client-go示例

    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 。

    代码如下：

    我们使用文件认证连接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.         If non-empty, write log files in this directory
    19.   -logtostderr
    20.         log to standard error instead of files
    21.   -stderrthreshold value
    22.         logs at or above this threshold go to stderr
    23.   -v value
    24.         log level for V logs
    25.   -vmodule value
    26.         comma-separated list of pattern=N settings for file-filtered logging

    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. Conditions:
    11.   Type        Status    Reason
    12.   ----        ------    ------
    13.   Available     True    MinimumReplicasAvailable
    14.   Progressing     True    ReplicaSetUpdated
    15. OldReplicaSets:    filebeat-test-2365467882 (2/2 replicas created)
    16. NewReplicaSet:    filebeat-test-2470325483 (2/2 replicas created)
    17. Events:
    18.   FirstSeen    LastSeen    Count    From                SubObjectPath    Type        ReasoMessage
    19.   ---------    --------    -----    ----                -------------    --------    ------------
    20.   2h        1m        3    {deployment-controller }            Normal        ScalingReplicaSet    Scaled down replica set filebeat-test-2365467882 to 2
    21.   1m        1m        1    {deployment-controller }            Normal        ScalingReplicaSet    Scaled up replica set filebeat-test-2470325483 to 1
    22.   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。

    我们可以看到有两个pod正在拉取image。

    还原为原先的镜像

    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。

    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。

    这也是dashboard最大的优势，简单、直接、高效。