gokuberneteskubernetes-go-client

kubernetes client-go: convert labelselector to label string


In the kubernetes client-go API (or another library that uses it), is there a utility function to convert a k8s.io/apimachinery/pkg/apis/meta/v1/LabelSelector to a string to fill the field LabelSelector in k8s.io/apimachinery/pkg/apis/meta/v1/ListOptions?

I digged through the code of client-go but I can't find a function like that.

The LabelSelector.Marshall() nor LabelSelector.String() give me that (unsurprisingly, because that's not their purpose, but I tried it anyway).

Background

I have spec descriptions like k8s.io/api/extensions/v1beta1/Deployment, and want to use it's set of selector labels (i.e. the Selector field) to query it's pods using

options := metav1.ListOptions{
    LabelSelector: <stringified labels>,
}

podList, err := clientset.CoreV1().Pods(<namespace>).List(options)

Solution

  • You can use LabelSelectorAsMap(LabelSelector) function to convert the labelselector into map[string]string map.

    Then, use SelectorFromSet function of package k8s.io/apimachinery/pkg/labels to convert map to selector/strings.

    Pseudo code:

    import (
        "k8s.io/apimachinery/pkg/labels"
        metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
    )
    
    func ListPod(labelSelector metav1.LabelSelector) {
    
        labelMap := metav1.LabelSelectorAsMap(labelSelector)
    
        options := metav1.ListOptions{
            LabelSelector: labels.SelectorFromSet(labelMap).String(),
        }
    
        podList, err := clientset.CoreV1().Pods("<namespace>").List(options)
    
    }