siva: location registry + transactioner

siva/checkpoint.go

@@ -19,17 +19,17 @@ var (
 
 const checkpointExtension = ".checkpoint"
 
-// Checkpoint tracks the status of a siva file and creates checkpoints to be
+// checkpoint tracks the status of a siva file and creates checkpoints to be
 // able to return back to a known state of that siva file.
-type Checkpoint struct {
+type checkpoint struct {
 	offset  int64
 	baseFs  billy.Filesystem
 	path    string
 	persist string
 }
 
-// NewCheckpoint builds a new Checkpoint.
-func NewCheckpoint(fs billy.Filesystem, path string) (*Checkpoint, error) {
+// newCheckpoint builds a new Checkpoint.
+func newCheckpoint(fs billy.Filesystem, path string) (*checkpoint, error) {
 	persist := path + checkpointExtension
 
 	if _, err := fs.Stat(path); err != nil && os.IsNotExist(err) {
@@ -38,7 +38,7 @@ func NewCheckpoint(fs billy.Filesystem, path string) (*Checkpoint, error) {
 			borges.ErrLocationNotExists.New(path))
 	}
 
-	c := &Checkpoint{
+	c := &checkpoint{
 		baseFs:  fs,
 		path:    path,
 		persist: persist,
@@ -64,7 +64,7 @@ func NewCheckpoint(fs billy.Filesystem, path string) (*Checkpoint, error) {
 
 // Apply applies if necessary the operations on the siva file to
 // leave it in the last correct state the checkpoint keeps.
-func (c *Checkpoint) Apply() error {
+func (c *checkpoint) Apply() error {
 	if c.offset > 0 {
 		f, err := c.baseFs.Open(c.path)
 		if err != nil {
@@ -82,7 +82,7 @@ func (c *Checkpoint) Apply() error {
 }
 
 // Save saves the current state of the siva file.
-func (c *Checkpoint) Save() error {
+func (c *checkpoint) Save() error {
 	info, err := c.baseFs.Stat(c.path)
 	if err != nil {
 		return ErrCannotUseSivaFile.Wrap(err)
@@ -98,7 +98,7 @@ func (c *Checkpoint) Save() error {
 }
 
 // Reset resets the checkpoint.
-func (c *Checkpoint) Reset() error {
+func (c *checkpoint) Reset() error {
 	if err := cleanup(c.baseFs, c.persist); err != nil {
 		return ErrCannotUseCheckpointFile.Wrap(err)
 	}

siva/checkpoint_test.go

@@ -19,7 +19,8 @@ func TestCheckpoint(t *testing.T) {
 	require.NoError(err)
 
 	fs := memfs.New()
-	lib := NewLibrary("test", fs, true)
+	lib, err := NewLibrary("test", fs, LibraryOptions{Transactional: true})
+	require.NoError(err)
 
 	var l borges.Location
 

siva/iterator.go

@@ -16,6 +16,7 @@ type repositoryIterator struct {
 
 var _ borges.RepositoryIterator = (*repositoryIterator)(nil)
 
+// Next implements the borges.RepositoryIterator interface.
 func (i *repositoryIterator) Next() (borges.Repository, error) {
 	for {
 		if i.pos >= len(i.remotes) {
@@ -39,6 +40,7 @@ func (i *repositoryIterator) Next() (borges.Repository, error) {
 	}
 }
 
+// ForEach implements the borges.RepositoryIterator interface.
 func (i *repositoryIterator) ForEach(f func(borges.Repository) error) error {
 	for {
 		r, err := i.Next()
@@ -56,4 +58,5 @@ func (i *repositoryIterator) ForEach(f func(borges.Repository) error) error {
 	}
 }
 
+// Close implements the borges.RepositoryIterator interface.
 func (i *repositoryIterator) Close() {}

siva/library.go

@@ -6,6 +6,7 @@ import (
 	"strings"
 
 	borges "github.com/src-d/go-borges"
+
 	"github.com/src-d/go-borges/util"
 	billy "gopkg.in/src-d/go-billy.v4"
 	butil "gopkg.in/src-d/go-billy.v4/util"
@@ -16,17 +17,37 @@ type Library struct {
 	id            borges.LibraryID
 	fs            billy.Filesystem
 	transactional bool
+	locReg        *locationRegistry
+}
+
+// LibraryOptions hold configuration options for the library.
+type LibraryOptions struct {
+	// Transactional enables transactions for repository writes.
+	Transactional bool
+	// RegistryCache is the maximum number of locations in the cache. A value
+	// of 0 disables the cache.
+	RegistryCache int
 }
 
 var _ borges.Library = (*Library)(nil)
 
 // NewLibrary creates a new siva.Library.
-func NewLibrary(id string, fs billy.Filesystem, transactional bool) *Library {
+func NewLibrary(
+	id string,
+	fs billy.Filesystem,
+	ops LibraryOptions,
+) (*Library, error) {
+	lr, err := newLocationRegistry(ops.RegistryCache)
+	if err != nil {
+		return nil, err
+	}
+
 	return &Library{
 		id:            borges.LibraryID(id),
 		fs:            fs,
-		transactional: transactional,
-	}
+		transactional: ops.Transactional,
+		locReg:        lr,
+	}, nil
 }
 
 // ID implements borges.Library interface.
@@ -114,8 +135,19 @@ func (l *Library) Repositories(mode borges.Mode) (borges.RepositoryIterator, err
 
 // Location implements borges.Library interface.
 func (l *Library) Location(id borges.LocationID) (borges.Location, error) {
+	if loc, ok := l.locReg.Get(id); ok {
+		return loc, nil
+	}
+
 	path := fmt.Sprintf("%s.siva", id)
-	return NewLocation(id, l, path)
+	loc, err := NewLocation(id, l, path)
+	if err != nil {
+		return nil, err
+	}
+
+	l.locReg.Add(loc)
+
+	return loc, nil
 }
 
 // Locations implements borges.Library interface.

siva/library_test.go

@@ -5,6 +5,7 @@ import (
 
 	borges "github.com/src-d/go-borges"
 	"github.com/src-d/go-borges/test"
+	"github.com/stretchr/testify/require"
 	"github.com/stretchr/testify/suite"
 	"gopkg.in/src-d/go-billy.v4/osfs"
 )
@@ -14,7 +15,10 @@ func TestLibrary(t *testing.T) {
 	fs := osfs.New("../_testdata/siva")
 
 	s.LibrarySingle = func() borges.Library {
-		return NewLibrary("foo", fs, false)
+		lib, err := NewLibrary("foo", fs, LibraryOptions{})
+		require.NoError(t, err)
+
+		return lib
 	}
 
 	suite.Run(t, s)

siva/location.go

@@ -9,47 +9,42 @@ import (
 	"gopkg.in/src-d/go-git.v4/config"
 )
 
-var (
-	// ErrMalformedData when checkpoint data is invalid.
-	ErrMalformedData = errors.NewKind("malformed data")
-	// ErrTransactioning is returned when a second transaction wants to start
-	// in the same location.
-	ErrTransactioning = errors.NewKind("already doing a transaction")
-)
+// ErrMalformedData when checkpoint data is invalid.
+var ErrMalformedData = errors.NewKind("malformed data")
 
+// Location represents a siva file archiving several git repositories.
 type Location struct {
-	id   borges.LocationID
-	path string
-	// cachedFS billy.Filesystem
-	cachedFS sivafs.SivaFS
-	library  *Library
-
-	// last good position
-	checkpoint     *Checkpoint
-	transactioning bool
+	id         borges.LocationID
+	path       string
+	cachedFS   sivafs.SivaFS
+	lib        *Library
+	checkpoint *checkpoint
+	txer       *transactioner
 }
 
 var _ borges.Location = (*Location)(nil)
 
-func NewLocation(id borges.LocationID, l *Library, path string) (*Location, error) {
-	checkpoint, err := NewCheckpoint(l.fs, path)
+// NewLocation creates a new Location object.
+func NewLocation(id borges.LocationID, lib *Library, path string) (*Location, error) {
+	cp, err := newCheckpoint(lib.fs, path)
 	if err != nil {
 		return nil, err
 	}
 
-	location := &Location{
+	loc := &Location{
 		id:         id,
 		path:       path,
-		library:    l,
-		checkpoint: checkpoint,
+		lib:        lib,
+		checkpoint: cp,
 	}
 
-	_, err = location.FS()
+	_, err = loc.FS()
 	if err != nil {
 		return nil, err
 	}
 
-	return location, nil
+	loc.txer = newTransactioner(loc, lib.locReg)
+	return loc, nil
 }
 
 func (l *Location) newFS() (sivafs.SivaFS, error) {
@@ -75,10 +70,12 @@ func (l *Location) FS() (sivafs.SivaFS, error) {
 	return sfs, nil
 }
 
+// ID implements the borges.Location interface.
 func (l *Location) ID() borges.LocationID {
 	return l.id
 }
 
+// Init implements the borges.Location interface.
 func (l *Location) Init(id borges.RepositoryID) (borges.Repository, error) {
 	has, err := l.Has(id)
 	if err != nil {
@@ -111,6 +108,7 @@ func (l *Location) Init(id borges.RepositoryID) (borges.Repository, error) {
 	return repo, nil
 }
 
+// Get implements the borges.Location interface.
 func (l *Location) Get(id borges.RepositoryID, mode borges.Mode) (borges.Repository, error) {
 	has, err := l.Has(id)
 	if err != nil {
@@ -124,6 +122,7 @@ func (l *Location) Get(id borges.RepositoryID, mode borges.Mode) (borges.Reposit
 	return l.repository(id, mode)
 }
 
+// GetOrInit implements the borges.Location interface.
 func (l *Location) GetOrInit(id borges.RepositoryID) (borges.Repository, error) {
 	has, err := l.Has(id)
 	if err != nil {
@@ -137,6 +136,7 @@ func (l *Location) GetOrInit(id borges.RepositoryID) (borges.Repository, error)
 	return l.Init(id)
 }
 
+// Has implements the borges.Location interface.
 func (l *Location) Has(name borges.RepositoryID) (bool, error) {
 	repo, err := l.repository("", borges.ReadOnlyMode)
 	if err != nil {
@@ -159,6 +159,7 @@ func (l *Location) Has(name borges.RepositoryID) (bool, error) {
 	return false, nil
 }
 
+// Repositories implements the borges.Location interface.
 func (l *Location) Repositories(mode borges.Mode) (borges.RepositoryIterator, error) {
 	var remotes []*config.RemoteConfig
 
@@ -183,21 +184,17 @@ func (l *Location) Repositories(mode borges.Mode) (borges.RepositoryIterator, er
 	}, nil
 }
 
-func (l *Location) transactional() bool {
-	return l.library.transactional
-}
-
 func (l *Location) baseFS() billy.Filesystem {
-	return l.library.fs
+	return l.lib.fs
 }
 
-func (l *Location) setupTransaction(mode borges.Mode) (sivafs.SivaFS, error) {
-	if !l.transactional() || mode != borges.RWMode {
+func (l *Location) getRepoFs(id borges.RepositoryID, mode borges.Mode) (sivafs.SivaFS, error) {
+	if !l.lib.transactional || mode != borges.RWMode {
 		return l.FS()
 	}
 
-	if l.transactioning {
-		return nil, ErrTransactioning.New()
+	if err := l.txer.Start(); err != nil {
+		return nil, err
 	}
 
 	fs, err := l.newFS()
@@ -209,34 +206,35 @@ func (l *Location) setupTransaction(mode borges.Mode) (sivafs.SivaFS, error) {
 		return nil, err
 	}
 
-	l.transactioning = true
 	return fs, nil
 }
 
-func (l *Location) Commit() error {
-	if !l.transactional() || !l.transactioning {
+// Commit persists transactional or write operations performed on the repositories.
+func (l *Location) Commit(mode borges.Mode) error {
+	if !l.lib.transactional || mode != borges.RWMode {
 		return nil
 	}
 
+	defer l.txer.Stop()
 	if err := l.checkpoint.Reset(); err != nil {
 		return err
 	}
 
-	l.transactioning = false
 	l.cachedFS = nil
 	return nil
 }
 
-func (l *Location) Rollback() error {
-	if !l.transactional() || !l.transactioning {
+// Rollback discard transactional or write operations performed on the repositories.
+func (l *Location) Rollback(mode borges.Mode) error {
+	if !l.lib.transactional || mode != borges.RWMode {
 		return nil
 	}
 
+	defer l.txer.Stop()
 	if err := l.checkpoint.Apply(); err != nil {
 		return err
 	}
 
-	l.transactioning = false
 	l.cachedFS = nil
 	return nil
 }
@@ -245,7 +243,7 @@ func (l *Location) repository(
 	id borges.RepositoryID,
 	mode borges.Mode,
 ) (borges.Repository, error) {
-	fs, err := l.setupTransaction(mode)
+	fs, err := l.getRepoFs(id, mode)
 	if err != nil {
 		return nil, err
 	}