增加client-go示例
Jimmy Song
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- [6. 开发指南](develop/index.md)
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- [6.1 开发环境搭建](develop/developing-environment.md)
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- [6.2 单元测试和集成测试](develop/testing.md)
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- [6.3 社区贡献](develop/contribute.md)
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- [6.3 client-go示例](develop/client-go-sample.md)
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- [6.4 社区贡献](develop/contribute.md)
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- [7. 附录](appendix/index.md)
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- [7.1 Docker最佳实践](appendix/docker-best-practice.md)
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- [7.2 问题记录](appendix/issues.md)
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# client-go示例
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访问kubernetes集群有几下几种方式：
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| 方式 | 特点 | 支持者 |
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| ---------------------------------------- | ---------------------------------------- | ------ |
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| Kubernetes dashboard | 直接通过Web UI进行操作，简单直接，可定制化程度低 | 官方支持 |
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| kubectl | 命令行操作，功能最全，但是比较复杂，适合对其进行进一步的分装，定制功能，版本适配最好 | 官方支持 |
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| [client-go](https://github.com/kubernetes/client-go) | 从kubernetes的代码中抽离出来的客户端包，简单易用，但需要小心区分kubernetes的API版本 | 官方支持 |
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| [client-python](https://github.com/kubernetes-incubator/client-python) | python客户端，kubernetes-incubator | 官方支持 |
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| [Java client](https://github.com/fabric8io/kubernetes-client) | fabric8中的一部分，kubernetes的java客户端 | redhat |
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下面，我们基于[client-go](https://github.com/kubernetes/client-go)，对Deployment升级镜像的步骤进行了定制，通过命令行传递一个Deployment的名字、应用容器名和新image名字的方式来升级。代码和使用方式见 https://github.com/rootsongjc/kubernetes-client-go-sample 。
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## kubernetes-client-go-sample
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代码如下：
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```Go
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package main
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import (
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"flag"
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"fmt"
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"os"
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"path/filepath"
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"k8s.io/apimachinery/pkg/api/errors"
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metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
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"k8s.io/client-go/kubernetes"
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"k8s.io/client-go/tools/clientcmd"
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)
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func main() {
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var kubeconfig *string
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if home := homeDir(); home != "" {
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kubeconfig = flag.String("kubeconfig", filepath.Join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
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} else {
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kubeconfig = flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
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}
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deploymentName := flag.String("deployment", "", "deployment name")
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imageName := flag.String("image", "", "new image name")
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appName := flag.String("app", "app", "application name")
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flag.Parse()
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if *deploymentName == "" {
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fmt.Println("You must specify the deployment name.")
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os.Exit(0)
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}
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if *imageName == "" {
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fmt.Println("You must specify the new image name.")
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os.Exit(0)
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}
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// use the current context in kubeconfig
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config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
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if err != nil {
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panic(err.Error())
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}
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// create the clientset
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clientset, err := kubernetes.NewForConfig(config)
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if err != nil {
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panic(err.Error())
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}
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deployment, err := clientset.AppsV1beta1().Deployments("default").Get(*deploymentName, metav1.GetOptions{})
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if err != nil {
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panic(err.Error())
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}
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if errors.IsNotFound(err) {
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fmt.Printf("Deployment not found\n")
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} else if statusError, isStatus := err.(*errors.StatusError); isStatus {
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fmt.Printf("Error getting deployment%v\n", statusError.ErrStatus.Message)
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} else if err != nil {
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panic(err.Error())
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} else {
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fmt.Printf("Found deployment\n")
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name := deployment.GetName()
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fmt.Println("name ->", name)
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containers := &deployment.Spec.Template.Spec.Containers
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found := false
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for i := range *containers {
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c := *containers
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if c[i].Name == *appName {
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found = true
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fmt.Println("Old image ->", c[i].Image)
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fmt.Println("New image ->", *imageName)
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c[i].Image = *imageName
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}
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}
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if found == false {
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fmt.Println("The application container not exist in the deployment pods.")
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os.Exit(0)
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}
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_, err := clientset.AppsV1beta1().Deployments("default").Update(deployment)
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if err != nil {
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panic(err.Error())
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}
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}
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}
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func homeDir() string {
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if h := os.Getenv("HOME"); h != "" {
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return h
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}
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return os.Getenv("USERPROFILE") // windows
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}
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```
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我们使用`kubeconfig`文件认证连接kubernetes集群，该文件默认的位置是`$HOME/.kube/config`。
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该代码编译后可以直接在kubernetes集群之外，任何一个可以连接到API server的机器上运行。
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**编译运行**
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```bash
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$ go get github.com/rootsongjc/kubernetes-client-go-sample
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$ cd $GOPATH/src/github.com/rootsongjc/kubernetes-client-go-sample
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$ make
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$ ./update-deployment-image -h
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Usage of ./update-deployment-image:
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-alsologtostderr
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log to standard error as well as files
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-app string
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application name (default "app")
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-deployment string
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deployment name
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-image string
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new image name
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-kubeconfig string
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(optional) absolute path to the kubeconfig file (default "/Users/jimmy/.kube/config")
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-log_backtrace_at value
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when logging hits line file:N, emit a stack trace
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-log_dir string
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If non-empty, write log files in this directory
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-logtostderr
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log to standard error instead of files
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-stderrthreshold value
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logs at or above this threshold go to stderr
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-v value
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log level for V logs
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-vmodule value
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comma-separated list of pattern=N settings for file-filtered logging
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```
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**使用不存在的image更新**
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```bash
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$ ./update-deployment-image -deployment filebeat-test -image sz-pg-oam-docker-hub-001.tendcloud.com/library/analytics-docker-test:Build_9
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Found deployment
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name -> filebeat-test
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Old image -> sz-pg-oam-docker-hub-001.tendcloud.com/library/analytics-docker-test:Build_8
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New image -> sz-pg-oam-docker-hub-001.tendcloud.com/library/analytics-docker-test:Build_9
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```
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查看Deployment的event。
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```Bash
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$ kubectl describe deployment filebeat-test
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Name: filebeat-test
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Namespace: default
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CreationTimestamp: Fri, 19 May 2017 15:12:28 +0800
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Labels: k8s-app=filebeat-test
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Selector: k8s-app=filebeat-test
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Replicas: 2 updated | 3 total | 2 available | 2 unavailable
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StrategyType: RollingUpdate
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MinReadySeconds: 0
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RollingUpdateStrategy: 1 max unavailable, 1 max surge
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Conditions:
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Type Status Reason
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---- ------ ------
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Available True MinimumReplicasAvailable
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Progressing True ReplicaSetUpdated
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OldReplicaSets: filebeat-test-2365467882 (2/2 replicas created)
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NewReplicaSet: filebeat-test-2470325483 (2/2 replicas created)
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Events:
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FirstSeen LastSeen Count From SubObjectPath Type ReasoMessage
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--------- -------- ----- ---- ------------- -------- ------------
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2h 1m 3 {deployment-controller } Normal ScalingReplicaSet Scaled down replica set filebeat-test-2365467882 to 2
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1m 1m 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set filebeat-test-2470325483 to 1
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1m 1m 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set filebeat-test-2470325483 to 2
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```
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可以看到老的ReplicaSet从3个replica减少到了2个，有2个使用新配置的replica不可用，目前可用的replica是2个。
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这是因为我们指定的镜像不存在，查看Deployment的pod的状态。
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```bash
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$ kubectl get pods -l k8s-app=filebeat-test
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NAME READY STATUS RESTARTS AGE
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filebeat-test-2365467882-4zwx8 2/2 Running 0 33d
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filebeat-test-2365467882-rqskl 2/2 Running 0 33d
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filebeat-test-2470325483-6vjbw 1/2 ImagePullBackOff 0 4m
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filebeat-test-2470325483-gc14k 1/2 ImagePullBackOff 0 4m
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```
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我们可以看到有两个pod正在拉取image。
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**还原为原先的镜像**
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将image设置为原来的镜像。
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```bash
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$ ./update-deployment-image -deployment filebeat-test -image sz-pg-oam-docker-hub-001.tendcloud.com/library/analytics-docker-test:Build_8
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Found deployment
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name -> filebeat-test
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Old image -> sz-pg-oam-docker-hub-001.tendcloud.com/library/analytics-docker-test:Build_9
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New image -> sz-pg-oam-docker-hub-001.tendcloud.com/library/analytics-docker-test:Build_8
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```
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现在再查看Deployment的状态。
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```bash
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$ kubectl describe deployment filebeat-test
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Name: filebeat-test
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Namespace: default
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CreationTimestamp: Fri, 19 May 2017 15:12:28 +0800
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Labels: k8s-app=filebeat-test
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Selector: k8s-app=filebeat-test
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Replicas: 3 updated | 3 total | 3 available | 0 unavailable
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StrategyType: RollingUpdate
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MinReadySeconds: 0
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RollingUpdateStrategy: 1 max unavailable, 1 max surge
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Conditions:
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Type Status Reason
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---- ------ ------
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Available True MinimumReplicasAvailable
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Progressing True NewReplicaSetAvailable
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OldReplicaSets: <none>
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NewReplicaSet: filebeat-test-2365467882 (3/3 replicas created)
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Events:
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FirstSeen LastSeen Count From SubObjectPath Type ReasoMessage
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--------- -------- ----- ---- ------------- -------- ------------
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2h 8m 3 {deployment-controller } Normal ScalingReplicaSet Scaled down replica set filebeat-test-2365467882 to 2
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8m 8m 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set filebeat-test-2470325483 to 1
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8m 8m 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set filebeat-test-2470325483 to 2
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2h 1m 3 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set filebeat-test-2365467882 to 3
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1m 1m 1 {deployment-controller } Normal ScalingReplicaSet Scaled down replica set filebeat-test-2470325483 to 0
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```
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可以看到available的replica个数恢复成3了。
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其实在使用该命令的过程中，通过kubernetes dashboard的页面上查看Deployment的状态更直观，更加方便故障排查。
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这也是dashboard最大的优势，简单、直接、高效。
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