1
0
Fork 0
mirror of https://github.com/restic/restic.git synced 2024-12-24 16:54:00 +00:00
restic/internal/restorer/filerestorer.go
Igor Fedorenko bda8d7722e restorer: Optimize empty file restore
don't create fileInfo structs for empty files. this saves memory.
this also avoids extra serial scan of all fileInfo, which should
make restore faster and more consistent.

Signed-off-by: Igor Fedorenko <igor@ifedorenko.com>
2018-10-14 17:39:42 +02:00

324 lines
9 KiB
Go

package restorer
import (
"context"
"io"
"path/filepath"
"github.com/restic/restic/internal/crypto"
"github.com/restic/restic/internal/debug"
"github.com/restic/restic/internal/errors"
"github.com/restic/restic/internal/restic"
)
// TODO if a blob is corrupt, there may be good blob copies in other packs
// TODO evaluate if it makes sense to split download and processing workers
// pro: can (slowly) read network and decrypt/write files concurrently
// con: each worker needs to keep one pack in memory
// 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 open output file handles
filesWriterCount = 32
// estimated average pack size used to calculate pack cache capacity
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 {
location string // file on local filesystem relative to restorer basedir
blobs []restic.ID // remaining blobs of the file
}
// information about a data pack required to restore one or more files
type packInfo struct {
// the pack id
id restic.ID
// 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
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 // 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 {
return &fileRestorer{
packLoader: packLoader,
key: key,
idx: idx,
filesWriter: newFilesWriter(filesWriterCount),
packCache: newPackCache(packCacheCapacity),
dst: dst,
}
}
func (r *fileRestorer) addFile(location string, content restic.IDs) {
r.files = append(r.files, &fileInfo{location: location, blobs: content})
}
func (r *fileRestorer) targetPath(location string) string {
return filepath.Join(r.dst, location)
}
// used to pass information among workers (wish golang channels allowed multivalues)
type processingInfo struct {
pack *packInfo
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
downloadCh := make(chan processingInfo)
feedbackCh := make(chan processingInfo)
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)
}
}
}
return nil
}
func (r *fileRestorer) downloadPack(ctx context.Context, pack *packInfo) (readerAtCloser, error) {
const MaxInt64 = 1<<63 - 1 // odd Go does not have this predefined somewhere
// calculate pack byte range
start, end := int64(MaxInt64), int64(0)
for file := range pack.files {
r.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, packBlobs []restic.Blob) bool {
if packID.Equal(pack.id) {
for _, blob := range packBlobs {
if start > int64(blob.Offset) {
start = int64(blob.Offset)
}
if end < int64(blob.Offset+blob.Length) {
end = int64(blob.Offset + blob.Length)
}
}
}
return true // keep going
})
}
packReader, err := r.packCache.get(pack.id, start, int(end-start), func(offset int64, length int, wr io.WriteSeeker) error {
h := restic.Handle{Type: restic.DataFile, Name: pack.id.String()}
return r.packLoader(ctx, h, length, offset, func(rd io.Reader) error {
// reset the file in case of a download retry
_, err := wr.Seek(0, io.SeekStart)
if err != nil {
return err
}
len, err := io.Copy(wr, rd)
if err != nil {
return err
}
if len != int64(length) {
return errors.Errorf("unexpected pack size: expected %d but got %d", length, len)
}
return nil
})
})
if err != nil {
return nil, err
}
return packReader, nil
}
func (r *fileRestorer) processPack(ctx context.Context, request processingInfo, rd readerAtCloser) {
defer rd.Close()
for file := range request.files {
target := r.targetPath(file.location)
r.idx.forEachFilePack(file, func(packIdx int, packID restic.ID, packBlobs []restic.Blob) bool {
for _, blob := range packBlobs {
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)
if err == nil {
err = r.filesWriter.writeToFile(target, buf)
}
if err != nil {
request.files[file] = err
break // could not restore the file
}
}
return false
})
}
}
func (r *fileRestorer) loadBlob(rd io.ReaderAt, blob restic.Blob) ([]byte, error) {
// TODO reconcile with Repository#loadBlob implementation
buf := make([]byte, blob.Length)
n, err := rd.ReadAt(buf, int64(blob.Offset))
if err != nil {
return nil, err
}
if n != int(blob.Length) {
return nil, errors.Errorf("error loading blob %v: wrong length returned, want %d, got %d", blob.ID.Str(), blob.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)
}
// check hash
if !restic.Hash(plaintext).Equal(blob.ID) {
return nil, errors.Errorf("blob %v returned invalid hash", blob.ID)
}
return plaintext, nil
}