use a new thread safe map

pkg/chunk/storage.go

@@ -381,23 +381,18 @@ func (s *Storage) Store(id RequestID, bytes []byte) (err error) {
 
 	if nil != chunk {
 		if chunk.valid(id) {
-			s.log.Debugf("Create chunk %v (exists: valid)", id)
 			return nil
 		}
 		s.log.Warnf("Create chunk %v(exists: overwrite)", id)
 	} else {
 		index := s.stack.Pop()
 		if index == -1 {
-			s.log.Debugf("Create chunk %v (failed)", id)
 			return fmt.Errorf("no buffers available")
 		}
 		chunk = s.buffers[index]
 		deleteID := chunk.id
 		if blankRequestID != deleteID {
 			delete(s.chunks, deleteID)
-			s.log.Debugf("Create chunk %v (reused)", id)
-		} else {
-			s.log.Debugf("Create chunk %v (stored)", id)
 		}
 		s.chunks[id] = index
 		chunk.item = s.stack.Push(index)