Docker: Use caching during Docker image builds.

Author: brycelelbach

.github/workflows/build-brev-tutorial-docker-images.yml

@@ -36,8 +36,10 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      - name: Get branch name
-        run: echo "GIT_BRANCH_NAME=${GITHUB_REF#refs/heads/}" >> $GITHUB_ENV
+      - name: Get branch name and short SHA
+        run: |
+          echo "GIT_BRANCH_NAME=${GITHUB_REF#refs/heads/}" >> $GITHUB_ENV
+          echo "GIT_SHORT_SHA=${GITHUB_SHA::7}" >> $GITHUB_ENV
 
       - name: Set image name
         id: set-image
@@ -71,22 +73,52 @@ jobs:
         run: |
           hpccm --recipe ${{ matrix.tutorial }}/brev/docker-recipe.py --format docker > ${{ matrix.tutorial }}/brev/dockerfile
 
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
       - name: Log in to GitHub Container Registry
         uses: docker/login-action@v3
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
-      - name: Build Docker image with Compose
-        run: docker compose -f ${{ matrix.tutorial }}/brev/docker-compose.yml build
-
-      - name: Tag Docker images
+      - name: Extract metadata from Docker Compose
+        id: compose-config
         run: |
-          docker tag "${{ steps.set-image.outputs.image_name }}:${GIT_BRANCH_NAME}-latest" "${{ steps.set-image.outputs.image_name }}:${GIT_BRANCH_NAME}-latest"
-          docker tag "${{ steps.set-image.outputs.image_name }}:${GIT_BRANCH_NAME}-latest" "${{ steps.set-image.outputs.image_name }}:${GIT_BRANCH_NAME}-git-${GITHUB_SHA::7}"
+          # This uses jq which is pre-installed on GitHub Actions runners
+          COMPOSE_DIR="${{ matrix.tutorial }}/brev"
+          cd "$COMPOSE_DIR"
 
-      - name: Push Docker images
-        run: |
-          docker push "${{ steps.set-image.outputs.image_name }}:${GIT_BRANCH_NAME}-latest"
-          docker push "${{ steps.set-image.outputs.image_name }}:${GIT_BRANCH_NAME}-git-${GITHUB_SHA::7}"
+          # `docker compose config` outputs the resolved configuration
+          # Extract context and dockerfile for the 'base' service
+          CONTEXT=$(docker compose config --format json | jq -r '.services.base.build.context // "."')
+          DOCKERFILE=$(docker compose config --format json | jq -r '.services.base.build.dockerfile // "Dockerfile"')
+
+          # Resolve paths relative to the docker-compose.yml location
+          # Then convert to paths relative to the repo root
+          CONTEXT_ABS=$(realpath -m "$CONTEXT")
+          CONTEXT_REL=$(realpath -m --relative-to="${GITHUB_WORKSPACE}" "$CONTEXT_ABS")
+
+          # Dockerfile path is relative to the context in docker-compose
+          # For build-push-action, it should be relative to the repo root
+          DOCKERFILE_ABS=$(realpath -m "$CONTEXT/$DOCKERFILE")
+          DOCKERFILE_REL=$(realpath -m --relative-to="${GITHUB_WORKSPACE}" "$DOCKERFILE_ABS")
+
+          echo "context=${CONTEXT_REL}" >> $GITHUB_OUTPUT
+          echo "dockerfile=${DOCKERFILE_REL}" >> $GITHUB_OUTPUT
+          echo "Using context: ${CONTEXT_REL}, dockerfile: ${DOCKERFILE_REL}"
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: ${{ steps.compose-config.outputs.context }}
+          file: ${{ steps.compose-config.outputs.dockerfile }}
+          build-args: |
+            GIT_BRANCH_NAME=${{ env.GIT_BRANCH_NAME }}
+          tags: |
+            ${{ steps.set-image.outputs.image_name }}:${{ env.GIT_BRANCH_NAME }}-latest
+            ${{ steps.set-image.outputs.image_name }}:${{ env.GIT_BRANCH_NAME }}-git-${{ env.GIT_SHORT_SHA }}
+          push: true
+          cache-from: type=registry,ref=${{ steps.set-image.outputs.image_name }}:buildcache
+          cache-to: type=registry,ref=${{ steps.set-image.outputs.image_name }}:buildcache,mode=max