Parameterize `runs-on` value for GitHub action - github

Question

I have this GitHub workflow that I need to parameterize on which runners runs. So in the YAML file I tried:
# ...
jobs:
process:
name: Process
runs-on: ${{ secrets.GH_RUNNER_TAG }}
# ...
However, I get this error:
The workflow is not valid. .github/workflows/action.yml (Line: 12, Col: 14): Unrecognized named-value: 'secrets'. Located at position 1 within expression: secrets.GH_RUNNER_TAG
Is the secrets injection not available for this element? Is there some other alternative? The value does not need to be a secret but I need to have it in one place and not edit hundreds of YAML files everytime the runner tag would change...
EDIT1:
I've tried, as GuiFalourd suggested, to create an environment variable at the workflow level which would hold the secret:
env:
RUNNER_LABEL: ${{ secrets.GH_RUNNER_TAG }}
jobs:
analyze:
name: Analyze
runs-on: $RUNNER_LABEL
And it doesn't work. The action gets stuck. I tried using:
$RUNNER_LABEL -> gets stuck
"$RUNNER_LABEL" -> gets stuck, too
${{ env.RUNNER_LABEL }} -> action does not start, outputs error:
The workflow is not valid. .github/workflows/action.yml (Line: 14, Col: 14): Unrecognized named-value: 'env'. Located at position 1 within expression: env.RUNNER_LABEL
Furthermore, I've checked that the env var is properly assigned, by placing a valid, hard-coded value for runs-on and setting first step as:
steps:
- name: Test
run: echo "$RUNNER_LABEL"
which produces "***" - proof that a secret has been output and redacted automatically by GitHub.

Answer 1

This is achievable using Reusable Workflow by configuring the "called" workflow to accept inputs from the caller.
The main pipeline which we can name it as "process" will use a shared codebase/pipeline lets call it "common" which can accept inputs, one of these inputs can be the runs-on value.
For example
# common.yml
name: parameterized job
on:
workflow_call:
inputs:
runner:
required: true
type: string
jobs:
common:
name: Common
runs-on: ${{ inputs.runner }}
steps:
- run: echo "Hello World"
# process.yml
name: process
on:
push:
jobs:
process:
uses: username/repo/.github/workflows/common.yml#branch
with:
runner: machine_with_specific_label # using ${{ env.MY_RUNNER_LABEL }} is possible as well