[RESOLVED] Mysql in catalogue: why have volume in sidekick?

1

Hi,
I’m looking at the mysql stack in the catalogue, and I can’t understand why the volume is set up in the sidekick and then the mysql service uses “volumes_from” the sidekick.

Why add another container + another linux distro (busybox) just to add a volume which could be mapped in the main mysql container?

Thanks in advance,
Andy

2

Hi,
Sorry, just wanted to provide details. Here is the relevant sections of the mysql docker compose:

mysql:
    image: mariadb:10.3.0
    environment:
      MYSQL_DATABASE: XXX
      MYSQL_PASSWORD: XXX
      MYSQL_ROOT_PASSWORD: XXX
      MYSQL_USER: XXX
    stdin_open: true
    tty: true
    volumes_from:
    - mysql-data
    ports:
    - 4407:3306/tcp
    labels:
      io.rancher.scheduler.affinity:host_label: database=yes
      io.rancher.sidekicks: mysql-data
      test: test
  mysql-data:
    image: busybox
    volumes:
    - /mnt/XXX/database:/var/lib/mysql
    labels:
      io.rancher.scheduler.affinity:host_label: database=yes
      io.rancher.container.start_once: 'true'

So the mysql-data sidekick launches once, and sets up the volume. It seems unnecessary to create a seperate container for this?

Regards,
Andy

3

This is called a “data-only container” and is how you did “volumes” in Docker before volumes existed. Changing it now would break in existing users of the catalog item.

4

Ah thanks Vincent. That explains my confusion. Appreciate the quick response.

Andy