[Bug]: A cron job is generating previews of every file causing previews folder to flood and filecache table to grow too large about server

[kesselb]

Sounds similiar to #45654

[muchachagrande]

Yes, as I searched for cron job and filecache I didn't find it.

Additional info:
When rebooted the server to stop the running tasks to apply the workaround I observed the following error in the NC log:

Error while running background job OCA\Files\BackgroundJob\ScanFiles

So that's the job that runs for so long... my guess is that the first run after the upgrade generated all the previews and the following runs after that are very slow because of the huge amount of files it generated before.

[didim99]

Have a same issue, after upgrading from NC27 to 29.0.2.
Some additional info (relevant for my installation):

• Related cron job starts only during maintenance window (at 01:00 for me).
• My primary storage contains ~500k files (total size is ~1.4TB, including versions and trashbin), and external storage (local folder) contains ~1.2M files (total size is ~1.6TB).
• My oc_filecache table contains ~2.1M rows.

After upgrading to NC29 and waiting few days my oc_filecache table grown over 8M rows (and over 6GB) and slow down entire MySQL server. I stop the NC server, kill background task process, deleted all content of preview folder and all rows from oc_filecache related to them (it takes over 10 hours!) and started server again. An next day I see that the preview folder grows again. I disabled background job at all to determine source of issue and wait one week, nothing happened. Then I disabled preview generation for external storage (via admin settings UI) and enabled cron job, and today preview folder grows again (seems to scanning external storage files because I have some errors in log related to external storage files). At this moment my preview folder has only 3k files and over 580k of empty directories! It seems a serious problem for large installations.