Kubebuilder Controller 开发

Kubernetes operator controller 开发详解

原理

Kubernetes operator controller 是个面向期望的编程模型，声明的期望对象就是 API Object（也称 k8s Runtime Object）

实例中，XcaReconciler 的和解循环（Reconcile 函数）监听所有 Xca 类型资源的变动，都会调用该函数进行协调

• 检查当前状态（副本数、容器镜像等）
• 对比当前状态和期望状态
• 如果不匹配则更新当前状态

代码部分

以 kubebuilder 生成代码为例：

• main.go 中注册 Xtls Controller

	if err = (&controllers.XtlsReconciler{
		Client: mgr.GetClient(),
		Scheme: mgr.GetScheme(),
	}).SetupWithManager(mgr); err != nil {
		setupLog.Error(err, "unable to create controller", "controller", "Xtls")
		os.Exit(1)
	}

• api/v1beta1/xca_types.go

// XcaSpec defines the desired state of Xca
type XcaSpec struct {
  // INSERT ADDITIONAL SPEC FIELDS - desired state of cluster
  // Important: Run "make" to regenerate code after modifying this file

  // Foo is an example field of Xca. Edit xca_types.go to remove/update
  Foo string `json:"foo,omitempty"`
}

// XcaStatus defines the observed state of Xca
type XcaStatus struct {
  // INSERT ADDITIONAL STATUS FIELD - define observed state of cluster
  // Important: Run "make" to regenerate code after modifying this file
	Active         bool         `json:"active,omitempty"`
	LastUpdateTime *metav1.Time `json:"last_update_time"`
}

• 控制器核心代码 controllers/xca_controller.go

// XcaReconciler reconciles a Xca object
type XcaReconciler struct {
	client.Client
	Scheme *runtime.Scheme
}

//+kubebuilder:rbac:groups=apps.xca.k8s.kb.cx,resources=xcas,verbs=get;list;watch;create;update;patch;delete
//+kubebuilder:rbac:groups=apps.xca.k8s.kb.cx,resources=xcas/status,verbs=get;update;patch
//+kubebuilder:rbac:groups=apps.xca.k8s.kb.cx,resources=xcas/finalizers,verbs=update

// Reconcile is part of the main kubernetes reconciliation loop which aims to
// move the current state of the cluster closer to the desired state.
// TODO(user): Modify the Reconcile function to compare the state specified by
// the Xca object against the actual cluster state, and then
// perform operations to make the cluster state reflect the state specified by
// the user.
//
// For more details, check Reconcile and its Result here:
// - https://pkg.go.dev/sigs.k8s.io/controller-runtime@v0.12.2/pkg/reconcile
func (r *XcaReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
  logger := log.FromContext(ctx, "namespace", req.Namespace)

  // 1. check resource exist
  var obj appsv1beta1.Xca
  if err := r.Get(ctx, req.NamespacedName, &obj); err != nil {
    if errors.IsNotFound(err) {
      logger.Info("fetch Xca not found", "name", obj.Name, "namespace", obj.Namespace)
      err = nil
    } else {
      logger.Error(err, "unable to fetch Xca")
    }

    //return ctrl.Result{}, client.IgnoreNotFound(err)
    return ctrl.Result{}, err
  }
  logger.Info("fetch Xca Object", "name", obj.Name, "namespace", obj.Namespace)

  // 2. check resource status
  if obj.Status.Active {
    logger.Info("Xca is ative", "name", obj.Name, "namespace", obj.Namespace)
    return ctrl.Result{}, nil
  }

  // 3. change to Active
  logger.Info("do something to set object to active", obj.Name, "namespace", obj.Namespace)

  obj.Status.Active = true
  obj.Status.LastUptateTime = &metav1.Time{Time: time.Now()}
  if err := r.Status().Update(ctx, &obj); err != nil {
    logger.Error(err, "update object status err", obj.Name, "namespace", obj.Namespace)
  }

  return ctrl.Result{}, nil
}

• 其中，和解循环中被管理的资源在这里配置

// SetupWithManager sets up the controller with the Manager.
func (r *XcaReconciler) SetupWithManager(mgr ctrl.Manager) error {
	return ctrl.NewControllerManagedBy(mgr).
		For(&appsv1beta1.Xca{}).
		Complete(r)
}

镜像

• Dockerfile 里镜像替换：gcr.io/distroless/static:nonroot -> gcriodistroless/static:nonroot