Support --platform parameter

[zhan9san]

Support --platform for molecule test command.

--platform TEXT        Name of the platform to test

e.g.

Only test role on centos-7 platform in default scenario, if no platform found, raise error.

molecule test --platform centos-7

Q: Why is this required?
A: Assume there are 10 platform docker images defined in molecule.yml and only one image(centos-7) are changed.

• With --platform, only one changed docker image would be tested via molecule test --platform centos-7
• Without --platform, all 10 platform docker image would be test while the other 9 are redundant.

More specifically, the run: molecule test can ben changed to run: molecule test --platform ${{ matrix.package }}.
https://github.com/zhan9san/systemd/blob/main/.github/workflows/ci.yml#L70

[mafalb]

I agree, that would be nice.
You can try a workaround:

run: molecule -e env-centos-7 test

in env-centos-7:

CI_IMAGE: quay.io/centos/centos:7
CI_HOSTNAME: ci-centos7

in molecule.yml:

platforms:
- name: ${CI_HOSTNAME:-ci-centos8}
  image: ${CI_IMAGE:-quay.io/centos/centos:8}
  ...

[zhan9san]

@mafalb
Thanks for your suggestion. There are 7 platforms.

But how about the others, like debian-9, debian-10, fedora-30, ubuntu-16.04 and ubuntu-18.04?

[mafalb]

you make an env file for each of them and you define a variable like matrix.platform (you called it matrix.package above, was this a typo?).

  run: molecule -e env-{{ matrix.platform }} test

[zhan9san]

Thank you.
The name is not the key point. But it's fine to name it matrix.platform

How do we define the other platforms in molecule.yml if we run test as below?

molecule -e env-{{ matrix.platform }} test

If I understand you correctly, it would be as below. But there will be multiple same platform names.
Correct me if I say anything wrong

platforms:
  - name: ${CI_HOSTNAME:-ci-centos8}
    image: ${CI_IMAGE:-quay.io/centos/centos:8}
    ...
  - name: ${CI_HOSTNAME:-debian-9}
    image: ${CI_IMAGE:-debian:9}
    ...
  - name: ${CI_HOSTNAME:-debian-10}
    image: ${CI_IMAGE:-debian:10}
    ...

[mafalb]

How do we define the other platforms in molecule.yml

You don't. You have one platform definition, but many env files.

platforms:
- name: ${CI_HOSTNAME}
  image: ${CI_IMAGE}
  ...

The values in the platform definition are not hardcoded, but filled by molecule with the values set in the env files.
To make it clearer I omitted the default value this time.
please see the section about variable substitution and default values in the documentation
https://molecule.readthedocs.io/en/latest/configuration.html#id1

[zhan9san]

Thank you @mafalb . I got your point.

There are 2 concerns.

1. It's not convenient to test all platforms if there all only one platform definition at once
2. As the command are different among different images, e.g. sbin/init for ubuntu-like while /usr/lib/systemd/systemd for centos-like

I created a PR, #3416 to fix this issue.

[zhan9san]

It would be better to filter data in https://github.com/ansible-community/molecule/blob/main/src/molecule/provisioner/ansible.py#L607

SOME_FILTERS_WITH_PLATFORM_NAME. I tried jmespath, but no luck

"molecule_yml": "{{ lookup('file', molecule_file) | from_yaml | SOME_FILTERS_WITH_PLATFORM_NAME}}",

Before:

dependency:
  name: galaxy
driver:
  name: docker
platforms:
  - name: ubuntu-18.04
    pre_build_image: true
    image: zhan9san/systemd:ubuntu-18.04
    privileged: true
    volumes:
      - /sys/fs/cgroup:/sys/fs/cgroup:ro
    command: "/sbin/init"
  - name: ubuntu-16.04
    pre_build_image: true
    image: zhan9san/systemd:ubuntu-16.04
    privileged: true
    volumes:
      - /sys/fs/cgroup:/sys/fs/cgroup:ro
    command: "sbin/init"

AFTER

dependency:
  name: galaxy
driver:
  name: docker
platforms:
  - name: ubuntu-18.04
    pre_build_image: true
    image: zhan9san/systemd:ubuntu-18.04
    privileged: true
    volumes:
      - /sys/fs/cgroup:/sys/fs/cgroup:ro
    command: "/sbin/init"

[zhan9san]

The alternative way is to add condition in create and destroy in each single molecule driver.

      when:
        - (molecule_platform_name is defined) and (item.name == molecule_platform_name)