github-actions

GitHub Actions

GitHub Actions is the CI/​CD platform native to GitHub. In 2025, it is the dominant CI/​CD tool, characterized by Reusable Workflows and OIDC integration for passwordless deployments.

When to Use

• GitHub-Hosted: Your code is already on GitHub. Deep integration with Issues/​PRs.
• Simplicity: No servers to manage (unlike Jenkins).
• Marketplace: Thousands of pre-built actions (setup-node, docker-build-push).

Quick Start

# .github/​workflows/​ci.yml
name: CI
on: [push, pull_request]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/​checkout@v4
      - uses: actions/​setup-node@v4
        with:
          node-version: "20"
      - run: npm ci
      - run: npm test

Core Concepts

Workflows

Defined in .github/​workflows/​*.yml. Triggered by events (push, release, schedule).

Runners

Virtual machines (Ubuntu/​Windows/​MacOS) that run your jobs. You can also host Self-Hosted Runners for cheaper/​faster builds in your VPC.

Actions

Reusable steps. actions/​checkout is an action. You can write your own in JS or Docker.

Best Practices (2025)

Do:

• Use Reusable Workflows: Define a standard "Deploy to Prod" workflow in one repo, and call it from 50 microservices.
• Use OIDC: Authenticate to AWS/​Azure/​GCP using permissions: id-token: write instead of long-lived secrets.
• Pin Actions: Use actions/​checkout@v4 or a specific SHA for immutability.

Don't:

• Don't hardcode secrets: Use Repository Secrets or Environment Secrets.
• Don't write huge shell scripts: If a step is >10 lines of bash, move it to a script file or a custom Action.

References

• GitHub Actions Documentation