Validate dask cluster name to contain only allowed characters

[dbalabka]

Having a "." in the cluster name leads to a hung cluster in the "Created" state:

❯ kubectl get daskclusters
NAME                                     WORKERS   STATUS    AGE
dmitry.balabka-cluster              1         Created   17h

While it is described in official k8s docs about Object Names, it would be great to have a validation in the dask library that raises at least a warning.
https://kubernetes.io/docs/concepts/overview/working-with-objects/names/

Code example:

from dask_kubernetes.operator import KubeCluster
 
# Create a Dask cluster by calling Kubernetes API via kubectl command based on provided specificatoin
cluster = KubeCluster(
    name="dmitry.balakba-cluster",
    namespace="dask-operator",
)
 
client = cluster.get_client()
 
# Renders cluster configuration in the cell output
client

[dbalabka]

It is possible that the Linux user name contains .. Basically, it might happen even w/o specifying a custom name because generated cluster name does not sanitize the name as well:

dask-kubernetes/dask_kubernetes/operator/kubecluster/kubecluster.py

Lines 254 to 256 in 03aa9db

	name = name.format(
	user=getpass.getuser(), uuid=str(uuid.uuid4())[:10], **os.environ
	)

Not sure should the validation happen in dask-kubernetes or kr8s/kopf

[jacobtomlinson]

It's interesting that the resource gets created, but I'm guessing if you look at the controller logs there are errors there when it tried to create the child components. Ideally the Kubernetes API would reject this name and give us an error that we can propagate back to the user. Maybe this is something we can configure in the CRD?

Otherwise yeah we will need to add some client-side checking. Although maybe we should do that in kr8s so that more folks can benefit from this.