云原生实战：Go操作Kubernetes API

云原生实战：Go操作KubernetesAPI一、核心概念client-go：K8s官方Go客户端，封装了与apiserver通信的细节。Clientset：对所有内置资源（Pod/Deployment/Service…）的强类型客户端。Informer：基于List-Watch的本地缓存，减少直接请求apiserver，事件驱动。Operator：自定义控制器+CRD，把业务逻辑封装成K8s资源。二、环境准备1.版本匹配（关键）client-go版本要和集群版本主版本一致，例如：K8s1.29→client-gov0.29.x2.初始化项目bash运行mkdirk8s-go-demo&&cdk8s-go-demogomodinitk8s-go-demo#安装依赖（示例用1.29）gogetk8s.io/client-go@v0.29.3gogetk8s.io/apimachinery@v0.29.3三、客户端初始化（两种方式）方式A：本地开发（用～/.kube/config）go运行packagemainimport( "context" "log" "path/filepath" "k8s.io/client-go/kubernetes" "k8s.io/client-go/rest" "k8s.io/client-go/tools/clientcmd" "k8s.io/client-go/util/homedir")funcmain(){ //1.加载kubeconfig varconfig*rest.Config varerrerror kubeconfig:=filepath.Join(homedir.HomeDir(),".kube","config") config,err=clientcmd.BuildConfigFromFlags("",kubeconfig) iferr!=nil{ log.Fatalf("Failedtobuildconfig:%v",err) } //2.创建Clientset clientset,err:=kubernetes.NewForConfig(config) iferr!=nil{ log.Fatalf("Failedtocreateclientset:%v",err) } log.Println("Connectedtoclustersuccessfully") _=clientset//后续用}方式B：集群内Pod中运行（InCluster）go运行config,err:=rest.InClusterConfig()iferr!=nil{ log.Fatalf("InClusterConfigfailed:%v",err)}clientset,err:=kubernetes.NewForConfig(config)四、基础CRUD实战1.列出所有Podgo运行import( corev1"k8s.io/api/core/v1" metav1"k8s.io/apimachinery/pkg/apis/meta/v1")pods,err:=clientset.CoreV1().Pods("").List(context.TODO(),metav1.ListOptions{})iferr!=nil{ log.Fatalf("Listpodsfailed:%v",err)}for_,p:=rangepods.Items{ log.Printf("Pod:%s/%sPhase:%s",p.Namespace,p.Name,p.Status.Phase)}2.创建NginxDeploymentgo运行appsv1"k8s.io/api/apps/v1"dep:=&appsv1.Deployment{ ObjectMeta:metav1.ObjectMeta{ Name:"nginx-demo", Namespace:"default", }, Spec:appsv1.DeploymentSpec{ Replicas:func()*int32{i:=int32(2);return&i}(), Selector:&metav1.LabelSelector{ MatchLabels:map[string]string{"app":"nginx"}, }, Template:corev1.PodTemplateSpec{ ObjectMeta:metav1.ObjectMeta{ Labels:map[string]string{"app":"nginx"}, }, Spec:corev1.PodSpec{ Containers:[]corev1.Container{ { Name:"nginx", Image:"nginx:1.25-alpine", Ports:[]corev1.ContainerPort{ {ContainerPort:80}, }, }, }, }, }, },}_,err:=clientset.AppsV1().Deployments("default").Create(context.TODO(),dep,metav1.CreateOptions{})iferr!=nil{ log.Fatalf("Createdeploymentfailed:%v",err)}log.Println("Deploymentnginx-democreated")3.更新Deployment（扩容到3副本）go运行//先Get再Update（乐观锁）dep,err:=clientset.AppsV1().Deployments("default").Get(context.TODO(),"nginx-demo",metav1.GetOptions{})iferr!=nil{ log.Fatal(err)}*dep.Spec.Replicas=3_,err=clientset.AppsV1().Deployments("default").Update(context.TODO(),dep,metav1.UpdateOptions{})iferr!=nil{ log.Fatal(err)}log.Println("Deploymentscaledto3replicas")4.删除Deploymentgo运行err=clientset.AppsV1().Deployments("default").Delete(context.TODO(),"nginx-demo",metav1.DeleteOptions{})iferr!=nil{ log.Fatal(err)}log.Println("Deploymentdeleted")五、高级：Watch与Informer1.简单Watch（实时监听Pod事件）go运行watchOpts:=metav1.ListOptions{Watch:true}w,err:=clientset.CoreV1().Pods("default").Watch(context.TODO(),watchOpts)iferr!=nil{ log.Fatal(err)}deferw.Stop()forevent:=rangew.ResultChan(){ log.Printf("Event:%vPod:%s",event.Type,event.Object.(*corev1.Pod).Name)}2.Informer实战（生产推荐）Informer会：第一次List全量然后Watch增量本地缓存，事件回调go运行import( "time" "k8s.io/client-go/informers" "k8s.io/client-go/tools/cache")//创建Informer工厂（10分钟同步一次）factory:=informers.NewSharedInformerFactory(clientset,10*time.Minute)podInformer:=factory.Core().V1().Pods()//注册事件回调podInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{ AddFunc:func(objinterface{}){ pod:=obj.(*corev1.Pod) log.Printf("PodAdded:%s/%s",pod.Namespace,pod.Name) }, UpdateFunc:func(oldObj,newObjinterface{}){ oldPod:=oldObj.(*corev1.Pod) newPod:=newObj.(*corev1.Pod) ifoldPod.ResourceVersion==newPod.ResourceVersion{ return } log.Printf("PodUpdated:%s/%s",newPod.Namespace,newPod.Name) }, DeleteFunc:func(objinterface{}){ pod:=obj.(*corev1.Pod) log.Printf("PodDeleted:%s/%s",pod.Namespace,pod.Name) },})//启动Informer（阻塞）factory.Start(context.TODO().Done())//等待缓存同步完成if!cache.WaitForCacheSync(context.TODO().Done(),podInformer.Informer().HasSynced){ log.Fatal("Failedtosynccaches")}log.Println("Informerrunning...")<-context.TODO().Done()六、进阶：简单Operator骨架（CRD+控制器）1.定义CRD结构体（示例：App）go运行import( metav1"k8s.io/apimachinery/pkg/apis/meta/v1" "k8s.io/apimachinery/pkg/runtime" "k8s.io/apimachinery/pkg/runtime/schema")//SchemeGroupVersion是CRD的GVKvarSchemeGroupVersion=schema.GroupVersion{ Group:"", Version:"v1",}typeAppstruct{ metav1.TypeMeta`json:",inline"` metav1.ObjectMeta`json:"metadata,omitempty"` SpecAppSpec`json:"spec"` StatusAppStatus`json:"status,omitempty"`}typeAppSpecstruct{ Replicas*int32`json:"replicas"` Imagestring`json:"image"`}typeAppStatusstruct{ ReadyReplicasint32`json:"readyReplicas"`}typeAppListstruct{ metav1.TypeMeta`json:",inline"` metav1.ListMeta`json:"metadata,omitempty"` Items[]App`json:"items"`}//注册到Schemefuncinit(){ SchemeBuilder.Register(&App{},&AppList{})}var( SchemeBuilder=runtime.NewSchemeBuilder(addKnownTypes) AddToScheme=SchemeBuilder.AddToScheme)funcaddKnownTypes(scheme*runtime.Scheme)error{ scheme.AddKnownTypes(SchemeGroupVersion, &App{}, &AppList{}, ) metav1.AddToGroupVersion(scheme,SchemeGroupVersion) returnnil}2.控制器Reconcile逻辑（简化版）go运行//Reconcile核心逻辑：对比期望状态与当前状态func(r*AppReconciler)Reconcile(ctxcontext.Context,reqctrl.Request)(ctrl.Result,error){ //1.获取App实例 app:=&appv1.App{} iferr:=r.Get(ctx,req.NamespacedName,app);err!=nil{ iferrors.IsNotFound(err){ //App被删除，清理资源 returnctrl.Result{},nil } returnctrl.Result{},err } //2.检查是否已有Deployment dep:=&appsv1.Deployment{} err:=r.Get(ctx,types.NamespacedName{Name:app.Name,Namespace:app.Namespace},dep) iferr!=nil{ iferrors.IsNotFound(err){ //3.没有则创建Deployment dep=r.newDeploymentForApp(app) iferr:=r.Create(ctx,dep);err!=nil{ returnctrl.Result{},err } log.Println("Deploymentcreate