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⚡ How a GitHub Actions Runner Works (Step by Step)

GitHub Actions runners execute workflows when triggered by events like code pushes, pull requests, or scheduled tasks. Here’s a step-by-step breakdown of how it works:

🚀 1. Triggering the Pipeline​

  • You push or pull code to GitHub (or trigger any defined event). 🔄
  • GitHub detects this event and assigns the job to an available runner (either GitHub-hosted or self-hosted). 🖥️

📌 Example Triggers:

  • push to main branch 📤
  • Opening a pull request 🔄
  • A cron job running at scheduled times ⏰

📥 2. Runner Fetches the Code​

  • The runner starts on a machine (either a GitHub-provided VM or your own self-hosted server). 🏗️
  • It clones (downloads) the latest code from your GitHub repository. 📂
  • The runner sets up the working environment as defined in the YAML workflow file.

🛠️ 3. Runner Executes the Steps​

  • It follows the instructions defined in the GitHub Actions YAML file (.github/workflows/your-workflow.yml).
  • Each step is executed in the specified order.

📌 Example Steps:
✅ Set up Node.js 🔧
✅ Install dependencies (e.g., npm install) 📦
✅ Run tests (e.g., npm test) 🧪
✅ Build the project (e.g., npm run build) 🏗️
✅ Lint and format code (e.g., eslint . --fix) 🎨

📡 4. Deploying to Another Server (Optional Step)​

  • The runner itself does not run your application; it only executes tasks like testing, building, and deploying.
  • If your YAML file includes an SSH step, the runner will:
    • 🔑 Use SSH to connect to the production server.
    • 📤 Copy the built files to the production server using rsync or scp.
    • 🔄 Restart services (e.g., pm2 restart app, docker-compose up -d).

🎯 Key Takeaways​

✅ GitHub Actions automates testing, building, and deployment processes.
✅ Runners execute jobs based on YAML workflow instructions.
✅ Self-hosted runners provide more control, while GitHub-hosted runners are managed automatically.
✅ Deployments often involve SSH & file transfers to production environments.

💡 With GitHub Actions, you can automate your entire CI/CD pipeline effortlessly! 🚀🔥