What is GitHub Actions? How do you create a basic workflow, and what are its key components?

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GitHub Actions is a CI/CD platform built directly into GitHub. It allows you to automate workflows for building, testing, and deploying code right from your repository. Because it is integrated with GitHub, there is no need to set up external CI servers.

Workflows are defined in YAML files stored in the .github/workflows directory of your repository. Each file represents one workflow.

Here are the key components of a GitHub Actions workflow.

Workflows are automated processes triggered by events. A repository can have multiple workflows for different purposes.

Events trigger workflows. Common events include push, pull_request, schedule for cron jobs, and workflow_dispatch for manual triggers.

Jobs are sets of steps that execute on the same runner. Jobs run in parallel by default, but you can configure dependencies between them.

Steps are individual tasks within a job. A step can run a shell command or use an action.

Actions are reusable units of code. GitHub provides many official actions, and the community contributes thousands more through the GitHub Marketplace.

Runners are servers that execute the jobs. GitHub provides hosted runners for Linux, Windows, and macOS. You can also use self-hosted runners.

Here is a basic workflow example:

name: CI Pipeline

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  build-and-test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: '20'
      - run: npm install
      - run: npm test
      - run: npm run build

This workflow triggers on pushes and pull requests to main. It runs on Ubuntu, checks out the code, sets up Node.js, installs dependencies, runs tests, and builds the application. The uses keyword references reusable actions, while run executes shell commands.