Kubernetes sample-controller 例子介绍

sample-controller

sample-controller 是 K8s 官方自定义 CDR 及控制器是实现的例子

通过使用这个自定义 CDR 控制器及阅读它的代码，基本可以了解如何制作一个 CDR 控制器

CDR 运作原理

网上有更好的文章，说明其运作原理：

• https://www.zhaohuabing.com/post/2023-03-09-how-to-create-a-k8s-controller/
• https://www.zhaohuabing.com/post/2023-04-04-how-to-create-a-k8s-controller-2/

CDR 定义 yaml 文件格式细节

官方文档： https://kubernetes.io/zh-cn/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/

sample-controller 目录文件说明

fananchong@myubuntu:~/k8s.io/sample-controller$ tree -L 2
.
|-- artifacts
|   `-- examples                            # CRD yaml 文件定义例子
|-- controller.go                           # 控制器实现
|-- hack                                    # k8s.io/code-generator 提供的生成 pkg/generated/ 、 pkg/apis/samplecontroller/v1alpha1/zz_generated.deepcopy.go
|   |-- boilerplate.go.txt
|   |-- custom-boilerplate.go.txt
|   |-- tools.go
|   |-- update-codegen.sh
|   `-- verify-codegen.sh
|-- main.go                                 # main 函数
|-- pkg
|   |-- apis                                # k8s.io/code-generator 根据 types.go 、 doc.go 来生成
|   |-- generated                           # 自动生成
|   `-- signals
`-- vendor                                  # go mod vendor|-- github.com|-- golang.org|-- google.golang.org|-- gopkg.in|-- k8s.io|-- modules.txt`-- sigs.k8s.io

controller.go 关键代码分析

1. Informer 监听事件
   fooInformer 监听 Foo CDR 事件
   deploymentInformer 监听 Deployment 事件

       // Set up an event handler for when Foo resources changefooInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{AddFunc: controller.enqueueFoo,UpdateFunc: func(old, new interface{}) {controller.enqueueFoo(new)},})// Set up an event handler for when Deployment resources change. This// handler will lookup the owner of the given Deployment, and if it is// owned by a Foo resource then the handler will enqueue that Foo resource for// processing. This way, we don't need to implement custom logic for// handling Deployment resources. More info on this pattern:// https://github.com/kubernetes/community/blob/8cafef897a22026d42f5e5bb3f104febe7e29830/contributors/devel/controllers.mddeploymentInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{AddFunc: controller.handleObject,UpdateFunc: func(old, new interface{}) {newDepl := new.(*appsv1.Deployment)oldDepl := old.(*appsv1.Deployment)if newDepl.ResourceVersion == oldDepl.ResourceVersion {// Periodic resync will send update events for all known Deployments.// Two different versions of the same Deployment will always have different RVs.return}controller.handleObject(new)},DeleteFunc: controller.handleObject,})
   

2. Foo CDR 事件处理
   压入工作队列

   // enqueueFoo takes a Foo resource and converts it into a namespace/name
   // string which is then put onto the work queue. This method should *not* be
   // passed resources of any type other than Foo.
   func (c *Controller) enqueueFoo(obj interface{}) {var key stringvar err errorif key, err = cache.MetaNamespaceKeyFunc(obj); err != nil {utilruntime.HandleError(err)return}c.workqueue.Add(key)
   }
   

3. Deployment 事件处理
   判断是属于 Foo 控制器创建的 Deployment ，压入队列

   // handleObject will take any resource implementing metav1.Object and attempt
   // to find the Foo resource that 'owns' it. It does this by looking at the
   // objects metadata.ownerReferences field for an appropriate OwnerReference.
   // It then enqueues that Foo resource to be processed. If the object does not
   // have an appropriate OwnerReference, it will simply be skipped.
   func (c *Controller) handleObject(obj interface{}) {var object metav1.Objectvar ok boollogger := klog.FromContext(context.Background())if object, ok = obj.(metav1.Object); !ok {tombstone, ok := obj.(cache.DeletedFinalStateUnknown)if !ok {utilruntime.HandleError(fmt.Errorf("error decoding object, invalid type"))return}object, ok = tombstone.Obj.(metav1.Object)if !ok {utilruntime.HandleError(fmt.Errorf("error decoding object tombstone, invalid type"))return}logger.V(4).Info("Recovered deleted object", "resourceName", object.GetName())}logger.V(4).Info("Processing object", "object", klog.KObj(object))if ownerRef := metav1.GetControllerOf(object); ownerRef != nil {// If this object is not owned by a Foo, we should not do anything more// with it.if ownerRef.Kind != "Foo" {return}foo, err := c.foosLister.Foos(object.GetNamespace()).Get(ownerRef.Name)if err != nil {logger.V(4).Info("Ignore orphaned object", "object", klog.KObj(object), "foo", ownerRef.Name)return}c.enqueueFoo(foo)return}
   }
   

4. Controller.Run 处理
   从队列中取出元素
   如果副本预期不一致，做 scale 处理

   // syncHandler compares the actual state with the desired, and attempts to
   // converge the two. It then updates the Status block of the Foo resource
   // with the current status of the resource.
   func (c *Controller) syncHandler(ctx context.Context, key string) error {// Convert the namespace/name string into a distinct namespace and namelogger := klog.LoggerWithValues(klog.FromContext(ctx), "resourceName", key)namespace, name, err := cache.SplitMetaNamespaceKey(key)if err != nil {utilruntime.HandleError(fmt.Errorf("invalid resource key: %s", key))return nil}// Get the Foo resource with this namespace/namefoo, err := c.foosLister.Foos(namespace).Get(name)if err != nil {// The Foo resource may no longer exist, in which case we stop// processing.if errors.IsNotFound(err) {utilruntime.HandleError(fmt.Errorf("foo '%s' in work queue no longer exists", key))return nil}return err}deploymentName := foo.Spec.DeploymentNameif deploymentName == "" {// We choose to absorb the error here as the worker would requeue the// resource otherwise. Instead, the next time the resource is updated// the resource will be queued again.utilruntime.HandleError(fmt.Errorf("%s: deployment name must be specified", key))return nil}// Get the deployment with the name specified in Foo.specdeployment, err := c.deploymentsLister.Deployments(foo.Namespace).Get(deploymentName)// If the resource doesn't exist, we'll create itif errors.IsNotFound(err) {deployment, err = c.kubeclientset.AppsV1().Deployments(foo.Namespace).Create(context.TODO(), newDeployment(foo), metav1.CreateOptions{})}// If an error occurs during Get/Create, we'll requeue the item so we can// attempt processing again later. This could have been caused by a// temporary network failure, or any other transient reason.if err != nil {return err}// If the Deployment is not controlled by this Foo resource, we should log// a warning to the event recorder and return error msg.if !metav1.IsControlledBy(deployment, foo) {msg := fmt.Sprintf(MessageResourceExists, deployment.Name)c.recorder.Event(foo, corev1.EventTypeWarning, ErrResourceExists, msg)return fmt.Errorf("%s", msg)}// If this number of the replicas on the Foo resource is specified, and the// number does not equal the current desired replicas on the Deployment, we// should update the Deployment resource.if foo.Spec.Replicas != nil && *foo.Spec.Replicas != *deployment.Spec.Replicas {logger.V(4).Info("Update deployment resource", "currentReplicas", *foo.Spec.Replicas, "desiredReplicas", *deployment.Spec.Replicas)deployment, err = c.kubeclientset.AppsV1().Deployments(foo.Namespace).Update(context.TODO(), newDeployment(foo), metav1.UpdateOptions{})}// If an error occurs during Update, we'll requeue the item so we can// attempt processing again later. This could have been caused by a// temporary network failure, or any other transient reason.if err != nil {return err}// Finally, we update the status block of the Foo resource to reflect the// current state of the worlderr = c.updateFooStatus(foo, deployment)if err != nil {return err}c.recorder.Event(foo, corev1.EventTypeNormal, SuccessSynced, MessageResourceSynced)return nil
   }