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Affected Stacks

The Atmos Affected Stacks GitHub Action makes it easy identify the affected atmos stacks for a pull request. Use it to build a matrix so you can run other actions based on what was affected.

This GitHub Action installs Atmos, then runs atmos describe affected, and outputs a comprehensive list of affected stacks, both as raw output and as a matrix to be used in subsequent GitHub action jobs.

Discover more details, including the full list of inputs and outputs, in the GitHub Action repository on GitHub.

How it works​

The describe affected command works by comparing two different Git commits to generate a list of affected Atmos components and stacks. It assumes that the current repo root is a Git checkout and accepts a parameter to specify the second commit.

Overall Process:

  1. Clone the target branch (--ref), check out the commit, or use the pre-cloned target repository
  2. Deep merge all stack configurations for the current working and remote target branches.
  3. Identify changes in the component directories.
  4. Compare each section of the stack configuration to detect differences.
  5. Output a matrix containing a list of affected components and stacks

Atmos checks component folders for changes first, marking all related components and stacks as affected when changes are detected. It then skips evaluating those stacks for differences, streamlining the process.

Usage Example​

.github/workflows/atmos-terraform-plan.yaml

name: Pull Request
on:
  pull_request:
    branches: [ 'main' ]
    types: [opened, synchronize, reopened, closed, labeled, unlabeled]

jobs:
  context:
    runs-on: ubuntu-latest
    steps:
      - id: affected
        uses: cloudposse/github-action-atmos-affected-stacks@v3
        with:
          atmos-config-path: ./rootfs/usr/local/etc/atmos/
          atmos-version: 1.63.0
          nested-matrices-count: 1

    outputs:
      affected: ${{ steps.affected.outputs.affected }}
      matrix: ${{ steps.affected.outputs.matrix }}

  # This job is an example how to use the affected stacks with the matrix strategy
  atmos-plan:
    needs: ["atmos-affected"]
    if: ${{ needs.atmos-affected.outputs.has-affected-stacks == 'true' }}
    name: ${{ matrix.stack_slug }}
    runs-on: ['self-hosted']
    strategy:
      max-parallel: 10
      fail-fast: false # Don't fail fast to avoid locking TF State
      matrix: ${{ fromJson(needs.atmos-affected.outputs.matrix) }}
    ## Avoid running the same stack in parallel mode (from different workflows)
    concurrency:
      group: ${{ matrix.stack_slug }}
      cancel-in-progress: false
    steps:
      - name: Plan Atmos Component
        uses: cloudposse/github-action-atmos-terraform-plan@v2
        with:
          component: ${{ matrix.component }}
          stack: ${{ matrix.stack }}
          atmos-config-path: ./rootfs/usr/local/etc/atmos/
          atmos-version: 1.63.0

Requirements​

This action has the requirements as Github Actions. Use the same config described there.