Span4 1つのリクエスト(処理)のTrace Trace ID = aaaa Span ID = bbb Trace ID = aaaa Span ID = ccc Parent Span ID = bbb Trace ID = aaaa Span ID = ddd Parent Span ID = ccc Trace ID = aaaa Span ID = eee Parent Span ID = ddd Trace IDとSpan ID (+Trace flag) を後続処理に伝搬 認証