Try building Docker image for CPU architectures in parallel

.github/workflows/processing-segmenter-build.yml

@@ -19,12 +19,25 @@ on:
 jobs:
   build:
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        platform:
+          - linux/amd64
+          - linux/arm64
+          - linux/arm/v7
+          - linux/arm/v6
     permissions:
       contents: read
       packages: write
     steps:
       - uses: actions/checkout@v4
 
+      - name: Prepare environment variables
+        run: |
+          platform=${{ matrix.platform }}
+          echo "PLATFORM_PAIR=${platform//\//-}" >> $GITHUB_ENV
+
       # Build and publish Docker container image
       - name: Get Docker metadata
         id: meta
@@ -53,14 +66,69 @@ jobs:
           username: ${{ github.repository_owner }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
-      - name: Build and push
+      - name: Build and push by digest
+        id: build
         uses: docker/build-push-action@v5
         with:
           context: ./processing/segmenter
           pull: true
           push: ${{ github.event_name == 'pull_request' || github.event_name == 'push' || github.event_name == 'push tag' }}
-          platforms: linux/arm/v7,linux/arm64,linux/amd64
+          platforms: ${{ matrix.platform }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           cache-from: type=gha
           cache-to: type=gha,mode=max
+          outputs: type=image,name=${{ env.REGISTRY_IMAGE }},push-by-digest=true,name-canonical=true,push=true
+
+      - name: Export digest
+        run: |
+          mkdir -p /tmp/digests
+          digest="${{ steps.build.outputs.digest }}"
+          touch "/tmp/digests/${digest#sha256:}"
+
+  merge:
+    runs-on: ubuntu-latest
+    needs:
+      - build
+    steps:
+      - name: Download digests
+        uses: actions/download-artifact@v4
+        with:
+          path: /tmp/digests
+          pattern: digests-*
+          merge-multiple: true
+
+      # Build and publish Docker container image
+      - name: Get Docker metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/planktoscope/backend-processing-segmenter
+          tags: |
+            type=match,pattern=v(.*),group=1
+            type=edge,branch=main
+            type=ref,event=branch,enable=${{ github.ref != format('refs/heads/{0}', 'main') && github.ref != format('refs/heads/{0}', 'main') }}
+            type=ref,event=pr
+            type=raw,value=latest,enable=${{ github.ref == format('refs/heads/{0}', 'stable') }}
+            type=sha
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        if: github.event_name == 'pull_request' || github.event_name == 'push' || github.event_name == 'push tag'
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Create manifest list and push
+        working-directory: /tmp/digests
+        run: |
+          docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
+            $(printf 'ghcr.io/planktoscope/backend-processing-segmenter@sha256:%s ' *)     
+
+      - name: Inspect image
+        run: |
+          docker buildx imagetools inspect ghcr.io/planktoscope/backend-processing-segmenter:${{ steps.meta.outputs.version }}