Azure Pipeline Cache@2 Docker缓存未复用问题求助

我正在Azure Pipeline中尝试通过Cache@2任务实现Docker构建的缓存优化，先后使用了两种Pipeline配置：

初始配置 #

stages:
  - stage: Build
    displayName: Build and push stage
    jobs:
      - job: Build
        displayName: Build
        pool:
          vmImage: "ubuntu-latest"
        steps:
          - script: |
              echo "##vso[task.setvariable variable=DOCKER_BUILDKIT]1"
            displayName: Enable Docker BuildKit

          - task: Docker@2
            displayName: Login to container registry
            inputs:
              command: login
              containerRegistry: $(dockerRegistryServiceConnection)

          - script: |
              mkdir -p $(Pipeline.Workspace)/.docker/cache
              echo "Contents of cache directory before build:"
              ls -la $(Pipeline.Workspace)/.docker/cache
            displayName: Ensure Docker cache directory exists

          - task: Bash@3
            displayName: Build and Push Docker Image to ACR
            inputs:
              targetType: inline
              script: |
                echo "Create new builder with docker-container driver..."
                docker buildx create --name builder --driver docker-container --bootstrap --use

                echo "Build image using the new builder..."
                docker buildx build --builder builder \
                  --cache-from=type=local,src=$(Pipeline.Workspace)/.docker/cache \
                  --cache-to=type=local,dest=$(Pipeline.Workspace)/.docker/cache,mode=max \
                  --tag $(containerRegistry)/$(imageRepository):$(releaseTag) \
                  --tag $(containerRegistry)/$(imageRepository):$(latestTag) \
                  --file $(dockerfilePath) \
                  $(buildContext) \
                  --push

          - task: Cache@2
            displayName: Save Docker layers cache
            inputs:
              key: $(cacheKey)
              path: $(Pipeline.Workspace)/.docker/cache

          - script: |
              echo "Contents of cache directory after build:"
              ls -la $(Pipeline.Workspace)/.docker/cache
              docker images
            displayName: List Docker Images and Cache Contents

          - script: |
              echo "Cache hit/miss info:"
              echo "Cache key: $(cacheKey)"
            displayName: Log cache information

该配置未生效，随后调整为以下版本：

EDIT 3配置 #

stages:
  - stage: Build
    displayName: Build and push stage
    jobs:
      - job: Build
        displayName: Build
        pool:
          vmImage: "ubuntu-latest"
        steps:
          - task: Docker@2
            displayName: Login to container registry
            inputs:
              command: login
              containerRegistry: $(dockerRegistryServiceConnection)

          - task: Cache@2
            displayName: Cache Docker image
            inputs:
              key: $(cacheKey)
              path: $(DOCKER_CACHE_DIR)
              cacheHitVar: CACHE_RESTORED

          - script: |
              echo "Checking for Docker cache directory..."
              if [ -d "$(DOCKER_CACHE_DIR)" ]; then
                echo "Cache directory exists. Listing contents..."
                ls -la $(DOCKER_CACHE_DIR)
                if [ -f "$(DOCKER_CACHE_DIR)/cache.tar" ]; then
                  echo "Cache file exists. Loading Docker cache..."
                  docker load -i $(DOCKER_CACHE_DIR)/cache.tar || echo "Failed to load cache"
                else
                  echo "Cache file does not exist."
                fi
              else
                echo "Cache directory does not exist. Skipping cache load."
              fi
            displayName: Load Docker cache if directory exists
            condition: eq(variables.CACHE_RESTORED, 'true')

          - task: Docker@2
            displayName: Build and Push Docker Image to ACR
            inputs:
              containerRegistry: $(dockerRegistryServiceConnection)
              repository: $(imageRepository)
              command: buildAndPush
              Dockerfile: $(dockerfilePath)
              buildContext: $(Build.SourcesDirectory)/services/api
              tags: |
                $(releaseTag)
                $(latestTag)

          - script: |
              echo "Saving Docker image to cache..."
              mkdir -p $(DOCKER_CACHE_DIR)
              IMAGE_TAG=$(containerRegistry)/$(imageRepository):$(releaseTag)
              if docker image inspect $IMAGE_TAG > /dev/null 2>&1; then
                docker save -o $(DOCKER_CACHE_DIR)/cache.tar $IMAGE_TAG
                echo "Docker image saved to cache."
              else
                echo "Image $IMAGE_TAG not found. Skipping cache save."
              fi
            displayName: Cache docker layers

          - script: |
              echo "Contents of cache directory after build:"
              ls -la $(DOCKER_CACHE_DIR)
              docker images
              echo "Cache hit/miss info:"
              echo "Cache key: $(cacheKey)"
            displayName: List Docker Images and Cache Contents

当前问题 #

EDIT 3配置已实现缓存命中、加载及保存，但Docker构建时仍未复用缓存层，每次都会重新安装所有依赖，构建时间显著增加。

已尝试的调试手段 #

• 初始使用Cache@2与Docker@2任务组合，未生效；
• 手动创建缓存目录；
• 手动从ACR拉取历史镜像供Docker缓存识别。

求助内容 #

1. 排查当前EDIT 3配置中缺失的部分，解决Docker缓存层复用问题；
2. 询问生产环境使用自托管VM代理进行Docker构建是否可行。

后续会补充相关排查结果，供他人参考。

内容的提问来源于stack exchange，提问作者Navemics