allow holder to close/open/close without panic on closing closed channel

holder.go

@@ -55,6 +55,7 @@ type Holder struct {
 	NewPrimaryTranslateStore func(interface{}) TranslateStore
 
 	// opened channel is closed once Open() completes.
+	once   sync.Once
 	opened chan struct{}
 
 	broadcaster broadcaster
@@ -101,6 +102,9 @@ func NewHolder() *Holder {
 
 // Open initializes the root data directory for the holder.
 func (h *Holder) Open() error {
+	// Reset closing in case Holder is being reopened.
+	h.closing = make(chan struct{})
+
 	h.setFileLimit()
 
 	h.Logger.Printf("open holder path: %s", h.Path)
@@ -154,7 +158,7 @@ func (h *Holder) Open() error {
 
 	h.Stats.Open()
 
-	close(h.opened)
+	h.once.Do(func() { close(h.opened) })
 	return nil
 }
 

holder_internal_test.go

@@ -287,3 +287,13 @@ func TestHolderCleaner_CleanHolder(t *testing.T) {
 		}
 	}
 }
+
+// Ensure holder can reopen.
+func TestHolderCleaner_Reopen(t *testing.T) {
+	h := NewHolder()
+	h.Path = "path"
+	h.Open()
+	h.Close()
+	h.Open()
+	h.Close()
+}