Fix writing 0 byte msgpack metadata

changelog/unreleased/fix-0-byte-msgpack.md

@@ -0,0 +1,5 @@
+Bugfix: fix writing 0 byte msgpack metadata
+
+File metadata is now written atomically to be more resilient during timeouts
+
+https://github.com/cs3org/reva/pull/4033

go.mod

@@ -138,6 +138,7 @@ require (
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
 	github.com/google/go-querystring v1.1.0 // indirect
 	github.com/google/pprof v0.0.0-20210720184732-4bb14d4b1be1 // indirect
+	github.com/google/renameio/v2 v2.0.0 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.13.0 // indirect
 	github.com/hashicorp/consul/api v1.15.2 // indirect
 	github.com/hashicorp/go-cleanhttp v0.5.2 // indirect

go.sum

@@ -781,6 +781,8 @@ github.com/google/pprof v0.0.0-20210609004039-a478d1d731e9/go.mod h1:kpwsk12EmLe
 github.com/google/pprof v0.0.0-20210720184732-4bb14d4b1be1 h1:K6RDEckDVWvDI9JAJYCmNdQXq6neHJOYx3V6jnqNEec=
 github.com/google/pprof v0.0.0-20210720184732-4bb14d4b1be1/go.mod h1:kpwsk12EmLew5upagYY7GY0pfYCcupk39gWOCRROcvE=
 github.com/google/renameio v0.1.0/go.mod h1:KWCgfxg9yswjAJkECMjeO8J8rahYeXnNhOm40UhjYkI=
+github.com/google/renameio/v2 v2.0.0 h1:UifI23ZTGY8Tt29JbYFiuyIU3eX+RNFtUwefq9qAhxg=
+github.com/google/renameio/v2 v2.0.0/go.mod h1:BtmJXm5YlszgC+TD4HOEEUFgkJP3nLxehU6hfe7jRt4=
 github.com/google/uuid v1.1.1/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/google/uuid v1.1.2/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/google/uuid v1.2.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=

pkg/storage/utils/decomposedfs/lookup/lookup.go

@@ -284,7 +284,7 @@ func refFromCS3(b []byte) (*provider.Reference, error) {
 func (lu *Lookup) CopyMetadata(ctx context.Context, src, target string, filter func(attributeName string) bool) (err error) {
 	// Acquire a read log on the source node
 	// write lock existing node before reading treesize or tree time
-	f, err := lockedfile.Open(lu.MetadataBackend().MetadataPath(src))
+	lock, err := lockedfile.OpenFile(lu.MetadataBackend().LockfilePath(src), os.O_RDONLY|os.O_CREATE, 0600)
 	if err != nil {
 		return err
 	}
@@ -293,15 +293,15 @@ func (lu *Lookup) CopyMetadata(ctx context.Context, src, target string, filter f
 		return errors.Wrap(err, "xattrs: Unable to lock source to read")
 	}
 	defer func() {
-		rerr := f.Close()
+		rerr := lock.Close()
 
 		// if err is non nil we do not overwrite that
 		if err == nil {
 			err = rerr
 		}
 	}()
 
-	return lu.CopyMetadataWithSourceLock(ctx, src, target, filter, f)
+	return lu.CopyMetadataWithSourceLock(ctx, src, target, filter, lock)
 }
 
 // CopyMetadataWithSourceLock copies all extended attributes from source to target.
@@ -312,11 +312,11 @@ func (lu *Lookup) CopyMetadataWithSourceLock(ctx context.Context, sourcePath, ta
 	switch {
 	case lockedSource == nil:
 		return errors.New("no lock provided")
-	case lockedSource.File.Name() != lu.MetadataBackend().MetadataPath(sourcePath):
+	case lockedSource.File.Name() != lu.MetadataBackend().LockfilePath(sourcePath):
 		return errors.New("lockpath does not match filepath")
 	}
 
-	attrs, err := lu.metadataBackend.AllWithLockedSource(ctx, sourcePath, lockedSource)
+	attrs, err := lu.metadataBackend.All(ctx, sourcePath)
 	if err != nil {
 		return err
 	}

pkg/storage/utils/decomposedfs/metadata/messagepack_backend.go

@@ -20,14 +20,17 @@ package metadata
 
 import (
 	"context"
+	"errors"
 	"io"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
 	"time"
 
 	"github.com/cs3org/reva/v2/pkg/storage/cache"
+	"github.com/google/renameio/v2"
 	"github.com/pkg/xattr"
 	"github.com/rogpeppe/go-internal/lockedfile"
 	"github.com/shamaton/msgpack/v2"
@@ -142,74 +145,65 @@ func (b MessagePackBackend) saveAttributes(ctx context.Context, path string, set
 		span.End()
 	}()
 
+	lockPath := b.LockfilePath(path)
 	metaPath := b.MetadataPath(path)
 	if acquireLock {
 		_, subspan := tracer.Start(ctx, "lockedfile.OpenFile")
-		f, err = lockedfile.OpenFile(metaPath, os.O_RDWR|os.O_CREATE, 0600)
-		subspan.End()
-	} else {
-		_, subspan := tracer.Start(ctx, "os.OpenFile")
-		f, err = os.OpenFile(metaPath, os.O_RDWR|os.O_CREATE, 0600)
+		f, err = lockedfile.OpenFile(lockPath, os.O_RDWR|os.O_CREATE, 0600)
 		subspan.End()
+		defer f.Close()
 	}
 	if err != nil {
 		return err
 	}
-	defer f.Close()
 
 	// Invalidate cache early
 	_, subspan := tracer.Start(ctx, "metaCache.RemoveMetadata")
 	_ = b.metaCache.RemoveMetadata(b.cacheKey(path))
 	subspan.End()
 
 	// Read current state
-	_, subspan = tracer.Start(ctx, "io.ReadAll")
+	_, subspan = tracer.Start(ctx, "os.ReadFile")
 	var msgBytes []byte
-	msgBytes, err = io.ReadAll(f)
+	msgBytes, err = os.ReadFile(metaPath)
 	subspan.End()
-	if err != nil {
-		return err
-	}
 	attribs := map[string][]byte{}
-	if len(msgBytes) > 0 {
+	switch {
+	case err != nil:
+		if !errors.Is(err, fs.ErrNotExist) {
+			return err
+		}
+	case len(msgBytes) == 0:
+		// ugh. an empty file? bail out
+		return errors.New("encountered empty metadata file")
+	default:
+		// only unmarshal if we read data
 		err = msgpack.Unmarshal(msgBytes, &attribs)
 		if err != nil {
 			return err
 		}
 	}
 
-	// set new metadata
+	// prepare metadata
 	for key, val := range setAttribs {
 		attribs[key] = val
 	}
 	for _, key := range deleteAttribs {
 		delete(attribs, key)
 	}
-
-	// Truncate file
-	_, err = f.Seek(0, io.SeekStart)
-	if err != nil {
-		return err
-	}
-	_, subspan = tracer.Start(ctx, "f.Truncate")
-	err = f.Truncate(0)
-	subspan.End()
-	if err != nil {
-		return err
-	}
-
-	// Write new metadata to file
 	var d []byte
 	d, err = msgpack.Marshal(attribs)
 	if err != nil {
 		return err
 	}
-	_, subspan = tracer.Start(ctx, "f.Write")
-	_, err = f.Write(d)
-	subspan.End()
+
+	// overwrite file atomically
+	_, subspan = tracer.Start(ctx, "renameio.Writefile")
+	err = renameio.WriteFile(metaPath, d, 0600)
 	if err != nil {
 		return err
 	}
+	subspan.End()
 
 	_, subspan = tracer.Start(ctx, "metaCache.PushToCache")
 	err = b.metaCache.PushToCache(b.cacheKey(path), attribs)
@@ -227,9 +221,13 @@ func (b MessagePackBackend) loadAttributes(ctx context.Context, path string, sou
 	}
 
 	metaPath := b.MetadataPath(path)
+	var msgBytes []byte
+
 	if source == nil {
-		_, subspan := tracer.Start(ctx, "lockedfile.Open")
-		source, err = lockedfile.Open(metaPath)
+		// // No cached entry found. Read from storage and store in cache
+		_, subspan := tracer.Start(ctx, "os.OpenFile")
+		// source, err = lockedfile.Open(metaPath)
+		source, err = os.Open(metaPath)
 		subspan.End()
 		// // No cached entry found. Read from storage and store in cache
 		if err != nil {
@@ -246,12 +244,16 @@ func (b MessagePackBackend) loadAttributes(ctx context.Context, path string, sou
 				return attribs, nil // no attributes set yet
 			}
 		}
-		defer source.(*lockedfile.File).Close()
+		_, subspan = tracer.Start(ctx, "io.ReadAll")
+		msgBytes, err = io.ReadAll(source)
+		source.(*os.File).Close()
+		subspan.End()
+	} else {
+		_, subspan := tracer.Start(ctx, "io.ReadAll")
+		msgBytes, err = io.ReadAll(source)
+		subspan.End()
 	}
 
-	_, subspan := tracer.Start(ctx, "io.ReadAll")
-	msgBytes, err := io.ReadAll(source)
-	subspan.End()
 	if err != nil {
 		return nil, err
 	}
@@ -262,7 +264,7 @@ func (b MessagePackBackend) loadAttributes(ctx context.Context, path string, sou
 		}
 	}
 
-	_, subspan = tracer.Start(ctx, "metaCache.PushToCache")
+	_, subspan := tracer.Start(ctx, "metaCache.PushToCache")
 	err = b.metaCache.PushToCache(b.cacheKey(path), attribs)
 	subspan.End()
 	if err != nil {
@@ -273,7 +275,9 @@ func (b MessagePackBackend) loadAttributes(ctx context.Context, path string, sou
 }
 
 // IsMetaFile returns whether the given path represents a meta file
-func (MessagePackBackend) IsMetaFile(path string) bool { return strings.HasSuffix(path, ".mpk") }
+func (MessagePackBackend) IsMetaFile(path string) bool {
+	return strings.HasSuffix(path, ".mpk") || strings.HasSuffix(path, ".mpk.lock")
+}
 
 // Purge purges the data of a given path
 func (b MessagePackBackend) Purge(path string) error {
@@ -304,6 +308,9 @@ func (b MessagePackBackend) Rename(oldPath, newPath string) error {
 // MetadataPath returns the path of the file holding the metadata for the given path
 func (MessagePackBackend) MetadataPath(path string) string { return path + ".mpk" }
 
+// LockfilePath returns the path of the lock file
+func (MessagePackBackend) LockfilePath(path string) string { return path + ".mpk.lock" }
+
 func (b MessagePackBackend) cacheKey(path string) string {
 	// rootPath is guaranteed to have no trailing slash
 	// the cache key shouldn't begin with a slash as some stores drop it which can cause

pkg/storage/utils/decomposedfs/metadata/metadata.go

@@ -52,6 +52,7 @@ type Backend interface {
 	Rename(oldPath, newPath string) error
 	IsMetaFile(path string) bool
 	MetadataPath(path string) string
+	LockfilePath(path string) string
 
 	AllWithLockedSource(ctx context.Context, path string, source io.Reader) (map[string][]byte, error)
 }
@@ -110,6 +111,9 @@ func (NullBackend) Rename(oldPath, newPath string) error { return errUnconfigure
 // MetadataPath returns the path of the file holding the metadata for the given path
 func (NullBackend) MetadataPath(path string) string { return "" }
 
+// LockfilePath returns the path of the lock file
+func (NullBackend) LockfilePath(path string) string { return "" }
+
 // AllWithLockedSource reads all extended attributes from the given reader
 // The path argument is used for storing the data in the cache
 func (NullBackend) AllWithLockedSource(ctx context.Context, path string, source io.Reader) (map[string][]byte, error) {

pkg/storage/utils/decomposedfs/metadata/metadata_test.go

@@ -31,9 +31,8 @@ import (
 
 var _ = Describe("Backend", func() {
 	var (
-		tmpdir   string
-		file     string
-		metafile string
+		tmpdir string
+		file   string
 
 		backend metadata.Backend
 	)
@@ -46,9 +45,6 @@ var _ = Describe("Backend", func() {
 
 	JustBeforeEach(func() {
 		file = path.Join(tmpdir, "file")
-		metafile = backend.MetadataPath(file)
-		_, err := os.Create(metafile)
-		Expect(err).ToNot(HaveOccurred())
 	})
 
 	AfterEach(func() {
@@ -147,10 +143,9 @@ var _ = Describe("Backend", func() {
 				Expect(v["bar"]).To(Equal([]byte("baz")))
 			})
 
-			It("returns an empty map", func() {
-				v, err := backend.All(context.Background(), file)
-				Expect(err).ToNot(HaveOccurred())
-				Expect(v).To(Equal(map[string][]byte{}))
+			It("fails when the metafile does not exist", func() {
+				_, err := backend.All(context.Background(), file)
+				Expect(err).To(HaveOccurred())
 			})
 		})
 
@@ -165,10 +160,9 @@ var _ = Describe("Backend", func() {
 				Expect(v).To(ConsistOf("foo", "bar"))
 			})
 
-			It("returns an empty list", func() {
-				v, err := backend.List(context.Background(), file)
-				Expect(err).ToNot(HaveOccurred())
-				Expect(v).To(Equal([]string{}))
+			It("fails when the metafile does not exist", func() {
+				_, err := backend.List(context.Background(), file)
+				Expect(err).To(HaveOccurred())
 			})
 		})
 

pkg/storage/utils/decomposedfs/metadata/xattrs_backend.go

@@ -24,6 +24,7 @@ import (
 	"os"
 	"path/filepath"
 	"strconv"
+	"strings"
 
 	"github.com/cs3org/reva/v2/pkg/storage/utils/filelocks"
 	"github.com/pkg/errors"
@@ -156,7 +157,7 @@ func (XattrsBackend) Remove(ctx context.Context, filePath string, key string) (e
 }
 
 // IsMetaFile returns whether the given path represents a meta file
-func (XattrsBackend) IsMetaFile(path string) bool { return false }
+func (XattrsBackend) IsMetaFile(path string) bool { return strings.HasSuffix(path, ".meta.lock") }
 
 // Purge purges the data of a given path
 func (XattrsBackend) Purge(path string) error { return nil }
@@ -167,6 +168,9 @@ func (XattrsBackend) Rename(oldPath, newPath string) error { return nil }
 // MetadataPath returns the path of the file holding the metadata for the given path
 func (XattrsBackend) MetadataPath(path string) string { return path }
 
+// LockfilePath returns the path of the lock file
+func (XattrsBackend) LockfilePath(path string) string { return path + ".meta.lock" }
+
 func cleanupLockfile(f *lockedfile.File) {
 	_ = f.Close()
 	_ = os.Remove(f.Name())

pkg/storage/utils/decomposedfs/revisions.go

@@ -70,7 +70,7 @@ func (fs *Decomposedfs) ListRevisions(ctx context.Context, ref *provider.Referen
 	np := n.InternalPath()
 	if items, err := filepath.Glob(np + node.RevisionIDDelimiter + "*"); err == nil {
 		for i := range items {
-			if fs.lu.MetadataBackend().IsMetaFile(items[i]) {
+			if fs.lu.MetadataBackend().IsMetaFile(items[i]) || strings.HasSuffix(items[i], ".lock") {
 				continue
 			}
 
@@ -237,7 +237,7 @@ func (fs *Decomposedfs) RestoreRevision(ctx context.Context, ref *provider.Refer
 				attributeName == prefixes.BlobsizeAttr
 		})
 		if err != nil {
-			return errtypes.InternalError("failed to copy blob xattrs to version node")
+			return errtypes.InternalError("failed to copy blob xattrs to version node: " + err.Error())
 		}
 
 		// remember mtime from node as new revision mtime
@@ -256,7 +256,7 @@ func (fs *Decomposedfs) RestoreRevision(ctx context.Context, ref *provider.Refer
 				attributeName == prefixes.BlobsizeAttr
 		})
 		if err != nil {
-			return errtypes.InternalError("failed to copy blob xattrs to old revision to node")
+			return errtypes.InternalError("failed to copy blob xattrs to old revision to node: " + err.Error())
 		}
 
 		revisionSize, err := fs.lu.MetadataBackend().GetInt64(ctx, restoredRevisionPath, prefixes.BlobsizeAttr)

pkg/storage/utils/decomposedfs/tree/tree.go

@@ -40,7 +40,6 @@ import (
 	"github.com/cs3org/reva/v2/pkg/storage/utils/decomposedfs/metadata/prefixes"
 	"github.com/cs3org/reva/v2/pkg/storage/utils/decomposedfs/node"
 	"github.com/cs3org/reva/v2/pkg/storage/utils/decomposedfs/options"
-	"github.com/cs3org/reva/v2/pkg/storage/utils/filelocks"
 	"github.com/cs3org/reva/v2/pkg/utils"
 	"github.com/google/uuid"
 	"github.com/pkg/errors"
@@ -750,17 +749,8 @@ func (t *Tree) Propagate(ctx context.Context, n *node.Node, sizeDiff int64) (err
 		// lock parent before reading treesize or tree time
 
 		_, subspan := tracer.Start(ctx, "lockedfile.OpenFile")
-		var parentFilename string
-		switch t.lookup.MetadataBackend().(type) {
-		case metadata.MessagePackBackend:
-			parentFilename = t.lookup.MetadataBackend().MetadataPath(n.ParentPath())
-			f, err = lockedfile.OpenFile(parentFilename, os.O_RDWR|os.O_CREATE, 0600)
-		case metadata.XattrsBackend:
-			// we have to use dedicated lockfiles to lock directories
-			// this only works because the xattr backend also locks folders with separate lock files
-			parentFilename = n.ParentPath() + filelocks.LockFileSuffix
-			f, err = lockedfile.OpenFile(parentFilename, os.O_RDWR|os.O_CREATE, 0600)
-		}
+		parentFilename := t.lookup.MetadataBackend().LockfilePath(n.ParentPath())
+		f, err = lockedfile.OpenFile(parentFilename, os.O_RDWR|os.O_CREATE, 0600)
 		subspan.End()
 		if err != nil {
 			sublog.Error().Err(err).