Continuous Delivery

# Complete CD pipeline
name: Deploy
on:
  push:
    branches: [main]

jobs:
  build:
    runs-on: ubuntu-latest
    outputs:
      version: ${{ steps.version.outputs.version }}
    steps:
      - uses: actions/checkout@v4
      - id: version
        run: echo "version=$(date +%Y%m%d)-${{ github.sha }}" >> $GITHUB_OUTPUT
      - run: npm ci && npm run build
      - uses: actions/upload-artifact@v4
        with:
          name: build-${{ steps.version.outputs.version }}
          path: dist/

  test:
    needs: build
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm ci && npm test

  deploy-staging:
    needs: [build, test]
    runs-on: ubuntu-latest
    environment: staging
    steps:
      - uses: actions/download-artifact@v4
        with:
          name: build-${{ needs.build.outputs.version }}
      - run: ./deploy.sh staging

  e2e-test:
    needs: deploy-staging
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm run test:e2e -- --base-url=$STAGING_URL

  deploy-production:
    needs: [deploy-staging, e2e-test]
    runs-on: ubuntu-latest
    environment: production
    steps:
      - uses: actions/download-artifact@v4
        with:
          name: build-${{ needs.build.outputs.version }}
      - run: ./deploy.sh production

# Kubernetes blue-green
apiVersion: v1
kind: Service
metadata:
  name: myapp
spec:
  selector:
    app: myapp
    version: blue  # Switch to 'green' for cutover
  ports:
    - port: 80

# Istio canary with traffic splitting
apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
  name: myapp
spec:
  hosts:
    - myapp
  http:
    - route:
        - destination:
            host: myapp
            subset: stable
          weight: 95
        - destination:
            host: myapp
            subset: canary
          weight: 5

apiVersion: apps/v1
kind: Deployment
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1        # Extra pods during update
      maxUnavailable: 0  # Always maintain capacity

# environments/production.yaml
database:
  host: prod-db.example.com
  pool_size: 20

cache:
  host: prod-redis.example.com
  ttl: 3600

features:
  new_dashboard: true
  beta_api: false

monitoring:
  log_level: info
  sample_rate: 0.1

# Promote same artifact through environments
deploy:
  stage: deploy
  script:
    - docker pull $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
    - docker tag $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA $CI_REGISTRY_IMAGE:$ENVIRONMENT
    - kubectl set image deployment/myapp myapp=$CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
  rules:
    - if: $CI_COMMIT_BRANCH == "main"
      variables:
        ENVIRONMENT: staging
    - if: $CI_COMMIT_TAG
      variables:
        ENVIRONMENT: production
      when: manual

MAJOR.MINOR.PATCH

1.0.0  → Initial release
1.0.1  → Patch (bug fix)
1.1.0  → Minor (new feature, backward compatible)
2.0.0  → Major (breaking change)

# Generate changelog from commits
- name: Generate Release Notes
  uses: release-drafter/release-drafter@v5
  with:
    config-name: release-drafter.yml
  env:
    GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

# Create release tag
git tag -a v1.2.0 -m "Release version 1.2.0"
git push origin v1.2.0

# Trigger production deploy on tag
on:
  push:
    tags:
      - 'v*'

# Kubernetes rollback
kubectl rollout undo deployment/myapp

# Or rollback to specific revision
kubectl rollout undo deployment/myapp --to-revision=2

┌─────────────────────────────────────────────────────────────────────────────┐
│                     DATABASE MIGRATION STRATEGY                              │
└─────────────────────────────────────────────────────────────────────────────┘

Forward-Only Migrations (Recommended):
1. Deploy backward-compatible schema change
2. Deploy application code
3. Clean up old schema (if needed)

Example: Adding a column
Step 1: Add column (nullable)        ← Schema v2
Step 2: Deploy code using new column ← App v2
Step 3: Backfill data
Step 4: Add NOT NULL constraint      ← Schema v3

// Using feature flags for safe rollout
const features = {
  newCheckoutFlow: {
    enabled: process.env.FEATURE_NEW_CHECKOUT === 'true',
    percentage: 10, // Gradual rollout
  },
};

function checkout(cart) {
  if (isFeatureEnabled('newCheckoutFlow', user)) {
    return newCheckoutFlow(cart);
  }
  return legacyCheckoutFlow(cart);
}

#!/bin/bash
# deploy.sh

set -e

ENVIRONMENT=$1
VERSION=${2:-latest}

echo "Deploying version $VERSION to $ENVIRONMENT"

# Validate environment
if [[ ! "$ENVIRONMENT" =~ ^(staging|production)$ ]]; then
  echo "Invalid environment: $ENVIRONMENT"
  exit 1
fi

# Pre-deployment checks
echo "Running pre-deployment checks..."
./scripts/health-check.sh $ENVIRONMENT

# Deploy
echo "Deploying..."
kubectl config use-context $ENVIRONMENT
kubectl set image deployment/myapp myapp=myapp:$VERSION

# Wait for rollout
echo "Waiting for rollout..."
kubectl rollout status deployment/myapp --timeout=5m

# Post-deployment verification
echo "Running smoke tests..."
./scripts/smoke-test.sh $ENVIRONMENT

echo "Deployment complete!"

# argocd/application.yaml
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/org/myapp-config
    targetRevision: HEAD
    path: environments/production
  destination:
    server: https://kubernetes.default.svc
    namespace: myapp
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

# Log all deployments
- name: Record Deployment
  run: |
    curl -X POST $AUDIT_API/deployments \
      -H "Authorization: Bearer $AUDIT_TOKEN" \
      -d '{
        "application": "${{ github.repository }}",
        "version": "${{ github.sha }}",
        "environment": "production",
        "deployer": "${{ github.actor }}",
        "timestamp": "'$(date -u +%Y-%m-%dT%H:%M:%SZ)'",
        "pipeline_url": "${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}"
      }'

deploy-production:
  environment:
    name: production
    url: https://myapp.example.com
  needs: [deploy-staging, e2e-tests]
  # Requires manual approval configured in GitHub settings
  steps:
    - name: Deploy
      run: ./deploy.sh production