How to set a dynamic gitlab job tag with a variable?

Question

I am trying to create a dynamic job that can switch between two gitlab runners depending on which tag it is given. I would like to do this with an environmental variable, but it seems this cannot be used. The following job:

runner_test:
  image: alpine
  tags:
    - $MY_RUNNER
  stage: deploy_main
  script:
    - echo foobar
  retry: 2

Results in a paused pipeline with the error: This job is stuck because you don't have any active runners online or available with any of these tags assigned to them: $MY_RUNNER

Answer 1

Dynamic job tags is achievable now (tested on 14.10). Variable interpolation works for job tags, and one way you can dynamically modify CI Variables is with the rules:variables key.

The following example would result in a default job tag of "staging" for most branches, and an override value of "production" for pipelines running against the project's default branch.

job:
  variables:
    RUNNER_TAG: staging           # default CI variable value
  rules:
    - if: $CI_COMMIT_REF_NAME == $CI_DEFAULT_BRANCH
      variables:
        RUNNER_TAG: production    # override CI variable value when the if: check is true
  tags:
    - $RUNNER_TAG                 # use the dynamic CI variable as a job tag
  script:
    - hello world from runner matching $RUNNER_TAG

Answer 2

Since this is not possible on older versions of Gitlab, as a work around for those on older verisons of Gitlab, to extend on the answer given by Rekovni, if you're looking to run environment specific runners:

.Deploy_template:
  stage: Deploy
  image:
    name: busybox/busybox:latest
    entrypoint: [""]
  rules:
    - when: manual
  before_script:
    - echo "Preflight tests"
  script:
    - echo "Start Deployment"
  after_script:
    - echo "Postflight tests"
  allow_failure: false


Deploy_feature:
  extends: .Deploy_template
  tags:
    - docker
    - feature
  rules:
    - if: $BRANCH =~ /feature/

Deploy_develop:
  extends: .Deploy_template
  tags:
    - docker
    - develop
  rules:
    - if: $BRANCH =~ /develop/

Deploy_stable:
  extends: .Deploy_template
  tags:
    - docker
    - stable
  rules:
    - if: $BRANCH =~ /stable/

Then you just repeat this for every job you have.

Answer 3

So if I have control of the repo branching structure, I make the CI branch names match the tags (e.g. dev, test, preprod, prod, etc). Then I can do something like this. However, this solution is not very portable for cases where you need to map the branch name to some other tag.

tags:
  - ${CI_COMMIT_BRANCH}

I really don't like the template, extends paradigm. It makes so much extra code. There must be a better way. There is this feature which is almost there. However, I cannot figure out how to make the source variable dynamically derived from another variable. Maybe it meets some people's use cases.