原文连接：https://blog.csdn.net/u012986012/article/details/119710511

kubebuilder是一个官方提供快速实现Operator的工具包，可快速生成k8s的CRD、Controller、Webhook，用户只需要实现业务逻辑。

类似工具还有operader-sdk，目前正在与Kubebuilder融合

kubebuilder封装了controller-runtime与controller-tools，通过controller-gen来生产代码，简化了用户创建Operator的步骤。

一般创建Operator流程如下：

1. 创建工作目录，初始化项目
2. 创建API，填充字段
3. 创建Controller，编写核心协调逻辑(Reconcile)
4. 创建Webhook，实现接口，可选
5. 验证测试
6. 发布到集群中

示例

我们准备创建一个2048的游戏，对外可以提供服务，也能方便地扩缩容。

准备环境

首先你需要有Kubernetes、Docker、Golang相关环境。
Linux下安装kubebuilder

curl -L -o kubebuilder https://go.kubebuilder.io/dl/latest/$(go env GOOS)/$(go env GOARCH)
chmod +x kubebuilder && mv kubebuilder /usr/local/bin/

 
 

 
 

Create Resource [y/n]
y #生成CR
Create Controller [y/n]
y #生成Controller

目录结构如下：

├── api
│   └── v1 # CRD定义
├── bin
│   └── controller-gen
├── config
│   ├── crd # crd配置
│   ├── default
│   ├── manager # operator部署文件
│   ├── prometheus
│   ├── rbac
│   └── samples # cr示例
├── controllers
│   ├── game_controller.go # controller逻辑
│   └── suite_test.go
├── Dockerfile
├── go.mod
├── go.sum
├── hack
│   └── boilerplate.go.txt # 头文件模板
├── main.go # 项目主函数
├── Makefile 
└── PROJECT #项目元数据

编写API

在mygame/api/v1/game_types.go定义我们需要的字段

Spec配置如下

type GameSpec struct {
	// Number of desired pods. This is a pointer to distinguish between explicit
	// zero and not specified. Defaults to 1.
	// +optional
	//+kubebuilder:default:=1 
	//+kubebuilder:validation:Minimum:=1
	Replicas *int32 `json:"replicas,omitempty" protobuf:"varint,1,opt,name=replicas"`
	// Docker image name
	// +optional
	Image string `json:"image,omitempty"`
	// Ingress Host name
	Host string `json:"host,omitempty"`
}

kubebuilder:default可以设置默认值

Status定义如下

const (
	Running  = "Running"
	Pending  = "Pending"
	NotReady = "NotReady"
	Failed   = "Failed"
)
type GameStatus struct {
	// Phase is the phase of guestbook
	Phase string `json:"phase,omitempty"`
	// replicas is the number of Pods created by the StatefulSet controller.
	Replicas int32 `json:"replicas"`
	// readyReplicas is the number of Pods created by the StatefulSet controller that have a Ready Condition.
	ReadyReplicas int32 `json:"readyReplicas"`
	// LabelSelector is label selectors for query over pods that should match the replica count used by HPA.
	LabelSelector string `json:"labelSelector,omitempty"`
}

另外需要添加scale接口

//+kubebuilder:subresource:scale:specpath=.spec.replicas,statuspath=.status.replicas,selectorpath=.status.labelSelector

 
 

 
 

编写Controller逻辑

Controller的核心逻辑在Reconcile中，我们只需要填充自己的业务逻辑

func (r *GameReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
	logger := log.FromContext(ctx)
	logger.Info("revice reconcile event", "name", req.String())
	// 获取game对象
	game := &myappv1.Game{}
	if err := r.Get(ctx, req.NamespacedName, game); err != nil {
		return ctrl.Result{}, client.IgnoreNotFound(err)
	}
  // 如果处在删除中直接跳过
	if game.DeletionTimestamp != nil {
		logger.Info("game in deleting", "name", req.String())
		return ctrl.Result{}, nil
	}
  // 同步资源，如果资源不存在创建deployment、ingress、service，并更新status
	if err := r.syncGame(ctx, game); err != nil {
		logger.Error(err, "failed to sync game", "name", req.String())
		return ctrl.Result{}, nil
	}
	return ctrl.Result{}, nil
}

添加rbac配置

//+kubebuilder:rbac:groups=apps,resources=deployments,verbs=get;list;watch;create;update;patch;delete
//+kubebuilder:rbac:groups=apps,resources=deployments/status,verbs=get;update;patch
//+kubebuilder:rbac:groups=core,resources=services,verbs=get;list;watch;create;update;patch;delete
//+kubebuilder:rbac:groups=networking,resources=ingresses,verbs=get;list;watch;create;update;patch;delete

具体syncGame逻辑如下

func (r *GameReconciler) syncGame(ctx context.Context, obj *myappv1.Game) error {
	logger := log.FromContext(ctx)
	game := obj.DeepCopy()
	name := types.NamespacedName{
		Namespace: game.Namespace,
		Name:      game.Name,
	}
  // 构造owner
	owner := []metav1.OwnerReference{
		{
			APIVersion:         game.APIVersion,
			Kind:               game.Kind,
			Name:               game.Name,
			Controller:         pointer.BoolPtr(true),
			BlockOwnerDeletion: pointer.BoolPtr(true),
			UID:                game.UID,
		},
	}
	labels := game.Labels
	labels[gameLabelName] = game.Name
	meta := metav1.ObjectMeta{
		Name:            game.Name,
		Namespace:       game.Namespace,
		Labels:          labels,
		OwnerReferences: owner,
	}
  // 获取对应deployment, 如不存在则创建
	deploy := &appsv1.Deployment{}
	if err := r.Get(ctx, name, deploy); err != nil {
		if !errors.IsNotFound(err) {
			return err
		}
		deploy = &appsv1.Deployment{
			ObjectMeta: meta,
			Spec:       getDeploymentSpec(game, labels),
		}
		if err := r.Create(ctx, deploy); err != nil {
			return err
		}
		logger.Info("create deployment success", "name", name.String())
	} else {
    // 如果存在对比和game生成的deployment是否一致，不一致则更新
		want := getDeploymentSpec(game, labels)
		get := getSpecFromDeployment(deploy)
		if !reflect.DeepEqual(want, get) {
			deploy = &appsv1.Deployment{
				ObjectMeta: meta,
				Spec:       want,
			}
			if err := r.Update(ctx, deploy); err != nil {
				return err
			}
			logger.Info("update deployment success", "name", name.String())
		}
	}
  //service创建
	svc := &corev1.Service{}
	if err := r.Get(ctx, name, svc); err != nil {
	  ...
	}
  // ingress创建
	ing := &networkingv1.Ingress{}
	if err := r.Get(ctx, name, ing); err != nil {
		...
	}
	newStatus := myappv1.GameStatus{
		Replicas:      *game.Spec.Replicas,
		ReadyReplicas: deploy.Status.ReadyReplicas,
	}
	if newStatus.Replicas == newStatus.ReadyReplicas {
		newStatus.Phase = myappv1.Running
	} else {
		newStatus.Phase = myappv1.NotReady
	}
  // 更新状态
	if !reflect.DeepEqual(game.Status, newStatus) {
		game.Status = newStatus
		logger.Info("update game status", "name", name.String())
		return r.Client.Status().Update(ctx, game)
	}
	return nil
}

默认情况下生成的controller只监听自定义资源，在示例中我们也需要监听game的子资源，如监听deployment是否符合预期

// SetupWithManager sets up the controller with the Manager.
func (r *GameReconciler) SetupWithManager(mgr ctrl.Manager) error {
	// 创建controller
	c, err := controller.New("game-controller", mgr, controller.Options{
		Reconciler:              r,
		MaxConcurrentReconciles: 3, //controller运行的worker数
	})
	if err != nil {
		return err
	}
	//监听自定义资源
	if err := c.Watch(&source.Kind{Type: &myappv1.Game{}}, &handler.EnqueueRequestForObject{}); err != nil {
		return err
	}
	//监听deployment,将owner信息即game namespace/name添加到队列
	if err := c.Watch(&source.Kind{Type: &appsv1.Deployment{}}, &handler.EnqueueRequestForOwner{
		OwnerType:    &myappv1.Game{},
		IsController: true,
	}); err != nil {
		return err
	}
	return nil
}

部署验证

安装CRD

make install

 
 

 
 

# 查看deploy
kubectl get deploy game-sample
NAME READY UP-TO-DATE AVAILABLE AGE
game-sample 1/1 1 1 6m

# 查看ingress
kubectl get ing game-sample
NAME CLASS HOSTS ADDRESS PORTS AGE
game-sample <none> mygame.io 192.168.49.2 80 7m

验证应用，在/etc/host中添加<Ingress ADDRESS Ip> mygame.io，访问浏览器如下图所示

验证扩容

kubectl scale games.myapp.qingwave.github.io game-sample --replicas 2
game.myapp.qingwave.github.io/game-sample scaled

# 扩容后
kubectl get games.myapp.qingwave.github.io
NAME PHASE HOST DESIRED CURRENT READY AGE
game-sample Running mygame.io 2 2 2 7m

同样的通过ValidateCreate、ValidateUpdate可实现validating webhook

func (r *Game) ValidateCreate() error {
	gamelog.Info("validate create", "name", r.Name)
	// Host不能包括通配符
	if strings.Contains(r.Spec.Host, "*") {
		return errors.New("host should not contain *")
	}
	return nil
}

本地验证webhook需要配置证书，在集群中测试更方便点，可参考官方文档。

总结

至此，我们已经实现了一个功能完全的game-operator，可以管理game资源的生命周期，创建/更新game时会自动创建deployment、service、ingress等资源，当deployment被误删或者误修改时也可以自动回复到期望状态，也实现了scale接口。

通过kubebuiler大大简化了开发operator的成本，我们只需要关心业务逻辑即可，不需要再手动去创建client/controller等，但同时kubebuilder生成的代码中屏蔽了很多细节，比如controller的最大worker数、同步时间、队列类型等参数设置，只有了解operator的原理才更好应用于生产。

引用

[1] https://book.kubebuilder.io/