improve targeting for arm64

Author: tobydriscoll

.devcontainer/Dockerfile

@@ -32,6 +32,8 @@ RUN curl -fsSL https://install.julialang.org | sh -s -- --yes --startup-selfupda
 
 ENV PATH="/home/vscode/.juliaup/bin:${PATH}"
 
+ENV JULIA_CPU_TARGET="generic;cortex-a57;thunderx2t99;carmel;apple-m1,clone_all"
+
 # Copy the environment files and workload into the baked-in project.
 COPY --chown=vscode:vscode Project.toml Manifest.toml /opt/julia-env/
 COPY --chown=vscode:vscode precompile_workload.jl /opt/julia-env/

.devcontainer/devcontainer.json

@@ -1,6 +1,6 @@
 {
   "name": "Julia 1.11.9",
-  "image": "ghcr.io/fncbook/julia-classroom:1.11.9@sha256:86004d91c003917936f591d4b03d933f207f0d150f4b43d964fa2eb683de3f75",
+  "image": "ghcr.io/fncbook/julia-classroom:1.11.9",
 
   "remoteEnv": {
     "PATH": "${containerEnv:PATH}:/home/vscode/.juliaup/bin",

.github/workflows/build-docker.yml

@@ -16,8 +16,18 @@ env:
   JULIA_VERSION: "1.11.9"
 
 jobs:
-  build-and-push:
-    runs-on: ubuntu-latest
+  build:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - platform: linux/amd64
+            runner: ubuntu-latest
+            suffix: amd64
+          - platform: linux/arm64
+            runner: ubuntu-24.04-arm
+            suffix: arm64
+    runs-on: ${{ matrix.runner }}
 
     steps:
       - name: Checkout
@@ -30,30 +40,25 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.CR_PAT }}
 
-      - name: Set up QEMU (for multi-arch builds)
-        uses: docker/setup-qemu-action@v3
-
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
-      - name: Build and push
+      - name: Build and push (${{ matrix.suffix }})
         id: build
         uses: docker/build-push-action@v6
         with:
           context: .
           file: .devcontainer/Dockerfile
-          platforms: linux/amd64,linux/arm64
+          platforms: ${{ matrix.platform }}
           push: true
           build-args: JULIA_VERSION=${{ env.JULIA_VERSION }}
-          tags: |
-            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.JULIA_VERSION }}
-            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest
-          # cache-from: type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:buildcache
-          cache-to: type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:buildcache,mode=max
+          tags: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.JULIA_VERSION }}-${{ matrix.suffix }}
+          cache-from: type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:buildcache-${{ matrix.suffix }}
+          cache-to: type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:buildcache-${{ matrix.suffix }},mode=max
 
       - name: Smoke test — cached packages load without recompiling
         run: |
-          IMAGE="${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}@${{ steps.build.outputs.digest }}"
+          IMAGE="${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.JULIA_VERSION }}-${{ matrix.suffix }}"
           docker pull "$IMAGE"
           docker run --rm "$IMAGE" julia -e '
             t_plots = @elapsed using Plots
@@ -66,11 +71,33 @@ jobs:
             t_ode   < 30 || error("using OrdinaryDiffEq too slow ($(t_ode)s) — cache miss?")
           '
 
+  manifest:
+    needs: build
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Log in to GHCR
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.CR_PAT }}
+
+      - name: Create multi-arch manifest
+        run: |
+          for TAG in ${{ env.JULIA_VERSION }} latest; do
+            docker buildx imagetools create \
+              --tag ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:$TAG \
+              ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.JULIA_VERSION }}-amd64 \
+              ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.JULIA_VERSION }}-arm64
+          done
+          docker buildx imagetools inspect ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.JULIA_VERSION }}
+
       - name: Report image digest
-        if: always() && steps.build.outputs.digest != ''
         run: |
-          DIGEST='${{ steps.build.outputs.digest }}'
-          REF="${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.JULIA_VERSION }}@${DIGEST}"
+          REF_BASE="${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.JULIA_VERSION }}"
+          DIGEST=$(docker buildx imagetools inspect "$REF_BASE" | awk '/^Digest:/ {print $2; exit}')
+          REF="${REF_BASE}@${DIGEST}"
           echo "::notice title=New image digest::${REF}"
           {
             echo "## New image pushed"