Share Kubernetes Version Through Relation Data

[mateoflorido]

Overview

Share the Kubernetes version through the Juju cluster relation databag.

Rationale

To add the refresh mechanism, we need a way to share the installed k8s bversion of our nodes via relation data. This will help the charm determine if the cluster is ready for an upgrade to a new version. Currently, the charm is blocked if there's a version mismatch within the cluster. In future PRs, we will add mechanisms to deliver these upgrades.

Testing

The databag shows how the version is shared by the charm units, with the leader announcing the Kubernetes version in the application databag.

k8s/1:
  workload-version: 1.31.2
  machine: "1"
  opened-ports:
  - 6443/tcp
  public-address: 10.65.65.158
  charm: local:k8s-0
  leader: true
  life: alive
  relation-info:
  - relation-id: 1
    endpoint: cluster
    related-endpoint: cluster
    application-data:
      k8s/0: joined-juju-055675-0
      k8s/1: joined-juju-055675-1
      version: 1.31.2
    local-unit:
      in-scope: true
      data:
        cluster-name: 201487f2-b9ad-4bc9-9942-48b44459db04
        egress-subnets: 10.65.65.158/32
        ingress-address: 10.65.65.158
        joined: 201487f2-b9ad-4bc9-9942-48b44459db04
        node-name: juju-055675-1
        private-address: 10.65.65.158
        version: 1.31.2
    related-units:
      k8s/0:
        in-scope: true
        data:
          egress-subnets: 10.65.65.15/32
          ingress-address: 10.65.65.15
          joined: 201487f2-b9ad-4bc9-9942-48b44459db04
          node-name: juju-055675-0
          private-address: 10.65.65.15
          version: 1.31.2
  - relation-id: 2
    endpoint: k8s-cluster
    related-endpoint: cluster
    application-data: {}
    related-units:
      k8s-worker/0:
        in-scope: true
        data:
          egress-subnets: 10.65.65.247/32
          ingress-address: 10.65.65.247
          joined: 201487f2-b9ad-4bc9-9942-48b44459db04
          node-name: juju-055675-2
          private-address: 10.65.65.247
          version: 1.31.2
      k8s-worker/1:
        in-scope: true
        data:
          egress-subnets: 10.65.65.62/32
          ingress-address: 10.65.65.62
          joined: 201487f2-b9ad-4bc9-9942-48b44459db04
          node-name: juju-055675-3
          private-address: 10.65.65.62
          version: 1.31.2

[HomayoonAlimohammadi]

Great work! Thanks a lot @mateoflorido! Overall LGTM, just some minor comments and questions. I also leave the approval to someone that actually knows something about k8s-operator :D

[addyess]

Looks pretty straight forward here. I have a few questions naturally

[addyess]

LGTM. Its up to you to use ReconcilerError or leave the asserts. whatever you think is cleaner

[addyess]

LGTM