• client-go示例
    • kubernetes-client-go-sample

    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。