Review feedback

Signed-off-by: Goutham Veeramachaneni <[email protected]>

wal.go

@@ -723,6 +723,13 @@ func (w *SegmentWAL) run(interval time.Duration) {
 
 // Close syncs all data and closes the underlying resources.
 func (w *SegmentWAL) Close() error {
+	// Make sure you can call Close() multiple times.
+	select {
+	case <-w.stopc:
+		return nil // Already closed.
+	default:
+	}
+
 	close(w.stopc)
 	<-w.donec
 
@@ -1262,18 +1269,20 @@ func MigrateWAL(logger log.Logger, dir string) (err error) {
 	if err != nil {
 		return errors.Wrap(err, "open new WAL")
 	}
-	// It should've already been closed as part of the previous finalization.
-	// Do it once again in case of prior errors.
+	// Make sure the new WAL is always Closed.
 	defer func() {
 		if err != nil {
 			repl.Close()
+			return
 		}
+		err = errors.Wrap(repl.Close(), "close new WAL")
 	}()
 
 	w, err := OpenSegmentWAL(dir, logger, time.Minute, nil)
 	if err != nil {
 		return errors.Wrap(err, "open old WAL")
 	}
+	defer w.Close()
 
 	rdr := w.Reader()
 
@@ -1307,9 +1316,9 @@ func MigrateWAL(logger log.Logger, dir string) (err error) {
 	if err != nil {
 		return errors.Wrap(err, "write new entries")
 	}
-	if err := repl.Close(); err != nil {
-		return errors.Wrap(err, "close new WAL")
-	}
+	// We explicitly close even when there is a defer for Windows to be
+	// able to delete it. The defer is in place to close it in-case there
+	// are errors above.
 	if err := w.Close(); err != nil {
 		return errors.Wrap(err, "close old WAL")
 	}

wal/wal.go

@@ -320,6 +320,8 @@ func (w *WAL) Repair(origErr error) error {
 	if err != nil {
 		return errors.Wrap(err, "open segment")
 	}
+	defer f.Close()
+
 	r := NewReader(bufio.NewReader(f))
 
 	for r.Next() {
@@ -329,6 +331,9 @@ func (w *WAL) Repair(origErr error) error {
 	}
 	// We expect an error here from r.Err(), so nothing to handle.
 
+	// We explicitly close even when there is a defer for Windows to be
+	// able to delete it. The defer is in place to close it in-case there
+	// are errors above.
 	if err := f.Close(); err != nil {
 		return errors.Wrap(err, "close corrupted file")
 	}