Dataset Thumbnail 404 Not Found - Broken Link after File Deletion

[taywll252]

Describe the bug
Short: Dataset thumbnail image HTTP 404 Not Found after image file deleted from dataset (thumbnail should have been removed but was not).

Long: After creating a new dataset and uploading files (nested in a variety of folders and subfolders), the dataset was automatically given a thumbnail of an extracted image file preview contained within the dataset. Later, many files were removed from the dataset, including all image files. File deletion was performed in a Google Chrome browser with the Clowder UI. Following deletion of files, the dataset's thumbnail was not removed (expected behavior being it should be removed when the image files were deleted). Instead, a missing image link with alt-text remained. Inspecting the image showed a link to a fileThumbnail (.com/fileThumbnail/{thumbnail_id}), which produced a HTTP 404 error.

To Reproduce
Steps to reproduce the behavior:

1. Create a new dataset
2. Upload files inside folders and nested folders (with an image file somewhere)
3. Observe if the dataset receives a thumbnail (expected)
4. Delete image files
5. Observe if the dataset no longer has a thumbnail (expected behavior) or a missing thumbnail link remains (unexpected behavior)
   Expected behavior
   Datasets may gain a thumbnail of an unloaded image file that has a preview extracted. Datasets should have their thumbnail removed if the image file is deleted (thumbnail also deleted).

Screenshots

Desktop (please complete the following information):

• OS: Windows 10
• Browser: Google Chrome (v93.0.4577.82) and Edge (v93.0.961.52)
• Clowder Version: 1.18.1#642 branch:master sha1:3e27a5411234172a69fb446e103d1e70b95398e4

Additional context
The dataset, folders, and files were all created/uploaded using Clowder APIs. File deletion was performed in-browser. Image preview extraction was automatically initiated upon file upload (default behavior), not initiated by the user manually.

[taywll252]

Correction: older version was actually v1.14.0

For further clarification, I'm not sure exactly what circumstances caused this error since I've had other datasets work just fine with deleting image files which also removed the thumbnail from the dataset. Or changed it to another if another image file was present in the dataset. The Clowder Version is the latest version my organization is using of Clowder. However, this problem dataset was created under an older version (v1.16.0), since it was made in July 2021, but we upgraded to 1.18.1 at the end of August.

[lmarini]

We are looking into this. We think it might be related to when you delete the first file that you added to the dataset (or the first one that has a thumbnail). The dataset gets that same thumnail id, but we might not remove that when we delete that original file.

[robkooper]

Maybe when we delete a file, see if that thumbnail id is associated with dataset/collection/space and update those with the next thumbnail.

[longshuicy]

I am looking into this issue by first try to reproduce your error:
I found that by deleting an image that used as thumbnail itself won't create any issue; it will successfully use the next image if availabe as thumbnail; Or just remove the thumnail at all.

HOWEVER, what i found might trigger this issue is

1. you upload an image and that is used as thumbnail in the dataset
2. then you move this image to a folder inside, thumbnail still preserves using that image
3. you delete that image, then there is a broken link

Just a status update. I will continue working to address this issue.