What is CI/CD?

Definition

CI/CD stands for Continuous Integration and Continuous Deployment (or Delivery). It's a set of practices and tools that automate the process of integrating code changes, running tests, and deploying to production.

• Continuous Integration (CI): Automatically build and test code every time a developer pushes changes. Catches bugs early.
• Continuous Delivery (CD): Automatically prepare code for release to production. Deployment requires manual approval.
• Continuous Deployment (CD): Automatically deploy every change that passes tests to production. No manual intervention.

CI/CD Pipeline Stages

1. Source: Developer pushes code to version control (Git).
2. Build: Compile code, install dependencies, build Docker images.
3. Test: Run unit tests, integration tests, linting, type checking.
4. Security scan: Check for vulnerabilities in dependencies and code.
5. Staging: Deploy to a staging environment for manual or automated testing.
6. Production: Deploy to production with rollback capability.

Popular CI/CD Tools

• GitHub Actions: Native CI/CD integrated into GitHub. Excellent for open-source and most projects.
• GitLab CI: Built-in CI/CD with GitLab. Powerful pipeline configuration.
• Jenkins: Self-hosted, highly customizable. Legacy choice with huge plugin ecosystem.
• CircleCI: Cloud-native CI/CD with fast builds and Docker support.
• ArgoCD: GitOps-based continuous delivery for Kubernetes.

Code Example

# .github/workflows/ci.yml - GitHub Actions for Python
name: CI
on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-python@v5
        with:
          python-version: '3.12'
      - run: pip install -r requirements.txt
      - run: pytest --cov=app tests/
      - run: ruff check .
      - run: mypy app/

Frequently Asked Questions

What is the difference between CI and CD?

CI (Continuous Integration) focuses on automatically building and testing code when changes are pushed. CD (Continuous Delivery/Deployment) extends this to automatically preparing or deploying releases. CI catches bugs early; CD ensures fast, reliable releases.