Merge pull request #2217 from restic/improve-memory-usage

WIP: improve memory usage

cmd/restic/cmd_cat.go

@@ -74,7 +74,7 @@ func runCat(gopts GlobalOptions, args []string) error {
 		fmt.Println(string(buf))
 		return nil
 	case "index":
-		buf, err := repo.LoadAndDecrypt(gopts.ctx, restic.IndexFile, id)
+		buf, err := repo.LoadAndDecrypt(gopts.ctx, nil, restic.IndexFile, id)
 		if err != nil {
 			return err
 		}
@@ -99,7 +99,7 @@ func runCat(gopts GlobalOptions, args []string) error {
 		return nil
 	case "key":
 		h := restic.Handle{Type: restic.KeyFile, Name: id.String()}
-		buf, err := backend.LoadAll(gopts.ctx, repo.Backend(), h)
+		buf, err := backend.LoadAll(gopts.ctx, nil, repo.Backend(), h)
 		if err != nil {
 			return err
 		}
@@ -150,7 +150,7 @@ func runCat(gopts GlobalOptions, args []string) error {
 	switch tpe {
 	case "pack":
 		h := restic.Handle{Type: restic.DataFile, Name: id.String()}
-		buf, err := backend.LoadAll(gopts.ctx, repo.Backend(), h)
+		buf, err := backend.LoadAll(gopts.ctx, nil, repo.Backend(), h)
 		if err != nil {
 			return err
 		}

internal/backend/test/tests.go

@@ -79,7 +79,7 @@ func (s *Suite) TestConfig(t *testing.T) {
 	var testString = "Config"
 
 	// create config and read it back
-	_, err := backend.LoadAll(context.TODO(), b, restic.Handle{Type: restic.ConfigFile})
+	_, err := backend.LoadAll(context.TODO(), nil, b, restic.Handle{Type: restic.ConfigFile})
 	if err == nil {
 		t.Fatalf("did not get expected error for non-existing config")
 	}
@@ -93,7 +93,7 @@ func (s *Suite) TestConfig(t *testing.T) {
 	// same config
 	for _, name := range []string{"", "foo", "bar", "0000000000000000000000000000000000000000000000000000000000000000"} {
 		h := restic.Handle{Type: restic.ConfigFile, Name: name}
-		buf, err := backend.LoadAll(context.TODO(), b, h)
+		buf, err := backend.LoadAll(context.TODO(), nil, b, h)
 		if err != nil {
 			t.Fatalf("unable to read config with name %q: %+v", name, err)
 		}
@@ -491,7 +491,7 @@ func (s *Suite) TestSave(t *testing.T) {
 		err := b.Save(context.TODO(), h, restic.NewByteReader(data))
 		test.OK(t, err)
 
-		buf, err := backend.LoadAll(context.TODO(), b, h)
+		buf, err := backend.LoadAll(context.TODO(), nil, b, h)
 		test.OK(t, err)
 		if len(buf) != len(data) {
 			t.Fatalf("number of bytes does not match, want %v, got %v", len(data), len(buf))
@@ -584,7 +584,7 @@ func (s *Suite) TestSaveFilenames(t *testing.T) {
 			continue
 		}
 
-		buf, err := backend.LoadAll(context.TODO(), b, h)
+		buf, err := backend.LoadAll(context.TODO(), nil, b, h)
 		if err != nil {
 			t.Errorf("test %d failed: Load() returned %+v", i, err)
 			continue
@@ -734,7 +734,7 @@ func (s *Suite) TestBackend(t *testing.T) {
 
 			// test Load()
 			h := restic.Handle{Type: tpe, Name: ts.id}
-			buf, err := backend.LoadAll(context.TODO(), b, h)
+			buf, err := backend.LoadAll(context.TODO(), nil, b, h)
 			test.OK(t, err)
 			test.Equals(t, ts.data, string(buf))
 

internal/backend/utils.go

@@ -1,20 +1,33 @@
 package backend
 
 import (
+	"bytes"
 	"context"
 	"io"
-	"io/ioutil"
 
 	"github.com/restic/restic/internal/restic"
 )
 
-// LoadAll reads all data stored in the backend for the handle.
+// LoadAll reads all data stored in the backend for the handle into the given
-func LoadAll(ctx context.Context, be restic.Backend, h restic.Handle) (buf []byte, err error) {
+// buffer, which is truncated. If the buffer is not large enough or nil, a new
-	err = be.Load(ctx, h, 0, 0, func(rd io.Reader) (ierr error) {
+// one is allocated.
-		buf, ierr = ioutil.ReadAll(rd)
+func LoadAll(ctx context.Context, buf []byte, be restic.Backend, h restic.Handle) ([]byte, error) {
-		return ierr
+	err := be.Load(ctx, h, 0, 0, func(rd io.Reader) error {
+		// make sure this is idempotent, in case an error occurs this function may be called multiple times!
+		wr := bytes.NewBuffer(buf[:0])
+		_, cerr := io.Copy(wr, rd)
+		if cerr != nil {
+			return cerr
+		}
+		buf = wr.Bytes()
+		return nil
 	})
-	return buf, err
+
+	if err != nil {
+		return nil, err
+	}
+
+	return buf, nil
 }
 
 // LimitedReadCloser wraps io.LimitedReader and exposes the Close() method.

internal/backend/utils_test.go

@@ -19,6 +19,7 @@ const MiB = 1 << 20
 
 func TestLoadAll(t *testing.T) {
 	b := mem.New()
+	var buf []byte
 
 	for i := 0; i < 20; i++ {
 		data := rtest.Random(23+i, rand.Intn(MiB)+500*KiB)
@@ -28,7 +29,7 @@ func TestLoadAll(t *testing.T) {
 		err := b.Save(context.TODO(), h, restic.NewByteReader(data))
 		rtest.OK(t, err)
 
-		buf, err := backend.LoadAll(context.TODO(), b, restic.Handle{Type: restic.DataFile, Name: id.String()})
+		buf, err := backend.LoadAll(context.TODO(), buf, b, restic.Handle{Type: restic.DataFile, Name: id.String()})
 		rtest.OK(t, err)
 
 		if len(buf) != len(data) {
@@ -43,55 +44,66 @@ func TestLoadAll(t *testing.T) {
 	}
 }
 
-func TestLoadSmallBuffer(t *testing.T) {
+func save(t testing.TB, be restic.Backend, buf []byte) restic.Handle {
-	b := mem.New()
+	id := restic.Hash(buf)
-
+	h := restic.Handle{Name: id.String(), Type: restic.DataFile}
-	for i := 0; i < 20; i++ {
+	err := be.Save(context.TODO(), h, restic.NewByteReader(buf))
-		data := rtest.Random(23+i, rand.Intn(MiB)+500*KiB)
+	if err != nil {
-
+		t.Fatal(err)
-		id := restic.Hash(data)
-		h := restic.Handle{Name: id.String(), Type: restic.DataFile}
-		err := b.Save(context.TODO(), h, restic.NewByteReader(data))
-		rtest.OK(t, err)
-
-		buf, err := backend.LoadAll(context.TODO(), b, restic.Handle{Type: restic.DataFile, Name: id.String()})
-		rtest.OK(t, err)
-
-		if len(buf) != len(data) {
-			t.Errorf("length of returned buffer does not match, want %d, got %d", len(data), len(buf))
-			continue
-		}
-
-		if !bytes.Equal(buf, data) {
-			t.Errorf("wrong data returned")
-			continue
-		}
 	}
+	return h
 }
 
-func TestLoadLargeBuffer(t *testing.T) {
+func TestLoadAllAppend(t *testing.T) {
 	b := mem.New()
 
-	for i := 0; i < 20; i++ {
+	h1 := save(t, b, []byte("foobar test string"))
-		data := rtest.Random(23+i, rand.Intn(MiB)+500*KiB)
+	randomData := rtest.Random(23, rand.Intn(MiB)+500*KiB)
+	h2 := save(t, b, randomData)
 
-		id := restic.Hash(data)
+	var tests = []struct {
-		h := restic.Handle{Name: id.String(), Type: restic.DataFile}
+		handle restic.Handle
-		err := b.Save(context.TODO(), h, restic.NewByteReader(data))
+		buf    []byte
-		rtest.OK(t, err)
+		want   []byte
+	}{
+		{
+			handle: h1,
+			buf:    nil,
+			want:   []byte("foobar test string"),
+		},
+		{
+			handle: h1,
+			buf:    []byte("xxx"),
+			want:   []byte("foobar test string"),
+		},
+		{
+			handle: h2,
+			buf:    nil,
+			want:   randomData,
+		},
+		{
+			handle: h2,
+			buf:    make([]byte, 0, 200),
+			want:   randomData,
+		},
+		{
+			handle: h2,
+			buf:    []byte("foobarbaz"),
+			want:   randomData,
+		},
+	}
 
-		buf, err := backend.LoadAll(context.TODO(), b, restic.Handle{Type: restic.DataFile, Name: id.String()})
+	for _, test := range tests {
-		rtest.OK(t, err)
+		t.Run("", func(t *testing.T) {
+			buf, err := backend.LoadAll(context.TODO(), test.buf, b, test.handle)
+			if err != nil {
+				t.Fatal(err)
+			}
 
-		if len(buf) != len(data) {
+			if !bytes.Equal(buf, test.want) {
-			t.Errorf("length of returned buffer does not match, want %d, got %d", len(data), len(buf))
+				t.Errorf("wrong data returned, want %q, got %q", test.want, buf)
-			continue
+			}
-		}
+		})
-
-		if !bytes.Equal(buf, data) {
-			t.Errorf("wrong data returned")
-			continue
-		}
 	}
 }
 

internal/cache/backend_test.go

@@ -17,7 +17,7 @@ import (
 )
 
 func loadAndCompare(t testing.TB, be restic.Backend, h restic.Handle, data []byte) {
-	buf, err := backend.LoadAll(context.TODO(), be, h)
+	buf, err := backend.LoadAll(context.TODO(), nil, be, h)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -147,7 +147,7 @@ func TestErrorBackend(t *testing.T) {
 	loadTest := func(wg *sync.WaitGroup, be restic.Backend) {
 		defer wg.Done()
 
-		buf, err := backend.LoadAll(context.TODO(), be, h)
+		buf, err := backend.LoadAll(context.TODO(), nil, be, h)
 		if err == testErr {
 			return
 		}

internal/checker/checker.go

@@ -49,7 +49,7 @@ func New(repo restic.Repository) *Checker {
 	return c
 }
 
-const defaultParallelism = 40
+const defaultParallelism = 5
 
 // ErrDuplicatePacks is returned when a pack is found in more than one index.
 type ErrDuplicatePacks struct {
@@ -74,82 +74,110 @@ func (err ErrOldIndexFormat) Error() string {
 // LoadIndex loads all index files.
 func (c *Checker) LoadIndex(ctx context.Context) (hints []error, errs []error) {
 	debug.Log("Start")
-	type indexRes struct {
+
-		Index *repository.Index
+	// track spawned goroutines using wg, create a new context which is
-		err   error
+	// cancelled as soon as an error occurs.
-		ID    string
+	wg, ctx := errgroup.WithContext(ctx)
+
+	type FileInfo struct {
+		restic.ID
+		Size int64
 	}
 
-	indexCh := make(chan indexRes)
+	type Result struct {
+		*repository.Index
+		restic.ID
+		Err error
+	}
 
-	worker := func(ctx context.Context, id restic.ID) error {
+	ch := make(chan FileInfo)
-		debug.Log("worker got index %v", id)
+	resultCh := make(chan Result)
-		idx, err := repository.LoadIndexWithDecoder(ctx, c.repo, id, repository.DecodeIndex)
-		if errors.Cause(err) == repository.ErrOldIndexFormat {
-			debug.Log("index %v has old format", id)
-			hints = append(hints, ErrOldIndexFormat{id})
 
-			idx, err = repository.LoadIndexWithDecoder(ctx, c.repo, id, repository.DecodeOldIndex)
+	// send list of index files through ch, which is closed afterwards
+	wg.Go(func() error {
+		defer close(ch)
+		return c.repo.List(ctx, restic.IndexFile, func(id restic.ID, size int64) error {
+			select {
+			case <-ctx.Done():
+				return nil
+			case ch <- FileInfo{id, size}:
+			}
+			return nil
+		})
+	})
+
+	// a worker receives an index ID from ch, loads the index, and sends it to indexCh
+	worker := func() error {
+		var buf []byte
+		for fi := range ch {
+			debug.Log("worker got file %v", fi.ID.Str())
+			var err error
+			var idx *repository.Index
+			idx, buf, err = repository.LoadIndexWithDecoder(ctx, c.repo, buf[:0], fi.ID, repository.DecodeIndex)
+			if errors.Cause(err) == repository.ErrOldIndexFormat {
+				debug.Log("index %v has old format", fi.ID.Str())
+				hints = append(hints, ErrOldIndexFormat{fi.ID})
+
+				idx, buf, err = repository.LoadIndexWithDecoder(ctx, c.repo, buf[:0], fi.ID, repository.DecodeOldIndex)
+			}
+
+			err = errors.Wrapf(err, "error loading index %v", fi.ID.Str())
+
+			select {
+			case resultCh <- Result{idx, fi.ID, err}:
+			case <-ctx.Done():
+			}
 		}
-
-		err = errors.Wrapf(err, "error loading index %v", id.Str())
-
-		select {
-		case indexCh <- indexRes{Index: idx, ID: id.String(), err: err}:
-		case <-ctx.Done():
-		}
-
 		return nil
 	}
 
-	go func() {
+	// final closes indexCh after all workers have terminated
-		defer close(indexCh)
+	final := func() error {
-		debug.Log("start loading indexes in parallel")
+		close(resultCh)
-		err := repository.FilesInParallel(ctx, c.repo.Backend(), restic.IndexFile, defaultParallelism,
+		return nil
-			repository.ParallelWorkFuncParseID(worker))
+	}
-		debug.Log("loading indexes finished, error: %v", err)
-		if err != nil {
-			panic(err)
-		}
-	}()
 
-	done := make(chan struct{})
+	// run workers on ch
-	defer close(done)
+	wg.Go(func() error {
+		return repository.RunWorkers(ctx, defaultParallelism, worker, final)
+	})
 
+	// receive decoded indexes
 	packToIndex := make(map[restic.ID]restic.IDSet)
+	wg.Go(func() error {
+		for res := range resultCh {
+			debug.Log("process index %v, err %v", res.ID, res.Err)
 
-	for res := range indexCh {
+			if res.Err != nil {
-		debug.Log("process index %v, err %v", res.ID, res.err)
+				errs = append(errs, res.Err)
-
+				continue
-		if res.err != nil {
-			errs = append(errs, res.err)
-			continue
-		}
-
-		idxID, err := restic.ParseID(res.ID)
-		if err != nil {
-			errs = append(errs, errors.Errorf("unable to parse as index ID: %v", res.ID))
-			continue
-		}
-
-		c.indexes[idxID] = res.Index
-		c.masterIndex.Insert(res.Index)
-
-		debug.Log("process blobs")
-		cnt := 0
-		for blob := range res.Index.Each(ctx) {
-			c.packs.Insert(blob.PackID)
-			c.blobs.Insert(blob.ID)
-			c.blobRefs.M[blob.ID] = 0
-			cnt++
-
-			if _, ok := packToIndex[blob.PackID]; !ok {
-				packToIndex[blob.PackID] = restic.NewIDSet()
 			}
-			packToIndex[blob.PackID].Insert(idxID)
-		}
 
-		debug.Log("%d blobs processed", cnt)
+			c.indexes[res.ID] = res.Index
+			c.masterIndex.Insert(res.Index)
+
+			debug.Log("process blobs")
+			cnt := 0
+			for blob := range res.Index.Each(ctx) {
+				c.packs.Insert(blob.PackID)
+				c.blobs.Insert(blob.ID)
+				c.blobRefs.M[blob.ID] = 0
+				cnt++
+
+				if _, ok := packToIndex[blob.PackID]; !ok {
+					packToIndex[blob.PackID] = restic.NewIDSet()
+				}
+				packToIndex[blob.PackID].Insert(res.ID)
+			}
+
+			debug.Log("%d blobs processed", cnt)
+		}
+		return nil
+	})
+
+	err := wg.Wait()
+	if err != nil {
+		errs = append(errs, err)
 	}
 
 	debug.Log("checking for duplicate packs")
@@ -163,7 +191,7 @@ func (c *Checker) LoadIndex(ctx context.Context) (hints []error, errs []error) {
 		}
 	}
 
-	err := c.repo.SetIndex(c.masterIndex)
+	err = c.repo.SetIndex(c.masterIndex)
 	if err != nil {
 		debug.Log("SetIndex returned error: %v", err)
 		errs = append(errs, err)
@@ -281,31 +309,52 @@ func loadSnapshotTreeIDs(ctx context.Context, repo restic.Repository) (restic.ID
 		sync.Mutex
 	}
 
-	snapshotWorker := func(ctx context.Context, strID string) error {
+	// track spawned goroutines using wg, create a new context which is
-		id, err := restic.ParseID(strID)
+	// cancelled as soon as an error occurs.
-		if err != nil {
+	wg, ctx := errgroup.WithContext(ctx)
-			return err
-		}
 
-		debug.Log("load snapshot %v", id)
+	ch := make(chan restic.ID)
 
-		treeID, err := loadTreeFromSnapshot(ctx, repo, id)
+	// send list of index files through ch, which is closed afterwards
-		if err != nil {
+	wg.Go(func() error {
-			errs.Lock()
+		defer close(ch)
-			errs.errs = append(errs.errs, err)
+		return repo.List(ctx, restic.SnapshotFile, func(id restic.ID, size int64) error {
-			errs.Unlock()
+			select {
+			case <-ctx.Done():
+				return nil
+			case ch <- id:
+			}
 			return nil
+		})
+	})
+
+	// a worker receives an index ID from ch, loads the snapshot and the tree,
+	// and adds the result to errs and trees.
+	worker := func() error {
+		for id := range ch {
+			debug.Log("load snapshot %v", id)
+
+			treeID, err := loadTreeFromSnapshot(ctx, repo, id)
+			if err != nil {
+				errs.Lock()
+				errs.errs = append(errs.errs, err)
+				errs.Unlock()
+				continue
+			}
+
+			debug.Log("snapshot %v has tree %v", id, treeID)
+			trees.Lock()
+			trees.IDs = append(trees.IDs, treeID)
+			trees.Unlock()
 		}
-
-		debug.Log("snapshot %v has tree %v", id, treeID)
-		trees.Lock()
-		trees.IDs = append(trees.IDs, treeID)
-		trees.Unlock()
-
 		return nil
 	}
 
-	err := repository.FilesInParallel(ctx, repo.Backend(), restic.SnapshotFile, defaultParallelism, snapshotWorker)
+	for i := 0; i < defaultParallelism; i++ {
+		wg.Go(worker)
+	}
+
+	err := wg.Wait()
 	if err != nil {
 		errs.errs = append(errs.errs, err)
 	}

internal/mock/repository.go

@@ -1,141 +0,0 @@
-package mock
-
-import (
-	"github.com/restic/restic/internal/crypto"
-	"github.com/restic/restic/internal/restic"
-)
-
-// Repository implements a mock Repository.
-type Repository struct {
-	BackendFn func() restic.Backend
-
-	KeyFn func() *crypto.Key
-
-	SetIndexFn func(restic.Index) error
-
-	IndexFn         func() restic.Index
-	SaveFullIndexFn func() error
-	SaveIndexFn     func() error
-	LoadIndexFn     func() error
-
-	ConfigFn func() restic.Config
-
-	LookupBlobSizeFn func(restic.ID, restic.BlobType) (uint, error)
-
-	ListFn     func(restic.FileType, <-chan struct{}) <-chan restic.ID
-	ListPackFn func(restic.ID) ([]restic.Blob, int64, error)
-
-	FlushFn func() error
-
-	SaveUnpackedFn     func(restic.FileType, []byte) (restic.ID, error)
-	SaveJSONUnpackedFn func(restic.FileType, interface{}) (restic.ID, error)
-
-	LoadJSONUnpackedFn func(restic.FileType, restic.ID, interface{}) error
-	LoadAndDecryptFn   func(restic.FileType, restic.ID) ([]byte, error)
-
-	LoadBlobFn func(restic.BlobType, restic.ID, []byte) (int, error)
-	SaveBlobFn func(restic.BlobType, []byte, restic.ID) (restic.ID, error)
-
-	LoadTreeFn func(restic.ID) (*restic.Tree, error)
-	SaveTreeFn func(t *restic.Tree) (restic.ID, error)
-}
-
-// Backend is a stub method.
-func (repo Repository) Backend() restic.Backend {
-	return repo.BackendFn()
-}
-
-// Key is a stub method.
-func (repo Repository) Key() *crypto.Key {
-	return repo.KeyFn()
-}
-
-// SetIndex is a stub method.
-func (repo Repository) SetIndex(idx restic.Index) error {
-	return repo.SetIndexFn(idx)
-}
-
-// Index is a stub method.
-func (repo Repository) Index() restic.Index {
-	return repo.IndexFn()
-}
-
-// SaveFullIndex is a stub method.
-func (repo Repository) SaveFullIndex() error {
-	return repo.SaveFullIndexFn()
-}
-
-// SaveIndex is a stub method.
-func (repo Repository) SaveIndex() error {
-	return repo.SaveIndexFn()
-}
-
-// LoadIndex is a stub method.
-func (repo Repository) LoadIndex() error {
-	return repo.LoadIndexFn()
-}
-
-// Config is a stub method.
-func (repo Repository) Config() restic.Config {
-	return repo.ConfigFn()
-}
-
-// LookupBlobSize is a stub method.
-func (repo Repository) LookupBlobSize(id restic.ID, t restic.BlobType) (uint, error) {
-	return repo.LookupBlobSizeFn(id, t)
-}
-
-// List is a stub method.
-func (repo Repository) List(t restic.FileType, done <-chan struct{}) <-chan restic.ID {
-	return repo.ListFn(t, done)
-}
-
-// ListPack is a stub method.
-func (repo Repository) ListPack(id restic.ID) ([]restic.Blob, int64, error) {
-	return repo.ListPackFn(id)
-}
-
-// Flush is a stub method.
-func (repo Repository) Flush() error {
-	return repo.FlushFn()
-}
-
-// SaveUnpacked is a stub method.
-func (repo Repository) SaveUnpacked(t restic.FileType, buf []byte) (restic.ID, error) {
-	return repo.SaveUnpackedFn(t, buf)
-}
-
-// SaveJSONUnpacked is a stub method.
-func (repo Repository) SaveJSONUnpacked(t restic.FileType, item interface{}) (restic.ID, error) {
-	return repo.SaveJSONUnpackedFn(t, item)
-}
-
-// LoadJSONUnpacked is a stub method.
-func (repo Repository) LoadJSONUnpacked(t restic.FileType, id restic.ID, item interface{}) error {
-	return repo.LoadJSONUnpackedFn(t, id, item)
-}
-
-// LoadAndDecrypt is a stub method.
-func (repo Repository) LoadAndDecrypt(t restic.FileType, id restic.ID) ([]byte, error) {
-	return repo.LoadAndDecryptFn(t, id)
-}
-
-// LoadBlob is a stub method.
-func (repo Repository) LoadBlob(t restic.BlobType, id restic.ID, buf []byte) (int, error) {
-	return repo.LoadBlobFn(t, id, buf)
-}
-
-// SaveBlob is a stub method.
-func (repo Repository) SaveBlob(t restic.BlobType, buf []byte, id restic.ID) (restic.ID, error) {
-	return repo.SaveBlobFn(t, buf, id)
-}
-
-// LoadTree is a stub method.
-func (repo Repository) LoadTree(id restic.ID) (*restic.Tree, error) {
-	return repo.LoadTreeFn(id)
-}
-
-// SaveTree is a stub method.
-func (repo Repository) SaveTree(t *restic.Tree) (restic.ID, error) {
-	return repo.SaveTreeFn(t)
-}

internal/repository/index.go

@@ -549,21 +549,21 @@ func DecodeOldIndex(buf []byte) (idx *Index, err error) {
 }
 
 // LoadIndexWithDecoder loads the index and decodes it with fn.
-func LoadIndexWithDecoder(ctx context.Context, repo restic.Repository, id restic.ID, fn func([]byte) (*Index, error)) (idx *Index, err error) {
+func LoadIndexWithDecoder(ctx context.Context, repo restic.Repository, buf []byte, id restic.ID, fn func([]byte) (*Index, error)) (*Index, []byte, error) {
 	debug.Log("Loading index %v", id)
 
-	buf, err := repo.LoadAndDecrypt(ctx, restic.IndexFile, id)
+	buf, err := repo.LoadAndDecrypt(ctx, buf[:0], restic.IndexFile, id)
 	if err != nil {
-		return nil, err
+		return nil, buf[:0], err
 	}
 
-	idx, err = fn(buf)
+	idx, err := fn(buf)
 	if err != nil {
 		debug.Log("error while decoding index %v: %v", id, err)
-		return nil, err
+		return nil, buf[:0], err
 	}
 
 	idx.id = id
 
-	return idx, nil
+	return idx, buf, nil
 }

internal/repository/key.go

@@ -184,7 +184,7 @@ func SearchKey(ctx context.Context, s *Repository, password string, maxKeys int,
 // LoadKey loads a key from the backend.
 func LoadKey(ctx context.Context, s *Repository, name string) (k *Key, err error) {
 	h := restic.Handle{Type: restic.KeyFile, Name: name}
-	data, err := backend.LoadAll(ctx, s.be, h)
+	data, err := backend.LoadAll(ctx, nil, s.be, h)
 	if err != nil {
 		return nil, err
 	}

internal/repository/parallel.go

@@ -1,65 +0,0 @@
-package repository
-
-import (
-	"context"
-
-	"github.com/restic/restic/internal/debug"
-	"github.com/restic/restic/internal/restic"
-	"golang.org/x/sync/errgroup"
-)
-
-// ParallelWorkFunc gets one file ID to work on. If an error is returned,
-// processing stops. When the contect is cancelled the function should return.
-type ParallelWorkFunc func(ctx context.Context, id string) error
-
-// ParallelIDWorkFunc gets one restic.ID to work on. If an error is returned,
-// processing stops. When the context is cancelled the function should return.
-type ParallelIDWorkFunc func(ctx context.Context, id restic.ID) error
-
-// FilesInParallel runs n workers of f in parallel, on the IDs that
-// repo.List(t) yields. If f returns an error, the process is aborted and the
-// first error is returned.
-func FilesInParallel(ctx context.Context, repo restic.Lister, t restic.FileType, n int, f ParallelWorkFunc) error {
-	g, ctx := errgroup.WithContext(ctx)
-
-	ch := make(chan string, n)
-	g.Go(func() error {
-		defer close(ch)
-		return repo.List(ctx, t, func(fi restic.FileInfo) error {
-			select {
-			case <-ctx.Done():
-			case ch <- fi.Name:
-			}
-			return nil
-		})
-	})
-
-	for i := 0; i < n; i++ {
-		g.Go(func() error {
-			for name := range ch {
-				err := f(ctx, name)
-				if err != nil {
-					return err
-				}
-			}
-			return nil
-		})
-	}
-
-	return g.Wait()
-}
-
-// ParallelWorkFuncParseID converts a function that takes a restic.ID to a
-// function that takes a string. Filenames that do not parse as a restic.ID
-// are ignored.
-func ParallelWorkFuncParseID(f ParallelIDWorkFunc) ParallelWorkFunc {
-	return func(ctx context.Context, s string) error {
-		id, err := restic.ParseID(s)
-		if err != nil {
-			debug.Log("invalid ID %q: %v", id, err)
-			return nil
-		}
-
-		return f(ctx, id)
-	}
-}

internal/repository/parallel_test.go

@@ -1,129 +0,0 @@
-package repository_test
-
-import (
-	"context"
-	"math/rand"
-	"testing"
-	"time"
-
-	"github.com/restic/restic/internal/errors"
-	"github.com/restic/restic/internal/restic"
-
-	"github.com/restic/restic/internal/repository"
-	rtest "github.com/restic/restic/internal/test"
-)
-
-type testIDs []string
-
-var lister = testIDs{
-	"40bb581cd36de952985c97a3ff6b21df41ee897d4db2040354caa36a17ff5268",
-	"2e15811a4d14ffac66d36a9ff456019d8de4c10c949d45b643f8477d17e92ff3",
-	"70c11b3ed521ad6b76d905c002ca98b361fca06aca060a063432c7311155a4da",
-	"8056a33e75dccdda701b6c989c7ed0cb71bbb6da13c6427fe5986f0896cc91c0",
-	"79d8776200596aa0237b10d470f7b850b86f8a1a80988ef5c8bee2874ce992e2",
-	"f9f1f29791c6b79b90b35efd083f17a3b163bbbafb1a2fdf43d46d56cffda289",
-	"3834178d05d0f6dd07f872ee0262ff1ace0f0f375768227d3c902b0b66591369",
-	"66d5cc68c9186414806f366ae5493ce7f229212993750a4992be4030f6af28c5",
-	"ebca5af4f397944f68cd215e3dfa2b197a7ba0f7c17d65d9f7390d0a15cde296",
-	"d4511ce6ff732d106275a57e40745c599e987c0da44c42cddbef592aac102437",
-	"f366202f0bfeefaedd7b49e2f21a90d3cbddb97d257a74d788dd34e19a684dae",
-	"a5c17728ab2433cd50636dd5c6c7068c7a44f2999d09c46e8f528466da8a059d",
-	"bae0f9492b9b208233029b87692a1a55cbd7fbe1cf3f6d7bc693ac266a6d6f0e",
-	"9d500187913c7510d71d1902703d312c7aaa56f1e98351385b9535fdabae595e",
-	"ffbddd8a4c1e54d258bb3e16d3929b546b61af63cb560b3e3061a8bef5b24552",
-	"201bb3abf655e7ef71e79ed4fb1079b0502b5acb4d9fad5e72a0de690c50a386",
-	"08eb57bbd559758ea96e99f9b7688c30e7b3bcf0c4562ff4535e2d8edeffaeed",
-	"e50b7223b04985ff38d9e11d1cba333896ef4264f82bd5d0653a028bce70e542",
-	"65a9421cd59cc7b7a71dcd9076136621af607fb4701d2e5c2af23b6396cf2f37",
-	"995a655b3521c19b4d0c266222266d89c8fc62889597d61f45f336091e646d57",
-	"51ec6f0bce77ed97df2dd7ae849338c3a8155a057da927eedd66e3d61be769ad",
-	"7b3923a0c0666431efecdbf6cb171295ec1710b6595eebcba3b576b49d13e214",
-	"2cedcc3d14698bea7e4b0546f7d5d48951dd90add59e6f2d44b693fd8913717d",
-	"fd6770cbd54858fdbd3d7b4239b985e5599180064d93ca873f27e86e8407d011",
-	"9edc51d8e6e04d05c9757848c1bfbfdc8e86b6330982294632488922e59fdb1b",
-	"1a6c4fbb24ad724c968b2020417c3d057e6c89e49bdfb11d91006def65eab6a0",
-	"cb3b29808cd0adfa2dca1f3a04f98114fbccf4eb487cdd4022f49bd70eeb049b",
-	"f55edcb40c619e29a20e432f8aaddc83a649be2c2d1941ccdc474cd2af03d490",
-	"e8ccc1763a92de23566b95c3ad1414a098016ece69a885fc8a72782a7517d17c",
-	"0fe2e3db8c5a12ad7101a63a0fffee901be54319cfe146bead7aec851722f82d",
-	"36be45a6ae7c95ad97cee1b33023be324bce7a7b4b7036e24125679dd9ff5b44",
-	"1685ed1a57c37859fbef1f7efb7509f20b84ec17a765605de43104d2fa37884b",
-	"9d83629a6a004c505b100a0b5d0b246833b63aa067aa9b59e3abd6b74bc4d3a8",
-	"be49a66b60175c5e2ee273b42165f86ef11bb6518c1c79950bcd3f4c196c98bd",
-	"0fd89885d821761b4a890782908e75793028747d15ace3c6cbf0ad56582b4fa5",
-	"94a767519a4e352a88796604943841fea21429f3358b4d5d55596dbda7d15dce",
-	"8dd07994afe6e572ddc9698fb0d13a0d4c26a38b7992818a71a99d1e0ac2b034",
-	"f7380a6f795ed31fbeb2945c72c5fd1d45044e5ab152311e75e007fa530f5847",
-	"5ca1ce01458e484393d7e9c8af42b0ff37a73a2fee0f18e14cff0fb180e33014",
-	"8f44178be3fe0a2bd41f922576fb7a9b19d589754504be746f56c759df328fda",
-	"12d33847c2be711c989f37360dd7aa8537fd14972262a4530634a08fdf32a767",
-	"31e077f5080f78846a00093caff2b6b839519cc47516142eeba9c41d4072a605",
-	"14f01db8a0054e70222b76d2555d70114b4bf8a0f02084324af2df226f14a795",
-	"7f5dbbaf31b4551828e8e76cef408375db9fbcdcdb6b5949f2d1b0c4b8632132",
-	"42a5d9b9bb7e4a16f23ba916bcf87f38c1aa1f2de2ab79736f725850a8ff6a1b",
-	"e06f8f901ea708beba8712a11b6e2d0be7c4b018d0254204ef269bcdf5e8c6cc",
-	"d9ba75785bf45b0c4fd3b2365c968099242483f2f0d0c7c20306dac11fae96e9",
-	"428debbb280873907cef2ec099efe1566e42a59775d6ec74ded0c4048d5a6515",
-	"3b51049d4dae701098e55a69536fa31ad2be1adc17b631a695a40e8a294fe9c0",
-	"168f88aa4b105e9811f5f79439cc1a689be4eec77f3361d42f22fe8f7ddc74a9",
-	"0baa0ab2249b33d64449a899cb7bd8eae5231f0d4ff70f09830dc1faa2e4abee",
-	"0c3896d346b580306a49de29f3a78913a41e14b8461b124628c33a64636241f2",
-	"b18313f1651c15e100e7179aa3eb8ffa62c3581159eaf7f83156468d19781e42",
-	"996361f7d988e48267ccc7e930fed4637be35fe7562b8601dceb7a32313a14c8",
-	"dfb4e6268437d53048d22b811048cd045df15693fc6789affd002a0fc80a6e60",
-	"34dd044c228727f2226a0c9c06a3e5ceb5e30e31cb7854f8fa1cde846b395a58",
-}
-
-func (tests testIDs) List(ctx context.Context, t restic.FileType, fn func(restic.FileInfo) error) error {
-	for i := 0; i < 500; i++ {
-		for _, id := range tests {
-			if ctx.Err() != nil {
-				return ctx.Err()
-			}
-
-			fi := restic.FileInfo{
-				Name: id,
-			}
-
-			err := fn(fi)
-			if err != nil {
-				return err
-			}
-		}
-	}
-
-	return nil
-}
-
-func TestFilesInParallel(t *testing.T) {
-	f := func(ctx context.Context, id string) error {
-		time.Sleep(1 * time.Millisecond)
-		return nil
-	}
-
-	for n := 1; n < 5; n++ {
-		err := repository.FilesInParallel(context.TODO(), lister, restic.DataFile, n*100, f)
-		rtest.OK(t, err)
-	}
-}
-
-var errTest = errors.New("test error")
-
-func TestFilesInParallelWithError(t *testing.T) {
-	f := func(ctx context.Context, id string) error {
-		time.Sleep(1 * time.Millisecond)
-
-		if rand.Float32() < 0.01 {
-			return errTest
-		}
-
-		return nil
-	}
-
-	for n := 1; n < 5; n++ {
-		err := repository.FilesInParallel(context.TODO(), lister, restic.DataFile, n*100, f)
-		if err != errTest {
-			t.Fatalf("wrong error returned, want %q, got %v", errTest, err)
-		}
-	}
-}

internal/repository/repository.go

@@ -9,7 +9,6 @@ import (
 	"io"
 	"os"
 
-	"github.com/restic/restic/internal/backend"
 	"github.com/restic/restic/internal/cache"
 	"github.com/restic/restic/internal/crypto"
 	"github.com/restic/restic/internal/debug"
@@ -18,6 +17,7 @@ import (
 	"github.com/restic/restic/internal/hashing"
 	"github.com/restic/restic/internal/pack"
 	"github.com/restic/restic/internal/restic"
+	"golang.org/x/sync/errgroup"
 )
 
 // Repository is used to access a repository in a backend.
@@ -66,15 +66,29 @@ func (r *Repository) PrefixLength(t restic.FileType) (int, error) {
 	return restic.PrefixLength(r.be, t)
 }
 
-// LoadAndDecrypt loads and decrypts data identified by t and id from the
+// LoadAndDecrypt loads and decrypts the file with the given type and ID, using
-// backend.
+// the supplied buffer (which must be empty). If the buffer is nil, a new
-func (r *Repository) LoadAndDecrypt(ctx context.Context, t restic.FileType, id restic.ID) (buf []byte, err error) {
+// buffer will be allocated and returned.
+func (r *Repository) LoadAndDecrypt(ctx context.Context, buf []byte, t restic.FileType, id restic.ID) ([]byte, error) {
+	if len(buf) != 0 {
+		panic("buf is not empty")
+	}
+
 	debug.Log("load %v with id %v", t, id)
 
 	h := restic.Handle{Type: t, Name: id.String()}
-	buf, err = backend.LoadAll(ctx, r.be, h)
+	err := r.be.Load(ctx, h, 0, 0, func(rd io.Reader) error {
+		// make sure this call is idempotent, in case an error occurs
+		wr := bytes.NewBuffer(buf[:0])
+		_, cerr := io.Copy(wr, rd)
+		if cerr != nil {
+			return cerr
+		}
+		buf = wr.Bytes()
+		return nil
+	})
+
 	if err != nil {
-		debug.Log("error loading %v: %v", h, err)
 		return nil, err
 	}
 
@@ -187,7 +201,7 @@ func (r *Repository) loadBlob(ctx context.Context, id restic.ID, t restic.BlobTy
 // LoadJSONUnpacked decrypts the data and afterwards calls json.Unmarshal on
 // the item.
 func (r *Repository) LoadJSONUnpacked(ctx context.Context, t restic.FileType, id restic.ID, item interface{}) (err error) {
-	buf, err := r.LoadAndDecrypt(ctx, t, id)
+	buf, err := r.LoadAndDecrypt(ctx, nil, t, id)
 	if err != nil {
 		return err
 	}
@@ -391,45 +405,86 @@ const loadIndexParallelism = 4
 func (r *Repository) LoadIndex(ctx context.Context) error {
 	debug.Log("Loading index")
 
-	errCh := make(chan error, 1)
+	// track spawned goroutines using wg, create a new context which is
-	indexes := make(chan *Index)
+	// cancelled as soon as an error occurs.
+	wg, ctx := errgroup.WithContext(ctx)
 
-	worker := func(ctx context.Context, id restic.ID) error {
+	type FileInfo struct {
-		idx, err := LoadIndex(ctx, r, id)
+		restic.ID
-		if err != nil {
+		Size int64
-			fmt.Fprintf(os.Stderr, "%v, ignoring\n", err)
+	}
+	ch := make(chan FileInfo)
+	indexCh := make(chan *Index)
+
+	// send list of index files through ch, which is closed afterwards
+	wg.Go(func() error {
+		defer close(ch)
+		return r.List(ctx, restic.IndexFile, func(id restic.ID, size int64) error {
+			select {
+			case <-ctx.Done():
+				return nil
+			case ch <- FileInfo{id, size}:
+			}
 			return nil
-		}
+		})
+	})
 
-		select {
+	// a worker receives an index ID from ch, loads the index, and sends it to indexCh
-		case indexes <- idx:
+	worker := func() error {
-		case <-ctx.Done():
+		var buf []byte
+		for fi := range ch {
+			var err error
+			var idx *Index
+			idx, buf, err = LoadIndexWithDecoder(ctx, r, buf[:0], fi.ID, DecodeIndex)
+			if err != nil && errors.Cause(err) == ErrOldIndexFormat {
+				idx, buf, err = LoadIndexWithDecoder(ctx, r, buf[:0], fi.ID, DecodeOldIndex)
+			}
+
+			select {
+			case indexCh <- idx:
+			case <-ctx.Done():
+			}
 		}
 
 		return nil
 	}
 
-	go func() {
+	// final closes indexCh after all workers have terminated
-		defer close(indexes)
+	final := func() error {
-		errCh <- FilesInParallel(ctx, r.be, restic.IndexFile, loadIndexParallelism,
+		close(indexCh)
-			ParallelWorkFuncParseID(worker))
+		return nil
-	}()
-
-	validIndex := restic.NewIDSet()
-	for idx := range indexes {
-		id, err := idx.ID()
-		if err == nil {
-			validIndex.Insert(id)
-		}
-		r.idx.Insert(idx)
 	}
 
-	err := r.PrepareCache(validIndex)
+	// run workers on ch
+	wg.Go(func() error {
+		return RunWorkers(ctx, loadIndexParallelism, worker, final)
+	})
+
+	// receive decoded indexes
+	validIndex := restic.NewIDSet()
+	wg.Go(func() error {
+		for idx := range indexCh {
+			id, err := idx.ID()
+			if err == nil {
+				validIndex.Insert(id)
+			}
+			r.idx.Insert(idx)
+		}
+		return nil
+	})
+
+	err := wg.Wait()
 	if err != nil {
 		return err
 	}
 
-	return <-errCh
+	// remove index files from the cache which have been removed in the repo
+	err = r.PrepareCache(validIndex)
+	if err != nil {
+		return err
+	}
+
+	return nil
 }
 
 // PrepareCache initializes the local cache. indexIDs is the list of IDs of
@@ -495,14 +550,15 @@ func (r *Repository) PrepareCache(indexIDs restic.IDSet) error {
 
 // LoadIndex loads the index id from backend and returns it.
 func LoadIndex(ctx context.Context, repo restic.Repository, id restic.ID) (*Index, error) {
-	idx, err := LoadIndexWithDecoder(ctx, repo, id, DecodeIndex)
+	idx, _, err := LoadIndexWithDecoder(ctx, repo, nil, id, DecodeIndex)
 	if err == nil {
 		return idx, nil
 	}
 
 	if errors.Cause(err) == ErrOldIndexFormat {
 		fmt.Fprintf(os.Stderr, "index %v has old format\n", id.Str())
-		return LoadIndexWithDecoder(ctx, repo, id, DecodeOldIndex)
+		idx, _, err := LoadIndexWithDecoder(ctx, repo, nil, id, DecodeOldIndex)
+		return idx, err
 	}
 
 	return nil, err

internal/repository/repository_test.go

@@ -244,7 +244,7 @@ func BenchmarkLoadAndDecrypt(b *testing.B) {
 	b.SetBytes(int64(length))
 
 	for i := 0; i < b.N; i++ {
-		data, err := repo.LoadAndDecrypt(context.TODO(), restic.DataFile, storageID)
+		data, err := repo.LoadAndDecrypt(context.TODO(), nil, restic.DataFile, storageID)
 		rtest.OK(b, err)
 		if len(data) != length {
 			b.Errorf("wanted %d bytes, got %d", length, len(data))

internal/repository/worker_group.go

@@ -0,0 +1,35 @@
+package repository
+
+import (
+	"context"
+
+	"golang.org/x/sync/errgroup"
+)
+
+// RunWorkers runs count instances of workerFunc using an errgroup.Group.
+// After all workers have terminated, finalFunc is run. If an error occurs in
+// one of the workers, it is returned. FinalFunc is always run, regardless of
+// any other previous errors.
+func RunWorkers(ctx context.Context, count int, workerFunc, finalFunc func() error) error {
+	wg, ctx := errgroup.WithContext(ctx)
+
+	// run workers
+	for i := 0; i < count; i++ {
+		wg.Go(workerFunc)
+	}
+
+	// wait for termination
+	err := wg.Wait()
+
+	// make sure finalFunc is run
+	finalErr := finalFunc()
+
+	// if the workers returned an error, return it to the caller (disregarding
+	// any error from finalFunc)
+	if err != nil {
+		return err
+	}
+
+	// if not, return the value finalFunc returned
+	return finalErr
+}

internal/restic/id.go

@@ -5,6 +5,7 @@ import (
 	"crypto/sha256"
 	"encoding/hex"
 	"encoding/json"
+	"fmt"
 	"io"
 
 	"github.com/restic/restic/internal/errors"
@@ -101,13 +102,33 @@ func (id ID) MarshalJSON() ([]byte, error) {
 
 // UnmarshalJSON parses the JSON-encoded data and stores the result in id.
 func (id *ID) UnmarshalJSON(b []byte) error {
-	var s string
+	// check string length
-	err := json.Unmarshal(b, &s)
+	if len(b) < 2 {
-	if err != nil {
+		return fmt.Errorf("invalid ID: %q", b)
-		return errors.Wrap(err, "Unmarshal")
 	}
 
-	_, err = hex.Decode(id[:], []byte(s))
+	if len(b)%2 != 0 {
+		return fmt.Errorf("invalid ID length: %q", b)
+	}
+
+	// check string delimiters
+	if b[0] != '"' && b[0] != '\'' {
+		return fmt.Errorf("invalid start of string: %q", b[0])
+	}
+
+	last := len(b) - 1
+	if b[0] != b[last] {
+		return fmt.Errorf("starting string delimiter (%q) does not match end (%q)", b[0], b[last])
+	}
+
+	// strip JSON string delimiters
+	b = b[1:last]
+
+	if len(b) != 2*len(id) {
+		return fmt.Errorf("invalid length for ID")
+	}
+
+	_, err := hex.Decode(id[:], b)
 	if err != nil {
 		return errors.Wrap(err, "hex.Decode")
 	}

internal/restic/id_test.go

@@ -51,10 +51,47 @@ func TestID(t *testing.T) {
 		var id3 ID
 		err = id3.UnmarshalJSON(buf)
 		if err != nil {
-			t.Fatal(err)
+			t.Fatalf("error for %q: %v", buf, err)
 		}
 		if !reflect.DeepEqual(id, id3) {
 			t.Error("ids are not equal")
 		}
 	}
 }
+
+func TestIDUnmarshal(t *testing.T) {
+	var tests = []struct {
+		s     string
+		valid bool
+	}{
+		{`"`, false},
+		{`""`, false},
+		{`'`, false},
+		{`"`, false},
+		{`"c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4"`, false},
+		{`"c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f"`, false},
+		{`"c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2"`, true},
+	}
+
+	wantID, err := ParseID("c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, test := range tests {
+		t.Run("", func(t *testing.T) {
+			id := &ID{}
+			err := id.UnmarshalJSON([]byte(test.s))
+			if test.valid && err != nil {
+				t.Fatal(err)
+			}
+			if !test.valid && err == nil {
+				t.Fatalf("want error for invalid value, got nil")
+			}
+
+			if test.valid && !id.Equal(wantID) {
+				t.Fatalf("wrong ID returned, want %s, got %s", wantID, id)
+			}
+		})
+	}
+}

internal/restic/repository.go

@@ -39,8 +39,11 @@ type Repository interface {
 	SaveUnpacked(context.Context, FileType, []byte) (ID, error)
 	SaveJSONUnpacked(context.Context, FileType, interface{}) (ID, error)
 
-	LoadJSONUnpacked(context.Context, FileType, ID, interface{}) error
+	LoadJSONUnpacked(ctx context.Context, t FileType, id ID, dest interface{}) error
-	LoadAndDecrypt(context.Context, FileType, ID) ([]byte, error)
+	// LoadAndDecrypt loads and decrypts the file with the given type and ID,
+	// using the supplied buffer (which must be empty). If the buffer is nil, a
+	// new buffer will be allocated and returned.
+	LoadAndDecrypt(ctx context.Context, buf []byte, t FileType, id ID) (data []byte, err error)
 
 	LoadBlob(context.Context, BlobType, ID, []byte) (int, error)
 	SaveBlob(context.Context, BlobType, []byte, ID) (ID, error)