grpc: server failed to encode response: rpc error: code = Internal desc = grpc: error while marshaling: proto: Marshal called with nil

Question

理想情况下，以下 RPC 应该接收消息并编组到 JSON。但是，遇到以下错误：ERROR: 2018/08/12 13:43:07 grpc: server failed to encode response: rpc error: code = Internal desc = grpc: error while marshaling: proto: Marshal called with nil

func (s *beaconServer) Transmit(ctx context.Context, batch *pb.Batch) (*pb.Empty, error) {
    var empty *pb.Empty

    var messageJSON bytes.Buffer
    marshaler := &jsonpb.Marshaler{
        OrigName: true,
    }
    err := marshaler.Marshal(&messageJSON, batch)
    if err != nil {
        return empty, err
    }

    log.Println(string(messageJSON.Bytes()))
    return empty, nil
}

..returns

2018/08/12 14:24:09 beacon.go:34: {"stream_id":"abc11","event_type":"e","events":[{"file_path":"/tmp/python.py","location":"256","count":"30"},{"file_path":"/tmp/temp.py","location":"253","count":"305"}],"start_time":"2038-01-19 03:14:07","end_time":"2038-01-19 03:14:27"}
ERROR: 2018/08/12 14:24:09 grpc: server failed to encode response:  rpc error: code = Internal desc = grpc: error while marshaling: proto: Marshal called with nil

Answer 1

错误可能不是由此代码块中的编组器引起的

当您执行 var empty *pb.Empty 时，您正在创建一个未初始化的变量 *pb.Empty，即 nil。很可能是上游试图编组这个 empty 的东西导致了错误。

此处可运行示例： https://play.golang.org/p/QsNCWXM615Q

如果你想初始化为空，那么你应该return new(pb.Empty), nil