			t.Errorf("file %v has wrong content: want %q, got %q", file.location, content, data)
 		}
 	}
-
-	rtest.OK(t, nil)
 }
 
 func TestFileRestorerBasic(t *testing.T) {
@@ -209,5 +193,13 @@ func TestFileRestorerBasic(t *testing.T) {
 				TestBlob{"data2-2", "pack2-2"},
 			},
 		},
+		TestFile{
+			name: "file3",
+			blobs: []TestBlob{
+				// same blob multiple times
+				TestBlob{"data3-1", "pack3-1"},
+				TestBlob{"data3-1", "pack3-1"},
+			},
+		},
 	})
 }

internal/restorer/fileswriter.go

@@ -4,98 +4,89 @@ import (
 	"os"
 	"sync"
 
-	"github.com/restic/restic/internal/debug"
+	"github.com/cespare/xxhash"
-	"github.com/restic/restic/internal/errors"
 )
 
-// Writes blobs to output files. Each file is written sequentially,
+// writes blobs to target files.
-// start to finish, but multiple files can be written to concurrently.
+// multiple files can be written to concurrently.
-// Implementation allows virtually unlimited number of logically open
+// multiple blobs can be concurrently written to the same file.
-// files, but number of phisically open files will never exceed number
+// TODO I am not 100% convinced this is necessary, i.e. it may be okay
-// of concurrent writeToFile invocations plus cacheCap.
+//      to use multiple os.File to write to the same target file
 type filesWriter struct {
-	lock       sync.Mutex          // guards concurrent access to open files cache
+	buckets []filesWriterBucket
-	inprogress map[string]struct{} // (logically) opened file writers
-	cache      map[string]*os.File // cache of open files
-	cacheCap   int                 // max number of cached open files
 }
 
-func newFilesWriter(cacheCap int) *filesWriter {
+type filesWriterBucket struct {
+	lock  sync.Mutex
+	files map[string]*os.File
+	users map[string]int
+}
+
+func newFilesWriter(count int) *filesWriter {
+	buckets := make([]filesWriterBucket, count)
+	for b := 0; b < count; b++ {
+		buckets[b].files = make(map[string]*os.File)
+		buckets[b].users = make(map[string]int)
+	}
 	return &filesWriter{
-		inprogress: make(map[string]struct{}),
+		buckets: buckets,
-		cache:      make(map[string]*os.File),
-		cacheCap:   cacheCap,
 	}
 }
 
-func (w *filesWriter) writeToFile(path string, blob []byte) error {
+func (w *filesWriter) writeToFile(path string, blob []byte, offset int64, create bool) error {
-	// First writeToFile invocation for any given path will:
+	bucket := &w.buckets[uint(xxhash.Sum64String(path))%uint(len(w.buckets))]
-	// - create and open the file
-	// - write the blob to the file
-	// - cache the open file if there is space, close the file otherwise
-	// Subsequent invocations will:
-	// - remove the open file from the cache _or_ open the file for append
-	// - write the blob to the file
-	// - cache the open file if there is space, close the file otherwise
-	// The idea is to cap maximum number of open files with minimal
-	// coordination among concurrent writeToFile invocations (note that
-	// writeToFile never touches somebody else's open file).
 
-	// TODO measure if caching is useful (likely depends on operating system
-	// and hardware configuration)
 	acquireWriter := func() (*os.File, error) {
-		w.lock.Lock()
+		bucket.lock.Lock()
-		defer w.lock.Unlock()
+		defer bucket.lock.Unlock()
-		if wr, ok := w.cache[path]; ok {
+
-			debug.Log("Used cached writer for %s", path)
+		if wr, ok := bucket.files[path]; ok {
-			delete(w.cache, path)
+			bucket.users[path]++
 			return wr, nil
 		}
+
 		var flags int
-		if _, append := w.inprogress[path]; append {
+		if create {
-			flags = os.O_APPEND | os.O_WRONLY
-		} else {
-			w.inprogress[path] = struct{}{}
 			flags = os.O_CREATE | os.O_TRUNC | os.O_WRONLY
+		} else {
+			flags = os.O_WRONLY
 		}
+
 		wr, err := os.OpenFile(path, flags, 0600)
 		if err != nil {
 			return nil, err
 		}
-		debug.Log("Opened writer for %s", path)
+
+		bucket.files[path] = wr
+		bucket.users[path] = 1
+
 		return wr, nil
 	}
-	cacheOrCloseWriter := func(wr *os.File) {
+
-		w.lock.Lock()
+	releaseWriter := func(wr *os.File) error {
-		defer w.lock.Unlock()
+		bucket.lock.Lock()
-		if len(w.cache) < w.cacheCap {
+		defer bucket.lock.Unlock()
-			w.cache[path] = wr
+
-		} else {
+		if bucket.users[path] == 1 {
-			wr.Close()
+			delete(bucket.files, path)
+			delete(bucket.users, path)
+			return wr.Close()
 		}
+		bucket.users[path]--
+		return nil
 	}
 
 	wr, err := acquireWriter()
 	if err != nil {
 		return err
 	}
-	n, err := wr.Write(blob)
+
-	cacheOrCloseWriter(wr)
+	_, err = wr.WriteAt(blob, offset)
+
 	if err != nil {
+		releaseWriter(wr)
 		return err
 	}
-	if n != len(blob) {
-		return errors.Errorf("error writing file %v: wrong length written, want %d, got %d", path, len(blob), n)
-	}
-	return nil
-}
 
-func (w *filesWriter) close(path string) {
+	return releaseWriter(wr)
-	w.lock.Lock()
-	defer w.lock.Unlock()
-	if wr, ok := w.cache[path]; ok {
-		wr.Close()
-		delete(w.cache, path)
-	}
-	delete(w.inprogress, path)
 }

internal/restorer/fileswriter_test.go

@@ -16,23 +16,21 @@ func TestFilesWriterBasic(t *testing.T) {
 	f1 := dir + "/f1"
 	f2 := dir + "/f2"
 
-	rtest.OK(t, w.writeToFile(f1, []byte{1}))
+	rtest.OK(t, w.writeToFile(f1, []byte{1}, 0, true))
-	rtest.Equals(t, 1, len(w.cache))
+	rtest.Equals(t, 0, len(w.buckets[0].files))
-	rtest.Equals(t, 1, len(w.inprogress))
+	rtest.Equals(t, 0, len(w.buckets[0].users))
 
-	rtest.OK(t, w.writeToFile(f2, []byte{2}))
+	rtest.OK(t, w.writeToFile(f2, []byte{2}, 0, true))
-	rtest.Equals(t, 1, len(w.cache))
+	rtest.Equals(t, 0, len(w.buckets[0].files))
-	rtest.Equals(t, 2, len(w.inprogress))
+	rtest.Equals(t, 0, len(w.buckets[0].users))
 
-	rtest.OK(t, w.writeToFile(f1, []byte{1}))
+	rtest.OK(t, w.writeToFile(f1, []byte{1}, 1, false))
-	w.close(f1)
+	rtest.Equals(t, 0, len(w.buckets[0].files))
-	rtest.Equals(t, 0, len(w.cache))
+	rtest.Equals(t, 0, len(w.buckets[0].users))
-	rtest.Equals(t, 1, len(w.inprogress))
 
-	rtest.OK(t, w.writeToFile(f2, []byte{2}))
+	rtest.OK(t, w.writeToFile(f2, []byte{2}, 1, false))
-	w.close(f2)
+	rtest.Equals(t, 0, len(w.buckets[0].files))
-	rtest.Equals(t, 0, len(w.cache))
+	rtest.Equals(t, 0, len(w.buckets[0].users))
-	rtest.Equals(t, 0, len(w.inprogress))
 
 	buf, err := ioutil.ReadFile(f1)
 	rtest.OK(t, err)

internal/restorer/packcache.go

@@ -1,243 +0,0 @@
-package restorer
-
-import (
-	"io"
-	"sync"
-
-	"github.com/restic/restic/internal/debug"
-	"github.com/restic/restic/internal/errors"
-	"github.com/restic/restic/internal/restic"
-)
-
-// packCache is thread safe in-memory cache of pack files required to restore
-// one or more files. The cache is meant to hold pack files that cannot be
-// fully used right away. This happens when pack files contains blobs from
-// "head" of some files and "middle" of other files. "Middle" blobs cannot be
-// written to their files until after blobs from some other packs are written
-// to the files first.
-//
-// While the cache is thread safe, implementation assumes (and enforces)
-// that individual entries are used by one client at a time. Clients must
-// #Close() entry's reader to make the entry available for use by other
-// clients. This limitation can be relaxed in the future if necessary.
-type packCache struct {
-	// guards access to cache internal data structures
-	lock sync.Mutex
-
-	// cache capacity
-	capacity          int
-	reservedCapacity  int
-	allocatedCapacity int
-
-	// pack records currently being used by active restore worker
-	reservedPacks map[restic.ID]*packCacheRecord
-
-	// unused allocated packs, can be deleted if necessary
-	cachedPacks map[restic.ID]*packCacheRecord
-}
-
-type packCacheRecord struct {
-	master *packCacheRecord
-	cache  *packCache
-
-	id     restic.ID // cached pack id
-	offset int64     // cached pack byte range
-
-	data []byte
-}
-
-type readerAtCloser interface {
-	io.Closer
-	io.ReaderAt
-}
-
-type bytesWriteSeeker struct {
-	pos  int
-	data []byte
-}
-
-func (wr *bytesWriteSeeker) Write(p []byte) (n int, err error) {
-	if wr.pos+len(p) > len(wr.data) {
-		return -1, errors.Errorf("not enough space")
-	}
-	n = copy(wr.data[wr.pos:], p)
-	wr.pos += n
-	return n, nil
-}
-
-func (wr *bytesWriteSeeker) Seek(offset int64, whence int) (int64, error) {
-	if offset != 0 || whence != io.SeekStart {
-		return -1, errors.Errorf("unsupported seek request")
-	}
-	wr.pos = 0
-	return 0, nil
-}
-
-func newPackCache(capacity int) *packCache {
-	return &packCache{
-		capacity:      capacity,
-		reservedPacks: make(map[restic.ID]*packCacheRecord),
-		cachedPacks:   make(map[restic.ID]*packCacheRecord),
-	}
-}
-
-func (c *packCache) reserve(packID restic.ID, offset int64, length int) (record *packCacheRecord, err error) {
-	c.lock.Lock()
-	defer c.lock.Unlock()
-
-	if offset < 0 || length <= 0 {
-		return nil, errors.Errorf("illegal pack cache allocation range %s {offset: %d, length: %d}", packID.Str(), offset, length)
-	}
-
-	if c.reservedCapacity+length > c.capacity {
-		return nil, errors.Errorf("not enough cache capacity: requested %d, available %d", length, c.capacity-c.reservedCapacity)
-	}
-
-	if _, ok := c.reservedPacks[packID]; ok {
-		return nil, errors.Errorf("pack is already reserved %s", packID.Str())
-	}
-
-	// the pack is available in the cache and currently unused
-	if pack, ok := c.cachedPacks[packID]; ok {
-		// check if cached pack includes requested byte range
-		// the range can shrink, but it never grows bigger unless there is a bug elsewhere
-		if pack.offset > offset || (pack.offset+int64(len(pack.data))) < (offset+int64(length)) {
-			return nil, errors.Errorf("cached range %d-%d is smaller than requested range %d-%d for pack %s", pack.offset, pack.offset+int64(len(pack.data)), length, offset+int64(length), packID.Str())
-		}
-
-		// move the pack to the used map
-		delete(c.cachedPacks, packID)
-		c.reservedPacks[packID] = pack
-		c.reservedCapacity += len(pack.data)
-
-		debug.Log("Using cached pack %s (%d bytes)", pack.id.Str(), len(pack.data))
-
-		if pack.offset != offset || len(pack.data) != length {
-			// restrict returned record to requested range
-			return &packCacheRecord{
-				cache:  c,
-				master: pack,
-				offset: offset,
-				data:   pack.data[int(offset-pack.offset) : int(offset-pack.offset)+length],
-			}, nil
-		}
-
-		return pack, nil
-	}
-
-	for c.allocatedCapacity+length > c.capacity {
-		// all cached packs will be needed at some point
-		// so it does not matter which one to purge
-		for _, cached := range c.cachedPacks {
-			delete(c.cachedPacks, cached.id)
-			c.allocatedCapacity -= len(cached.data)
-			debug.Log("dropped cached pack %s (%d bytes)", cached.id.Str(), len(cached.data))
-			break
-		}
-	}
-
-	pack := &packCacheRecord{
-		cache:  c,
-		id:     packID,
-		offset: offset,
-	}
-	c.reservedPacks[pack.id] = pack
-	c.allocatedCapacity += length
-	c.reservedCapacity += length
-
-	return pack, nil
-}
-
-// get returns reader of the specified cached pack. Uses provided load func
-// to download pack content if necessary.
-// The returned reader is only able to read pack within byte range specified
-// by offset and length parameters, attempts to read outside that range will
-// result in an error.
-// The returned reader must be closed before the same packID can be requested
-// from the cache again.
-func (c *packCache) get(packID restic.ID, offset int64, length int, load func(offset int64, length int, wr io.WriteSeeker) error) (readerAtCloser, error) {
-	pack, err := c.reserve(packID, offset, length)
-	if err != nil {
-		return nil, err
-	}
-
-	if pack.data == nil {
-		releasePack := func() {
-			delete(c.reservedPacks, pack.id)
-			c.reservedCapacity -= length
-			c.allocatedCapacity -= length
-		}
-		wr := &bytesWriteSeeker{data: make([]byte, length)}
-		err = load(offset, length, wr)
-		if err != nil {
-			releasePack()
-			return nil, err
-		}
-		if wr.pos != length {
-			releasePack()
-			return nil, errors.Errorf("invalid read size")
-		}
-		pack.data = wr.data
-		debug.Log("Downloaded and cached pack %s (%d bytes)", pack.id.Str(), len(pack.data))
-	}
-
-	return pack, nil
-}
-
-// releases the pack record back to the cache
-func (c *packCache) release(pack *packCacheRecord) error {
-	c.lock.Lock()
-	defer c.lock.Unlock()
-
-	if _, ok := c.reservedPacks[pack.id]; !ok {
-		return errors.Errorf("invalid pack release request")
-	}
-
-	delete(c.reservedPacks, pack.id)
-	c.cachedPacks[pack.id] = pack
-	c.reservedCapacity -= len(pack.data)
-
-	return nil
-}
-
-// remove removes specified pack from the cache and frees
-// corresponding cache space. should be called after the pack
-// was fully used up by the restorer.
-func (c *packCache) remove(packID restic.ID) error {
-	c.lock.Lock()
-	defer c.lock.Unlock()
-
-	if _, ok := c.reservedPacks[packID]; ok {
-		return errors.Errorf("invalid pack remove request, pack %s is reserved", packID.Str())
-	}
-
-	pack, ok := c.cachedPacks[packID]
-	if !ok {
-		return errors.Errorf("invalid pack remove request, pack %s is not cached", packID.Str())
-	}
-
-	delete(c.cachedPacks, pack.id)
-	c.allocatedCapacity -= len(pack.data)
-
-	return nil
-}
-
-// ReadAt reads len(b) bytes from the pack starting at byte offset off.
-// It returns the number of bytes read and the error, if any.
-func (r *packCacheRecord) ReadAt(b []byte, off int64) (n int, err error) {
-	if off < r.offset || off+int64(len(b)) > r.offset+int64(len(r.data)) {
-		return -1, errors.Errorf("read outside available range")
-	}
-	return copy(b, r.data[off-r.offset:]), nil
-}
-
-// Close closes the pack reader and releases corresponding cache record
-// to the cache. Once closed, the record can be reused by subsequent
-// requests for the same packID or it can be purged from the cache to make
-// room for other packs
-func (r *packCacheRecord) Close() (err error) {
-	if r.master != nil {
-		return r.cache.release(r.master)
-	}
-	return r.cache.release(r)
-}

internal/restorer/packcache_test.go

@@ -1,305 +0,0 @@
-package restorer
-
-import (
-	"io"
-	"testing"
-
-	"github.com/restic/restic/internal/errors"
-	"github.com/restic/restic/internal/restic"
-	rtest "github.com/restic/restic/internal/test"
-)
-
-func assertNotOK(t *testing.T, msg string, err error) {
-	rtest.Assert(t, err != nil, msg+" did not fail")
-}
-
-func TestBytesWriterSeeker(t *testing.T) {
-	wr := &bytesWriteSeeker{data: make([]byte, 10)}
-
-	n, err := wr.Write([]byte{1, 2})
-	rtest.OK(t, err)
-	rtest.Equals(t, 2, n)
-	rtest.Equals(t, []byte{1, 2}, wr.data[0:2])
-
-	n64, err := wr.Seek(0, io.SeekStart)
-	rtest.OK(t, err)
-	rtest.Equals(t, int64(0), n64)
-
-	n, err = wr.Write([]byte{0, 1, 2, 3, 4})
-	rtest.OK(t, err)
-	rtest.Equals(t, 5, n)
-	n, err = wr.Write([]byte{5, 6, 7, 8, 9})
-	rtest.OK(t, err)
-	rtest.Equals(t, 5, n)
-	rtest.Equals(t, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, wr.data)
-
-	// negative tests
-	_, err = wr.Write([]byte{1})
-	assertNotOK(t, "write overflow", err)
-	_, err = wr.Seek(1, io.SeekStart)
-	assertNotOK(t, "unsupported seek", err)
-}
-
-func TestPackCacheBasic(t *testing.T) {
-	assertReader := func(expected []byte, offset int64, rd io.ReaderAt) {
-		actual := make([]byte, len(expected))
-		rd.ReadAt(actual, offset)
-		rtest.Equals(t, expected, actual)
-	}
-
-	c := newPackCache(10)
-
-	id := restic.NewRandomID()
-
-	// load pack to the cache
-	rd, err := c.get(id, 10, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		rtest.Equals(t, int64(10), offset)
-		rtest.Equals(t, 5, length)
-		wr.Write([]byte{1, 2, 3, 4, 5})
-		return nil
-	})
-	rtest.OK(t, err)
-	assertReader([]byte{1, 2, 3, 4, 5}, 10, rd)
-
-	// must close pack reader before can request it again
-	_, err = c.get(id, 10, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		t.Error("unexpected cache load call")
-		return nil
-	})
-	assertNotOK(t, "double-reservation", err)
-
-	// close the pack reader and get it from cache
-	rd.Close()
-	rd, err = c.get(id, 10, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		t.Error("unexpected cache load call")
-		return nil
-	})
-	rtest.OK(t, err)
-	assertReader([]byte{1, 2, 3, 4, 5}, 10, rd)
-
-	// close the pack reader and remove the pack from cache, assert the pack is loaded on request
-	rd.Close()
-	c.remove(id)
-	rd, err = c.get(id, 10, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		rtest.Equals(t, int64(10), offset)
-		rtest.Equals(t, 5, length)
-		wr.Write([]byte{1, 2, 3, 4, 5})
-		return nil
-	})
-	rtest.OK(t, err)
-	assertReader([]byte{1, 2, 3, 4, 5}, 10, rd)
-}
-
-func TestPackCacheInvalidRange(t *testing.T) {
-	c := newPackCache(10)
-
-	id := restic.NewRandomID()
-
-	_, err := c.get(id, -1, 1, func(offset int64, length int, wr io.WriteSeeker) error {
-		t.Error("unexpected cache load call")
-		return nil
-	})
-	assertNotOK(t, "negative offset request", err)
-
-	_, err = c.get(id, 0, 0, func(offset int64, length int, wr io.WriteSeeker) error {
-		t.Error("unexpected cache load call")
-		return nil
-	})
-	assertNotOK(t, "zero length request", err)
-
-	_, err = c.get(id, 0, -1, func(offset int64, length int, wr io.WriteSeeker) error {
-		t.Error("unexpected cache load call")
-		return nil
-	})
-	assertNotOK(t, "negative length", err)
-}
-
-func TestPackCacheCapacity(t *testing.T) {
-	c := newPackCache(10)
-
-	id1, id2, id3 := restic.NewRandomID(), restic.NewRandomID(), restic.NewRandomID()
-
-	// load and reserve pack1
-	rd1, err := c.get(id1, 0, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		wr.Write([]byte{1, 2, 3, 4, 5})
-		return nil
-	})
-	rtest.OK(t, err)
-
-	// load and reserve pack2
-	_, err = c.get(id2, 0, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		wr.Write([]byte{1, 2, 3, 4, 5})
-		return nil
-	})
-	rtest.OK(t, err)
-
-	// can't load pack3 because not enough space in the cache
-	_, err = c.get(id3, 0, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		t.Error("unexpected cache load call")
-		return nil
-	})
-	assertNotOK(t, "request over capacity", err)
-
-	// release pack1 and try again
-	rd1.Close()
-	rd3, err := c.get(id3, 0, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		wr.Write([]byte{1, 2, 3, 4, 5})
-		return nil
-	})
-	rtest.OK(t, err)
-
-	// release pack3 and load pack1 (should not come from cache)
-	rd3.Close()
-	loaded := false
-	rd1, err = c.get(id1, 0, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		wr.Write([]byte{1, 2, 3, 4, 5})
-		loaded = true
-		return nil
-	})
-	rtest.OK(t, err)
-	rtest.Equals(t, true, loaded)
-}
-
-func TestPackCacheDownsizeRecord(t *testing.T) {
-	c := newPackCache(10)
-
-	id := restic.NewRandomID()
-
-	// get bigger range first
-	rd, err := c.get(id, 5, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		wr.Write([]byte{1, 2, 3, 4, 5})
-		return nil
-	})
-	rtest.OK(t, err)
-	rd.Close()
-
-	// invalid "resize" requests
-	_, err = c.get(id, 5, 10, func(offset int64, length int, wr io.WriteSeeker) error {
-		t.Error("unexpected pack load")
-		return nil
-	})
-	assertNotOK(t, "resize cached record", err)
-
-	// invalid before cached range request
-	_, err = c.get(id, 0, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		t.Error("unexpected pack load")
-		return nil
-	})
-	assertNotOK(t, "before cached range request", err)
-
-	// invalid after cached range request
-	_, err = c.get(id, 10, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		t.Error("unexpected pack load")
-		return nil
-	})
-	assertNotOK(t, "after cached range request", err)
-
-	// now get smaller "nested" range
-	rd, err = c.get(id, 7, 1, func(offset int64, length int, wr io.WriteSeeker) error {
-		t.Error("unexpected pack load")
-		return nil
-	})
-	rtest.OK(t, err)
-
-	// assert expected data
-	buf := make([]byte, 1)
-	rd.ReadAt(buf, 7)
-	rtest.Equals(t, byte(3), buf[0])
-	_, err = rd.ReadAt(buf, 0)
-	assertNotOK(t, "read before downsized pack range", err)
-	_, err = rd.ReadAt(buf, 9)
-	assertNotOK(t, "read after downsized pack range", err)
-
-	// can't request downsized record again
-	_, err = c.get(id, 7, 1, func(offset int64, length int, wr io.WriteSeeker) error {
-		t.Error("unexpected pack load")
-		return nil
-	})
-	assertNotOK(t, "double-allocation of cache record subrange", err)
-
-	// can't request another subrange of the original record
-	_, err = c.get(id, 6, 1, func(offset int64, length int, wr io.WriteSeeker) error {
-		t.Error("unexpected pack load")
-		return nil
-	})
-	assertNotOK(t, "allocation of another subrange of cache record", err)
-
-	// release downsized record and assert the original is back in the cache
-	rd.Close()
-	rd, err = c.get(id, 5, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		t.Error("unexpected pack load")
-		return nil
-	})
-	rtest.OK(t, err)
-	rd.Close()
-}
-
-func TestPackCacheFailedDownload(t *testing.T) {
-	c := newPackCache(10)
-	assertEmpty := func() {
-		rtest.Equals(t, 0, len(c.cachedPacks))
-		rtest.Equals(t, 10, c.capacity)
-		rtest.Equals(t, 0, c.reservedCapacity)
-		rtest.Equals(t, 0, c.allocatedCapacity)
-	}
-
-	_, err := c.get(restic.NewRandomID(), 0, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		return errors.Errorf("expected induced test error")
-	})
-	assertNotOK(t, "not enough bytes read", err)
-	assertEmpty()
-
-	_, err = c.get(restic.NewRandomID(), 0, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		wr.Write([]byte{1})
-		return nil
-	})
-	assertNotOK(t, "not enough bytes read", err)
-	assertEmpty()
-
-	_, err = c.get(restic.NewRandomID(), 0, 5, func(offset int64, length int, wr io.WriteSeeker) error {
-		wr.Write([]byte{1, 2, 3, 4, 5, 6})
-		return nil
-	})
-	assertNotOK(t, "too many bytes read", err)
-	assertEmpty()
-}
-
-func TestPackCacheInvalidRequests(t *testing.T) {
-	c := newPackCache(10)
-
-	id := restic.NewRandomID()
-
-	//
-	rd, _ := c.get(id, 0, 1, func(offset int64, length int, wr io.WriteSeeker) error {
-		wr.Write([]byte{1})
-		return nil
-	})
-	assertNotOK(t, "remove() reserved pack", c.remove(id))
-	rtest.OK(t, rd.Close())
-	assertNotOK(t, "multiple reader Close() calls)", rd.Close())
-
-	//
-	rtest.OK(t, c.remove(id))
-	assertNotOK(t, "double remove() the same pack", c.remove(id))
-}
-
-func TestPackCacheRecord(t *testing.T) {
-	rd := &packCacheRecord{
-		offset: 10,
-		data:   []byte{1},
-	}
-	buf := make([]byte, 1)
-	n, err := rd.ReadAt(buf, 10)
-	rtest.OK(t, err)
-	rtest.Equals(t, 1, n)
-	rtest.Equals(t, byte(1), buf[0])
-
-	_, err = rd.ReadAt(buf, 0)
-	assertNotOK(t, "read before loaded range", err)
-
-	_, err = rd.ReadAt(buf, 11)
-	assertNotOK(t, "read after loaded range", err)
-
-	_, err = rd.ReadAt(make([]byte, 2), 10)
-	assertNotOK(t, "read more than available data", err)
-}

internal/restorer/packheap.go

@@ -1,51 +0,0 @@
-package restorer
-
-// packHeap is a heap of packInfo references
-// @see https://golang.org/pkg/container/heap/
-// @see https://en.wikipedia.org/wiki/Heap_(data_structure)
-type packHeap struct {
-	elements []*packInfo
-
-	// returns true if download of any of the files is in progress
-	inprogress func(files map[*fileInfo]struct{}) bool
-}
-
-func (pq *packHeap) Len() int { return len(pq.elements) }
-
-func (pq *packHeap) Less(a, b int) bool {
-	packA, packB := pq.elements[a], pq.elements[b]
-
-	ap := pq.inprogress(packA.files)
-	bp := pq.inprogress(packB.files)
-	if ap && !bp {
-		return true
-	}
-
-	if packA.cost < packB.cost {
-		return true
-	}
-
-	return false
-}
-
-func (pq *packHeap) Swap(i, j int) {
-	pq.elements[i], pq.elements[j] = pq.elements[j], pq.elements[i]
-	pq.elements[i].index = i
-	pq.elements[j].index = j
-}
-
-func (pq *packHeap) Push(x interface{}) {
-	n := len(pq.elements)
-	item := x.(*packInfo)
-	item.index = n
-	pq.elements = append(pq.elements, item)
-}
-
-func (pq *packHeap) Pop() interface{} {
-	old := pq.elements
-	n := len(old)
-	item := old[n-1]
-	item.index = -1 // for safety
-	pq.elements = old[0 : n-1]
-	return item
-}

internal/restorer/packqueue.go

@@ -1,224 +0,0 @@
-package restorer
-
-import (
-	"container/heap"
-
-	"github.com/restic/restic/internal/debug"
-	"github.com/restic/restic/internal/restic"
-)
-
-// packQueue tracks remaining file contents restore work and decides what pack
-// to download and files to write next.
-//
-// The packs in the queue can be in one of three states: waiting, ready and
-// in-progress.
-// Waiting packs are the packs that only have blobs from the "middle" of their
-// corresponding files and therefore cannot be used until blobs from some other
-// packs are written to the files first.
-// In-progress packs are the packs that were removed from the queue by #nextPack
-// and must be first returned to the queue before they are considered again.
-// Ready packs are the packs can be immediately used to restore at least one
-// file. Internally ready packs are kept in a heap and are ordered according
-// to these criteria:
-// - Packs with "head" blobs of in-progress files are considered first. The
-//   idea is to complete restore of in-progress files before starting restore
-//   of other files. This is both more intuitive and also reduces number of
-//   open file handles needed during restore.
-// - Packs with smallest cost are considered next. Pack cost is measured in
-//   number of other packs required before all blobs in the pack can be used
-//   and the pack can be removed from the pack cache.
-//   For example, consisder a file that requires two blobs, blob1 from pack1
-//   and blob2 from pack2. The cost of pack2 is 1, because blob2 cannot be
-//   used before blob1 is available. The higher the cost, the longer the pack
-//   must be cached locally to avoid redownload.
-//
-// Pack queue implementation is NOT thread safe. All pack queue methods must
-// be called from single gorouting AND packInfo and fileInfo instances must
-// be updated synchronously from the same gorouting.
-type packQueue struct {
-	idx filePackTraverser
-
-	packs      map[restic.ID]*packInfo // waiting and ready packs
-	inprogress map[*packInfo]struct{}  // inprogress packs
-
-	heap *packHeap // heap of ready packs
-}
-
-func newPackQueue(idx filePackTraverser, files []*fileInfo, inprogress func(files map[*fileInfo]struct{}) bool) (*packQueue, error) {
-	packs := make(map[restic.ID]*packInfo) // all packs
-
-	// create packInfo from fileInfo
-	for _, file := range files {
-		err := idx.forEachFilePack(file, func(packIdx int, packID restic.ID, _ []restic.Blob) bool {
-			pack, ok := packs[packID]
-			if !ok {
-				pack = &packInfo{
-					id:    packID,
-					index: -1,
-					files: make(map[*fileInfo]struct{}),
-				}
-				packs[packID] = pack
-			}
-			pack.files[file] = struct{}{}
-			pack.cost += packIdx
-
-			return true // keep going
-		})
-		if err != nil {
-			// repository index is messed up, can't do anything
-			return nil, err
-		}
-	}
-
-	// create packInfo heap
-	pheap := &packHeap{inprogress: inprogress}
-	headPacks := restic.NewIDSet()
-	for _, file := range files {
-		idx.forEachFilePack(file, func(packIdx int, packID restic.ID, _ []restic.Blob) bool {
-			if !headPacks.Has(packID) {
-				headPacks.Insert(packID)
-				pack := packs[packID]
-				pack.index = len(pheap.elements)
-				pheap.elements = append(pheap.elements, pack)
-			}
-			return false // only first pack
-		})
-	}
-	heap.Init(pheap)
-
-	return &packQueue{idx: idx, packs: packs, heap: pheap, inprogress: make(map[*packInfo]struct{})}, nil
-}
-
-// isEmpty returns true if the queue is empty, i.e. there are no more packs to
-// download and files to write to.
-func (h *packQueue) isEmpty() bool {
-	return len(h.packs) == 0 && len(h.inprogress) == 0
-}
-
-// nextPack returns next ready pack and corresponding files ready for download
-// and processing. The returned pack and the files are marked as "in progress"
-// internally and must  be first returned to the queue before they are
-// considered by #nextPack again.
-func (h *packQueue) nextPack() (*packInfo, []*fileInfo) {
-	debug.Log("Ready packs %d, outstanding packs %d, inprogress packs %d", h.heap.Len(), len(h.packs), len(h.inprogress))
-
-	if h.heap.Len() == 0 {
-		return nil, nil
-	}
-
-	pack := heap.Pop(h.heap).(*packInfo)
-	h.inprogress[pack] = struct{}{}
-	debug.Log("Popped pack %s (%d files), heap size=%d", pack.id.Str(), len(pack.files), len(h.heap.elements))
-	var files []*fileInfo
-	for file := range pack.files {
-		h.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, packBlobs []restic.Blob) bool {
-			debug.Log("Pack #%d %s (%d blobs) used by %s", packIdx, packID.Str(), len(packBlobs), file.location)
-			if pack.id == packID {
-				files = append(files, file)
-			}
-			return false // only interested in the fist pack here
-		})
-	}
-
-	return pack, files
-}
-
-// requeuePack conditionally adds back to the queue pack previously returned by
-// #nextPack.
-// If the pack is needed to restore any incomplete files, adds the pack to the
-// queue and adjusts order of all affected packs in the queue. Has no effect
-// if the pack is not required to restore any files.
-// Returns true if the pack was added to the queue, false otherwise.
-func (h *packQueue) requeuePack(pack *packInfo, success []*fileInfo, failure []*fileInfo) bool {
-	debug.Log("Requeue pack %s (%d/%d/%d files/success/failure)", pack.id.Str(), len(pack.files), len(success), len(failure))
-
-	// maintain inprogress pack set
-	delete(h.inprogress, pack)
-
-	affectedPacks := make(map[*packInfo]struct{})
-	affectedPacks[pack] = struct{}{} // this pack is alwats affected
-
-	// apply download success/failure to the packs
-	onFailure := func(file *fileInfo) {
-		h.idx.forEachFilePack(file, func(packInx int, packID restic.ID, _ []restic.Blob) bool {
-			pack := h.packs[packID]
-			delete(pack.files, file)
-			pack.cost -= packInx
-			affectedPacks[pack] = struct{}{}
-			return true // keep going
-		})
-	}
-	for _, file := range failure {
-		onFailure(file)
-	}
-	onSuccess := func(pack *packInfo, file *fileInfo) {
-		remove := true
-		h.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, _ []restic.Blob) bool {
-			if packID.Equal(pack.id) {
-				// the pack has more blobs required by the file
-				remove = false
-			}
-			otherPack := h.packs[packID]
-			otherPack.cost--
-			affectedPacks[otherPack] = struct{}{}
-			return true // keep going
-		})
-		if remove {
-			delete(pack.files, file)
-		}
-	}
-	for _, file := range success {
-		onSuccess(pack, file)
-	}
-
-	// drop/update affected packs
-	isReady := func(affectedPack *packInfo) (ready bool) {
-		for file := range affectedPack.files {
-			h.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, _ []restic.Blob) bool {
-				if packID.Equal(affectedPack.id) {
-					ready = true
-				}
-				return false // only file's first pack matters
-			})
-			if ready {
-				break
-			}
-		}
-		return ready
-	}
-	for affectedPack := range affectedPacks {
-		if _, inprogress := h.inprogress[affectedPack]; !inprogress {
-			if len(affectedPack.files) == 0 {
-				// drop the pack if it isn't inprogress and has no files that need it
-				if affectedPack.index >= 0 {
-					// This can't happen unless there is a bug elsewhere:
-					// - "current" pack isn't in the heap, hence its index must be < 0
-					// - "other" packs can't be ready (i.e. in heap) unless they have other files
-					//   in which case len(affectedPack.files) must be > 0
-					debug.Log("corrupted ready heap: removed unexpected ready pack %s", affectedPack.id.Str())
-					heap.Remove(h.heap, affectedPack.index)
-				}
-				delete(h.packs, affectedPack.id)
-			} else {
-				ready := isReady(affectedPack)
-				switch {
-				case ready && affectedPack.index < 0:
-					heap.Push(h.heap, affectedPack)
-				case ready && affectedPack.index >= 0:
-					heap.Fix(h.heap, affectedPack.index)
-				case !ready && affectedPack.index >= 0:
-					// This can't happen unless there is a bug elsewhere:
-					// - "current" pack isn't in the heap, hence its index must be < 0
-					// - "other" packs can't have same head blobs as the "current" pack,
-					//   hence "other" packs can't change their readiness
-					debug.Log("corrupted ready heap: removed unexpected waiting pack %s", affectedPack.id.Str())
-					heap.Remove(h.heap, affectedPack.index)
-				case !ready && affectedPack.index < 0:
-					// do nothing
-				}
-			}
-		}
-	}
-
-	return len(pack.files) > 0
-}

internal/restorer/packqueue_test.go

@@ -1,236 +0,0 @@
-package restorer
-
-import (
-	"testing"
-
-	"github.com/restic/restic/internal/restic"
-	rtest "github.com/restic/restic/internal/test"
-)
-
-func processPack(t *testing.T, data *TestRepo, pack *packInfo, files []*fileInfo) {
-	for _, file := range files {
-		data.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, packBlobs []restic.Blob) bool {
-			// assert file's head pack
-			rtest.Equals(t, pack.id, packID)
-			file.blobs = file.blobs[len(packBlobs):]
-			return false // only interested in the head pack
-		})
-	}
-}
-
-func TestPackQueueBasic(t *testing.T) {
-	data := newTestRepo([]TestFile{
-		TestFile{
-			name: "file",
-			blobs: []TestBlob{
-				TestBlob{"data1", "pack1"},
-				TestBlob{"data2", "pack2"},
-			},
-		},
-	})
-
-	queue, err := newPackQueue(data.idx, data.files, func(_ map[*fileInfo]struct{}) bool { return false })
-	rtest.OK(t, err)
-
-	// assert initial queue state
-	rtest.Equals(t, false, queue.isEmpty())
-	rtest.Equals(t, 0, queue.packs[data.packID("pack1")].cost)
-	rtest.Equals(t, 1, queue.packs[data.packID("pack2")].cost)
-
-	// get first pack
-	pack, files := queue.nextPack()
-	rtest.Equals(t, "pack1", data.packName(pack))
-	rtest.Equals(t, 1, len(files))
-	rtest.Equals(t, false, queue.isEmpty())
-	// TODO assert pack is inprogress
-
-	// can't process the second pack until the first one is processed
-	{
-		pack, files := queue.nextPack()
-		rtest.Equals(t, true, pack == nil)
-		rtest.Equals(t, true, files == nil)
-		rtest.Equals(t, false, queue.isEmpty())
-	}
-
-	// requeue the pack without processing
-	rtest.Equals(t, true, queue.requeuePack(pack, []*fileInfo{}, []*fileInfo{}))
-	rtest.Equals(t, false, queue.isEmpty())
-	rtest.Equals(t, 0, queue.packs[data.packID("pack1")].cost)
-	rtest.Equals(t, 1, queue.packs[data.packID("pack2")].cost)
-
-	// get the first pack again
-	pack, files = queue.nextPack()
-	rtest.Equals(t, "pack1", data.packName(pack))
-	rtest.Equals(t, 1, len(files))
-	rtest.Equals(t, false, queue.isEmpty())
-
-	// process the first pack and return it to the queue
-	processPack(t, data, pack, files)
-	rtest.Equals(t, false, queue.requeuePack(pack, files, []*fileInfo{}))
-	rtest.Equals(t, 0, queue.packs[data.packID("pack2")].cost)
-
-	// get the second pack
-	pack, files = queue.nextPack()
-	rtest.Equals(t, "pack2", data.packName(pack))
-	rtest.Equals(t, 1, len(files))
-	rtest.Equals(t, false, queue.isEmpty())
-
-	// process the second pack and return it to the queue
-	processPack(t, data, pack, files)
-	rtest.Equals(t, false, queue.requeuePack(pack, files, []*fileInfo{}))
-
-	// all packs processed
-	rtest.Equals(t, true, queue.isEmpty())
-}
-
-func TestPackQueueFailedFile(t *testing.T) {
-	// point of this test is to assert that enqueuePack removes
-	// all references to files that failed restore
-
-	data := newTestRepo([]TestFile{
-		TestFile{
-			name: "file",
-			blobs: []TestBlob{
-				TestBlob{"data1", "pack1"},
-				TestBlob{"data2", "pack2"},
-			},
-		},
-	})
-
-	queue, err := newPackQueue(data.idx, data.files, func(_ map[*fileInfo]struct{}) bool { return false })
-	rtest.OK(t, err)
-
-	pack, files := queue.nextPack()
-	rtest.Equals(t, false, queue.requeuePack(pack, []*fileInfo{}, files /*failed*/))
-	rtest.Equals(t, true, queue.isEmpty())
-}
-
-func TestPackQueueOrderingCost(t *testing.T) {
-	// assert pack1 is selected before pack2:
-	// pack1 is ready to restore file1, pack2 is ready to restore file2
-	// but pack2 cannot be immediately used to restore file1
-
-	data := newTestRepo([]TestFile{
-		TestFile{
-			name: "file1",
-			blobs: []TestBlob{
-				TestBlob{"data1", "pack1"},
-				TestBlob{"data2", "pack2"},
-			},
-		},
-		TestFile{
-			name: "file2",
-			blobs: []TestBlob{
-				TestBlob{"data2", "pack2"},
-			},
-		},
-	})
-
-	queue, err := newPackQueue(data.idx, data.files, func(_ map[*fileInfo]struct{}) bool { return false })
-	rtest.OK(t, err)
-
-	// assert initial pack costs
-	rtest.Equals(t, 0, data.pack(queue, "pack1").cost)
-	rtest.Equals(t, 0, data.pack(queue, "pack1").index) // head of the heap
-	rtest.Equals(t, 1, data.pack(queue, "pack2").cost)
-	rtest.Equals(t, 1, data.pack(queue, "pack2").index)
-
-	pack, files := queue.nextPack()
-	// assert selected pack and queue state
-	rtest.Equals(t, "pack1", data.packName(pack))
-	// process the pack
-	processPack(t, data, pack, files)
-	rtest.Equals(t, false, queue.requeuePack(pack, files, []*fileInfo{}))
-}
-
-func TestPackQueueOrderingInprogress(t *testing.T) {
-	// finish restoring one file before starting another
-
-	data := newTestRepo([]TestFile{
-		TestFile{
-			name: "file1",
-			blobs: []TestBlob{
-				TestBlob{"data1-1", "pack1-1"},
-				TestBlob{"data1-2", "pack1-2"},
-			},
-		},
-		TestFile{
-			name: "file2",
-			blobs: []TestBlob{
-				TestBlob{"data2-1", "pack2-1"},
-				TestBlob{"data2-2", "pack2-2"},
-			},
-		},
-	})
-
-	var inprogress *fileInfo
-	queue, err := newPackQueue(data.idx, data.files, func(files map[*fileInfo]struct{}) bool {
-		_, found := files[inprogress]
-		return found
-	})
-	rtest.OK(t, err)
-
-	// first pack of a file
-	pack, files := queue.nextPack()
-	rtest.Equals(t, 1, len(files))
-	file := files[0]
-	processPack(t, data, pack, files)
-	inprogress = files[0]
-	queue.requeuePack(pack, files, []*fileInfo{})
-
-	// second pack of the same file
-	pack, files = queue.nextPack()
-	rtest.Equals(t, 1, len(files))
-	rtest.Equals(t, true, file == files[0]) // same file as before
-	processPack(t, data, pack, files)
-	inprogress = nil
-	queue.requeuePack(pack, files, []*fileInfo{})
-
-	// first pack of the second file
-	pack, files = queue.nextPack()
-	rtest.Equals(t, 1, len(files))
-	rtest.Equals(t, false, file == files[0]) // different file as before
-}
-
-func TestPackQueuePackMultiuse(t *testing.T) {
-	// the same pack is required multiple times to restore the same file
-
-	data := newTestRepo([]TestFile{
-		TestFile{
-			name: "file",
-			blobs: []TestBlob{
-				TestBlob{"data1", "pack1"},
-				TestBlob{"data2", "pack2"},
-				TestBlob{"data3", "pack1"}, // pack1 reuse, new blob
-				TestBlob{"data2", "pack2"}, // pack2 reuse, same blob
-			},
-		},
-	})
-
-	queue, err := newPackQueue(data.idx, data.files, func(_ map[*fileInfo]struct{}) bool { return false })
-	rtest.OK(t, err)
-
-	pack, files := queue.nextPack()
-	rtest.Equals(t, "pack1", data.packName(pack))
-	rtest.Equals(t, 1, len(pack.files))
-	processPack(t, data, pack, files)
-	rtest.Equals(t, true, queue.requeuePack(pack, files, []*fileInfo{}))
-
-	pack, files = queue.nextPack()
-	rtest.Equals(t, "pack2", data.packName(pack))
-	rtest.Equals(t, 1, len(pack.files))
-	processPack(t, data, pack, files)
-	rtest.Equals(t, true, queue.requeuePack(pack, files, []*fileInfo{}))
-
-	pack, files = queue.nextPack()
-	rtest.Equals(t, "pack1", data.packName(pack))
-	processPack(t, data, pack, files)
-	rtest.Equals(t, false, queue.requeuePack(pack, files, []*fileInfo{}))
-
-	pack, files = queue.nextPack()
-	rtest.Equals(t, "pack2", data.packName(pack))
-	processPack(t, data, pack, files)
-	rtest.Equals(t, false, queue.requeuePack(pack, files, []*fileInfo{}))
-
-	rtest.Equals(t, true, queue.isEmpty())
-}

internal/restorer/restorer.go

@@ -206,7 +206,7 @@ func (res *Restorer) RestoreTo(ctx context.Context, dst string) error {
 
 	idx := restic.NewHardlinkIndex()
 
-	filerestorer := newFileRestorer(dst, res.repo.Backend().Load, res.repo.Key(), filePackTraverser{lookup: res.repo.Index().Lookup})
+	filerestorer := newFileRestorer(dst, res.repo.Backend().Load, res.repo.Key(), res.repo.Index().Lookup)
 
 	// first tree pass: create directories and collect all files to restore
 	err = res.traverseTree(ctx, dst, string(filepath.Separator), *res.sn.Tree, treeVisitor{
@@ -249,7 +249,7 @@ func (res *Restorer) RestoreTo(ctx context.Context, dst string) error {
 		return err
 	}
 
-	err = filerestorer.restoreFiles(ctx, func(location string, err error) { res.Error(location, err) })
+	err = filerestorer.restoreFiles(ctx)
 	if err != nil {
 		return err
 	}