/tmp is filling up, when occ preview:generate-all is used

[ErikSteiner]

Describe the bug

Temporary files are written to the Docker host under /var/lib/docker/overlay2 until the hard drive is full and the host dies. The corresponding container can be traced back to the app container of the attached Docker compose. Under /tmp of the container, 43 GB of data accumulates in a very short time, each of which is filled in folders of approx. 500 MB.

The problem first occurred after Memories was installed and a cron job was activated to create the preview images.

I would be grateful for any help in finding out the reasons for this.

This is the content in the docker container app:

# ls -lah
total 43G
drwxrwxrwt 1 root root 4.0K Oct 29 14:35 .
drwxr-xr-x 1 root root 4.0K Oct 28 20:31 ..
-rwxr-xr-x 1 1004 1004 8.5M Oct 28 20:32 exiftool-ocgh0x2ccfv3-12.70-c435c63a
-rwxr-xr-x 1 1004 1004 7.4M Oct 28 20:36 exiftool-ocgh0x2ccfv3-12.70-f3319c53
-rwxr-xr-x 1 1004 1004 4.9M Oct 28 20:32 go-vod-ocgh0x2ccfv3-0.2.5-7345fee3
drwx------ 3 1004 1004 4.0K Oct 28 20:36 par-53595354454d
-rw------- 1 1004 1004 502M Oct 28 22:14 php0xPDBG
-rw------- 1 1004 1004 504M Oct 29 07:54 php10sO80
-rw------- 1 1004 1004 501M Oct 29 07:48 php1EO9WC
-rw------- 1 1004 1004 501M Oct 29 07:52 php2Oh3y6
-rw------- 1 1004 1004 502M Oct 28 22:12 php32xkfQ
-rw------- 1 1004 1004 502M Oct 28 22:17 php3JQIq4
-rw------- 1 1004 1004 501M Oct 29 07:54 php5eLAGJ
-rw------- 1 1004 1004 501M Oct 29 07:48 php64sSUM
-rw------- 1 1004 1004 503M Oct 29 07:56 php7PBuCy
-rw------- 1 1004 1004 505M Oct 28 22:17 php7qvkrz
...

Docker Compose: docker-compose.txt

Cron job on Docker Host:
/etc/systemd/system/nextcloud-preview-generator.service:

[Unit]
Description=Nextcloud Preview Generator

[Service]
Type=oneshot
User=root
IOSchedulingClass=2
IOSchedulingPriority=7
ExecStart=/usr/bin/docker compose -f /docker/nextcloud/docker-compose.yml exec app php occ preview:generate-all

[Install]
WantedBy=basic.target

Cron timer:
/etc/systemd/system/nextcloud-preview-generator.timer:

[Unit]
Description=Run Nextcloud Preview Generator daily at 04:00

[Timer]
OnCalendar=*-*-* 4:00:00
Persistent=true

[Install]
WantedBy=timers.target

Steps To Reproduce

No response

Platform

- OS: Ubuntu 22.04.5 LTS (GNU/Linux 5.15.0-1068-kvm x86_64)
- Browser: N/A
- Memories Version: 7.4.1
- Nextcloud Version: Nextcloud Hub 8 (29.0.8)
- PHP Version: 8.2.24

Screenshots

No response

Additional context

• Any errors in the JS console?
• Any errors in the Nextcloud server logs?

[pulsejet]

Does this issue go away if you don't run the cron job to generate previews? In that case it's a bug in preview generator https://github.com/nextcloud/previewgenerator

[ErikSteiner]

As far as I can understand, the problem is due to php-fpm. It creates phpxxxxx files under /tmp. If these only occur when uploading and especially when using WebDAV, I would say that the problem has nothing to do with the preview or memories. The fact that the PHP process dies and leaves a file under /tmp has been fixed by adjusting php-fpm settings.

[pulsejet]

For the record, can you indicate which setting this is?

[ErikSteiner]

Sorry for the delay. I had disassembled my PC for a long time.

Here are the relevant settings with which I have had no problems since then. The settings cannot be adopted one-to-one. They are calculated and are linked in the docker-compose excerpt.

zz-pm.conf

[www]
pm.max_children = 64
pm.start_servers = 16
pm.min_spare_servers = 16
pm.max_spare_servers = 48

  app:
    build: ./mediadc
    restart: unless-stopped
    user: ${UID}:${GID}
    depends_on:
...
    volumes:
...
      # zz-pm.conf needs root:root
      # https://chrismoore.ca/2018/10/finding-the-correct-pm-max-children-settings-for-php-fpm/
      # calculator: https://tideways.com/profiler/blog/an-introduction-to-php-fpm-tuning 
      - ./zz-pm.conf:/usr/local/etc/php-fpm.d/zz-pm.conf
      - /etc/localtime:/etc/localtime:ro
      - /etc/timezone:/etc/timezone:ro
    tmpfs:
      - /tmp:exec