Kubernetes Runtime在vendor/k8s.io/apimachinery/pkg/runtime中实现，它提供了通用资源类型runtime.Object。
    runtime.Object是Kubernetes类型系统的基石。
    资源对象（Resource Object）都有一个共同的结构runtime.Object。
    runtime.Object被设计为接口，作为资源对象的通用资源对象。

    1.      Pod资源对象可以和runtime.Object相互转化   Deployment资源对象可以和runtime.Object相互转化
    2. ---------------              ------------------                 --------------------
    3. | &core.Pod{} |    <---->    | runtime.Object |    <------>     | &apps.Deployment |
    4. ---------------              ------------------                 --------------------

    runtime.Object结构如下：
    代码路径：vendor/k8s.io/apimachinery/pkg/runtime/interfaces.go

    1. // Object interface must be supported by all API types registered with Scheme. Since objects in a scheme are
    2. // expected to be serialized to the wire, the interface an Object must provide to the Scheme allows
    3. // serializers to set the kind, version, and group the object is represented as. An Object may choose
    4. // to return a no-op ObjectKindAccessor in cases where it is not expected to be serialized.
    5. type Object interface {
    6.     GetObjectKind() schema.ObjectKind
    7.     DeepCopyObject() Object
    8. }

    代码路径：vendor/k8s.io/apimachinery/pkg/runtime/schema/interfaces.go

    1. // All objects that are serialized from a Scheme encode their type information. This interface is used
    2. // by serialization to set type information from the Scheme onto the serialized version of an object.
    3. // For objects that cannot be serialized or have unique requirements, this interface may be a no-op.
    4. type ObjectKind interface {
    5.     // SetGroupVersionKind sets or clears the intended serialized kind of an object. Passing kind nil
    6.     // should clear the current setting.
    7.     SetGroupVersionKind(kind GroupVersionKind)
    8.     // GroupVersionKind returns the stored group, version, and kind of an object, or an empty struct
    9.     // if the object does not expose or provide these fields.
    10.     GroupVersionKind() GroupVersionKind
    11. }

    runtime.Object提供了两个方法

    • GetObjectKind() schema.ObjectKind：用于设置并返回GroupVersionKind
    • DeepCopyObject() Object：用于深拷贝当前资源对象并返回

      深拷贝将数据结构重新克隆一份，不与原始对象共享任何内容。

    如何确认一个资源队形是否可以转换为runtime.Object通用资源对象？
    需要确认资源对象是否实现了GetObjectKind和DeepCopyObject方法。
    Kubernetes的每一个资源对象都嵌入了metav1.TypeMeta类型，metav1.TypeMeta实现了GetObjectKind方法，所有资源对象都实现了该方法。
    Kubernetes的每一个资源对象都实现了DeepCodeObject方法，该方法一般被定义在zz_generated.deepcopy.go文件中。

    Kubernetes的任意资源对象可以通过runtime.Object存储他的类型，并允许深度复制操作。
    下面的代码示例将资源对象转换为runtime.Object，然后再转换回资源对象

    1. package main
    3. import (
    4.     "reflect"
    6.     metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
    7.     "k8s.io/apimachinery/pkg/runtime"
    8.     "k8s.io/kubernetes/pkg/apis/core"
    9. )
    11. func main() {
    13.     pod := &core.Pod{
    14.         TypeMeta: metav1.TypeMeta{
    15.             Kind: "Pod",
    16.         },
    17.         ObjectMeta: metav1.ObjectMeta{
    18.             Labels: map[string]string{"foo": "foo"},
    19.         },
    20.     }
    22.     obj := runtime.Object(pod)
    24.     pod2, ok := obj.(*core.Pod)
    26.     if !ok {
    27.         panic("unexpected")
    28.     }
    30.     if !reflect.DeepEqual(pod, pod2) {
    31.         panic("unexpected")
    32.     }
    33. }

    导入k8s.io/kubernetes依赖时，会遇到类似下面的错误

    1. k8s.io/api@v0.0.0: reading k8s.io/api/go.mod at revision v0.0.0: unknown revision v0.0.0

    使用replace命令解决

    1. replace (
    2.     k8s.io/api => k8s.io/api v0.0.0-20190620084959-7cf5895f2711
    3.     k8s.io/apiextensions-apiserver => k8s.io/apiextensions-apiserver v0.0.0-20190620085554-14e95df34f1f
    4.     k8s.io/apimachinery => k8s.io/apimachinery v0.0.0-20190612205821-1799e75a0719
    5.     k8s.io/apiserver => k8s.io/apiserver v0.0.0-20190620085212-47dc9a115b18
    6.     k8s.io/cli-runtime => k8s.io/cli-runtime v0.0.0-20190620085706-2090e6d8f84c
    7.     k8s.io/client-go => k8s.io/client-go v0.0.0-20190620085101-78d2af792bab
    8.     k8s.io/cloud-provider => k8s.io/cloud-provider v0.0.0-20190620090043-8301c0bda1f0
    9.     k8s.io/cluster-bootstrap => k8s.io/cluster-bootstrap v0.0.0-20190620090013-c9a0fc045dc1
    10.     k8s.io/code-generator => k8s.io/code-generator v0.0.0-20190612205613-18da4a14b22b
    11.     k8s.io/component-base => k8s.io/component-base v0.0.0-20190620085130-185d68e6e6ea
    12.     k8s.io/cri-api => k8s.io/cri-api v0.0.0-20190531030430-6117653b35f1
    13.     k8s.io/csi-translation-lib => k8s.io/csi-translation-lib v0.0.0-20190620090116-299a7b270edc
    14.     k8s.io/kube-aggregator => k8s.io/kube-aggregator v0.0.0-20190620085325-f29e2b4a4f84
    15.     k8s.io/kube-controller-manager => k8s.io/kube-controller-manager v0.0.0-20190620085942-b7f18460b210
    16.     k8s.io/kube-proxy => k8s.io/kube-proxy v0.0.0-20190620085809-589f994ddf7f
    17.     k8s.io/kube-scheduler => k8s.io/kube-scheduler v0.0.0-20190620085912-4acac5405ec6
    18.     k8s.io/kubectl => k8s.io/kubectl v0.0.0-20201008135616-e95e378e5972
    19.     k8s.io/kubelet => k8s.io/kubelet v0.0.0-20190620085838-f1cb295a73c9
    20.     k8s.io/legacy-cloud-providers => k8s.io/legacy-cloud-providers v0.0.0-20190620090156-2138f2c9de18
    21.     k8s.io/metrics => k8s.io/metrics v0.0.0-20190620085625-3b22d835f165
    22.     k8s.io/sample-apiserver => k8s.io/sample-apiserver v0.0.0-20190620085408-1aef9010884e
    23. )