This document provides step-by-step guide to download pipeline logs from Data Fusion UI
...
Data Fusion logs can be retrieved from Stack driver as documented here. In the event stackdriver logging is not enabled, the pipeline logs can be fetched from Data Fusion UI.
...
Navigate to the pipeline from pipeline details page.
...
2. Navigate to the specific run of the pipeline.
3. Click on Logs.
...
4. Click on Download all logs.
...