make docker image(s) multi-platform and include linux/arm64

[trentm]

Motivating discussion issue: https://discuss.elastic.co/t/arm-64-apm-attacher-images/359952

To use the APM attacher for Kubernetes (https://www.elastic.co/guide/en/apm/attacher/current/apm-attacher.html) on a k8s deployment on linux/arm64 -- which I'm guessing is an option on the managed k8s services (who wouldn't want to use Graviton, for example?) -- requires that the involved images support the linux/arm64 platform. As well the linux/amd64 platform support should remain.

This means multi-platform Docker images: https://docs.docker.com/build/building/multi-platform/
Which is straightforward in GH actions if already using the docker/build-push-action action, see https://docs.docker.com/build/ci/github-actions/multi-platform/

At the least we need this for the published docker.elastic.co/observability/apm-agent-nodejs image.
Likely we'll need it for the attacher image, docker.elastic.co/observability/apm-attacher, as well. I'm still following up on that.

[trentm]

nomenclature

A "multi-platform image" is actually a separate Docker image for each platform (each with its own SHA identifier and manifest), and a "manifest list" that is metadata about the included images. This manifest list is the thing that is tagged for reference.

For example, look at the current alpine:latest image:

% docker buildx imagetools inspect alpine:latest
 Name:      docker.io/library/alpine:latest
MediaType: application/vnd.docker.distribution.manifest.list.v2+json
Digest:    sha256:77726ef6b57ddf65bb551896826ec38bc3e53f75cdde31354fbffb4f25238ebd

Manifests:
  Name:      docker.io/library/alpine:latest@sha256:216266c86fc4dcef5619930bd394245824c2af52fd21ba7c6fa0e618657d4c3b
  MediaType: application/vnd.docker.distribution.manifest.v2+json
  Platform:  linux/amd64

  Name:      docker.io/library/alpine:latest@sha256:4a6ffef76277d8c1d912ad489e0c09ddc09fdf7aefae51750a33dc47478c0cc0
  MediaType: application/vnd.docker.distribution.manifest.v2+json
  Platform:  linux/arm/v6

  Name:      docker.io/library/alpine:latest@sha256:1c3b93ed450e26eac89b471d6d140e2f99488f489739b8b8ea5e8202dd086f82
  MediaType: application/vnd.docker.distribution.manifest.v2+json
  Platform:  linux/arm64/v8
...

building a multi-platform image locally

(Here are some notes on creating a multi-platform image for apm-agent-nodejs locally on macOS. This is for educational purposes. The real answer will be to make the GH workflow changes to release.yml.)

tl;dr:

./dev-utils/make-distribution.sh   # script that creates "./build/dist/nodejs/"
docker buildx create --name builder --driver=docker-container
docker login
docker buildx build --builder builder --build-arg AGENT_DIR=/build/dist/nodejs --platform linux/amd64,linux/arm64 --push -t $IMAGE_NAME:$IMAGE_TAG .

The Docker docs article https://docs.docker.com/build/building/multi-platform/ shows how to use docker buildx build ... to create multi-platform images. In my case I'm using Docker Desktop which defaults to a "docker" builder that does not support building multi-platform. There are options for other builds. I'm using the docker-container builder option, because that appears to be the option suggested to be used with the docker/build-push-action GH action that we'll eventually be using in CI.

First you need to create a builder. I named it "builder":

docker buildx create --name builder --driver=docker-container

Then use it with the --builder BUILDER-NAME option.
The --platform PLATFORMS option specifies the platforms to include.

docker login   # cat ~/.docker/config.json
docker buildx build --builder builder --build-arg AGENT_DIR=/build/dist/nodejs --platform linux/amd64,linux/arm64 --push -t trentm/enode:5 .

Note that to use the multi-platform image, it needs to be published to a registry. You cannot just have it in your local Docker (e.g. the list of docker images). For my local testing I published to trentm/enode:5 for playing. You can see it at: https://hub.docker.com/repository/docker/trentm/enode/tags

using in GH Actions

My understanding, from https://docs.docker.com/build/ci/github-actions/multi-platform/, is that we will just need:

      # add this step to create the "builder"
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3

      - name: Build and push
        uses: docker/build-push-action@v5
        with:
          context: .
          platforms: linux/amd64,linux/arm64   # <--- add this
          push: true
          tags: user/app:latest

[trentm]

note to self: enode10

[heisGarvit]

@trentm any tentative date? when this will go live?

[trentm]

@heisGarvit Sorry for the delay. I hope to have a fix for this and then a release later this week.