CODEWITHSUNDEEP
gokuberneteskubernetes-apiserverclient-go
Inian
Inian

Reputation: 85895

Using client-go API to list pods managed by a deployment controller not working

I'm using the native client-go API in Go to get the list of Pods managed by a Deployment type controller under a given namespace ("default"), but the returned list is not containing the list of Pods

labelSelector := labels.Set(obj.Spec.Selector.MatchLabels)

where obj is of type *appsv1.Deployment from https://pkg.go.dev/k8s.io/api/apps/v1?tab=doc#Deployment

podsList, err := getPodList(string(labelSelector.AsSelector().String()), kubeClient, res.Namespace)

with the function definition being

func getPodList( labelSelector string, client kubernetes.Interface, ns string ) (*corev1.PodList, error) {     
     options := metav1.ListOptions{
         LabelSelector: labelSelector,
     }

     podList, err := client.CoreV1().Pods(ns).List(options)
     return podList, err
 }

The type returned - https://pkg.go.dev/k8s.io/api/core/v1?tab=doc#PodList should contain the Items []Pod slice which is not available in my returned information.

Using the following packages in the Go code

appsv1 "k8s.io/api/apps/v1"    
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/labels"
"k8s.io/client-go/kubernetes"

Upvotes: 0

Views: 6345

Answers (1)

Inian
Inian

Reputation: 85895

It seems I got it working all along, but just handled the return type of CoreV1().Pods(ns).List(options) incorrectly. It was returning a pointer to a slice of PodList - https://pkg.go.dev/k8s.io/api/core/v1?tab=doc#PodList

Here is the minimal code, which I made work which could be useful for posterity

package main

import (
        "fmt"
        metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
        "k8s.io/client-go/kubernetes"
        "k8s.io/client-go/tools/clientcmd"
        "os"
        "path/filepath"
)

func main() {

        kubeconfig := filepath.Join(
                os.Getenv("HOME"), ".kube", "config",
        )

        // Initialize kubernetes-client
        cfg, err := clientcmd.BuildConfigFromFlags("", kubeconfig)
        if err != nil {
                fmt.Printf("Error building kubeconfig: %v\n", err)
                os.Exit(1)
        }

        // create new client with the given config
        // https://pkg.go.dev/k8s.io/client-go/kubernetes?tab=doc#NewForConfig
        kubeClient, err := kubernetes.NewForConfig(cfg)
        if err != nil {
                fmt.Printf("Error building kubernetes clientset: %v\n", err)
                os.Exit(2)
        }

        // use the app's label selector name. Remember this should match with 
        // the deployment selector's matchLabels. Replace <APPNAME> with the 
        // name of your choice
        options := metav1.ListOptions{
                LabelSelector: "app=<APPNAME>",
        }

        // get the pod list
        // https://pkg.go.dev/k8s.io/[email protected]+incompatible/kubernetes/typed/core/v1?tab=doc#PodInterface
        podList, _ := kubeClient.CoreV1().Pods("default").List(options)

        // List() returns a pointer to slice, derefernce it, before iterating
        for _, podInfo := range (*podList).Items {
                fmt.Printf("pods-name=%v\n", podInfo.Name)
                fmt.Printf("pods-status=%v\n", podInfo.Status.Phase)
                fmt.Printf("pods-condition=%v\n", podInfo.Status.Conditions)
        }
}

Upvotes: 3

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