storage/tsdb/tsdb.go
func (s *ReadyStorage) Appender() (storage.Appender, error) {
	if x := s.get(); x != nil {
		return x.Appender()
	}
	return nil, ErrNotReady
}
func (s *ReadyStorage) Appender() (storage.Appender, error) {
	if x := s.get(); x != nil {
		return x.Appender()
	}
	return nil, ErrNotReady
}
// Appender implements the Storage interface.