Define container ports for MeshMetric so that PodMonitor can consume them

[slonka]

Description

PodMonitor requires a port to be defined so that it can be matched and configure prometheus. For sidecars we can work around this by having a container patch:

apiVersion: kuma.io/v1alpha1
kind: ContainerPatch
metadata:
  name: sc-container-patch
  namespace: kuma-system
spec:
  sidecarPatch:
    - op: add
      path: /ports
      value: '[{ "containerPort": 5670, "name":"metrics"}]'

and then the sidecar shows up:

for Builtin Gateway we need to change the controller code:

kuma/pkg/plugins/runtime/k8s/controllers/gateway_instance_controller.go

Line 251 in 4df8c07

container.Name = k8s_util.KumaGatewayContainerName

to generate the ports based on MeshMetric.

A possible other solution would be to have the Container Patch also patch gateways.

I used https://github.com/prometheus-operator/kube-prometheus?tab=readme-ov-file#quickstart to install prometheus operator.

xrel: #5180 (comment)

[Automaat]

Triage: If we really need this support in Gateway it should be done in MeshGatewayInstance podTemplate