cache: handle errors when bolt tries to start

cache/cache.go

@@ -330,9 +330,9 @@ func NewFs(name, rpath string) (fs.Fs, error) {
 
 	dbPath = filepath.Join(dbPath, name+".db")
 	fs.Infof(name, "Storage DB path: %v", dbPath)
-	f.cache = GetPersistent(dbPath, *cacheDbPurge)
+	f.cache, err = GetPersistent(dbPath, *cacheDbPurge)
 	if err != nil {
-		return nil, err
+		return nil, errors.Wrapf(err, "failed to start cache db")
 	}
 	// Trap SIGINT and SIGTERM to close the DB handle gracefully
 	c := make(chan os.Signal, 1)

cache/cache_internal_test.go

@@ -44,7 +44,8 @@ func TestInternalInit(t *testing.T) {
 
 	// delete the default path
 	dbPath := filepath.Join(fs.CacheDir, "cache-backend", *RemoteName+".db")
-	boltDb = cache.GetPersistent(dbPath, true)
+	boltDb, err = cache.GetPersistent(dbPath, true)
+	require.NoError(t, err)
 	fstest.Initialise()
 
 	if len(*WrapRemote) == 0 {

cache/storage_persistent.go

@@ -30,27 +30,23 @@ const (
 )
 
 var boltMap = make(map[string]*Persistent)
-var boltMapMx sync.RWMutex
+var boltMapMx sync.Mutex
 
 // GetPersistent returns a single instance for the specific store
-func GetPersistent(dbPath string, refreshDb bool) *Persistent {
-	// read lock to check if it exists
-	boltMapMx.RLock()
-	if b, ok := boltMap[dbPath]; ok {
-		boltMapMx.RUnlock()
-		return b
-	}
-	boltMapMx.RUnlock()
-
-	// write lock to create one but let's check a 2nd time
+func GetPersistent(dbPath string, refreshDb bool) (*Persistent, error) {
+	// write lock to create one
 	boltMapMx.Lock()
 	defer boltMapMx.Unlock()
 	if b, ok := boltMap[dbPath]; ok {
-		return b
+		return b, nil
 	}
 
-	boltMap[dbPath] = newPersistent(dbPath, refreshDb)
-	return boltMap[dbPath]
+	bb, err := newPersistent(dbPath, refreshDb)
+	if err != nil {
+		return nil, err
+	}
+	boltMap[dbPath] = bb
+	return boltMap[dbPath], nil
 }
 
 // Persistent is a wrapper of persistent storage for a bolt.DB file
@@ -64,7 +60,7 @@ type Persistent struct {
 }
 
 // newPersistent builds a new wrapper and connects to the bolt.DB file
-func newPersistent(dbPath string, refreshDb bool) *Persistent {
+func newPersistent(dbPath string, refreshDb bool) (*Persistent, error) {
 	dataPath := strings.TrimSuffix(dbPath, filepath.Ext(dbPath))
 
 	b := &Persistent{
@@ -74,10 +70,11 @@ func newPersistent(dbPath string, refreshDb bool) *Persistent {
 
 	err := b.Connect(refreshDb)
 	if err != nil {
-		fs.Errorf(dbPath, "error opening storage cache: %v", err)
+		fs.Errorf(dbPath, "Error opening storage cache. Is there another rclone running on the same remote? %v", err)
+		return nil, err
 	}
 
-	return b
+	return b, nil
 }
 
 // String will return a human friendly string for this DB (currently the dbPath)