client-go示例

访问kubernetes集群有几下几种方式：

方式 特点 支持者
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
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
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
client-python python客户端，kubernetes-incubator 官方支持
Java client fabric8中的一部分，kubernetes的java客户端 redhat

下面，我们基于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 。

kubernetes-client-go-sample

代码如下：

  1. package main
  3. import (
  4.     "flag"
  5.     "fmt"
  6.     "os"
  7.     "path/filepath"
  9.     "k8s.io/apimachinery/pkg/api/errors"
  10.     metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
  11.     "k8s.io/client-go/kubernetes"
  12.     "k8s.io/client-go/tools/clientcmd"
  13. )
  15. func main() {
  16.     var kubeconfig *string
  17.     if home := homeDir(); home != "" {
  18.         kubeconfig = flag.String("kubeconfig", filepath.Join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
  19.     } else {
  20.         kubeconfig = flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
  21.     }
  22.     deploymentName := flag.String("deployment", "", "deployment name")
  23.     imageName := flag.String("image", "", "new image name")
  24.     appName := flag.String("app", "app", "application name")
  26.     flag.Parse()
  27.     if *deploymentName == "" {
  28.         fmt.Println("You must specify the deployment name.")
  29.         os.Exit(0)
  30.     }
  31.     if *imageName == "" {
  32.         fmt.Println("You must specify the new image name.")
  33.         os.Exit(0)
  34.     }
  35.     // use the current context in kubeconfig
  36.     config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
  37.     if err != nil {
  38.         panic(err.Error())
  39.     }
  41.     // create the clientset
  42.     clientset, err := kubernetes.NewForConfig(config)
  43.     if err != nil {
  44.         panic(err.Error())
  45.     }
  46.     deployment, err := clientset.AppsV1beta1().Deployments("default").Get(*deploymentName, metav1.GetOptions{})
  47.     if err != nil {
  48.         panic(err.Error())
  49.     }
  50.     if errors.IsNotFound(err) {
  51.         fmt.Printf("Deployment not found\n")
  52.     } else if statusError, isStatus := err.(*errors.StatusError); isStatus {
  53.         fmt.Printf("Error getting deployment%v\n", statusError.ErrStatus.Message)
  54.     } else if err != nil {
  55.         panic(err.Error())
  56.     } else {
  57.         fmt.Printf("Found deployment\n")
  58.         name := deployment.GetName()
  59.         fmt.Println("name ->", name)
  60.         containers := &deployment.Spec.Template.Spec.Containers
  61.         found := false
  62.         for i := range *containers {
  63.             c := *containers
  64.             if c[i].Name == *appName {
  65.                 found = true
  66.                 fmt.Println("Old image ->", c[i].Image)
  67.                 fmt.Println("New image ->", *imageName)
  68.                 c[i].Image = *imageName
  69.             }
  70.         }
  71.         if found == false {
  72.             fmt.Println("The application container not exist in the deployment pods.")
  73.             os.Exit(0)
  74.         }
  75.         _, err := clientset.AppsV1beta1().Deployments("default").Update(deployment)
  76.         if err != nil {
  77.             panic(err.Error())
  78.         }
  79.     }
  80. }
  82. func homeDir() string {
  83.     if h := os.Getenv("HOME"); h != "" {
  84.         return h
  85.     }
  86.     return os.Getenv("USERPROFILE") // windows
  87. }

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。

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。

编译运行

  1. $ go get github.com/rootsongjc/kubernetes-client-go-sample
  2. $ cd $GOPATH/src/github.com/rootsongjc/kubernetes-client-go-sample
  3. $ make
  4. $ ./update-deployment-image -h
  5. Usage of ./update-deployment-image:
  6.   -alsologtostderr
  7.         log to standard error as well as files
  8.   -app string
  9.         application name (default "app")
  10.   -deployment string
  11.         deployment name
  12.   -image string
  13.         new image name
  14.   -kubeconfig string
  15.         (optional) absolute path to the kubeconfig file (default "/Users/jimmy/.kube/config")
  16.   -log_backtrace_at value
  17.         when logging hits line file:N, emit a stack trace
  18.   -log_dir string
  19.         If non-empty, write log files in this directory
  20.   -logtostderr
  21.         log to standard error instead of files
  22.   -stderrthreshold value
  23.         logs at or above this threshold go to stderr
  24.   -v value
  25.         log level for V logs
  26.   -vmodule value
  27.         comma-separated list of pattern=N settings for file-filtered logging

使用不存在的image更新

  1.  $ ./update-deployment-image -deployment filebeat-test -image harbor-001.jimmysong.io/library/analytics-docker-test:Build_9 
  2. Found deployment
  3. name -> filebeat-test
  4. Old image -> harbor-001.jimmysong.io/library/analytics-docker-test:Build_8
  5. New image -> harbor-001.jimmysong.io/library/analytics-docker-test:Build_9

查看Deployment的event。

  1. $ kubectl describe deployment filebeat-test   
  2. Name:            filebeat-test
  3. Namespace:        default
  4. CreationTimestamp:    Fri, 19 May 2017 15:12:28 +0800
  5. Labels:            k8s-app=filebeat-test
  6. Selector:        k8s-app=filebeat-test
  7. Replicas:        2 updated | 3 total | 2 available | 2 unavailable
  8. StrategyType:        RollingUpdate
  9. MinReadySeconds:    0
  10. RollingUpdateStrategy:    1 max unavailable, 1 max surge
  11. Conditions:
  12.   Type        Status    Reason
  13.   ----        ------    ------
  14.   Available     True    MinimumReplicasAvailable
  15.   Progressing     True    ReplicaSetUpdated
  16. OldReplicaSets:    filebeat-test-2365467882 (2/2 replicas created)
  17. NewReplicaSet:    filebeat-test-2470325483 (2/2 replicas created)
  18. Events:
  19.   FirstSeen    LastSeen    Count    From                SubObjectPath    Type        ReasoMessage
  20.   ---------    --------    -----    ----                -------------    --------    ------------
  21.   2h        1m        3    {deployment-controller }            Normal        ScalingReplicaSet    Scaled down replica set filebeat-test-2365467882 to 2
  22.   1m        1m        1    {deployment-controller }            Normal        ScalingReplicaSet    Scaled up replica set filebeat-test-2470325483 to 1
  23.   1m        1m        1    {deployment-controller }            Normal        ScalingReplicaSet    Scaled up replica set filebeat-test-2470325483 to 2

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。

这是因为我们指定的镜像不存在，查看Deployment的pod的状态。

  1. $ kubectl get pods -l k8s-app=filebeat-test
  2. NAME                             READY     STATUS             RESTARTS   AGE
  3. filebeat-test-2365467882-4zwx8   2/2       Running            0          33d
  4. filebeat-test-2365467882-rqskl   2/2       Running            0          33d
  5. filebeat-test-2470325483-6vjbw   1/2       ImagePullBackOff   0          4m
  6. filebeat-test-2470325483-gc14k   1/2       ImagePullBackOff   0          4m

我们可以看到有两个pod正在拉取image。

还原为原先的镜像

将image设置为原来的镜像。

  1. $ ./update-deployment-image -deployment filebeat-test -image harbor-001.jimmysong.io/library/analytics-docker-test:Build_8
  2. Found deployment
  3. name -> filebeat-test
  4. Old image -> harbor-001.jimmysong.io/library/analytics-docker-test:Build_9
  5. New image -> harbor-001.jimmysong.io/library/analytics-docker-test:Build_8

现在再查看Deployment的状态。

  1. $ kubectl describe deployment filebeat-test   
  2. Name:            filebeat-test
  3. Namespace:        default
  4. CreationTimestamp:    Fri, 19 May 2017 15:12:28 +0800
  5. Labels:            k8s-app=filebeat-test
  6. Selector:        k8s-app=filebeat-test
  7. Replicas:        3 updated | 3 total | 3 available | 0 unavailable
  8. StrategyType:        RollingUpdate
  9. MinReadySeconds:    0
  10. RollingUpdateStrategy:    1 max unavailable, 1 max surge
  11. Conditions:
  12.   Type        Status    Reason
  13.   ----        ------    ------
  14.   Available     True    MinimumReplicasAvailable
  15.   Progressing     True    NewReplicaSetAvailable
  16. OldReplicaSets:    <none>
  17. NewReplicaSet:    filebeat-test-2365467882 (3/3 replicas created)
  18. Events:
  19.   FirstSeen    LastSeen    Count    From                SubObjectPath    Type        ReasoMessage
  20.   ---------    --------    -----    ----                -------------    --------    ------------
  21.   2h        8m        3    {deployment-controller }            Normal        ScalingReplicaSet    Scaled down replica set filebeat-test-2365467882 to 2
  22.   8m        8m        1    {deployment-controller }            Normal        ScalingReplicaSet    Scaled up replica set filebeat-test-2470325483 to 1
  23.   8m        8m        1    {deployment-controller }            Normal        ScalingReplicaSet    Scaled up replica set filebeat-test-2470325483 to 2
  24.   2h        1m        3    {deployment-controller }            Normal        ScalingReplicaSet    Scaled up replica set filebeat-test-2365467882 to 3
  25.   1m        1m        1    {deployment-controller }            Normal        ScalingReplicaSet    Scaled down replica set filebeat-test-2470325483 to 0

可以看到available的replica个数恢复成3了。

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。

使用kubernetes dashboard进行故障排查

这也是dashboard最大的优势，简单、直接、高效。