A go program that clears nodePorts for a service on K8s

remove-nodeport.go

package main

import (
	"context"
	"flag"
	"fmt"
	"log"
	"os"

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

var version = "unknown"

func main() {
	svc := flag.String("svc", "", "Service to update")
	namespace := flag.String("n", "default", "Namespace")
	ver := flag.Bool("version", false, "Print version and quit")
	flag.Parse()

	if *ver {
		fmt.Println(version)
		os.Exit(0)
	}

	if *svc == "" {
		log.Fatalln("No service specified. Use -help")
	}

	removeNodeport(*namespace, *svc)

	os.Exit(0)
}

func getClientset() (*kubernetes.Clientset, error) {
	config, err := rest.InClusterConfig()
	if err != nil {
		kubeconfig :=
			clientcmd.NewDefaultClientConfigLoadingRules().GetDefaultFilename()
		config, err = clientcmd.BuildConfigFromFlags("", kubeconfig)
		if err != nil {
			return nil, err
		}
	}
	return kubernetes.NewForConfig(config)
}

func removeNodeport(namespace, service string) {
	clientset, err := getClientset()
	if err != nil {
		log.Fatalln("Failed to create k8s client; ", err)
	}

	svci := clientset.CoreV1().Services(namespace)
	svc, err := svci.Get(context.TODO(), service, meta.GetOptions{})
	if err != nil {
		log.Fatalf("Failed to get service [%s:%s]; %v\n", namespace, service, err)
	}

	// Check that the service has "type: LoadBalancer"
	if svc.Spec.Type != core.ServiceTypeLoadBalancer {
		log.Fatalln("Service is not type: LoadBalancer")
	}

	if svc.Spec.AllocateLoadBalancerNodePorts == nil {
		fmt.Println("AllocateLoadBalancerNodePorts nil")
	} else {
		fmt.Println("AllocateLoadBalancerNodePorts ", *svc.Spec.AllocateLoadBalancerNodePorts)
	}

	for i,_ := range svc.Spec.Ports {
		svc.Spec.Ports[i].NodePort = 0
	}

	svc, err = svci.Update(context.TODO(), svc, meta.UpdateOptions{})
	if err != nil {
		log.Fatalf("Failed to update service [%s:%s]; %v\n", namespace, service, err)
	}
}