Kubernetes 中 Informer 的使用

// staging/src/k8s.io/apimachinery/pkg/watch/watch.go// Interface 可以被任何知道如何 watch 和通知变化的对象实现type Interface interface {  // Stops watching. Will close the channel returned by ResultChan(). Releases  // any resources used by the watch.  Stop()
  // Returns a chan which will receive all the events. If an error occurs  // or Stop() is called, this channel will be closed, in which case the  // watch should be completely cleaned up.  ResultChan() <-chan Event}

// staging/src/k8s.io/apimachinery/pkg/watch/watch.go// EventType 定义可能的事件类型type EventType string
const (  Added    EventType = "ADDED"  Modified EventType = "MODIFIED"  Deleted  EventType = "DELETED"  Bookmark EventType = "BOOKMARK"  Error    EventType = "ERROR"
  DefaultChanSize int32 = 100)
// Event represents a single event to a watched resource.// +k8s:deepcopy-gen=truetype Event struct {  Type EventType
  // Object is:  //  * If Type is Added or Modified: the new state of the object.  //  * If Type is Deleted: the state of the object immediately before deletion.  //  * If Type is Bookmark: the object (instance of a type being watched) where  //    only ResourceVersion field is set. On successful restart of watch from a  //    bookmark resourceVersion, client is guaranteed to not get repeat event  //    nor miss any events.  //  * If Type is Error: *api.Status is recommended; other types may make sense  //    depending on context.  Object runtime.Object}

package main
import (  "flag"  "fmt"  "path/filepath"  "time"
  v1 "k8s.io/api/apps/v1"  "k8s.io/apimachinery/pkg/labels"  "k8s.io/client-go/informers"  "k8s.io/client-go/kubernetes"  "k8s.io/client-go/rest"  "k8s.io/client-go/tools/cache"  "k8s.io/client-go/tools/clientcmd"  "k8s.io/client-go/util/homedir")
func main() {  var err error  var config *rest.Config
  var kubeconfig *string
  if home := homedir.HomeDir(); home != "" {    kubeconfig = flag.String("kubeconfig", filepath.Join(home, ".kube", "config"), "[可选] kubeconfig 绝对路径")  } else {    kubeconfig = flag.String("kubeconfig", "", "kubeconfig 绝对路径")  }  // 初始化 rest.Config 对象  if config, err = rest.InClusterConfig(); err != nil {    if config, err = clientcmd.BuildConfigFromFlags("", *kubeconfig); err != nil {      panic(err.Error())    }  }  // 创建 Clientset 对象  clientset, err := kubernetes.NewForConfig(config)  if err != nil {    panic(err.Error())  }
  // 初始化 informer factory（为了测试方便这里设置每30s重新 List 一次）  informerFactory := informers.NewSharedInformerFactory(clientset, time.Second*30)  // 对 Deployment 监听  deployInformer := informerFactory.Apps().V1().Deployments()  // 创建 Informer（相当于注册到工厂中去，这样下面启动的时候就会去 List & Watch 对应的资源）  informer := deployInformer.Informer()  // 创建 Lister  deployLister := deployInformer.Lister()  // 注册事件处理程序  informer.AddEventHandler(cache.ResourceEventHandlerFuncs{    AddFunc:    onAdd,    UpdateFunc: onUpdate,    DeleteFunc: onDelete,  })
  stopper := make(chan struct{})  defer close(stopper)
  // 启动 informer，List & Watch  informerFactory.Start(stopper)  // 等待所有启动的 Informer 的缓存被同步  informerFactory.WaitForCacheSync(stopper)
  // 从本地缓存中获取 default 中的所有 deployment 列表  deployments, err := deployLister.Deployments("default").List(labels.Everything())  if err != nil {    panic(err)  }  for idx, deploy := range deployments {    fmt.Printf("%d -> %s\n", idx+1, deploy.Name)  }  <-stopper}
func onAdd(obj interface{}) {  deploy := obj.(*v1.Deployment)  fmt.Println("add a deployment:", deploy.Name)}
func onUpdate(old, new interface{}) {  oldDeploy := old.(*v1.Deployment)  newDeploy := new.(*v1.Deployment)  fmt.Println("update deployment:", oldDeploy.Name, newDeploy.Name)}
func onDelete(obj interface{}) {  deploy := obj.(*v1.Deployment)  fmt.Println("delete a deployment:", deploy.Name)}

$ go run main.goadd a deployment: dingtalk-hookadd a deployment: spin-orcaadd a deployment: argocd-serveradd a deployment: istio-egressgatewayadd a deployment: vault-agent-injectoradd a deployment: rook-ceph-osd-0add a deployment: rook-ceph-osd-2add a deployment: code-server......1 -> nginx2 -> helloworld-v13 -> productpage-v14 -> details-v1......