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Describe Affected Now Detects Deleted Components and Stacks

· 4 min read
Andriy Knysh
Andriy Knysh
Principal Architect @ Cloud Posse

Atmos now automatically detects components and stacks that have been deleted in your current branch compared to the target branch. This enables CI/CD pipelines to trigger terraform destroy workflows for removed infrastructure.

The Problem​

Previously, atmos describe affected only detected components that were modified between two Git commits. It worked by iterating over stacks in HEAD (current branch) and comparing them to BASE (target branch). This meant:

  • Components removed from a stack were invisible to the affected detection
  • Entire stacks that were deleted went unnoticed
  • CI/CD pipelines had no automated way to know which resources needed terraform destroy
  • Users had to manually identify and destroy removed components, risking resource leaks

The Solution​

The describe affected command now performs a second pass that iterates over BASE stacks to detect deletions:

  1. Deleted components: Components that exist in BASE but not in HEAD (within the same stack)
  2. Deleted stacks: Entire stacks that exist in BASE but not in HEAD

Deleted components are marked with new fields in the output:

{
  "component": "monitoring",
  "component_type": "terraform",
  "stack": "prod-us-east-1",
  "affected": "deleted",
  "deleted": true,
  "deletion_type": "component"
}

New Output Fields​

FieldTypeDescription
deletedbooleantrue if the component was deleted
deletion_typestringcomponent (removed from stack) or stack (entire stack deleted)

New Affected Reasons​

ReasonDescription
deletedComponent was removed from a stack
deleted.stackEntire stack was deleted

Filtering Deleted vs Modified Components​

Use the --query flag or jq to separate deleted components from modified ones:

# Get only deleted components (for destruction)
atmos describe affected --query '[.[] | select(.deleted == true)]'

# Get only modified components (for apply)
atmos describe affected --query '[.[] | select(.deleted != true)]'

Using with List Affected​

The atmos list affected command also supports deleted detection, providing a human-readable table view:

# List all affected components including deleted ones
atmos list affected

# Filter deleted components in JSON format
atmos list affected --format json | jq '[.[] | select(.deleted == true)]'

# Custom columns showing deletion status
atmos list affected --columns "Component={{ .component }},Stack={{ .stack }},Deleted={{ .deleted }}"

The deleted and deletion_type fields are available for custom column templates.

CI/CD Integration Example​

Here's how to separate apply and destroy workflows in GitHub Actions:

warning

Review deletions carefully before destroying infrastructure. The destroy job below uses --auto-approve for automation purposes. In production environments, consider adding a manual approval gate or requiring PR review before executing destroy operations to prevent accidental resource deletion.

jobs:
  detect-changes:
    runs-on: ubuntu-latest
    outputs:
      modified: ${{ steps.affected.outputs.modified }}
      deleted: ${{ steps.affected.outputs.deleted }}
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - uses: cloudposse/github-action-setup-atmos@v2

      - name: Detect affected
        id: affected
        run: |
          atmos describe affected --format json > affected.json

          # Separate modified and deleted components
          jq '[.[] | select(.deleted != true)]' affected.json > modified.json
          jq '[.[] | select(.deleted == true)]' affected.json > deleted.json

          echo "modified=$(cat modified.json | jq -c)" >> $GITHUB_OUTPUT
          echo "deleted=$(cat deleted.json | jq -c)" >> $GITHUB_OUTPUT

  apply:
    needs: detect-changes
    if: needs.detect-changes.outputs.modified != '[]'
    strategy:
      matrix:
        include: ${{ fromJson(needs.detect-changes.outputs.modified) }}
    steps:
      - uses: actions/checkout@v4
      - uses: cloudposse/github-action-setup-atmos@v2
      - run: atmos terraform apply ${{ matrix.component }} -s ${{ matrix.stack }}

  destroy:
    needs: detect-changes
    if: needs.detect-changes.outputs.deleted != '[]'
    environment: production  # Requires manual approval
    strategy:
      matrix:
        include: ${{ fromJson(needs.detect-changes.outputs.deleted) }}
    steps:
      # Check out BASE branch - deleted component config only exists there
      - uses: actions/checkout@v4
        with:
          ref: ${{ github.base_ref }}
      - uses: cloudposse/github-action-setup-atmos@v2
      - run: atmos terraform destroy ${{ matrix.component }} -s ${{ matrix.stack }} --auto-approve

Edge Cases​

  • Abstract components (metadata.type: abstract) are not reported as deleted since they are blueprints and not provisioned
  • Component renames appear as both a deletion (old name) and a new component (new name)