[Bug]: Automatic (not on-demand) preview generation fills disk about server

[kesselb]

What is worse is that even with enable_previews => false in config.php the preview folder is growing too

#45697

[artonge]

I may have miss understood your last comment. There is a difference between "we need to generate the blurhash after preview generation" and "we need to always generate a blurhash (after causing a preview generation)"

To be clearer, blurhash generation should not trigger preview generation ;)

[kesselb]

Can confirm.

Steps to reproduce:

• Connect desktop client to Nextcloud
• Copy an image
• See the post request for the bulk upload endpoint
• Max Preview + 256er Previews are generated

To monitor the preview folder for create events:
inotifywait -m -r -e create /path/to/preview/folder

Output:

preview/1/0/ CREATE,ISDIR a
preview/1/0/a/b/2/6/9/39539/ CREATE 2560-1440-max.jpg
preview/1/0/a/b/2/6/9/39539/ CREATE 256-144.jpg
preview/b/5/7/ CREATE,ISDIR 7
preview/b/5/7/7/2/e/7/39548/ CREATE 1920-1080-max.jpg
preview/b/5/7/7/2/e/7/39548/ CREATE 256-144.jpg
preview/e/4/ CREATE,ISDIR 9
preview/e/4/9/f/1/7/b/39556/ CREATE 2559-1599-max.jpg
preview/e/4/9/f/1/7/b/39556/ CREATE 256-160.jpg
preview/c/a/b/ CREATE,ISDIR 8
preview/c/a/b/8/c/3/7/39565/ CREATE 1920-1080-max.jpg
preview/c/a/b/8/c/3/7/39565/ CREATE 256-144.jpg
preview/7/1/ CREATE,ISDIR c
preview/7/1/c/7/2/2/e/39573/ CREATE 1920-1200-max.png
preview/7/1/c/7/2/2/e/39573/ CREATE 256-160.png

That could be

server/lib/private/Blurhash/Listener/GenerateBlurhashMetadata.php

Line 73 in 4e2ada0

$preview = $this->preview->getPreview($file, 256, 256);

, however adding a return before getPreview had no effect on my end.

[kesselb]

cc @ArtificialOwl @artonge

[marcos-guerrero]

What is worse is that even with enable_previews => false in config.php the preview folder is growing too
I dropped 4 images on my desktop app and

root@maqueta-nextcloud-backend2:~# inotifywait -m -r -e create /disco_datos_nextcloud/nextcloud_data/appdata_XXX/preview/
Setting up watches.  Beware: since -r was given, this may take a while!
Watches established.
/disco_datos_nextcloud/nextcloud_data/appdata_XXX/preview/5/6/1/ CREATE,ISDIR f
/disco_datos_nextcloud/nextcloud_data/appdata_XXX/preview/0/3/9/ CREATE,ISDIR 7
/disco_datos_nextcloud/nextcloud_data/appdata_XXX/preview/4/7/a/f/ CREATE,ISDIR d
/disco_datos_nextcloud/nextcloud_data/appdata_XXX/preview/7/f/8/2/ CREATE,ISDIR f

I'm on nc 29.0.2

[artonge]

We indeed need to generate the blurhash after the preview generation:

• emit an event when a preview is created with the original and preview File objects
  

  server/lib/private/Preview/Generator.php

  Lines 77 to 87 in 0ddfe9e

  	$this->eventDispatcher->dispatchTyped(new BeforePreviewFetchedEvent(
  	$file,
  	$width,
  	$height,
  	$crop,
  	$mode,
  	));
  	// since we only ask for one preview, and the generate method return the last one it created, it returns the one we want
  	return $this->generatePreviews($file, [$specification], $mimeType);
  	}

• in the listener generate and update the blurhash metadata

[csware]

@artonge
I may have miss understood your last comment. There is a difference between "we need to generate the blurhash after preview generation" and "we need to always generate a blurhash (after causing a preview generation)"