coredns charm-image resource is amd64 only

[Adam Dyess]

the 1.25/stable and 1.26/edge (about to be stable) version of this charm are released to charmhub with an amd64 specific image. The charm should work with the entire architecture that it supported by the upstream image

Currently these are the arches that the charm itself attests to support
        - amd64
        - arm
        - arm64
        - ppc64le
        - s390x

The intended image coredns/coredns:1.6.7 also supports this architectures

however, charmcraft tools (and perhaps charmhub itself) do not facilitate mutli-arch images to be published as a resource attached to a k8s charm.

Juju however allows you to deploy with any image, not just the image from charmhhub -- so the following workaround applies until then.

$ cat <<EOF > coredns.json
{"ImageName": "rocks.canonical.com:443/cdk/coredns/coredns:1.6.7"}
EOF

$ juju deploy coredns --coredns-image=./coredns.json --constraints="arch=${ARCH}" --trust

--- or if the charm is already deployed ---

$ juju attach-resource coredns --coredns-image=./coredns.json

[Adam Dyess (addyess)]

Upgrading coredns image to 1.10.0 -- let's target this image to be the one supported by multiarch
https://github.com/charmed-kubernetes/charm-coredns/pull/35

[Adam Dyess (addyess)]

While this above image update in #1 is nice -- it doesn't solve the problem that the oci-image resource is still solely amd64. The only current solution is to build the coredns charm for a specific bases-index and match its release with the appropriate architecture resource

Pseudo code of process would be something like this:
* change the charmcraft.yaml to split the bases apart by supported arch:

bases:
  - build-on: # bases-index 0
    - name: "ubuntu"
      channel: "22.04"
      architectures: ["amd64"]
    run-on:
    - name: "ubuntu"
      channel: "22.04"
      architectures: ["amd64"]
  - build-on: # bases-index 1
    - name: "ubuntu"
      channel: "22.04"
      architectures: ["amd64"]
    run-on:
    - name: "ubuntu"
      channel: "22.04"
      architectures: ["arm"]
  - build-on: # bases-index 2
    - name: "ubuntu"
      channel: "22.04"
      architectures: ["amd64"]
    run-on:
    - name: "ubuntu"
      channel: "22.04"
      architectures: ["arm64"]
  - build-on: # bases-index 3
    - name: "ubuntu"
      channel: "22.04"
      architectures: ["amd64"]
    run-on:
    - name: "ubuntu"
      channel: "22.04"
      architectures: ["ppc64le"]
  - build-on: # bases-index 4
    - name: "ubuntu"
      channel: "22.04"
      architectures: ["amd64"]
    run-on:
    - name: "ubuntu"
      channel: "22.04"
      architectures: ["s390x"]

for arch in charmcraft.yaml:
    charm_file = $(charmcraft pack -v --bases-index $(index_from_arch $arch))
    charm_id = $(charmcraft upload $charm_file)
    docker pull --platform=linux/$arch ${upstream_image}
    resource_id = $(charmcraft upload-resource --image resource-name ${upstream_image})
    charmcraft release coredns --revision=${charm_id} --resource resource-name=${resource_id}
done

[Adam Dyess (addyess)]

This PR was introduced to help with this
https://github.com/charmed-kubernetes/charm-coredns/pull/36

Also, the build process now uses a launchpad builder to build each arch's charm and independently publish the correct resources

https://github.com/charmed-kubernetes/jenkins/pull/1376