kubectl源码分析之rollout undo

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 目前刚开始写一个月，一共写了18篇原创文章，文章目录如下：

​​istio多集群探秘，部署了50次多集群后我得出的结论​​

​​istio多集群链路追踪，附实操视频​​

​​istio防故障利器，你知道几个,istio新手不要读，太难！​​

​​istio业务权限控制，原来可以这么玩​​

​​istio实现非侵入压缩，微服务之间如何实现压缩​​

​​不懂envoyfilter也敢说精通istio系列-http-rbac-不要只会用AuthorizationPolicy配置权限​​

​​不懂envoyfilter也敢说精通istio系列-02-http-corsFilter-不要只会vs​​

​​不懂envoyfilter也敢说精通istio系列-03-http-csrf filter-再也不用再代码里写csrf逻辑了​​

​​不懂envoyfilter也敢说精通istio系列http-jwt_authn-不要只会RequestAuthorization​​

​​不懂envoyfilter也敢说精通istio系列-05-fault-filter-故障注入不止是vs​​

​​不懂envoyfilter也敢说精通istio系列-06-http-match-配置路由不只是vs​​

​​不懂envoyfilter也敢说精通istio系列-07-负载均衡配置不止是dr​​

​​不懂envoyfilter也敢说精通istio系列-08-连接池和断路器​​

​​不懂envoyfilter也敢说精通istio系列-09-http-route filter​​

​​不懂envoyfilter也敢说精通istio系列-network filter-redis proxy​​

​​不懂envoyfilter也敢说精通istio系列-network filter-HttpConnectionManager​​

​​不懂envoyfilter也敢说精通istio系列-ratelimit-istio ratelimit完全手册​​

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type UndoOptions struct {//undo结构体
  PrintFlags *genericclioptions.PrintFlags
  ToPrinter  func(string) (printers.ResourcePrinter, error)

  Builder          func() *resource.Builder
  ToRevision       int64
  DryRun           bool
  Resources        []string
  Namespace        string
  EnforceNamespace bool
  RESTClientGetter genericclioptions.RESTClientGetter

  resource.FilenameOptions
  genericclioptions.IOStreams
}

func NewRolloutUndoOptions(streams genericclioptions.IOStreams) *UndoOptions {
  return &UndoOptions{//初始化结构体
    PrintFlags: genericclioptions.NewPrintFlags("rolled back").WithTypeSetter(scheme.Scheme),
    IOStreams:  streams,
    ToRevision: int64(0),
  }
}

//创建undo命令
func NewCmdRolloutUndo(f cmdutil.Factory, streams genericclioptions.IOStreams) *cobra.Command {
  o := NewRolloutUndoOptions(streams)//初始化结构体

  validArgs := []string{"deployment", "daemonset", "statefulset"}

  cmd := &cobra.Command{//创建cobra命令
    Use:                   "undo (TYPE NAME | TYPE/NAME) [flags]",
    DisableFlagsInUseLine: true,
    Short:                 i18n.T("Undo a previous rollout"),
    Long:                  undoLong,
    Example:               undoExample,
    Run: func(cmd *cobra.Command, args []string) {
      cmdutil.CheckErr(o.Complete(f, cmd, args))//准备
      cmdutil.CheckErr(o.Validate())//校验
      cmdutil.CheckErr(o.RunUndo())//运行
    },
    ValidArgs: validArgs,//有效参数
  }

  cmd.Flags().Int64Var(&o.ToRevision, "to-revision", o.ToRevision, "The revision to rollback to. Default to 0 (last revision).")//to-revision选项
  usage := "identifying the resource to get from a server."
  cmdutil.AddFilenameOptionFlags(cmd, &o.FilenameOptions, usage)//文件选项
  cmdutil.AddDryRunFlag(cmd)//干跑选项
  o.PrintFlags.AddFlags(cmd)//打印选项
  return cmd
}

//准备函数
func (o *UndoOptions) Complete(f cmdutil.Factory, cmd *cobra.Command, args []string) error {
  o.Resources = args//设置资源
  o.DryRun = cmdutil.GetDryRunFlag(cmd)//设置干跑

  var err error
  if o.Namespace, o.EnforceNamespace, err = f.ToRawKubeConfigLoader().Namespace(); err != nil {//设置Namespace和EnforceNamespace
    return err
  }

  o.ToPrinter = func(operation string) (printers.ResourcePrinter, error) {//printflag转printer函数
    o.PrintFlags.NamePrintFlags.Operation = operation
    if o.DryRun {
      o.PrintFlags.Complete("%s (dry run)")
    }
    return o.PrintFlags.ToPrinter()
  }

  o.RESTClientGetter = f//设置RestClientGetter
  o.Builder = f.NewBuilder//设置Builder

  return err
}

//校验函数
func (o *UndoOptions) Validate() error {
  if len(o.Resources) == 0 && cmdutil.IsFilenameSliceEmpty(o.Filenames, o.Kustomize) {//资源和文件至少有一个
    return fmt.Errorf("required resource not specified")
  }
  return nil
}

//运行
func (o *UndoOptions) RunUndo() error {
  r := o.Builder().
    WithScheme(scheme.Scheme, scheme.Scheme.PrioritizedVersionsAllGroups()...).
    NamespaceParam(o.Namespace).DefaultNamespace().
    FilenameParam(o.EnforceNamespace, &o.FilenameOptions).
    ResourceTypeOrNameArgs(true, o.Resources...).
    ContinueOnError().
    Latest().
    Flatten().
    Do()//构造REsult对象
  if err := r.Err(); err != nil {
    return err
  }

  err := r.Visit(func(info *resource.Info, err error) error {//visit Result
    if err != nil {
      return err
    }
    rollbacker, err := polymorphichelpers.RollbackerFn(o.RESTClientGetter, info.ResourceMapping())//获取回滚器
    if err != nil {
      return err
    }

    result, err := rollbacker.Rollback(info.Object, nil, o.ToRevision, o.DryRun)//执行回滚
    if err != nil {
      return err
    }

    printer, err := o.ToPrinter(result)//print flag转printer
    if err != nil {
      return err
    }

    return printer.PrintObj(info.Object, o.Out)//打印结果
  })

  return err
}

//执行回滚
func (r *DeploymentRollbacker) Rollback(obj runtime.Object, updatedAnnotations map[string]string, toRevision int64, dryRun bool) (string, error) {
  if toRevision < 0 {//回滚范本不能小于0
    return "", revisionNotFoundErr(toRevision)
  }
  accessor, err := meta.Accessor(obj)//访问对象
  if err != nil {
    return "", fmt.Errorf("failed to create accessor for kind %v: %s", obj.GetObjectKind(), err.Error())
  }
  name := accessor.GetName()//获取obj名称
  namespace := accessor.GetNamespace()//获取obj namespace

  // TODO: Fix this after kubectl has been removed from core. It is not possible to convert the runtime.Object
  // to the external appsv1 Deployment without round-tripping through an internal version of Deployment. We're
  // currently getting rid of all internal versions of resources. So we specifically request the appsv1 version
  // here. This follows the same pattern as for DaemonSet and StatefulSet.
  deployment, err := r.c.AppsV1().Deployments(namespace).Get(name, metav1.GetOptions{})//获取deployment
  if err != nil {
    return "", fmt.Errorf("failed to retrieve Deployment %s: %v", name, err)
  }

  rsForRevision, err := deploymentRevision(deployment, r.c, toRevision)//获取对应版本的rs
  if err != nil {
    return "", err
  }
  if dryRun {//如果是干盘返回
    return printTemplate(&rsForRevision.Spec.Template)
  }
  if deployment.Spec.Paused {//如果deploy已经暂停，返回错误
    return "", fmt.Errorf("you cannot rollback a paused deployment; resume it first with 'kubectl rollout resume deployment/%s' and try again", name)
  }

  // Skip if the revision already matches current Deployment
  if equalIgnoreHash(&rsForRevision.Spec.Template, &deployment.Spec.Template) {//如果要更新的rs的template和现在的deploy的template一样则，返回提示template一样
    return fmt.Sprintf("%s (current template already matches revision %d)", rollbackSkipped, toRevision), nil
  }

  // remove hash label before patching back into the deployment
  delete(rsForRevision.Spec.Template.Labels, appsv1.DefaultDeploymentUniqueLabelKey)//删除rs的pod-template-hash标签

  // compute deployment annotations
  annotations := map[string]string{}//设置annotation
  for k := range annotationsToSkip {
    if v, ok := deployment.Annotations[k]; ok {
      annotations[k] = v
    }
  }
  for k, v := range rsForRevision.Annotations {
    if !annotationsToSkip[k] {
      annotations[k] = v
    }
  }

  // make patch to restore
  patchType, patch, err := getDeploymentPatch(&rsForRevision.Spec.Template, annotations)//获取patch
  if err != nil {
    return "", fmt.Errorf("failed restoring revision %d: %v", toRevision, err)
  }

  // Restore revision
  if _, err = r.c.AppsV1().Deployments(namespace).Patch(name, patchType, patch); err != nil {//应用patch到服务端
    return "", fmt.Errorf("failed restoring revision %d: %v", toRevision, err)
  }
  return rollbackSuccess, nil//返回成功
}