client-go gin的简单整合四-list-watch初探 _整合

犀渠玉剑良家子，白马金羁侠少年。这篇文章主要讲述client-go gin的简单整合四-list-watch初探相关的知识，希望能为你提供帮助。
背景：完成了client-go gin的简单整合三（list列表相关再进阶关于Pods），恩如果有代理是可以看到每次的请求都要访问后端服务的，如何避免频繁调用后端apiserver呢？list-watch监听机制可以使用一下？
关于list-watch:参照：https://blog.51cto.com/u_15127559/3377812(错别字好多？最后还是引用了沈老师的ppt上面的概念！),

list http短链接调用资源的api，获取列表。
使用http长连接持续监听资源，有变化则返回一个WatchEvent
client-go informerclient-go k8s.io/client-go/tools/cache包informer对象对list-watch机制进行了封装
初始化调用List api获得全量list 缓存（本地缓存）
调用watch api watch资源，当资源发生变更通过一定机制维护缓存，减少访问apiserver的压力

个人觉得不错的文章Client-go源码分析之Reflector,华为云不错的视频list-watch机制原理详解,
client-go(kubernetes)的ListerWatcher解析.
client-go gin的简单整合四-list-watch 以deployment简单例子的开始文件名 /src/service/test.go，监控deployment的变化，开始其实是不是可以跟java是的弄一个单独的测试包？这里就简单操作了偷懒......
cache.NewInformer()开始：

cache.NewInformer()

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goland查看源码功能：

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实现Handler方法：
只实现了OnUpdate方法（仅仅打印deployment名字），OnAdd，OnDelete是空的：

type DepHandler struct func (d *DepHandler) OnAdd(obj interface) func (d *DepHandler) OnUpdate(oldObj, newObj interface) if dep, ok := newObj.(*v1.Deployment); ok fmt.Println(dep.Name)func (d *DepHandler) OnDelete(obj interface)

最终test.go如下：

package mainimport ( "fmt" "k8s-demo1/src/lib" v1 "k8s.io/api/apps/v1" "k8s.io/apimachinery/pkg/fields" "k8s.io/apimachinery/pkg/util/wait" "k8s.io/client-go/tools/cache" )type DepHandler struct func (d *DepHandler) OnAdd(obj interface) func (d *DepHandler) OnUpdate(oldObj, newObj interface) if dep, ok := newObj.(*v1.Deployment); ok fmt.Println(dep.Name)func (d *DepHandler) OnDelete(obj interface) func main() s, c := cache.NewInformer(cache.NewListWatchFromClient(lib.K8sClient.AppsV1().RESTClient(), "deployments", "default", fields.Everything()), & v1.Deployment, 0, & DepHandler, ) c.Run(wait.NeverStop) s.List()

关于s c 源码中Store, Controller

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运行test.go
go run test.go
手动修改nginx deployment副本数量，查看 goland输出：

[zhangpeng@zhangpeng ~]$ kubectl get deployments NAMEREADYUP-TO-DATEAVAILABLEAGE nginx2/22210d [zhangpeng@zhangpeng ~]$ kubectl get deployment NAMEREADYUP-TO-DATEAVAILABLEAGE nginx2/22210d [zhangpeng@zhangpeng ~]$ kubectl scale deployment/nginx --replicas=3 deployment.apps/nginx scaled [zhangpeng@zhangpeng ~]$

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注：resource 是deployments，不能是deployment, *DepHandler 为什么加指针运算符？
实现一个pod的list-watch?首先停止test.go，并注释掉test.go中代码。

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创建了一个/src/service/test1.go,照着test.go来一遍：

package mainimport ( "fmt" "k8s-demo1/src/lib" corev1 "k8s.io/api/core/v1" "k8s.io/apimachinery/pkg/fields" "k8s.io/apimachinery/pkg/util/wait" "k8s.io/client-go/tools/cache" )type PodHandler struct func (p *PodHandler) OnAdd(obj interface) func (p *PodHandler) OnUpdate(oldObj, newObj interface) if pods, ok := newObj.(*corev1.Pod); ok fmt.Println(pods.Name)func (p *PodHandler) OnDelete(obj interface) func main() s, c := cache.NewInformer(cache.NewListWatchFromClient(lib.K8sClient.CoreV1().RESTClient(), "pods", "default", fields.Everything()), & corev1.Pod, 0, & PodHandler, ) c.Run(wait.NeverStop) s.List()

注意：pod 的api是 corev1。参照：https://github.com/kubernetes/client-go/blob/release-1.23/informers/core/v1/pod.go#L58
运行test1.go,修改default 下nginx deployment副本数：

[zhangpeng@zhangpeng ~]$ kubectl scale deployment/nginx --replicas=3 deployment.apps/nginx scaled

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SharedInformerFactory工厂模式思考一下为什么要使用工厂模式呢？
关于SharedInformerFactory参考：https://stackoverflow.com/questions/40975307/how-to-watch-events-on-a-kubernetes-service-using-its-go-client,https://qiankunli.github.io/2020/07/20/client_go.html
先test1.go的pod开始：

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src/service/test1.go

package mainimport ( "fmt" "k8s-demo1/src/lib" corev1 "k8s.io/api/core/v1" "k8s.io/apimachinery/pkg/util/wait" "k8s.io/client-go/informers" )type PodHandler struct func (p *PodHandler) OnAdd(obj interface) func (p *PodHandler) OnUpdate(oldObj, newObj interface) if pods, ok := newObj.(*corev1.Pod); ok fmt.Println(pods.Name)func (p *PodHandler) OnDelete(obj interface) func main() factory := informers.NewSharedInformerFactory(lib.K8sClient, 0) podinformer := factory.Core().V1().Pods() podinformer.Informer().AddEventHandler(& PodHandler) factory.Start(wait.NeverStop) select

写的时候以为直接corev1......发现是core().v1(),为什么要用select呢？参照：https://blog.csdn.net/cbmljs/article/details/93497415。阻塞，防止程序退出！运行test1.go程序，修改nginx deployment副本：

[zhangpeng@zhangpeng ~]$ kubectl scale deployment/nginx --replicas=4 deployment.apps/nginx scaled

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可不可以deployment pod list-watch搞在一起呢？现在写了一个test.go,test1.go?貌似也是可以的......先搞在一起，如下：

package mainimport ( "fmt" "k8s-demo1/src/lib" v1 "k8s.io/api/apps/v1" corev1 "k8s.io/api/core/v1" "k8s.io/apimachinery/pkg/util/wait" "k8s.io/client-go/informers" )type PodHandler struct func (p *PodHandler) OnAdd(obj interface) func (p *PodHandler) OnUpdate(oldObj, newObj interface) if pods, ok := newObj.(*corev1.Pod); ok fmt.Println(pods.Name)func (p *PodHandler) OnDelete(obj interface) type DepHandler struct func (d *DepHandler) OnAdd(obj interface) func (d *DepHandler) OnUpdate(oldObj, newObj interface) if dep, ok := newObj.(*v1.Deployment); ok fmt.Println(dep.Name)func (d *DepHandler) OnDelete(obj interface) func main() factory := informers.NewSharedInformerFactory(lib.K8sClient, 0) podinformer := factory.Core().V1().Pods() podinformer.Informer().AddEventHandler(& PodHandler) depinformer := factory.Apps().V1().Deployments() depinformer.Informer().AddEventHandler(& DepHandler) factory.Start(wait.NeverStop) select

运行test1.go ，更改nginx deployment副本数量，打印了deployment name 和pod name！

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Handler OnAdd
补全一下OnAdd方法，打印一下pod deployment列表：

func (p *PodHandler) OnAdd(obj interface) fmt.Println(obj.(*corev1.Pod).Name)func (d *DepHandler) OnAdd(obj interface) fmt.Println(obj.(*v1.Deployment).Name)

package mainimport ( "fmt" "k8s-demo1/src/lib" v1 "k8s.io/api/apps/v1" corev1 "k8s.io/api/core/v1" "k8s.io/apimachinery/pkg/util/wait" "k8s.io/client-go/informers" )type PodHandler struct func (p *PodHandler) OnAdd(obj interface) fmt.Println(obj.(*corev1.Pod).Name)func (p *PodHandler) OnUpdate(oldObj, newObj interface) if pods, ok := newObj.(*corev1.Pod); ok fmt.Println(pods.Name)func (p *PodHandler) OnDelete(obj interface) type DepHandler struct func (d *DepHandler) OnAdd(obj interface) fmt.Println(obj.(*v1.Deployment).Name)func (d *DepHandler) OnUpdate(oldObj, newObj interface) if dep, ok := newObj.(*v1.Deployment); ok fmt.Println(dep.Name)func (d *DepHandler) OnDelete(obj interface) func main() factory := informers.NewSharedInformerFactory(lib.K8sClient, 0) podinformer := factory.Core().V1().Pods() podinformer.Informer().AddEventHandler(& PodHandler) depinformer := factory.Apps().V1().Deployments() depinformer.Informer().AddEventHandler(& DepHandler) factory.Start(wait.NeverStop) select

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sync.Map为什么引用sync.Map呢？Go语言sync.Map（在并发环境中使用的map），还是考虑并发原因！
拿deployment为例，打印一下develop namespace命名空间下的deployment列表：
test1.go

package mainimport ( "context" "fmt" "github.com/gin-gonic/gin" "k8s-demo1/src/lib" v1 "k8s.io/api/apps/v1" "k8s.io/apimachinery/pkg/util/wait" "k8s.io/client-go/informers" "log" "sync" "time" )type DeploymentMap struct data sync.Mapfunc (depmap *DeploymentMap) Add(dep *v1.Deployment) if list, ok := depmap.data.Load(dep.Namespace); ok list = append(list.([]*v1.Deployment), dep) depmap.data.Store(dep.Namespace, list) else depmap.data.Store(dep.Namespace, []*v1.Deploymentdep)type DepHandler struct func (d *DepHandler) OnAdd(obj interface) //fmt.Println(obj.(*v1.Deployment).Name) DepMap.Add(obj.(*v1.Deployment))func (d *DepHandler) OnUpdate(oldObj, newObj interface) if dep, ok := newObj.(*v1.Deployment); ok fmt.Println(dep.Name)func (d *DepHandler) OnDelete(obj interface) var DepMap *DeploymentMapfunc init() DepMap = & DeploymentMapfunc main() factory := informers.NewSharedInformerFactory(lib.K8sClient, 0) depinformer := factory.Apps().V1().Deployments() depinformer.Informer().AddEventHandler(& DepHandler) factory.Start(wait.NeverStop) c, _ := context.WithTimeout(context.Background(), time.Second*3) select case < -c.Done(): log.Fatal("time out") default: r := gin.New() r.GET("/", func(c *gin.Context) var res []string DepMap.data.Range(func(key, value interface) bool if key == "develop" for _, item := range value.([]*v1.Deployment) res = append(res, item.Name)return true) c.JSON(200, res)) r.Run(":8080")

【client-go gin的简单整合四-list-watch初探】没有作具体的路由，直接测试一下访问：http://127.0.0.1:8080/