Memory usage issue since 19.01 upgrade

Nextcloud version 19.01
Debian 9.13
Apache 2.4.25
PHP version 7.3

19.01 became available a few days ago for me. Since the upgrade I started getting memory issues where a large about of swap would be used but not main physical memory.

As this is a personal server and since it was still working I didn’t have time to look into it until today.

I have a Zabbix server monitor all my home devices. You can see everything is normal until the 14th.

The issue happens every night exactly at 4am.

None of my scripts run at 4am but I found something that does.

Aug 22 04:00:01 Heighliner CRON[6796]: (www-data) CMD (/usr/bin/php -f /var/www/html/nextcloud/occ preview:pre-generate)

Aug 22 04:00:01 Heighliner CRON[6797]: (www-data) CMD (php -f /var/www/html/nextcloud/cron.php)


Is this normal behavior?
Can this job be safely disabled?

Thanks for any input.



Did you have the preview pre-generation already enabled in NC 18? Is someone uploading more images than usually? If not this could be a bug of this function…

If you disable this, the previews will be generated the first time you open the folder in the webinterface, so it will slow down the web interface…

For me that looks like the command from

Maybe your system is generating thumbnail previews from your images which would be a valid reason for heavy memory usage. You installed preview generator?

I did not have preview pre-generation consciously enabled in NC 18. The system has no other users than me. At most a few of pictures are uploaded each day from my phone.

Preview Generator 2.3.0 is installed. It is not something I recall installing myself unless it came as part of a bundle or as part of NC 19 itself.

Just tried to run the generate-all vvv command and got the following

And it reproduced the problem.

What is really weird is that process now using all the swap is java which on my system means elasticsearch

Here is line 649 from the file mentioned in the error.