CI/CD Pipeline — Build, Test, Deploy Automation

CI/CD কী?

• CI — Continuous Integration: merge → build → test automated
• CD — Continuous Delivery: auto deploy to staging
• CD — Continuous Deployment: auto deploy to prod

Pipeline Stages

Code Push
  ↓
Build (compile, package)
  ↓
Test (unit, integration)
  ↓
Code Analysis (SAST, lint)
  ↓
Artifact (Docker image)
  ↓
Deploy Staging
  ↓
E2E Test + DAST
  ↓
Approval Gate
  ↓
Deploy Production
  ↓
Smoke Test + Monitor

GitHub Actions ⭐

# .github/workflows/ci.yml
name: CI
on:
  push: { branches: [main] }
  pull_request: { branches: [main] }

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with: { node-version: 20, cache: npm }
      - run: npm ci
      - run: npm run lint
      - run: npm test -- --coverage
      - uses: codecov/codecov-action@v4

  docker:
    needs: build
    if: github.ref == 'refs/heads/main'
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: docker/login-action@v3
        with:
          username: ${{ secrets.DOCKER_USER }}
          password: ${{ secrets.DOCKER_PASS }}
      - uses: docker/build-push-action@v5
        with:
          push: true
          tags: myapp:${{ github.sha }}

GitLab CI

# .gitlab-ci.yml
stages: [build, test, deploy]

build:
  stage: build
  script:
    - npm ci
    - npm run build
  artifacts:
    paths: [dist/]

test:
  stage: test
  script: [npm test]
  coverage: '/Lines\s*:\s*(\d+\.?\d*)%/'

deploy:
  stage: deploy
  only: [main]
  script: [./deploy.sh]
  environment: production

Other CI/CD Tools

Jenkins (self-host), CircleCI, Travis CI, Azure DevOps, AWS CodePipeline, Bitbucket Pipelines, Drone।

Deployment Strategies ⭐

Recreate (downtime)

Stop old → Deploy new → Start
❌ Downtime

Rolling Update

v1 v1 v1 v1
→ v1 v1 v1 v2
→ v1 v1 v2 v2
→ v1 v2 v2 v2
→ v2 v2 v2 v2
✅ Kubernetes default

Blue-Green ⭐

Blue (live)  v1  ← traffic
Green        v2  (new)
↓ Test Green
↓ Switch LB
Green (live) v2 ← traffic
Blue         v1  (standby for rollback)

Canary ⭐

v1 (95% traffic) → v2 (5%)
Monitor errors/latency
OK → v1 (90%), v2 (10%)
OK → v1 (50%), v2 (50%)
OK → v2 (100%)
Fail → rollback

A/B Testing

Two versions simultaneously — feature experiment, not just deployment।

Feature Flags

if (featureFlag('new-checkout', user)) {
  renderNewCheckout();
} else {
  renderOldCheckout();
}

Tools: LaunchDarkly, Unleash, Split.io, Flagsmith।

সুবিধা: deploy ≠ release, gradual rollout, instant kill switch, A/B test, trunk-based dev enables।

Rollback Strategy

• Versioned artifacts (tag, don't delete)
• DB migration reversible
• Feature flag kill switch
• Blue-green instant switch
• Automated on smoke test fail
• Runbook for manual steps

Pipeline Best Practices

• Fast feedback (parallel jobs)
• Fail fast
• Cache dependencies
• Secrets in vault (not code)
• Ephemeral runners
• Infrastructure as Code (Terraform)
• Notify on failure (Slack, email)
• Metrics: lead time, deploy frequency, MTTR, change fail rate (DORA)