publish_docker.yml

# Recipe based on: https://docs.docker.com/build/ci/github-actions/multi-platform/#distribute-build-across-multiple-runners
name: Build and publish platform dependent docker image
on:
  push:
    branches:
      - "release"
    tags:
      - "v*"
  pull_request:
    branches:
      - "release"
  workflow_dispatch:

env:
  REGISTRY: ghcr.io
  IMAGE_NAME: ${{ github.repository }}

jobs:
  build:
    strategy:
      matrix:
        os: ["ubuntu-24.04", "ubuntu-24.04-arm"]
    runs-on: ${{ matrix.os }}

    permissions:
      contents: read
      packages: write

    steps:
      - name: Checkout repository
        uses: actions/checkout@v4

      - name: Log in to the Container registry
        uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3

      - name: Extract metadata (tags, labels) for Docker
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}

      - name: Set architecture tag (amd64)
        if: ${{ matrix.os == 'ubuntu-24.04' }}
        run: echo "ARCH_TAG=amd64" >> $GITHUB_ENV

      - name: Set architecture tag (arm)
        if: ${{ contains(matrix.os, 'arm') }}
        run: echo "ARCH_TAG=arm64" >> $GITHUB_ENV

      - name: Build and push by digest
        id: build
        uses: docker/build-push-action@v6
        with:
          file: docker/Dockerfile
          platforms: ${{ env.ARCH_TAG }}
          labels: ${{ steps.meta.outputs.labels }}
          outputs: type=image,"name=${{ env.REGISTRY }}/${{ env.IMAGE_NAME}}",push-by-digest=true,name-canonical=true,push=true

      - name: Export digest
        run: |
          mkdir -p ${{ runner.temp }}/digests
          digest="${{ steps.build.outputs.digest }}"
          touch "${{ runner.temp }}/digests/${digest#sha256:}"          

      - name: Upload digest
        if: github.event_name == 'push'
        uses: actions/upload-artifact@v4
        with:
          name: digests-${{ env.ARCH_TAG }}
          path: ${{ runner.temp }}/digests/*
          if-no-files-found: error
          retention-days: 1
  
  merge-and-publish:
    if: github.event_name == 'push'
    runs-on: ubuntu-latest
    needs:
      - build
    steps:
      - name: Download digests
        uses: actions/download-artifact@v4
        with:
          path: ${{ runner.temp }}/digests
          pattern: digests-*
          merge-multiple: true

      - name: Log in to the Container registry
        uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Extract metadata (tags, labels) for Docker
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
        

      - name: Create manifest list and push
        working-directory: ${{ runner.temp }}/digests
        run: |
          docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
            $(printf '${{ env.REGISTRY }}/${{ env.IMAGE_NAME}}@sha256:%s ' *)          

      - name: Inspect image
        run: |
          docker buildx imagetools inspect ${{ env.REGISTRY }}/${{ env.IMAGE_NAME}}:${{ steps.meta.outputs.version }}