Method OnEnd

cpp/src/arrow/util/tracing_internal.cc:115–120

 public:
  using sdktrace::BatchSpanProcessor::BatchSpanProcessor;
  void OnEnd(std::unique_ptr<sdktrace::Recordable>&& span) noexcept override {
    std::stringstream thread_id;
    thread_id << std::this_thread::get_id();
    span->SetAttribute("thread.id", thread_id.str());
    sdktrace::BatchSpanProcessor::OnEnd(std::move(span));
  }
};

std::unique_ptr<sdktrace::SpanExporter> InitializeExporter() {