Allow the charm to set extra-labels it wishes to manage not set by user

[addyess]

Overview

User config via juju can add node labels but failed to be able to intentionally remove labels
These changes allow the charm to specify labels ending with "-" to remove those labels

Details

• creates an option to raise an exceptions when invalid labels are detected
• allows for labels whose values endswith "-" to be removed (the label key will be removed entirely)

EG)
a node has labels not applied by the charm like this:

Name:               juju-ecc100-1
Roles:              <none>
Labels:             beta.kubernetes.io/arch=amd64
                    beta.kubernetes.io/os=linux
                    hostname=juju-ecc100-1
                    unwanted-label-is-here=any-value
                    juju-application=k8s
                    juju-charm=k8s
                    juju.io/cloud=vsphere
                    kubernetes.io/arch=amd64
                    kubernetes.io/hostname=juju-ecc100-1
                    kubernetes.io/os=linux

by applying this config, the charm should be able to intentionally remove this label

juju config label-maker-charm label-config="unwanted-label-is-here=-"

[louiseschmidtgen]

Thanks Adam!
Have we thought about any alternative implementations, maybe a charm action to remove the label?
I feel like the UX could be a little bit better.
Excuse my ideas if this was already discussed :)

[addyess]

I'm all ears @louiseschmidtgen. I do like that it's one config item to rule them all and it works very similarly to the way you apply labels with kubectl.

if you want to remove a node label using kubectl one simply:

kubectl label node <nodename> <label>-

and to add it back

kubectl label node <nodename> <label>=<value>

[louiseschmidtgen]

I see your point.
A charm action would also not translate so well into the terraform world. With the config you can change the terraform plan.

[louiseschmidtgen]

LGTM