leejunkim

Github Actions

4 min read

Definition

GitHub’s CD system is called GitHub Actions

  • Configure it by creating YAML files (with .yml or .yaml extensions) inside a .github/workflows directory in your repository → This file defines the entire automated process

Main keywords

  • name: The name of your workflow, which will appear in the “Actions” tab on GitHub.
  • on: This defines the trigger that starts the workflow. It can be a Git event, a schedule, or a manual trigger.
    • Examples: push (runs on every push), pull_request (runs when a pull request is created or updated), workflow_dispatch (allows manual triggering).
  • jobs: A workflow is made up of one or more jobs. By default, jobs run in parallel on different virtual machines.
    • Each job in a GitHub Actions workflow runs on its own fresh, isolated virtual machine (or “runner”)
  • job_id (e.g., build, test): This is the unique identifier for a job within the jobs section.
  • runs-on: Specifies the type of virtual machine (or “runner”) to execute the job on. Common choices are ubuntu-latest, windows-latest, and macos-latest.
  • steps: A job contains a sequence of tasks called steps. Steps are executed in order within a job.
  • uses: A powerful keyword that lets you use pre-built actions created by the community or GitHub itself. This saves you from writing complex scripts. For example, actions/checkout@v4 is a standard action to check out your repository’s code onto the runner.
  • run: Executes command-line commands directly on the runner’s shell. This is where you’ll put your build, test, and deployment commands.
  • with: Used to provide input parameters to an action specified with uses.

Github runner

What

A GitHub Runner is a virtual machine that executes your workflow jobs. Think of it as a temporary, clean computer in the cloud that GitHub provides to run your commands.

  • Isolated and Ephemeral
    • Each job in your workflow gets its own brand-new runner.
    • When the job is finished, the runner is COMPLETELY DESTROYED!! NOTHING is carried over from one job to another. This guarantees a clean and predictable environment for every job.
  • Pre-configured Environment
    • These virtual machines aren’t empty. They come pre-installed with a wide range of common software, such as Git, docker, various programming languages (Node.js, Python, Java), and build tools, so you don’t have to install them from scratch.
  • With actions/checkout@v3
    • the runner is a clean machine. ⇒empty (no code) by default.
    • The actions/checkout step is the command that securely downloads your source code from your repository onto the runner

Basic Template

# Name of the workflow
name: Java CI with Gradle and Docker
 
# Triggers for the workflow
on:
  push:
    branches: [ "main" ]
  pull_request:
    branches: [ "main" ]
 
# A workflow run is made up of one or more jobs
jobs:
  # This job is named "build-and-test"
  build-and-test:
    # The type of runner that the job will run on
    runs-on: ubuntu-latest
 
    # Steps represent a sequence of tasks that will be executed as part of the job
    steps:
      # Step 1: Checks-out your repository under $GITHUB_WORKSPACE
      - name: Checkout repository code
        uses: actions/checkout@v4
 
      # Step 2: Set up JDK 17
      - name: Set up JDK 17
        uses: actions/setup-java@v4
        with:
          java-version: '17'
          distribution: 'temurin' # Popular open-source distribution of Java
 
      # Step 3: Grant execute permission for gradlew
      - name: Grant execute permission for gradlew
        run: chmod +x gradlew
 
      # Step 4: Build with Gradle and run tests
      - name: Build with Gradle
        run: ./gradlew build
 
      # Step 5: Set up Docker Buildx
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3
 
      # Step 6: Log in to Docker Hub (replace with your registry if different)
      # You'll need to add DOCKERHUB_USERNAME and DOCKERHUB_TOKEN as secrets in your GitHub repository settings
      - name: Log in to Docker Hub
        uses: docker/login-action@v3
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}
 
      # Step 7: Build and push Docker image
      - name: Build and push Docker image
        uses: docker/build-push-action@v5
        with:
          context: .
          file: ./Dockerfile
          push: true
          tags: ${{ secrets.DOCKERHUB_USERNAME }}/your-app-name:latest # Replace with your Docker Hub username and app name

Graph View

Backlinks