kubernetes - 如何使用分数格式(即 X/Y)为自定义资源显示 kubectl 列

Question

在 Kubernetes 中，是否可以使用 CRD 的“additionalPrinterColumns”字段使用分数格式(即 X/Y)显示列？

更准确地说，我希望 kubectl 使用与下面的 READY 字段相同的格式显示 CR 字段的描述:

kubectl get statefulsets.apps <my-statefulset>
NAME              READY   AGE
<my-statefulset>  2/2     18m

能否提供“additionalPrinterColumns”部分的内容？

Answer 1

不幸的是，additionalPrinterColumns 仅支持 Simple JsonPath，因此我们不能在 JsonPath 中使用 .status.readyReplicas/.status.replicas，并且 GET 操作由 kube-apiserver 处理，因此 Operator 不参与 GET 操作。因此，我建议的最简单方法是在 .status 中创建一个名为 ready 的新字段，其值为“readyReplicas/replicas”，并在每次更新 readyReplicas 和副本时更新它。

然后放在additionalPrinterColumns下面

   additionalPrinterColumns:
    - jsonPath: .status.ready
      name: Ready
      type: string

对于 StatefulSet，他们在 https://github.com/kubernetes/kubernetes/blob/master/pkg/printers/internalversion/printers.go 中使用以下代码打印 READY 列的值

    statefulSetColumnDefinitions := []metav1.TableColumnDefinition{
        {Name: "Name", Type: "string", Format: "name", Description: metav1.ObjectMeta{}.SwaggerDoc()["name"]},
        {Name: "Ready", Type: "string", Description: "Number of the pod with ready state"},
        {Name: "Age", Type: "string", Description: metav1.ObjectMeta{}.SwaggerDoc()["creationTimestamp"]},
        {Name: "Containers", Type: "string", Priority: 1, Description: "Names of each container in the template."},
        {Name: "Images", Type: "string", Priority: 1, Description: "Images referenced by each container in the template."},
    }
    h.TableHandler(statefulSetColumnDefinitions, printStatefulSet)
    h.TableHandler(statefulSetColumnDefinitions, printStatefulSetList)


func printStatefulSet(obj *apps.StatefulSet, options printers.GenerateOptions) ([]metav1.TableRow, error) {
    row := metav1.TableRow{
        Object: runtime.RawExtension{Object: obj},
    }
    desiredReplicas := obj.Spec.Replicas
    readyReplicas := obj.Status.ReadyReplicas
    createTime := translateTimestampSince(obj.CreationTimestamp)
    row.Cells = append(row.Cells, obj.Name, fmt.Sprintf("%d/%d", int64(readyReplicas), int64(desiredReplicas)), createTime)
    if options.Wide {
        names, images := layoutContainerCells(obj.Spec.Template.Spec.Containers)
        row.Cells = append(row.Cells, names, images)
    }
    return []metav1.TableRow{row}, nil
}

func printStatefulSetList(list *apps.StatefulSetList, options printers.GenerateOptions) ([]metav1.TableRow, error) {
    rows := make([]metav1.TableRow, 0, len(list.Items))
    for i := range list.Items {
        r, err := printStatefulSet(&list.Items[i], options)
        if err != nil {
            return nil, err
        }
        rows = append(rows, r...)
    }
    return rows, nil
}