Build multi-arch docker images (#944)

* Allow building docker image with different platform

This allow to build the correct image when host plateform is not amd64.
Related doc : https://docs.docker.com/build/building/multi-platform/

* Update docker-image GHA workflow to build multi-arch docker images

* Add bits of documentation about multi-platform images

---------

Co-authored-by: Alessandro De Maria <ademaria@isomorphiclabs.com>
Co-authored-by: Ricardo Amaro <ricardo.amaro@gmail.com>

.github/workflows/docker-image.yml

@@ -40,11 +40,19 @@ jobs:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
+      # Setup QEMU and Buildx to build multi-platform image
+      # This was inspired by this example : https://docs.docker.com/build/ci/github-actions/examples/#multi-platform-images
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v2
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
       - name: Build PR/versioned tags
         if: github.ref != 'refs/heads/master'
         uses: docker/build-push-action@v2
         with:
           tags: kapicorp/kapitan:${{ format('{0}', env.REF_NAME ) }}
+          platforms: linux/amd64,linux/arm64
           push: ${{ github.event_name != 'pull_request' }}  # push image only on non-pull_requests
           file: Dockerfile
       # TODO push and tag as latest if release (and not RC)
@@ -53,6 +61,7 @@ jobs:
         if: github.ref == 'refs/heads/master'
         with:
           tags: kapicorp/kapitan:${{ format('{0}', env.REF_NAME ) }},kapicorp/kapitan:latest
+          platforms: linux/amd64,linux/arm64
           file: Dockerfile
       - name: Test Dockerfile in current ref
         run: |
@@ -63,4 +72,5 @@ jobs:
         if: startsWith(github.ref, 'refs/tags/')
         with:
           tags: kapicorp/kapitan:${{ format('{0}', env.MAJOR_VERSION ) }}
+          platforms: linux/amd64,linux/arm64
           file: Dockerfile

Dockerfile

@@ -1,6 +1,8 @@
 # Build the virtualenv for Kapitan
 FROM python:3.7-slim AS python-builder
 
+ARG TARGETARCH
+
 RUN mkdir /kapitan
 WORKDIR /kapitan
 
@@ -18,7 +20,7 @@ RUN apt-get update \
         build-essential
 
 # Install Go (for go-jsonnet)
-RUN curl -fsSL -o go.tar.gz https://go.dev/dl/go1.17.3.linux-amd64.tar.gz \
+RUN curl -fsSL -o go.tar.gz https://go.dev/dl/go1.17.3.linux-${TARGETARCH}.tar.gz \
     && tar -C /usr/local -xzf go.tar.gz \
     && rm go.tar.gz
 

README.md

@@ -8,7 +8,7 @@
 [![Releases](https://img.shields.io/github/release/kapicorp/kapitan.svg)](https://github.com/kapicorp/kapitan/releases)
 [![Docker Image Size](https://img.shields.io/docker/image-size/kapicorp/kapitan/latest.svg)](https://hub.docker.com/r/kapicorp/kapitan)
 
-<img src="docs/images/kapitan_logo.png" width="25">  
+<img src="docs/images/kapitan_logo.png" width="25">
 
 
 **`Kapitan`** aims to be your *one-stop tool* to help you manage the ever growing complexity of your configurations.
@@ -53,6 +53,14 @@ System-wide (not recommended):
 sudo pip3 install --upgrade kapitan
 ```
 
+## Build Kapitan
+
+### Docker
+
+To build a docker image for the architecture of your machine, run `docker build . -t you-kapitan-image`, and to build for a specific platform, add `--platform linux/arm64`.
+
+To build a multi-platform image (as the CI does), follow [the docker multi-platform documentation](https://docs.docker.com/build/building/multi-platform/).
+
 ## Related projects
 
 * [Tesoro](https://github.com/kapicorp/tesoro) - Kubernetes Admission Controller for Kapitan Secrets