In the Gitlab CI pipeline, how can I conditionally run jobs in parallel?

Question

Say, for example, my pipeline contains the following job:

sast-container:
  <<: *branches
  allow_failure: true
  parallel:
    matrix:
      - CI_REGISTRY_IMAGE: $CI_REGISTRY_IMAGE/address-check-stub
      - CI_REGISTRY_IMAGE: $CI_REGISTRY_IMAGE/manual-service-stub
      - CI_REGISTRY_IMAGE: $CI_REGISTRY_IMAGE/employment-record-stub

and I want each of the jobs in the matrix if and only if there has been a change to the code that effects them.

I was thinking along the lines of something like this:

sast-container:
  <<: *branches
  allow_failure: true
  parallel:
    matrix:
      only:
        changes:
          - stub-services/address-check-stub      
            - CI_REGISTRY_IMAGE: $CI_REGISTRY_IMAGE/address-check-stub
      only:
        changes:
          - stub-services/address-check-stub  
            - CI_REGISTRY_IMAGE: $CI_REGISTRY_IMAGE/manual-service-stub
      only:
        changes:
          - stub-services/address-check-stub  
            - CI_REGISTRY_IMAGE: $CI_REGISTRY_IMAGE/employment-record-stub

which, of course, to nobody's surprise (including my own), doesn't work.

Answer 1

came across your post looking for a similar situation.

Here I post you what I did to make it work, hope it helps for your case:

...
terraform format:
  stage: validate
  script:
    - gitlab-terraform fmt
  parallel:
    matrix:
      - TARGET: test
      - TARGET: qa
  environment:
    name: $TARGET
    action: verify
  rules:
    - changes:
        - terraform/$TARGET/**/*
...

With that code, I manage to create specific jobs for a given env(TARGET) only if the terraform/$TARGET/**/* folder contains modifications.

Hope it helps!