Retrieve kubernetes nodes that do not contain label using apimachinery/client-go

Question

I want to fetch the list (if any) of kubernetes nodes that do not contain a label.

I have managed to do the opposite using client-go

    labelSelector := metav1.LabelSelector{
        MatchLabels: map[string]string{
            "somelabel": "somevalue",
        },
    }
    labelMap, err := metav1.LabelSelectorAsMap(&labelSelector)
    if err != nil {
        return false, errors.Wrap(err, "error converting node label selector to map")
    }
    nodeListOptions := metav1.ListOptions{
        LabelSelector: labels.SelectorFromSet(labelMap).String(),
    }
    nodes, err := clientset.CoreV1().Nodes().List(nodeListOptions)
    if err != nil {
        return false, errors.Wrap(err, "error getting node list")
    }

What I want to achieve is to convert the following kubectl invocation

kubectl get ns --selector='!label_name'

into client-go code.

Is this feasible?

Answer 1

I think one has to use the Requirement type of the apimachinery's labels package and create Selector constructs based on this.

nodeReq, err := labels.NewRequirement("label_name", selection.DoesNotExist, []string{})
    if err != nil {
        return false, errors.Wrap(err, "error creating selector requirement")
    }
    selector := labels.NewSelector()
    selector = selector.Add(*nodeReq)
    if err != nil {
        return false, errors.Wrap(err, "error converting node label selector to map")
    }
    nodeListOptions := metav1.ListOptions{
        LabelSelector: selector.String(),
    }
    nodes, err := clientset.CoreV1().Nodes().List(nodeListOptions)