Client-go操作Deployment

在工作中需要对kubernetes进行自定义资源的开发，操作K8s的资源肯定是必不可少的。K8s原生语言是用Go编写的，所以在CRD中使用client-go来操作资源。本次介绍一下使用client-go来操作Deployment。

1. 创建main函数

func main() {homePath := homedir.HomeDir()if homePath == "" {panic("homePath is empty")}kubeConfig := filepath.Join(homePath, ".kube", "config")config, err := clientcmd.BuildConfigFromFlags("", kubeConfig)if err != nil {panic(err)}// use the config to create a clientclientSet, err := kubernetes.NewForConfig(config)if err != nil {panic(err)}dpClient := clientSet.AppsV1().Deployments(corev1.NamespaceDefault)log.Println("start handle deployments...")// 创建一个deploymenterr = createDeployment(dpClient)if err != nil {panic(err)}log.Println("create deployment success")<-time.Tick(time.Minute * 1)// 修改一个deploymenterr = updateDeployment(dpClient)if err != nil {panic(err)}log.Println("update deployment success")<-time.Tick(time.Minute * 1)// 删除一个deploymenterr = deleteDeployment(dpClient)if err != nil {panic(err)}log.Println("delete deployment success")
}

这里创建了一个main函数，首先获取到kubernetes配置文件并创建出clientSet，再使用clientSet创建出来操作deployment的客户端。

随后定义了三个函数，分别是：

创建Deployment：createDeployment

修改Deployment：updateDeployment

删除Deployment：deleteDeployment

2. 创建Deployment

接下来编写createDeployment函数，此函数将在kubernetes集群中生成Deployment

func createDeployment(dpClient v1.DeploymentInterface) error {replicas := int32(3)newDp := appv1.Deployment{ObjectMeta: metav1.ObjectMeta{Name: "nginx-deployment",},Spec: appv1.DeploymentSpec{Replicas: &replicas,Selector: &metav1.LabelSelector{MatchLabels: map[string]string{"app": "nginx",},},Template: corev1.PodTemplateSpec{ObjectMeta: metav1.ObjectMeta{// 这里的label要和上面的selector的label一致Labels: map[string]string{"app": "nginx",},},Spec: corev1.PodSpec{Containers: []corev1.Container{{Name:  "nginx",Image: "nginx:1.16",Ports: []corev1.ContainerPort{{ContainerPort: 80,Name:          "http",Protocol:      corev1.ProtocolTCP,},},},},},},},}_, err := dpClient.Create(context.TODO(), &newDp, metav1.CreateOptions{})if err != nil {return err}return nil
}

定义副本数量3个，编写Deployment配置，定义ObjectMeta、Spec、Template各种参数

这里提一句Selector中"app": “nginx” 和 Template中是一样的，因为Deployment是通过标签关连到所属副本中pod的

3. 修改Deployment

在接下来的操作中，将nginx的版本变更一下，来达到修改的目的

func updateDeployment(dpClient v1.DeploymentInterface) error {dp, err := dpClient.Get(context.TODO(), "nginx-deployment", metav1.GetOptions{})if err != nil {return err}dp.Spec.Template.Spec.Containers[0].Image = "nginx:1.17"updateDp, err := dpClient.Update(context.TODO(), dp, metav1.UpdateOptions{})if err != nil {return err}return retry.RetryOnConflict(retry.DefaultRetry, func() error {_, err := dpClient.Update(context.TODO(), updateDp, metav1.UpdateOptions{})return err})
}

此处的操作为现将之前创建好的dp获取到，然后进行nginx镜像版本的变更，随后进行使用客户端进行更新操作

此外还通过retry.RetryOnConflict来解决更新冲突

4. 删除Deployment

func deleteDeployment(dpClient v1.DeploymentInterface) error {deletePolicy := metav1.DeletePropagationForegrounderr := dpClient.Delete(context.TODO(), "nginx-deployment", metav1.DeleteOptions{PropagationPolicy: &deletePolicy,})if err != nil {return err}return nil
}

这里的删除操作定义了删除选项，表示前台级联删除。在这种模式下，删除操作会首先返回删除的资源，然后在后台删除关联的依赖对象。在 Kubernetes API 中，前台级联删除的表现形式是：首先将删除的对象的 metadata.deletionTimestamp 字段设置为当前时间，然后客户端会在此对象的 metadata.finalizers 列表中看到值 foregroundDeletion。在依赖对象被删除后，Kubernetes 垃圾收集器会最后删除这个对象。

5. build

代码编写完成打包成二进制

go build -o ./handle_deployment

此时观察deployment所有流程效果

完整代码地址：https://github.com/xiaowei6688/k8s_go_example/tree/dev/handle_deployment