Support file locking

TODO: Actually check for locks in cleanup.go

backends/localfs/localfs.go

@@ -16,6 +16,7 @@ import (
 type LocalfsBackend struct {
 	metaPath  string
 	filesPath string
+	locksPath string
 }
 
 type MetadataJSON struct {
@@ -127,6 +128,29 @@ func (b LocalfsBackend) writeMetadata(key string, metadata backends.Metadata) er
 	return nil
 }
 
+func (b LocalfsBackend) Lock(filename string) (err error) {
+	lockPath := path.Join(b.locksPath, filename)
+
+	lock, err := os.Create(lockPath)
+	if err != nil {
+		return err
+	}
+
+	lock.Close()
+	return
+}
+
+func (b LocalfsBackend) Unlock(filename string) (err error) {
+	lockPath := path.Join(b.locksPath, filename)
+
+	err = os.Remove(lockPath)
+	if err != nil {
+		return err
+	}
+
+	return
+}
+
 func (b LocalfsBackend) Put(key string, r io.Reader, expiry time.Time, deleteKey, accessKey string, srcIp string) (m backends.Metadata, err error) {
 	filePath := path.Join(b.filesPath, key)
 
@@ -201,9 +225,10 @@ func (b LocalfsBackend) List() ([]string, error) {
 	return output, nil
 }
 
-func NewLocalfsBackend(metaPath string, filesPath string) LocalfsBackend {
+func NewLocalfsBackend(metaPath string, filesPath string, locksPath string) LocalfsBackend {
 	return LocalfsBackend{
 		metaPath:  metaPath,
 		filesPath: filesPath,
+		locksPath: locksPath,
 	}
 }

backends/s3/s3.go

@@ -3,6 +3,7 @@ package s3
 import (
 	"io"
 	"io/ioutil"
+	"log"
 	"net/http"
 	"os"
 	"strconv"
@@ -156,6 +157,16 @@ func unmapMetadata(input map[string]*string) (m backends.Metadata, err error) {
 	return
 }
 
+func (b S3Backend) Lock(filename string) (err error) {
+	log.Printf("Locking is not supported on S3")
+	return
+}
+
+func (b S3Backend) Unlock(filename string) (err error) {
+	log.Printf("Locking is not supported on S3")
+	return
+}
+
 func (b S3Backend) Put(key string, r io.Reader, expiry time.Time, deleteKey, accessKey string, srcIp string) (m backends.Metadata, err error) {
 	tmpDst, err := ioutil.TempFile("", "linx-server-upload")
 	if err != nil {

backends/storage.go

@@ -12,6 +12,8 @@ type StorageBackend interface {
 	Exists(key string) (bool, error)
 	Head(key string) (Metadata, error)
 	Get(key string) (Metadata, io.ReadCloser, error)
+	Lock(filename string) (error)
+	Unlock(filename string) (error)
 	Put(key string, r io.Reader, expiry time.Time, deleteKey, accessKey string, srcIp string) (Metadata, error)
 	PutMetadata(key string, m Metadata) error
 	ServeFile(key string, w http.ResponseWriter, r *http.Request) error
@@ -25,3 +27,4 @@ type MetaStorageBackend interface {
 
 var NotFoundErr = errors.New("File not found.")
 var FileEmptyError = errors.New("Empty file")
+var FileLockedError = errors.New("Locked file")