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1、介绍
client-go 是用来和 k8s 集群交互的go语言客户端库#xff0c;地址为#xff1a;https://github.com/kubernetes/client-go client-go 的版本有两种标识方式#xff1a;
v0.x.y (For each v1.x.y Kubernetes…想学习K8S源码可以加 mkjnnm
1、介绍
client-go 是用来和 k8s 集群交互的go语言客户端库地址为https://github.com/kubernetes/client-go client-go 的版本有两种标识方式
v0.x.y (For each v1.x.y Kubernetes release, the major version (first digit) would remain 0)kubernetes-1.x.y
ps: k8s 发布v1.30.0 版本时client-go 会同步发布两个版本 v0.30.0 (推荐使用)和 kubernetes-1.30.0
如果你想使用最新版本的客户端库你可以运行如下命令
go get k8s.io/client-golatest
如果你想使用特定版本推荐使用如下命令
go get k8s.io/client-gov0.20.4
2、目录结构
client-go 包含以下几部分
The kubernetes package contains the clientset to access Kubernetes API.The discovery package is used to discover APIs supported by a Kubernetes API server.The dynamic package contains a dynamic client that can perform generic operations on arbitrary Kubernetes API objects.The plugin/pkg/client/auth packages contain optional authentication plugins for obtaining credentials from external sources.The transport package is used to set up auth and start a connection.The tools/cache package is useful for writing controllers.
3、使用
1.初始化
集群内初始化集群外初始化
如果你的应用跑在集群中的pod上推荐使用集群内初始化否则使用集群外初始化。
// 集群外初始化 client
// 需要集群的 kubeconfig 配置文件
func main() {var kubeconfig *stringif 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 kubeconfigconfig, err : clientcmd.BuildConfigFromFlags(, *kubeconfig)if err ! nil {panic(err.Error())}// create the clientsetclientset, err : kubernetes.NewForConfig(config)if err ! nil {panic(err.Error())}
}2. 列出集群内pod资源
pods, err : clientset.CoreV1().Pods().List(context.TODO(), metav1.ListOptions{})if err ! nil {panic(err.Error())}fmt.Printf(There are %d pods in the cluster\n, len(pods.Items))
上述代码在client- go仓库下examples目录
你可以运行该代码
cd out-of-cluster-client-configuration
go build -o app .
./app -kubeconfig/path/to/xxx3. deployment资源CRUD - typed (clientset)方式
以下代码创建一个有2个副本数的deployment然后更新副本数为1升级nginx镜像版本最后删除 deploymentsClient : clientset.AppsV1().Deployments(apiv1.NamespaceDefault)deployment : appsv1.Deployment{ObjectMeta: metav1.ObjectMeta{Name: demo-deployment,},Spec: appsv1.DeploymentSpec{Replicas: int32Ptr(2),Selector: metav1.LabelSelector{MatchLabels: map[string]string{app: demo,},},Template: apiv1.PodTemplateSpec{ObjectMeta: metav1.ObjectMeta{Labels: map[string]string{app: demo,},},Spec: apiv1.PodSpec{Containers: []apiv1.Container{{Name: web,Image: nginx:1.12,Ports: []apiv1.ContainerPort{{Name: http,Protocol: apiv1.ProtocolTCP,ContainerPort: 80,},},},},},},},}// Create Deploymentfmt.Println(Creating deployment...)result, err : deploymentsClient.Create(context.TODO(), deployment, metav1.CreateOptions{})if err ! nil {panic(err)}fmt.Printf(Created deployment %q.\n, result.GetObjectMeta().GetName())// Update Deploymentprompt()fmt.Println(Updating deployment...)// You have two options to Update() this Deployment://// 1. Modify the deployment variable and call: Update(deployment).// This works like the kubectl replace command and it overwrites/loses changes// made by other clients between you Create() and Update() the object.// 2. Modify the result returned by Get() and retry Update(result) until// you no longer get a conflict error. This way, you can preserve changes made// by other clients between Create() and Update(). This is implemented below// using the retry utility package included with client-go. (RECOMMENDED)//// More Info:// https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#concurrency-control-and-consistencyretryErr : retry.RetryOnConflict(retry.DefaultRetry, func() error {// Retrieve the latest version of Deployment before attempting update// RetryOnConflict uses exponential backoff to avoid exhausting the apiserverresult, getErr : deploymentsClient.Get(context.TODO(), demo-deployment, metav1.GetOptions{})if getErr ! nil {panic(fmt.Errorf(Failed to get latest version of Deployment: %v, getErr))}result.Spec.Replicas int32Ptr(1) // reduce replica countresult.Spec.Template.Spec.Containers[0].Image nginx:1.13 // change nginx version_, updateErr : deploymentsClient.Update(context.TODO(), result, metav1.UpdateOptions{})return updateErr})if retryErr ! nil {panic(fmt.Errorf(Update failed: %v, retryErr))}fmt.Println(Updated deployment...)// List Deploymentsprompt()fmt.Printf(Listing deployments in namespace %q:\n, apiv1.NamespaceDefault)list, err : deploymentsClient.List(context.TODO(), metav1.ListOptions{})if err ! nil {panic(err)}for _, d : range list.Items {fmt.Printf( * %s (%d replicas)\n, d.Name, *d.Spec.Replicas)}// Delete Deploymentprompt()fmt.Println(Deleting deployment...)deletePolicy : metav1.DeletePropagationForegroundif err : deploymentsClient.Delete(context.TODO(), demo-deployment, metav1.DeleteOptions{PropagationPolicy: deletePolicy,}); err ! nil {panic(err)}fmt.Println(Deleted deployment.)
}func prompt() {fmt.Printf(- Press Return key to continue.)scanner : bufio.NewScanner(os.Stdin)for scanner.Scan() {break}if err : scanner.Err(); err ! nil {panic(err)}fmt.Println()
}func int32Ptr(i int32) *int32 { return i }
4.deployment资源CRUD - dynamic方式
使用typed方式创建资源虽然方便但是需要事先使用client-gen生成且会与某个特定版本耦合不够通用所以我们可以使用 unstructured.Unstructured 来表示集群中任意对象。 client, err : dynamic.NewForConfig(config)if err ! nil {panic(err)}deploymentRes : schema.GroupVersionResource{Group: apps, Version: v1, Resource: deployments}deployment : unstructured.Unstructured{Object: map[string]interface{}{apiVersion: apps/v1,kind: Deployment,metadata: map[string]interface{}{name: demo-deployment,},spec: map[string]interface{}{replicas: 2,selector: map[string]interface{}{matchLabels: map[string]interface{}{app: demo,},},template: map[string]interface{}{metadata: map[string]interface{}{labels: map[string]interface{}{app: demo,},},spec: map[string]interface{}{containers: []map[string]interface{}{{name: web,image: nginx:1.12,ports: []map[string]interface{}{{name: http,protocol: TCP,containerPort: 80,},},},},},},},},}// Create Deploymentfmt.Println(Creating deployment...)result, err : client.Resource(deploymentRes).Namespace(apiv1.NamespaceDefault).Create(context.TODO(), deployment, metav1.CreateOptions{})if err ! nil {panic(err)}fmt.Printf(Created deployment %q.\n, result.GetName())
5. discoveryClient
3-4小节我们学习了 typed client 和 dynamic client 这两个client使用来操作集群中资源比如创建 deployment删除pod。discovery client 不同他是用来发现服务端支持的组、版本、资源类型
// Package discovery provides ways to discover server-supported
// API groups, versions and resources.我们可以查询服务端支持的组与版本、某个组的资源列表
func main() {var kubeconfig *stringif 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 kubeconfigconfig, err : clientcmd.BuildConfigFromFlags(, *kubeconfig)if err ! nil {panic(err.Error())}// *查询服务端支持的组列表discoveryClient : discovery.NewDiscoveryClientForConfigOrDie(config)gs, err : discoveryClient.ServerGroups()if err ! nil {panic(err.Error())}spew.Dump(gs.Groups)// *查询core/v1 组下的资源列表rs, err : discoveryClient.ServerResourcesForGroupVersion(v1)if err ! nil {panic(err.Error())}for _, r : range rs.APIResources {fmt.Println(r.Name)}}// 输出支持的组列表
/*
(v1.APIGroup) APIGroup{Name:apps,Versions:[]GroupVersionForDiscovery{GroupVersionForDiscovery{GroupVersion:apps/v1,Version:v1,},},PreferredVersion:GroupVersionForDiscovery{GroupVersion:apps/v1,Version:v1,},ServerAddressByClientCIDRs:[]ServerAddressByClientCIDR{},},
(v1.APIGroup) APIGroup{Name:events.k8s.io,Versions:[]GroupVersionForDiscovery{GroupVersionForDiscovery{GroupVersion:events.k8s.io/v1,Version:v1,},},PreferredVersion:GroupVersionForDiscovery{GroupVersion:events.k8s.io/v1,Version:v1,},ServerAddressByClientCIDRs:[]ServerAddressByClientCIDR{},},
...
*/// 输出core/v1组下的资源列表
/*
pods/status
podtemplates
replicationcontrollers
replicationcontrollers/scale
replicationcontrollers/status
resourcequotas
resourcequotas/status
secrets
serviceaccounts
...
*/
6. restClient
上面三种客户端都是基于 restClient 封装的restClient 是 client-go 最基础的客户端对http request 进行了封装更加灵活一般我们用不到。
// 根据配置信息构建restClient实例restClient, err : rest.RESTClientFor(config)if err!nil {panic(err.Error())}// 保存pod结果的数据结构实例result : corev1.PodList{}// 指定namespacenamespace : kube-system// 设置请求参数然后发起请求// GET请求err restClient.Get().// 指定namespace参考path : /api/v1/namespaces/{namespace}/podsNamespace(namespace).// 查找多个pod参考path : /api/v1/namespaces/{namespace}/podsResource(pods).// 指定大小限制和序列化工具VersionedParams(metav1.ListOptions{Limit:100}, scheme.ParameterCodec).// 请求Do(context.TODO()).// 结果存入resultInto(result)
4、局限
使用 client 操作集群中资源会导致频繁的轮询k8s client-go 包提供了更加高效的方式informer 。
informer 提供了一种机制来监视 Kubernetes 集群内资源的变化并做出反应。它使开发人员能够接收有关各种 Kubernetes 对象例如 Pod、服务、部署等状态的实时更新。
Informer 将集群中的资源缓存在本地来减少频繁的API调用提高性能并优化资源利用率。
