如何与client-go动态切换kubernetes上下文?

Question

我正在构建一个CLI应用程序，该应用程序允许我在shell中对kubecconfig中匹配给定正则表达式的任何kube集群运行任意命令。我想使用官方的client-go包来完成这个任务，但是由于某些原因，切换kube上下文不太直观。因此，我从修改repo中的示例集群外程序开始，我正在努力将上下文切换到我指定的上下文。下面是我开始使用的代码，它获取kubecconfig中加载的集群中的pod数量:

package main
import (
"context"
"flag"
"fmt"
"path/filepath"
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"
)
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()
// use the current context in kubeconfig
config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
if err != nil {
panic(err.Error())
}
// create the clientset
clientset, err := kubernetes.NewForConfig(config)
if err != nil {
panic(err.Error())
}
pods, err := clientset.CoreV1().Pods("").List(context.TODO(), metav1.ListOptions{})
if err != nil {
panic(err.Error())
}
fmt.Printf("There are %d pods in the test clustern", len(pods.Items))
}

不幸的是，我不知道如何用kubecconfig中定义的名称加载特定的集群。我很想有一种SwitchContext("cluster-name")函数，但配置，ClientConfigs, RawConfigs和restclient的数量。配置把我搞糊涂了。任何帮助将不胜感激!

系统:Ubuntu 22.04, Intel, kube服务器版本1.23.8-gke。1900，客户端版本1.25.3

Answer 1

您可以通过clientcmd包中的NewNonInteractiveDeferredLoadingClientConfig方法覆盖当前上下文。

package main
import (
"context"
"flag"
"fmt"
"k8s.io/client-go/rest"
"path/filepath"
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"
)
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()
// use the current context in kubeconfig
config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
if err != nil {
panic(err.Error())
}
// using `contextName` context in kubeConfig
contextName := "gce"
config, err = buildConfigWithContextFromFlags(contextName, *kubeconfig)
if err != nil {
panic(err)
}
// create the clientset
clientset, err := kubernetes.NewForConfig(config)
if err != nil {
panic(err.Error())
}
pods, err := clientset.CoreV1().Pods("").List(context.TODO(), metav1.ListOptions{})
if err != nil {
panic(err.Error())
}
fmt.Printf("There are %d pods in the test clustern", len(pods.Items))
}
func buildConfigWithContextFromFlags(context string, kubeconfigPath string) (*rest.Config, error) {
return clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
&clientcmd.ClientConfigLoadingRules{ExplicitPath: kubeconfigPath},
&clientcmd.ConfigOverrides{
CurrentContext: context,
}).ClientConfig()
}