Merge pull request #84 from mcarmonaa/improvement/siva-reload-metadata

siva: reload metadata

Author: jfontan

siva/library.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"os"
 	"path/filepath"
 	"strings"
 	"sync"
@@ -31,7 +32,7 @@ type Library struct {
 	locReg   *locationRegistry
 	locMu    sync.Mutex
 	options  *LibraryOptions
-	metadata *LibraryMetadata
+	metadata *libMetadata
 }
 
 // LibraryOptions hold configuration options for the library.
@@ -61,23 +62,20 @@ type LibraryOptions struct {
 	// Performance enables performance options in read only git repositories
 	// (ExclusiveAccess and KeepDescriptors).
 	Performance bool
-	// DontGenerateID stops the library from generating a library ID if it's
-	// not provided or already in metadata.
-	DontGenerateID bool
+	// MetadataReadOnly doesn't create or modify metadata for the library.
+	MetadataReadOnly bool
 }
 
 var _ borges.Library = (*Library)(nil)
 
 const (
-	timeout = 20 * time.Second
-	// txTimeout is the default transaction TransactionTimeout.
+	timeout           = 20 * time.Second
 	txTimeout         = 60 * time.Second
 	registryCacheSize = 10000
 )
 
-// NewLibrary creates a new siva.Library. If id is not provided the library ID
-// is read from the existing metadata or generated if not available and the
-// option DontGenerateID is not set.
+// NewLibrary creates a new siva.Library. When is not in MetadataReadOnly it
+// will generate an id if not provided the first time the metadata is created.
 func NewLibrary(
 	id string,
 	fs billy.Filesystem,
@@ -90,24 +88,23 @@ func NewLibrary(
 		ops = &(*options)
 	}
 
-	metadata, err := loadLibraryMetadata(fs)
-	if err != nil {
-		// TODO: skip metadata if corrupted?
-		return nil, err
-	}
+	var (
+		metadata *libMetadata
+		err      error
+	)
 
-	if metadata == nil {
-		metadata = NewLibraryMetadata("", -1)
+	if ops.MetadataReadOnly {
+		metadata, err = loadLibraryMetadata(fs)
+	} else {
+		metadata, err = loadOrCreateLibraryMetadata(id, fs)
 	}
 
-	if id == "" {
-		if metadata.ID == "" && !ops.DontGenerateID {
-			metadata.GenerateID()
-		}
+	if err != nil && !os.IsNotExist(err) {
+		return nil, err
+	}
 
+	if metadata != nil && id == "" {
 		id = metadata.ID
-	} else {
-		metadata.SetID(id)
 	}
 
 	if ops.RegistryCache <= 0 {
@@ -137,21 +134,14 @@ func NewLibrary(
 		tmp = osfs.New(dir)
 	}
 
-	lib := &Library{
+	return &Library{
 		id:       borges.LibraryID(id),
 		fs:       fs,
 		tmp:      tmp,
 		locReg:   lr,
 		options:  ops,
 		metadata: metadata,
-	}
-
-	err = lib.SaveMetadata()
-	if err != nil {
-		return nil, err
-	}
-
-	return lib, nil
+	}, nil
 }
 
 // ID implements borges.Library interface.
@@ -349,24 +339,20 @@ func (l *Library) locations(ctx context.Context) ([]borges.Location, error) {
 }
 
 // Version returns version stored in metadata or -1 if not defined.
-func (l *Library) Version() int {
-	return l.metadata.Version()
-}
-
-// SetVersion sets the current version to the given number.
-func (l *Library) SetVersion(n int) {
-	if l.metadata == nil {
-		l.metadata = NewLibraryMetadata(string(l.id), -1)
+func (l *Library) Version() (int, error) {
+	if l.metadata != nil {
+		return l.metadata.version()
 	}
 
-	l.metadata.SetVersion(n)
+	return -1, nil
 }
 
-// SaveMetadata writes the metadata to the library yaml file.
-func (l *Library) SaveMetadata() error {
-	if l.metadata != nil && l.metadata.dirty {
-		return l.metadata.Save(l.fs)
+// SetVersion sets the current version to the given number.
+func (l *Library) SetVersion(n int) error {
+	if l.metadata == nil {
+		return nil
 	}
 
-	return nil
+	l.metadata.setVersion(n)
+	return l.metadata.save()
 }

siva/location.go

@@ -36,7 +36,7 @@ type Location struct {
 	lib        *Library
 	checkpoint *checkpoint
 	txer       *transactioner
-	metadata   *LocationMetadata
+	metadata   *locationMetadata
 
 	// references and config cache
 	refs    memory.ReferenceStorage
@@ -58,10 +58,14 @@ func newLocation(
 	path string,
 	create bool,
 ) (*Location, error) {
-	metadata, err := loadLocationMetadata(lib.fs, locationMetadataPath(path))
-	if err != nil {
-		// TODO: skip metadata if corrupted? log a warning?
-		return nil, err
+	var metadata *locationMetadata
+	if lib.metadata != nil {
+		var err error
+		metadata, err = loadOrCreateLocationMetadata(lib.fs, string(id))
+		if err != nil {
+			// TODO: skip metadata if corrupted? log a warning?
+			return nil, err
+		}
 	}
 
 	cp, err := newCheckpoint(lib.fs, path, create)
@@ -104,7 +108,11 @@ func (l *Location) checkAndUpdate() error {
 		return err
 	}
 
-	version := l.lib.Version()
+	version, err := l.lib.Version()
+	if err != nil {
+		return err
+	}
+
 	if l.fSize == stat.Size() && l.fTime == stat.ModTime() &&
 		l.version == version && l.checkpoint.Offset() == cp.Offset() {
 		return nil
@@ -175,9 +183,18 @@ func (l *Location) fs(mode borges.Mode, cp *checkpoint) (sivafs.SivaFS, error) {
 			return nil, borges.ErrLocationNotExists.New(string(l.id))
 		}
 
-		if l.metadata != nil {
-			version := l.lib.Version()
-			if o := l.metadata.Offset(version); o > 0 {
+		if l.lib.metadata != nil {
+			version, err := l.lib.Version()
+			if err != nil {
+				return nil, err
+			}
+
+			o, err := l.metadata.offset(version)
+			if err != nil {
+				return nil, err
+			}
+
+			if o > 0 {
 				offset = o
 			}
 		}
@@ -561,40 +578,40 @@ func (l *Location) repository(
 	return newRepository(id, sto, fs, mode, l.lib.options.Transactional, l)
 }
 
-func (l *Location) createMetadata() {
-	if l.metadata == nil {
-		l.metadata = NewLocationMetadata(make(map[int]Version))
-	}
-}
-
 // LastVersion returns the last defined version number in metadata or -1 if
 // there are not versions.
 func (l *Location) LastVersion() int {
-	return l.metadata.Last()
+	return l.metadata.last()
 }
 
-// Version returns an specific version. Second return value is false if the
-// version does not exist.
-func (l *Location) Version(v int) (Version, bool) {
-	return l.metadata.Version(v)
+// Version returns an specific version. If the given version does not exist
+// an error is returned.
+func (l *Location) Version(v int) (*Version, error) {
+	if l.lib.metadata != nil {
+		return l.metadata.version(v)
+	}
+
+	return nil, errLocVersionNotExists.New()
 }
 
 // SetVersion adds or changes a version to the location.
-func (l *Location) SetVersion(n int, v Version) {
-	l.createMetadata()
-	l.metadata.SetVersion(n, v)
+func (l *Location) SetVersion(n int, v *Version) {
+	if l.lib.metadata != nil {
+		l.metadata.setVersion(n, v)
+	}
 }
 
 // DeleteVersion removes the given version number.
 func (l *Location) DeleteVersion(n int) {
-	l.createMetadata()
-	l.metadata.DeleteVersion(n)
+	if l.lib.metadata != nil {
+		l.metadata.deleteVersion(n)
+	}
 }
 
 // SaveMetadata writes the location metadata to disk.
 func (l *Location) SaveMetadata() error {
-	if l.metadata != nil && l.metadata.Dirty() {
-		return l.metadata.Save(l.lib.fs, l.path)
+	if l.metadata != nil {
+		return l.metadata.save()
 	}
 
 	return nil