如何用GitHub Action缓存多阶段构建的共享Docker基础镜像？

核心问题分析 #

你当前的配置混淆了Docker构建层缓存与共享Builder镜像缓存的作用：cache-from/to仅用于缓存Docker构建过程中的中间层，而ghcr.io/dancing-star/packages-image-full作为基础镜像，需要单独处理缓存逻辑，避免每次构建重新拉取。另外注意：环境变量BUILD_IMAGE_NAME的路径与Dockerfile中引用的镜像路径不一致，这会直接导致缓存失效，需先修正该拼写错误。

具体优化配置 #

1. 修改GitHub Action配置（.github/workflows/docky.yaml） #

使用actions/cache缓存Builder镜像的tar包，避免重复从GHCR拉取；同时调整build-push-action的参数，确保复用本地已缓存的镜像：

name: Build Docker

on:
  push:
    branches: [ main ]
    tags:
      - v*

env:
  IMAGE_NAME: project-docker
  # 修正镜像路径，与Dockerfile保持一致
  BUILDER_IMAGE: ghcr.io/dancing-star/packages-image-full:latest
  # 基于依赖锁文件生成缓存key，依赖更新时自动重新拉取镜像
  BUILDER_IMAGE_CACHE_KEY: builder-image-${{ hashFiles('**/package-lock.json', '**/yarn.lock') }}
  # 若不需要随依赖更新镜像，可使用固定key：builder-image-latest

jobs:
  build:
    runs-on: ubuntu-latest
    permissions:
      packages: write
      contents: read
    steps:
      - name: Checkout
        uses: actions/checkout@v3

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2

      - name: Login to GitHub Container Registry
        uses: docker/login-action@v2
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.DOCKER_DEPLOY_GITHUB }}

      # 将Builder镜像缓存到GitHub Actions缓存
      - name: Cache Builder Image
        id: cache-builder
        uses: actions/cache@v3
        with:
          path: /tmp/builder-image.tar
          key: ${{ env.BUILDER_IMAGE_CACHE_KEY }}

      # 缓存未命中时，拉取镜像并保存为tar包
      - name: Pull and Save Builder Image
        if: steps.cache-builder.outputs.cache-hit != 'true'
        run: |
          docker pull ${{ env.BUILDER_IMAGE }}
          docker save -o /tmp/builder-image.tar ${{ env.BUILDER_IMAGE }}

      # 缓存命中时，加载本地tar包到Docker
      - name: Load Cached Builder Image
        if: steps.cache-builder.outputs.cache-hit == 'true'
        run: |
          docker load -i /tmp/builder-image.tar

      - name: Build and push
        uses: docker/build-push-action@v4
        with:
          context: .
          file: Dockerfile
          push: true
          # 替换为你实际要推送的最终镜像标签
          tags: ghcr.io/your-username/${{ env.IMAGE_NAME }}:latest
          # 保留构建层缓存，优化后续构建
          cache-from: type=registry,ref=ghcr.io/your-username/${{ env.IMAGE_NAME }}:buildcache
          cache-to: type=registry,ref=ghcr.io/your-username/${{ env.IMAGE_NAME }}:buildcache,mode=max
          # 强制使用本地已有的Builder镜像，禁止重新拉取
          pull: false

2. Dockerfile小优化 #

添加--mount=type=cache缓存npm临时文件，进一步压缩构建耗时：

FROM ghcr.io/dancing-star/packages-image-full:latest AS builder

WORKDIR /var/dancing-star

COPY . .

# 挂载npm缓存目录，避免重复下载临时依赖
RUN --mount=type=cache,target=/tmp/node-cache \
    npm config set cache /tmp/node-cache --global \
    && npm run prod \
    && rm -rf src

FROM alpine
WORKDIR /var/dancing-star
# 简化COPY命令，提升可读性
COPY --from=builder /var/dancing-star/dist ./dist
COPY --from=builder /var/dancing-star/assets ./assets
COPY --from=builder /var/dancing-star/config ./config
COPY --from=builder /var/dancing-star/scripts ./scripts
COPY --from=builder /var/dancing-star/*.{json,md,js} ./

# CMD [ "pm2-runtime", "start", "app.pm2.json", "--env", "production" ]

关键优化点说明 #

• 单独缓存Builder镜像：通过actions/cache将镜像保存为本地tar包，下次构建直接加载，省去远程拉取的时间。
• 路径一致性修正：确保环境变量与Dockerfile中的镜像地址完全匹配，避免缓存失效。
• pull: false参数：强制Docker使用本地已有的基础镜像，不再发起远程拉取请求。
• 分层缓存配合：构建层缓存（cache-from/to）与基础镜像缓存分开配置，最大化优化构建效率。

内容的提问来源于stack exchange，提问作者Pian0_M4n