Docker Build Push Action（開發者如何工作）

Frictionless Automation

Building and pushing Docker images manually is exposed, error-prone, and time-consuming. Automating these steps ensures predictability and adds hours to the bottom line, especially when the team scales or updates are more frequent.

Frictionless Integration

The Docker Build Push Action works out of the box with GitHub repositories to create workflows around events such as code pushes, pull requests, or a schedule.

Standard Building of Images

Automation ensures that every time Docker images are built, they are the same; hence, reducing errors/discrepancies across multiple environments such as development, staging, and production.

Easy Deployment

With the automated building of Docker images with the build, and their push to the repositories, the deployment can get relatively easy. Tools like Kubernetes or Docker Swarm can be used to pull or build multi-platform images straight from the Docker registry, and hence reduce downtime.

How the Docker Build Push Action Works

The Build and Push Docker action does three core things:

1. Set Up Docker Login: Container registry authentication to securely push Docker images.
2. Image Build: Runs Docker build commands using a Dockerfile which contains instructions.
3. Push to Registry: It pushes the built image to a target container registry.

These steps are defined in a GitHub Actions workflow file (.github/workflows/your-workflow.yml), where you specify triggers, build configurations, and registry credentials.

Implement Docker Build Push Action

1: Prepare Your Repository

• Add a Dockerfile describing the containerized application.
• Add any configuration files or scripts required for the build.

# Use Node.js as the base image
FROM node:14

# Set the working directory
WORKDIR /app

# Copy package.json and install dependencies
COPY package.json .
RUN npm install

# Copy the application code
COPY . .

# Expose the application’s port
EXPOSE 3000

# Start the application
CMD ["npm", "start"]

2: Add Registry Credentials as GitHub Secrets

To build and push Docker images to a container registry, you need credentials. Add these as GitHub Secrets:

• Go into your repository settings on GitHub.
• Go to Secrets and Variables > Actions.

Add the following secrets:

• USERNAME: Your Docker Hub username.
• PASSWORD: Your Docker Hub access token or password.

For other registries, this is similar but sometimes requires extra credentials, for example, AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY for Amazon ECR.

3: Create GitHub Actions workflow

Add the below line on the YAML workflow file in .github/workflows/docker-build-push.yml.

name: Docker Build and Push

on:
  push:
    branches:
      - main

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      # Step 1: Check out the repository
      - name: Checkout code
        uses: actions/checkout@v3

      # Step 2: Log in to Docker Hub
      - name: Log in to Docker Hub
        uses: docker/login-action@v2
        with:
          username: ${{ secrets.USERNAME }}
          password: ${{ secrets.PASSWORD }}

      # Step 3: Build and push the Docker image
      - name: Build and push
        uses: docker/build-push-action@v4
        with:
          context: .
          push: true
          tags: username/repository:latest

name: Docker Build and Push

on:
  push:
    branches:
      - main

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      # Step 1: Check out the repository
      - name: Checkout code
        uses: actions/checkout@v3

      # Step 2: Log in to Docker Hub
      - name: Log in to Docker Hub
        uses: docker/login-action@v2
        with:
          username: ${{ secrets.USERNAME }}
          password: ${{ secrets.PASSWORD }}

      # Step 3: Build and push the Docker image
      - name: Build and push
        uses: docker/build-push-action@v4
        with:
          context: .
          push: true
          tags: username/repository:latest

Push to Main: The workflow will trigger every push that occurs to the main branch.

Checkout Code: Utilize the actions/checkout action to check out the repository.

Login to Registry: Authenticate with Docker Hub using the provided secrets.

Build and Push: It runs the Docker Build Push Action that will build the image from the current directory until the context and push it to username/repository: latest.

Commit the workflow file to your repository. With a simple push, the workflow will trigger to build the image and push it into your specified registry.