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prune: Parallelize repack command
This commit is contained in:
Michael Eischer
Alexander Neumann
parent
8a0dbe7c1a
commit
b373f164fe
8
changelog/unreleased/pull-2941
Normal file
8
changelog/unreleased/pull-2941
Normal file
@ -0,0 +1,8 @@
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Enhancement: Speed up repacking step of prune command
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The repack step of the prune command, which moves still used file parts into
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new pack files such that the old ones can be garbage collected later on, now
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processes multiple pack files in parallel. This is especially beneficial for
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high latency backends or when using a fast network connection.
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https://github.com/restic/restic/pull/2941
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@ -2,14 +2,19 @@ package repository
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import (
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"context"
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"os"
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"sync"
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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/fs"
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"github.com/restic/restic/internal/pack"
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"github.com/restic/restic/internal/restic"
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"golang.org/x/sync/errgroup"
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)
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const numRepackWorkers = 8
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// Repack takes a list of packs together with a list of blobs contained in
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// these packs. Each pack is loaded and the blobs listed in keepBlobs is saved
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// into a new pack. Returned is the list of obsolete packs which can then
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@ -22,91 +27,166 @@ func Repack(ctx context.Context, repo restic.Repository, packs restic.IDSet, kee
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debug.Log("repacking %d packs while keeping %d blobs", len(packs), len(keepBlobs))
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for packID := range packs {
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// load the complete pack into a temp file
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h := restic.Handle{Type: restic.PackFile, Name: packID.String()}
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wg, ctx := errgroup.WithContext(ctx)
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tempfile, hash, packLength, err := DownloadAndHash(ctx, repo.Backend(), h)
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if err != nil {
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return nil, errors.Wrap(err, "Repack")
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}
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debug.Log("pack %v loaded (%d bytes), hash %v", packID, packLength, hash)
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if !packID.Equal(hash) {
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return nil, errors.Errorf("hash does not match id: want %v, got %v", packID, hash)
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}
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_, err = tempfile.Seek(0, 0)
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if err != nil {
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return nil, errors.Wrap(err, "Seek")
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}
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blobs, err := pack.List(repo.Key(), tempfile, packLength)
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if err != nil {
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return nil, err
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}
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debug.Log("processing pack %v, blobs: %v", packID, len(blobs))
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var buf []byte
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for _, entry := range blobs {
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h := restic.BlobHandle{ID: entry.ID, Type: entry.Type}
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if !keepBlobs.Has(h) {
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continue
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downloadQueue := make(chan restic.ID)
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wg.Go(func() error {
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defer close(downloadQueue)
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for packID := range packs {
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select {
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case downloadQueue <- packID:
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case <-ctx.Done():
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return ctx.Err()
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}
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}
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return nil
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})
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debug.Log(" process blob %v", h)
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type repackJob struct {
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tempfile *os.File
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hash restic.ID
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packLength int64
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}
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processQueue := make(chan repackJob)
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// used to close processQueue once all downloaders have finished
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var downloadWG sync.WaitGroup
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if uint(cap(buf)) < entry.Length {
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buf = make([]byte, entry.Length)
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}
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buf = buf[:entry.Length]
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downloader := func() error {
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defer downloadWG.Done()
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for packID := range downloadQueue {
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// load the complete pack into a temp file
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h := restic.Handle{Type: restic.PackFile, Name: packID.String()}
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n, err := tempfile.ReadAt(buf, int64(entry.Offset))
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tempfile, hash, packLength, err := DownloadAndHash(ctx, repo.Backend(), h)
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if err != nil {
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return nil, errors.Wrap(err, "ReadAt")
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return errors.Wrap(err, "Repack")
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}
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if n != len(buf) {
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return nil, errors.Errorf("read blob %v from %v: not enough bytes read, want %v, got %v",
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h, tempfile.Name(), len(buf), n)
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debug.Log("pack %v loaded (%d bytes), hash %v", packID, packLength, hash)
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if !packID.Equal(hash) {
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return errors.Errorf("hash does not match id: want %v, got %v", packID, hash)
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}
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nonce, ciphertext := buf[:repo.Key().NonceSize()], buf[repo.Key().NonceSize():]
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plaintext, err := repo.Key().Open(ciphertext[:0], nonce, ciphertext, nil)
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select {
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case processQueue <- repackJob{tempfile, hash, packLength}:
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case <-ctx.Done():
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return ctx.Err()
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}
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}
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return nil
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}
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downloadWG.Add(numRepackWorkers)
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for i := 0; i < numRepackWorkers; i++ {
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wg.Go(downloader)
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}
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wg.Go(func() error {
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downloadWG.Wait()
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close(processQueue)
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return nil
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})
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var keepMutex sync.Mutex
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worker := func() error {
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for job := range processQueue {
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tempfile, packID, packLength := job.tempfile, job.hash, job.packLength
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_, err = tempfile.Seek(0, 0)
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if err != nil {
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return nil, err
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return errors.Wrap(err, "Seek")
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}
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id := restic.Hash(plaintext)
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if !id.Equal(entry.ID) {
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debug.Log("read blob %v/%v from %v: wrong data returned, hash is %v",
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h.Type, h.ID, tempfile.Name(), id)
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return nil, errors.Errorf("read blob %v from %v: wrong data returned, hash is %v",
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h, tempfile.Name(), id)
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}
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// We do want to save already saved blobs!
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_, _, err = repo.SaveBlob(ctx, entry.Type, plaintext, entry.ID, true)
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blobs, err := pack.List(repo.Key(), tempfile, packLength)
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if err != nil {
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return nil, err
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return err
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}
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debug.Log(" saved blob %v", entry.ID)
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debug.Log("processing pack %v, blobs: %v", packID, len(blobs))
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var buf []byte
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for _, entry := range blobs {
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h := restic.BlobHandle{ID: entry.ID, Type: entry.Type}
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keepBlobs.Delete(h)
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}
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keepMutex.Lock()
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shouldKeep := keepBlobs.Has(h)
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keepMutex.Unlock()
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if err = tempfile.Close(); err != nil {
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return nil, errors.Wrap(err, "Close")
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}
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if !shouldKeep {
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continue
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}
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if err = fs.RemoveIfExists(tempfile.Name()); err != nil {
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return nil, errors.Wrap(err, "Remove")
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}
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if p != nil {
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p.Report(restic.Stat{Blobs: 1})
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debug.Log(" process blob %v", h)
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if uint(cap(buf)) < entry.Length {
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buf = make([]byte, entry.Length)
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}
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buf = buf[:entry.Length]
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n, err := tempfile.ReadAt(buf, int64(entry.Offset))
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if err != nil {
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return errors.Wrap(err, "ReadAt")
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}
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if n != len(buf) {
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return errors.Errorf("read blob %v from %v: not enough bytes read, want %v, got %v",
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h, tempfile.Name(), len(buf), n)
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}
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nonce, ciphertext := buf[:repo.Key().NonceSize()], buf[repo.Key().NonceSize():]
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plaintext, err := repo.Key().Open(ciphertext[:0], nonce, ciphertext, nil)
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if err != nil {
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return err
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}
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id := restic.Hash(plaintext)
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if !id.Equal(entry.ID) {
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debug.Log("read blob %v/%v from %v: wrong data returned, hash is %v",
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h.Type, h.ID, tempfile.Name(), id)
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return errors.Errorf("read blob %v from %v: wrong data returned, hash is %v",
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h, tempfile.Name(), id)
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}
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keepMutex.Lock()
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// recheck whether some other worker was faster
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shouldKeep = keepBlobs.Has(h)
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if shouldKeep {
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keepBlobs.Delete(h)
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}
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keepMutex.Unlock()
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if !shouldKeep {
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continue
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}
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// We do want to save already saved blobs!
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_, _, err = repo.SaveBlob(ctx, entry.Type, plaintext, entry.ID, true)
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if err != nil {
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return err
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}
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debug.Log(" saved blob %v", entry.ID)
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}
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if err = tempfile.Close(); err != nil {
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return errors.Wrap(err, "Close")
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}
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if err = fs.RemoveIfExists(tempfile.Name()); err != nil {
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return errors.Wrap(err, "Remove")
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}
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if p != nil {
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p.Report(restic.Stat{Blobs: 1})
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}
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}
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return nil
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}
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for i := 0; i < numRepackWorkers; i++ {
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wg.Go(worker)
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}
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if err := wg.Wait(); err != nil {
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return nil, err
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}
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if err := repo.Flush(ctx); err != nil {
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