fetch pod & node

main.go

package main

import (
	"bytes"
	"flag"
	"fmt"
	"html/template"
	"os"
	"path/filepath"

	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/clientcmd"
)

func main() {
	// creates the in-cluster config
	config, err := rest.InClusterConfig()
	if err != nil {
		// creates the out-of-cluster config
		var kubeconfig *string
		if home := os.Getenv("HOME"); home != "" {
			kubeconfig = flag.String("kubeconfig", filepath.Join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
		} else {
			kubeconfig = flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
		}
		flag.Parse()

		// use the current context in kubeconfig
		config, err = clientcmd.BuildConfigFromFlags("", *kubeconfig)
		if err != nil {
			panic(err.Error())
		}
	}

	// creates the clientset
	clientset, err := kubernetes.NewForConfig(config)
	if err != nil {
		panic(err.Error())
	}

	output, err := outputPods(clientset, "docker-desktop", Tmpl)
	if err != nil {
		panic(err.Error())
	}
	fmt.Printf(output)
}

var Tmpl = `
{{range .Items}}Node Name: {{.Spec.NodeName}}
Pod  Name: {{.ObjectMeta.Name}}
Pod Namespace: {{.ObjectMeta.Namespace}}

{{end}}
`

func outputPods(clientset *kubernetes.Clientset, nodeName string, tmpl string) (string, error) {
	pods, err := clientset.CoreV1().Pods("default").List(metav1.ListOptions{
		FieldSelector: "spec.nodeName=" + nodeName,
	})
	if err != nil {
		return "", err
	}

	t, err := template.New("output").Parse(tmpl)
	if err != nil {
		return "", err
	}

	b := new(bytes.Buffer)
	err = t.Execute(b, pods)
	return b.String(), err
}

result.txt

$ go run main.go

Node Name: docker-desktop
Pod  Name: nginx-pod
Pod Namespace: default

Node Name: docker-desktop
Pod  Name: nginx-pod2
Pod Namespace: default

@bells17, thanks for your sharing of the code.

I have tried this bit of your code.
However i have one more query, just in case i have multiple nodes and list pods under one Node Name instead of getting it repeated everytime.
How shall we do it. I tried this on the modified code.
It didnot worked.

However i have one more query, just in case i have multiple nodes and list pods under one Node Name instead of getting it repeated everytime.

Is this mean below?

• you want to fetch all pods.
• And you want to generate a list of pods divided for each node.

By the way, I saw your profile. It seems you are in Japan.
I speak Japanese fluently more than English.
If you can speak Japanese too, I can describe it better than English.

Hi @bells17,

Thanks for your reply. Yes, i work from Japan location recently got shifted to Japan.
I am sorry, i dont speak japanese.

However, about the my queries.

Yes, i want to fetch all pods.
Yes, want to list all pods for multiple different nodes provided by user.

Thanks for assisting & supporting me.

No worries!

I updated script to below.
Could you review it?

package main

import (
	"bytes"
	"flag"
	"fmt"
	"html/template"
	"os"
	"path/filepath"

	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/clientcmd"
)

func main() {
	// creates the in-cluster config
	config, err := rest.InClusterConfig()
	if err != nil {
		// creates the out-of-cluster config
		var kubeconfig *string
		if home := os.Getenv("HOME"); home != "" {
			kubeconfig = flag.String("kubeconfig", filepath.Join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
		} else {
			kubeconfig = flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
		}
		flag.Parse()

		// use the current context in kubeconfig
		config, err = clientcmd.BuildConfigFromFlags("", *kubeconfig)
		if err != nil {
			panic(err.Error())
		}
	}

	// creates the clientset
	clientset, err := kubernetes.NewForConfig(config)
	if err != nil {
		panic(err.Error())
	}

	// output, err := outputPods(clientset, "docker-desktop", Tmpl)
	output, err := outputAllPodsPerEachNode(clientset, Tmpl2)
	if err != nil {
		panic(err.Error())
	}
	fmt.Printf(output)
}

var Tmpl = `
{{range .Items}}Node Name: {{.Spec.NodeName}}
Pod  Name: {{.ObjectMeta.Name}}
Pod Namespace: {{.ObjectMeta.Namespace}}

{{end}}
`

func outputPods(clientset *kubernetes.Clientset, nodeName string, tmpl string) (string, error) {
	pods, err := clientset.CoreV1().Pods("default").List(metav1.ListOptions{
		FieldSelector: "spec.nodeName=" + nodeName,
	})
	if err != nil {
		return "", err
	}

	t, err := template.New("output").Parse(tmpl)
	if err != nil {
		return "", err
	}

	b := new(bytes.Buffer)
	err = t.Execute(b, pods)
	return b.String(), err
}

var Tmpl2 = `
{{ range $key, $value := . }}
Node Name: {{$key}}

{{ range $k, $pod := $value }}
Pod  Name: {{$pod.ObjectMeta.Name}}
Pod Namespace: {{$pod.ObjectMeta.Namespace}}
{{ end }}

{{end}}
`

func outputAllPodsPerEachNode(clientset *kubernetes.Clientset, tmpl string) (string, error) {
	pods, err := clientset.CoreV1().Pods("default").List(metav1.ListOptions{})
	if err != nil {
		return "", err
	}

	podsPerNode := map[string][]corev1.Pod{}
	for _, pod := range pods.Items {
		name := pod.Spec.NodeName
		if _, ok := podsPerNode[name]; !ok {
			podsPerNode[name] = []corev1.Pod{}
		}
		podsPerNode[name] = append(podsPerNode[name], pod)
	}

	t, err := template.New("output").Parse(tmpl)
	if err != nil {
		return "", err
	}

	b := new(bytes.Buffer)
	err = t.Execute(b, podsPerNode)
	return b.String(), err
}

output

go run main.go                                                                                                                          18:46:26


Node Name: docker-desktop


Pod  Name: nginx-pod
Pod Namespace: default

Pod  Name: nginx-pod2
Pod Namespace: default

@bells17, I'm sorry to trouble you again.

Recently our team had changed the cluster configuration as insecure and while i'm doing InClusterConfig(), it would be make secure communication. So, i am not able retrieve pods.

However, i did try to make the TLSConfig as insecure: true.
I get error as specifying a root certificates file with the insecure flag is not allowed.

I even tried to make the null configuration of certificates in TLSConfig as below.

config.TLSClientConfig.Insecure = true
config.TLSClientConfig.CertFile = nil
config.TLSClientConfig.CertData = nil
config.TLSClientConfig.CAData = nil

Can you please help me out in this step?

@sravankumar777

Recently our team had changed the cluster configuration as insecure

Sorry, I have never tried this setting.
Could you tell me about the details of this setting?