K8S Backend - Ability to add a side container to a step (pod)

[eliasscosta]

Clear and concise description of the problem

Sometimes we have a test step where they need to run inside a docker image (dind), because a few tests are written with the TestContainer library.

To achieve it, we need to configure one step like this:

  allTests:
    image: docker:24.0.9
    commands:
      - apk add openjdk17
      - dockerd-entrypoint.sh --registry-mirror=http://myprivate-mirror.ior:5000 1> /dev/null 2> /dev/null &
      - ./gradlew test myTEST
    when:
      event: push

This example is in the easy mode, but sometimes we need to install more than one jdk or the dind image doesn't have the library in the OS packages.

Suggested solution

The solution was to add into the backend_options a way to create a side container with the main step container.

  allTests:
    image: openjdk17
    commands:
      - ./gradlew test myTEST
    when:
      event: push
    backend_options:
      kubernetes:
        container: 
          - image: docker:dind
            env: []

Then both containers can start and we can access the docker in the local host and execute the tests with the TestContainers.

Alternative

No response

Additional context

No response

Validations

• Checked that the feature isn't part of the next version already [https://woodpecker-ci.org/faq#which-version-of-woodpecker-should-i-use]
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.