Automation Patterns

Automation Patterns

Common patterns for running Copybara in CI/CD pipelines.

Pattern 1: On Push

Sync immediately when source changes:

name: Sync on Push

on:
  push:
    branches: [main]
    paths:
      - "src/**"

jobs:
  sync:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - run: java -jar copybara.jar migrate copy.bara.sky export --ignore-noop

Best for: Real-time synchronization

Pattern 2: Scheduled

Sync on a schedule:

name: Scheduled Sync

on:
  schedule:
    - cron: "0 0 * * *" # Daily at midnight

jobs:
  sync:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - run: java -jar copybara.jar migrate copy.bara.sky export --ignore-noop

Best for: Batching changes, reducing noise

Pattern 3: Manual Trigger

On-demand synchronization:

name: Manual Sync

on:
  workflow_dispatch:
    inputs:
      workflow:
        description: "Workflow to run"
        required: true
        default: "export"
        type: choice
        options:
          - export
          - import
      init_history:
        description: "Initialize history (first-time sync)"
        type: boolean
        default: false

jobs:
  sync:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - run: |
          FLAGS="--ignore-noop"
          if [ "${{ inputs.init_history }}" = "true" ]; then
            FLAGS="--init-history"
          fi
          java -jar copybara.jar migrate copy.bara.sky ${{ inputs.workflow }} $FLAGS

Best for: Controlled deployments, initial setup

Pattern 4: PR-Triggered

Sync when PRs are merged:

name: Sync on PR Merge

on:
  pull_request:
    types: [closed]
    branches: [main]

jobs:
  sync:
    if: github.event.pull_request.merged == true
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - run: java -jar copybara.jar migrate copy.bara.sky export --ignore-noop

Best for: Ensuring reviewed changes are synced

Pattern 5: Multi-Stage

Validate before syncing:

name: Validate and Sync

on:
  push:
    branches: [main]

jobs:
  validate:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: java -jar copybara.jar validate copy.bara.sky export

  sync:
    needs: validate
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - run: java -jar copybara.jar migrate copy.bara.sky export --ignore-noop

Best for: Catching config errors early

Pattern 6: Matrix Sync

Sync multiple workflows in parallel:

name: Multi-Workflow Sync

on:
  push:
    branches: [main]

jobs:
  sync:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        workflow: [export-core, export-cli, export-docs]
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - run: java -jar copybara.jar migrate copy.bara.sky ${{ matrix.workflow }} --ignore-noop

Best for: Monorepo extractions

Pattern 7: Conditional Sync

Sync based on changed paths:

name: Conditional Sync

on:
  push:
    branches: [main]

jobs:
  detect-changes:
    runs-on: ubuntu-latest
    outputs:
      src: ${{ steps.filter.outputs.src }}
      docs: ${{ steps.filter.outputs.docs }}
    steps:
      - uses: actions/checkout@v4
      - uses: dorny/paths-filter@v3
        id: filter
        with:
          filters: |
            src:
              - 'src/**'
            docs:
              - 'docs/**'

  sync-src:
    needs: detect-changes
    if: needs.detect-changes.outputs.src == 'true'
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - run: java -jar copybara.jar migrate copy.bara.sky export-src --ignore-noop

  sync-docs:
    needs: detect-changes
    if: needs.detect-changes.outputs.docs == 'true'
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - run: java -jar copybara.jar migrate copy.bara.sky export-docs --ignore-noop

Best for: Selective syncing based on changes

Pattern 8: Approval Gate

Require approval before syncing:

name: Gated Sync

on:
  push:
    branches: [main]

jobs:
  preview:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - run: |
          java -jar copybara.jar migrate copy.bara.sky export \
            --folder-destination /tmp/preview
      - run: |
          echo "## Preview" >> $GITHUB_STEP_SUMMARY
          find /tmp/preview -type f | head -20 >> $GITHUB_STEP_SUMMARY

  approve:
    needs: preview
    runs-on: ubuntu-latest
    environment: production # Requires approval
    steps:
      - run: echo "Approved!"

  sync:
    needs: approve
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - run: java -jar copybara.jar migrate copy.bara.sky export --ignore-noop

Best for: High-risk syncs requiring human approval

Error Handling

Robust error handling:

- name: Run Copybara
  id: copybara
  continue-on-error: true
  run: |
    java -jar copybara.jar migrate copy.bara.sky export 2>&1 | tee copybara.log
    exit ${PIPESTATUS[0]}

- name: Handle result
  run: |
    if [ "${{ steps.copybara.outcome }}" = "success" ]; then
      echo "Sync completed successfully"
    elif grep -q "NOOP" copybara.log; then
      echo "No changes to sync - this is OK"
    else
      echo "Sync failed!"
      cat copybara.log
      exit 1
    fi

Notifications

Notify on sync status:

- name: Notify on failure
  if: failure()
  uses: slackapi/slack-github-action@v2
  with:
    webhook: ${{ secrets.SLACK_WEBHOOK }}
    payload: |
      {
        "text": "Copybara sync failed: ${{ github.repository }}"
      }

Concurrency Control

Prevent parallel syncs:

concurrency:
  group: copybara-${{ github.workflow }}
  cancel-in-progress: false # Don't cancel running syncs

Tip

Set cancel-in-progress: false to ensure syncs complete even if new commits arrive.

Next Steps

• GitHub Actions setup
• Authentication