Get Node and Pod Resource Usages using K8s metricsClient

main.go

package main

// https://cloud.tencent.com/developer/ask/sof/115441746

import (
	"bytes"
	"context"
	"flag"
	"fmt"
	"log"
	"path/filepath"
	"time"

	v1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/tools/clientcmd"
	"k8s.io/client-go/util/homedir"

	"k8s.io/kubectl/pkg/metricsutil"
	metricsapi "k8s.io/metrics/pkg/apis/metrics"
	metricsv1beta1api "k8s.io/metrics/pkg/apis/metrics/v1beta1"
	metrics "k8s.io/metrics/pkg/client/clientset/versioned"
)

var (
	namespaceName = "infra"
	podName       = "thanos-xxx-7dfbffbd4b-nbvvd"
	nodeName      = "cn-hongkong.i-j6cjxxxx"
)

func main() {
	var kubeconfig *string
	if home := homedir.HomeDir(); 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()

	// Init Kubernetes REST Client
	config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
	if err != nil {
		panic(err.Error())
	}

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

	metricsClient, err := metrics.NewForConfig(config)
	if err != nil {
		panic(err)
	}

	for {
		podOutput, err := RunTopPod(metricsClient, podName, namespaceName)
		if err != nil {
			log.Println(err)
		}
		nodeOutput, err := RunTopNode(clientset, metricsClient, nodeName)
		if err != nil {
			log.Println(err)
		}

		fmt.Println(podOutput, nodeOutput)
		time.Sleep(3 * time.Second)
	}
}

func RunTopPod(metricsClient metrics.Interface, podName string, namespaceName string) (string, error) {
	var buf bytes.Buffer
	printer := metricsutil.NewTopCmdPrinter(&buf)

	m, err := metricsClient.MetricsV1beta1().PodMetricses(namespaceName).Get(context.TODO(), podName, metav1.GetOptions{})
	if err != nil {
		return "", err
	}

	versionedMetrics := &metricsv1beta1api.PodMetricsList{}
	versionedMetrics.Items = []metricsv1beta1api.PodMetrics{*m}

	metrics := &metricsapi.PodMetricsList{}
	err = metricsv1beta1api.Convert_v1beta1_PodMetricsList_To_metrics_PodMetricsList(versionedMetrics, metrics, nil)
	if err != nil {
		return "", err
	}
	printer.PrintPodMetrics(metrics.Items, false, false, false, "CPU", false)
	fmt.Fprintf(&buf, "Collected: %s ago, at %s\n", m.ObjectMeta.CreationTimestamp.Time.Sub(m.Timestamp.Time), m.Timestamp.Time)
	return buf.String(), nil
}

func RunTopNode(clientset kubernetes.Interface, metricsClient metrics.Interface, nodeName string) (string, error) {
	var buf bytes.Buffer
	printer := metricsutil.NewTopCmdPrinter(&buf)

	node, err := clientset.CoreV1().Nodes().Get(context.TODO(), nodeName, metav1.GetOptions{})
	if err != nil {
		return "", err
	}
	availableResources := make(map[string]v1.ResourceList)
	availableResources[node.Name] = node.Status.Allocatable

	m, err := metricsClient.MetricsV1beta1().NodeMetricses().Get(context.TODO(), nodeName, metav1.GetOptions{})
	if err != nil {
		return "", err
	}

	versionedMetrics := &metricsv1beta1api.NodeMetricsList{}
	versionedMetrics.Items = []metricsv1beta1api.NodeMetrics{*m}

	metrics := &metricsapi.NodeMetricsList{}
	err = metricsv1beta1api.Convert_v1beta1_NodeMetricsList_To_metrics_NodeMetricsList(versionedMetrics, metrics, nil)
	if err != nil {
		return "", err
	}
	printer.PrintNodeMetrics(metrics.Items, availableResources, false, "CPU")
	fmt.Fprintf(&buf, "Collected: %s ago, At %s\n", m.ObjectMeta.CreationTimestamp.Time.Sub(m.Timestamp.Time), m.Timestamp.Time)
	return buf.String(), nil
}

K8s Metrics API (Also used by HPA)

Source code from kubectl top node and kubectl top pod, see RunTopPod

Simple example: Get current resource usage of a pod in Kubernetes with Go client