kubectl源码分析之set selector_kubectl set selector-优快云博客

type SetSelectorOptions struct {//set selector结构体
	// Bound
	ResourceBuilderFlags *genericclioptions.ResourceBuilderFlags
	PrintFlags           *genericclioptions.PrintFlags
	RecordFlags          *genericclioptions.RecordFlags
	dryrun               bool

	// set by args
	resources []string
	selector  *metav1.LabelSelector

	// computed
	WriteToServer  bool
	PrintObj       printers.ResourcePrinterFunc
	Recorder       genericclioptions.Recorder
	ResourceFinder genericclioptions.ResourceFinder

	// set at initialization
	genericclioptions.IOStreams
}

func NewSelectorOptions(streams genericclioptions.IOStreams) *SetSelectorOptions {
	return &SetSelectorOptions{//初始化结构体
		ResourceBuilderFlags: genericclioptions.NewResourceBuilderFlags().
			WithScheme(scheme.Scheme).
			WithAll(false).
			WithLocal(false).
			WithLatest(),
		PrintFlags:  genericclioptions.NewPrintFlags("selector updated").WithTypeSetter(scheme.Scheme),
		RecordFlags: genericclioptions.NewRecordFlags(),

		Recorder: genericclioptions.NoopRecorder{},

		IOStreams: streams,
	}
}

//创建set selector命令
func NewCmdSelector(f cmdutil.Factory, streams genericclioptions.IOStreams) *cobra.Command {
	o := NewSelectorOptions(streams)//初始化结构体

	cmd := &cobra.Command{//创建cobra命令
		Use:                   "selector (-f FILENAME | TYPE NAME) EXPRESSIONS [--resource-version=version]",
		DisableFlagsInUseLine: true,
		Short:                 i18n.T("Set the selector on a resource"),
		Long:                  fmt.Sprintf(selectorLong, validation.LabelValueMaxLength),
		Example:               selectorExample,
		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.RunSelector())//运行
		},
	}

	o.ResourceBuilderFlags.AddFlags(cmd.Flags())//构造资源flag
	o.PrintFlags.AddFlags(cmd)//设置打印flag
	o.RecordFlags.AddFlags(cmd)//设置record选项

	cmd.Flags().String("resource-version", "", "If non-empty, the selectors update will only succeed if this is the current resource-version for the object. Only valid when specifying a single resource.")//设置resource version选项
	cmdutil.AddDryRunFlag(cmd)//设置干跑选项

	return cmd
}

//准备函数
func (o *SetSelectorOptions) Complete(f cmdutil.Factory, cmd *cobra.Command, args []string) error {
	var err error

	o.RecordFlags.Complete(cmd)//record flag complete
	o.Recorder, err = o.RecordFlags.ToRecorder()//record flag转recorder
	if err != nil {
		return err
	}

	o.dryrun = cmdutil.GetDryRunFlag(cmd)//设置干跑

	o.resources, o.selector, err = getResourcesAndSelector(args)//设置resource和selector
	if err != nil {
		return err
	}

	o.ResourceFinder = o.ResourceBuilderFlags.ToBuilder(f, o.resources)//设置resorucebuilder
	o.WriteToServer = !(*o.ResourceBuilderFlags.Local || o.dryrun)//判断是否写到服务器

	if o.dryrun {
		o.PrintFlags.Complete("%s (dry run)")
	}
	printer, err := o.PrintFlags.ToPrinter()//打印选项转printer
	if err != nil {
		return err
	}
	o.PrintObj = printer.PrintObj//设置printObj函数

	return err
}

func (o *SetSelectorOptions) Validate() error {
	if o.selector == nil {//selector不能为空
		return fmt.Errorf("one selector is required")
	}
	return nil
}

//运行
func (o *SetSelectorOptions) RunSelector() error {
	r := o.ResourceFinder.Do()//从builder获取result

	return r.Visit(func(info *resource.Info, err error) error {//访问result
		patch := &Patch{Info: info}//构造patch
		CalculatePatch(patch, scheme.DefaultJSONEncoder(), func(obj runtime.Object) ([]byte, error) {//计算patch
			selectErr := updateSelectorForObject(info.Object, *o.selector)//更新对象selector
			if selectErr != nil {
				return nil, selectErr
			}

			// record this change (for rollout history)
			if err := o.Recorder.Record(patch.Info.Object); err != nil {//判断是否更新change-cause注解
				klog.V(4).Infof("error recording current command: %v", err)
			}

			return runtime.Encode(scheme.DefaultJSONEncoder(), info.Object)//obj转json
		})

		if patch.Err != nil {
			return patch.Err
		}
		if !o.WriteToServer {//如果不写到服务器则打印
			return o.PrintObj(info.Object, o.Out)
		}

		actual, err := resource.NewHelper(info.Client, info.Mapping).Patch(info.Namespace, info.Name, types.StrategicMergePatchType, patch.Patch, nil)//应用patch到服务器
		if err != nil {
			return err
		}

		return o.PrintObj(actual, o.Out)//打印对象
	})
}

//更新对象selector
func updateSelectorForObject(obj runtime.Object, selector metav1.LabelSelector) error {
	copyOldSelector := func() (map[string]string, error) {//获取selector
		if len(selector.MatchExpressions) > 0 {//不支持matchExpression
			return nil, fmt.Errorf("match expression %v not supported on this object", selector.MatchExpressions)
		}
		dst := make(map[string]string)
		for label, value := range selector.MatchLabels {//遍历matchLabels
			dst[label] = value//设置labels map
		}
		return dst, nil//返回labels map
	}
	var err error
	switch t := obj.(type) {//判断对象
	case *v1.Service://如果是service
		t.Spec.Selector, err = copyOldSelector()//设置selector
	default:
		err = fmt.Errorf("setting a selector is only supported for Services")
	}
	return err
}