使用终结器

Finalizers 允许控制器实现异步预删除钩子。假设您为每个 API 类型的对象创建一个外部资源（例如存储桶），并且您希望在 Kubernetes 中删除对象时删除相关的外部资源，您可以使用 finalizer 来实现这一点。

您可以在Kubernetes参考文档中阅读更多关于最终器的信息。下面的部分演示了如何在控制器的Reconcile方法中注册和触发预删除钩子。

需要注意的关键点是，最终处理器导致对象的“删除“变成“更新“，以设置删除时间戳。对象上存在删除时间戳表明该对象正在被删除。否则，如果没有最终处理器，删除会表现为一个调整过程，其中对象在缓存中丢失。

亮点：

  • 如果对象没有被删除且没有注册终结器，则在 Kubernetes 中添加终结器并更新该对象。
  • 如果对象正在被删除，并且最终器仍然在最终器列表中，那么请执行预删除逻辑，移除最终器并更新对象。
  • 确保预删除逻辑是幂等的。
../../cronjob-tutorial/testdata/finalizer_example.go
Apache License

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Imports

First, we start out with some standard imports. As before, we need the core controller-runtime library, as well as the client package, and the package for our API types.

package controllers

import (
	"context"

	"k8s.io/kubernetes/pkg/apis/batch"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"

	batchv1 "tutorial.kubebuilder.io/project/api/v1"
)

By default, kubebuilder will include the RBAC rules necessary to update finalizers for CronJobs.

// +kubebuilder:rbac:groups=batch.tutorial.kubebuilder.io,resources=cronjobs,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups=batch.tutorial.kubebuilder.io,resources=cronjobs/status,verbs=get;update;patch
// +kubebuilder:rbac:groups=batch.tutorial.kubebuilder.io,resources=cronjobs/finalizers,verbs=update

The code snippet below shows skeleton code for implementing a finalizer.

func (r *CronJobReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
	log := r.Log.WithValues("cronjob", req.NamespacedName)

	cronJob := &batchv1.CronJob{}
	if err := r.Get(ctx, req.NamespacedName, cronJob); err != nil {
		log.Error(err, "unable to fetch CronJob")
		// we'll ignore not-found errors, since they can't be fixed by an immediate
		// requeue (we'll need to wait for a new notification), and we can get them
		// on deleted requests.
		return ctrl.Result{}, client.IgnoreNotFound(err)
	}

	// name of our custom finalizer
	myFinalizerName := "batch.tutorial.kubebuilder.io/finalizer"

	// examine DeletionTimestamp to determine if object is under deletion
	if cronJob.ObjectMeta.DeletionTimestamp.IsZero() {
		// The object is not being deleted, so if it does not have our finalizer,
		// then let's add the finalizer and update the object. This is equivalent
		// to registering our finalizer.
		if !controllerutil.ContainsFinalizer(cronJob, myFinalizerName) {
			controllerutil.AddFinalizer(cronJob, myFinalizerName)
			if err := r.Update(ctx, cronJob); err != nil {
				return ctrl.Result{}, err
			}
		}
	} else {
		// The object is being deleted
		if controllerutil.ContainsFinalizer(cronJob, myFinalizerName) {
			// our finalizer is present, so let's handle any external dependency
			if err := r.deleteExternalResources(cronJob); err != nil {
				// if fail to delete the external dependency here, return with error
				// so that it can be retried.
				return ctrl.Result{}, err
			}

			// remove our finalizer from the list and update it.
			controllerutil.RemoveFinalizer(cronJob, myFinalizerName)
			if err := r.Update(ctx, cronJob); err != nil {
				return ctrl.Result{}, err
			}
		}

		// Stop reconciliation as the item is being deleted
		return ctrl.Result{}, nil
	}

	// Your reconcile logic

	return ctrl.Result{}, nil
}

func (r *Reconciler) deleteExternalResources(cronJob *batch.CronJob) error {
	//
	// delete any external resources associated with the cronJob
	//
	// Ensure that delete implementation is idempotent and safe to invoke
	// multiple times for same object.
}