Separate locking into data store implementation

The goal is to allow different locking mechanism to be used for different
storages. For example, in-memory for very few uploads, a file locker in
conjunction with the FileStore or an external service, such as ZooKeeper.

lockingstore/lockingstore.go

@@ -0,0 +1,67 @@
+package lockingstore
+
+type Locker interface {
+	LockUpload(id string) error
+	UnlockUpload(id string) error
+}
+
+type LockingStore struct {
+	tusd.DataStore
+	Locker *Locker
+}
+
+func (store LockingStore) WriteChunk(id string, offset int64, src io.Reader) (int64, error) {
+	if err := store.LockUpload(id); err != nil {
+		return 0, err
+	}
+
+	defer func() {
+		if unlockErr := store.UnlockUpload(id); unlockErr != nil {
+			err = unlockErr
+		}
+	}()
+
+	return store.DataStore.WriteChunk(id, offset, src)
+}
+
+func (store LockingStore) GetInfo(id string) (FileInfo, error) {
+	if err := store.LockUpload(id); err != nil {
+		return nil, err
+	}
+
+	defer func() {
+		if unlockErr := store.UnlockUpload(id); unlockErr != nil {
+			err = unlockErr
+		}
+	}()
+
+	return store.DataStore.GetInfo(id)
+}
+
+func (store LockingStore) GetReader(id string) (io.Reader, error) {
+	if err := store.LockUpload(id); err != nil {
+		return nil, err
+	}
+
+	defer func() {
+		if unlockErr := store.UnlockUpload(id); unlockErr != nil {
+			err = unlockErr
+		}
+	}()
+
+	return store.DataStore.GetReader(id)
+}
+
+func (store LockingStore) Terminate(id string) error {
+	if err := store.LockUpload(id); err != nil {
+		return err
+	}
+
+	defer func() {
+		if unlockErr := store.UnlockUpload(id); unlockErr != nil {
+			err = unlockErr
+		}
+	}()
+
+	return store.DataStore.Terminate(id)
+}

lockingstore/memorylocker.go

@@ -0,0 +1,35 @@
+package lockingstore
+
+import (
+	"github.com/tus/tusd"
+)
+
+type MemoryLocker struct {
+	locks map[string]bool
+}
+
+func New() *MemoryLocker {
+	return &MemoryLocker{
+		locks: make(map[string]bool),
+	}
+}
+
+func (locker *MemoryLocker) LockUpload(id string) error {
+
+	// Ensure file is not locked
+	if _, ok := locker.locks[id]; ok {
+		return tusd.ErrFileLocked
+	}
+
+	handler.locks[id] = true
+
+	return nil
+}
+
+func (locker *MemoryLocker) UnlockUpload(id string) error {
+	// Deleting a non-existing key does not end in unexpected errors or panic
+	// since this operation results in a no-op
+	delete(locker.locks, id)
+
+	return nil
+}

unrouted_handler.go

@@ -75,7 +75,6 @@ type UnroutedHandler struct {
 	dataStore     DataStore
 	isBasePathAbs bool
 	basePath      string
-	locks         map[string]bool
 	logger        *log.Logger
 
 	// For each finished upload the corresponding info object will be sent using
@@ -114,7 +113,6 @@ func NewUnroutedHandler(config Config) (*UnroutedHandler, error) {
 		dataStore:       config.DataStore,
 		basePath:        base,
 		isBasePathAbs:   uri.IsAbs(),
-		locks:           make(map[string]bool),
 		CompleteUploads: make(chan FileInfo),
 		logger:          logger,
 	}
@@ -288,8 +286,7 @@ func (handler *UnroutedHandler) HeadFile(w http.ResponseWriter, r *http.Request)
 	w.WriteHeader(http.StatusNoContent)
 }
 
-// PatchFile adds a chunk to an upload. Only allowed if the upload is not
+// PatchFile adds a chunk to an upload. Only allowed enough space is left.
-// locked and enough space is left.
 func (handler *UnroutedHandler) PatchFile(w http.ResponseWriter, r *http.Request) {
 
 	// Check for presence of application/offset+octet-stream
@@ -311,20 +308,6 @@ func (handler *UnroutedHandler) PatchFile(w http.ResponseWriter, r *http.Request
 		return
 	}
 
-	// Ensure file is not locked
-	if _, ok := handler.locks[id]; ok {
-		handler.sendError(w, r, ErrFileLocked)
-		return
-	}
-
-	// Lock file for further writes (heads are allowed)
-	handler.locks[id] = true
-
-	// File will be unlocked regardless of an error or success
-	defer func() {
-		delete(handler.locks, id)
-	}()
-
 	info, err := handler.dataStore.GetInfo(id)
 	if err != nil {
 		handler.sendError(w, r, err)
@@ -387,20 +370,6 @@ func (handler *UnroutedHandler) GetFile(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
-	// Ensure file is not locked
-	if _, ok := handler.locks[id]; ok {
-		handler.sendError(w, r, ErrFileLocked)
-		return
-	}
-
-	// Lock file for further writes (heads are allowed)
-	handler.locks[id] = true
-
-	// File will be unlocked regardless of an error or success
-	defer func() {
-		delete(handler.locks, id)
-	}()
-
 	info, err := handler.dataStore.GetInfo(id)
 	if err != nil {
 		handler.sendError(w, r, err)
@@ -438,20 +407,6 @@ func (handler *UnroutedHandler) DelFile(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
-	// Ensure file is not locked
-	if _, ok := handler.locks[id]; ok {
-		handler.sendError(w, r, ErrFileLocked)
-		return
-	}
-
-	// Lock file for further writes (heads are allowed)
-	handler.locks[id] = true
-
-	// File will be unlocked regardless of an error or success
-	defer func() {
-		delete(handler.locks, id)
-	}()
-
 	err = handler.dataStore.Terminate(id)
 	if err != nil {
 		handler.sendError(w, r, err)