Allow customizing the cmetrics container port (default: 10255)

[sean80221123]

Problem
The current chart hardcodes the cmetrics container port to 10255 in:

https://github.com/Kong/charts/blob/kong-2.49.0/charts/kong/templates/_helpers.tpl#L913
https://github.com/Kong/charts/blob/kong-2.49.0/charts/kong/templates/deployment.yaml#L138

However, port 10255 is deprecated on GKE due to security concerns:

🔗 https://cloud.google.com/kubernetes-engine/docs/how-to/disable-kubelet-readonly-port

Using this port causes issues or conflicts on clusters where the kubelet readonly port is disabled (which is the default in modern GKE versions).

I need to change the port from 10255 to 10250 or another custom port.
Is there a way for me to configure this in the current chart, or would the maintainers consider making this configurable in the official chart?

[pmalek]

👋

We'd be open to make this field configurable but it has to be taken into consideration that the address metrics endpoint is being configured at is controlled via the metrics-bind-address CLI flag.

So that whenever users change the container port, they would need to change that CLI flag (or the corresponding env) as well.

Since we do expose the envs directly in the chart there's no easy way of doing it reliably other than cross checking this possibly new config option in values.yaml with env.metrics_bind_address.

I believe that the simplest solution (that will have its flaws) is to add a new field that will control this port and explicitly documenting it that this has to be set to the same port as in the metrics-bind-address.