深入 kubernetes API 的源码实现

apiVersion: v1
kind: Pod
metadata:
  name: webserver
  labels:
    app: webserver
spec:
  containers:
  - name: webserver
    image: nginx
    ports:
    - containerPort: 80

// source code from https://github.com/kubernetes/api/blob/master/core/v1/types.go
type Pod struct {
    // 从TypeMeta字段名可以看出该字段定义Pod类型的元信息，类似于面向对象编程里面
    // Class本身的元信息，类似于Pod类型的API分组、API版本等
    metav1.TypeMeta `json:",inline"`
    // ObjectMeta字段定义单个Pod对象的元信息。每个kubernetes资源对象都有自己的元信息，
    // 例如名字、命名空间、标签、注释等等，kuberentes把这些公共的属性提取出来就是
    // metav1.ObjectMeta，成为了API对象类型的父类
    metav1.ObjectMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"`
    // PodSpec表示Pod类型的对象定义规范，最为代表性的就是CPU、内存的资源使用。
    // 这个字段和YAML中spec字段对应
    Spec PodSpec `json:"spec,omitempty" protobuf:"bytes,2,opt,name=spec"`
    // PodStatus表示Pod的状态，比如是运行还是挂起、Pod的IP等等。Kubernetes会根据pod在
    // 集群中的实际状态来更新PodStatus字段
    Status PodStatus `json:"status,omitempty" protobuf:"bytes,3,opt,name=status"`
}

// source code from https://github.com/kubernetes/api/blob/master/core/v1/types.go
type PodList struct {
    // PodList也需要继承metav1.TypeMeta，毕竟对象列表也好、单体对象也好都需要类型属性。
    // PodList比[]Pod类型在yaml或者json表达上多了类型描述，当需要根据YAML构建对象列表的时候，
    // 就可以根据类型描述反序列成为PodList。而[]Pod则不可以，必须确保YAML就是[]Pod序列化的
    // 结果，否则就会报错。这就无法实现一个通用的对象序列化/反序列化。
    metav1.TypeMeta `json:",inline"`
    // 与Pod不同，PodList继承了metav1.ListMeta，metav1.ListMeta是所有资源对象列表类型的父类，
    // ListMeta定义了所有对象列表类型实例的公共属性。
    metav1.ListMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"`
    // Items字段则是PodList定义的本质，表示Pod资源对象的列表，所以说PodList就是[]Pod基础上加了一些
    // 跟类型和对象列表相关的元信息
    Items []Pod `json:"items" protobuf:"bytes,2,rep,name=items"`

// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/types.go
//
// TypeMeta describes an individual object in an API response or request
// with strings representing the type of the object and its API schema version.
// Structures that are versioned or persisted should inline TypeMeta.
type TypeMeta struct {
	// Kind is a string value representing the REST resource this object represents.
	// Servers may infer this from the endpoint the client submits requests to.
	// Cannot be updated.
	Kind string `json:"kind,omitempty" protobuf:"bytes,1,opt,name=kind"`

	// APIVersion defines the versioned schema of this representation of an object.
	// Servers should convert recognized schemas to the latest internal value, and
	// may reject unrecognized values.
	APIVersion string `json:"apiVersion,omitempty" protobuf:"bytes,2,opt,name=apiVersion"`
}

// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/runtime/schema/interfaces.go
//
// All objects that are serialized from a Scheme encode their type information. This interface is used
// by serialization to set type information from the Scheme onto the serialized version of an object.
// For objects that cannot be serialized or have unique requirements, this interface may be a no-op.
type ObjectKind interface {
	// SetGroupVersionKind sets or clears the intended serialized kind of an object. Passing kind nil
	// should clear the current setting.
	SetGroupVersionKind(kind GroupVersionKind)
	// GroupVersionKind returns the stored group, version, and kind of an object, or an empty struct
	// if the object does not expose or provide these fields.
	GroupVersionKind() GroupVersionKind
}

// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/types.go

func (obj *TypeMeta) GetObjectKind() schema.ObjectKind { return obj }

// SetGroupVersionKind satisfies the ObjectKind interface for all objects that embed TypeMeta
func (obj *TypeMeta) SetGroupVersionKind(gvk schema.GroupVersionKind) {
	obj.APIVersion, obj.Kind = gvk.ToAPIVersionAndKind()
}

// GroupVersionKind satisfies the ObjectKind interface for all objects that embed TypeMeta
func (obj *TypeMeta) GroupVersionKind() schema.GroupVersionKind {
	return schema.FromAPIVersionAndKind(obj.APIVersion, obj.Kind)
}

// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/types.go
//
// ObjectMeta is metadata that all persisted resources must have, which includes all objects
// users must create.
type ObjectMeta struct {
	// Name must be unique within a namespace. Is required when creating resources, although
	// some resources may allow a client to request the generation of an appropriate name
	// automatically. Name is primarily intended for creation idempotence and configuration
	// definition.
	Name string `json:"name,omitempty" protobuf:"bytes,1,opt,name=name"`

	// GenerateName is an optional prefix, used by the server, to generate a unique
    // name ONLY IF the Name field has not been provided.
    // Populated by the system. Read-only.
	GenerateName string `json:"generateName,omitempty" protobuf:"bytes,2,opt,name=generateName"`

	// Namespace defines the space within which each name must be unique. An empty namespace is
	// equivalent to the "default" namespace, but "default" is the canonical representation.
	// Not all objects are required to be scoped to a namespace - the value of this field for
	// those objects will be empty.
	Namespace string `json:"namespace,omitempty" protobuf:"bytes,3,opt,name=namespace"`

    // SelfLink is a URL representing this object.
    // Populated by the system. Read-only.
	SelfLink string `json:"selfLink,omitempty" protobuf:"bytes,4,opt,name=selfLink"`

	// UID is the unique in time and space value for this object. It is typically generated by
	// the server on successful creation of a resource and is not allowed to change on PUT
    // operations.
    // Populated by the system. Read-only.
	UID types.UID `json:"uid,omitempty" protobuf:"bytes,5,opt,name=uid,casttype=k8s.io/kubernetes/pkg/types.UID"`

	// An opaque value that represents the internal version of this object that can
	// be used by clients to determine when objects have changed. May be used for optimistic
	// concurrency, change detection, and the watch operation on a resource or set of resources.
	// Clients must treat these values as opaque and passed unmodified back to the server.
    // They may only be valid for a particular resource or set of resources.
    // Populated by the system. Read-only.
	ResourceVersion string `json:"resourceVersion,omitempty" protobuf:"bytes,6,opt,name=resourceVersion"`

	// A sequence number representing a specific generation of the desired state.
	// Populated by the system. Read-only.
	Generation int64 `json:"generation,omitempty" protobuf:"varint,7,opt,name=generation"`

	// CreationTimestamp is a timestamp representing the server time when this object was
	// created. It is not guaranteed to be set in happens-before order across separate operations.
	// Clients may not set this value. It is represented in RFC3339 form and is in UTC.
    // Populated by the system. Read-only.
	CreationTimestamp Time `json:"creationTimestamp,omitempty" protobuf:"bytes,8,opt,name=creationTimestamp"`

	// DeletionTimestamp is RFC 3339 date and time at which this resource will be deleted. This
	// field is set by the server when a graceful deletion is requested by the user, and is not
	// directly settable by a client. The resource is expected to be deleted (no longer visible
	// from resource lists, and not reachable by name) after the time in this field, once the
	// finalizers list is empty. As long as the finalizers list contains items, deletion is blocked.
	// Once the deletionTimestamp is set, this value may not be unset or be set further into the
	// future, although it may be shortened or the resource may be deleted prior to this time.
	// For example, a user may request that a pod is deleted in 30 seconds. The Kubelet will react
	// by sending a graceful termination signal to the containers in the pod. After that 30 seconds,
	// the Kubelet will send a hard termination signal (SIGKILL) to the container and after cleanup,
	// remove the pod from the API. In the presence of network partitions, this object may still
	// exist after this timestamp, until an administrator or automated process can determine the
	// resource is fully terminated.
	// If not set, graceful deletion of the object has not been requested.
	//
	// Populated by the system when a graceful deletion is requested.
	// Read-only.
	DeletionTimestamp *Time `json:"deletionTimestamp,omitempty" protobuf:"bytes,9,opt,name=deletionTimestamp"`

	// Number of seconds allowed for this object to gracefully terminate before
	// it will be removed from the system. Only set when deletionTimestamp is also set.
	// May only be shortened.
	// Read-only.
	DeletionGracePeriodSeconds *int64 `json:"deletionGracePeriodSeconds,omitempty" protobuf:"varint,10,opt,name=deletionGracePeriodSeconds"`

	// Map of string keys and values that can be used to organize and categorize
	// (scope and select) objects. May match selectors of replication controllers
	// and services.
	Labels map[string]string `json:"labels,omitempty" protobuf:"bytes,11,rep,name=labels"`

	// Annotations is an unstructured key value map stored with a resource that may be
	// set by external tools to store and retrieve arbitrary metadata. They are not
	// queryable and should be preserved when modifying objects.
	Annotations map[string]string `json:"annotations,omitempty" protobuf:"bytes,12,rep,name=annotations"`

	// List of objects depended by this object. If ALL objects in the list have
	// been deleted, this object will be garbage collected. If this object is managed by a controller,
	// then an entry in this list will point to this controller, with the controller field set to true.
	OwnerReferences []OwnerReference `json:"ownerReferences,omitempty" patchStrategy:"merge" patchMergeKey:"uid" protobuf:"bytes,13,rep,name=ownerReferences"`

	// Must be empty before the object is deleted from the registry. Each entry
	// is an identifier for the responsible component that will remove the entry
	// from the list. If the deletionTimestamp of the object is non-nil, entries
	// in this list can only be removed.
	// Finalizers may be processed and removed in any order.  Order is NOT enforced
	// because it introduces significant risk of stuck finalizers.
	// finalizers is a shared field, any actor with permission can reorder it.
	// If the finalizer list is processed in order, then this can lead to a situation
	// in which the component responsible for the first finalizer in the list is
	// waiting for a signal (field value, external system, or other) produced by a
	// component responsible for a finalizer later in the list, resulting in a deadlock.
	// Without enforced ordering finalizers are free to order amongst themselves and
	// are not vulnerable to ordering changes in the list.
	Finalizers []string `json:"finalizers,omitempty" patchStrategy:"merge" protobuf:"bytes,14,rep,name=finalizers"`

	// The name of the cluster which the object belongs to.
	// This is used to distinguish resources with same name and namespace in different clusters.
	// This field is not set anywhere right now and apiserver is going to ignore it if set in create or update request.
	ClusterName string `json:"clusterName,omitempty" protobuf:"bytes,15,opt,name=clusterName"`

	// ManagedFields maps workflow-id and version to the set of fields
	// that are managed by that workflow. This is mostly for internal
	// housekeeping, and users typically shouldn't need to set or
	// understand this field. A workflow can be the user's name, a
	// controller's name, or the name of a specific apply path like
	// "ci-cd". The set of fields is always in the version that the
	// workflow used when modifying the object.
	ManagedFields []ManagedFieldsEntry `json:"managedFields,omitempty" protobuf:"bytes,17,rep,name=managedFields"`
}

// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/meta.go
//
// Object lets you work with object metadata from any of the versioned or
// internal API objects. Attempting to set or retrieve a field on an object that does
// not support that field (Name, UID, Namespace on lists) will be a no-op and return
// a default value.
type Object interface {
	GetNamespace() string
	SetNamespace(namespace string)
	GetName() string
	SetName(name string)
	GetGenerateName() string
	SetGenerateName(name string)
	GetUID() types.UID
	SetUID(uid types.UID)
	GetResourceVersion() string
	SetResourceVersion(version string)
	GetGeneration() int64
	SetGeneration(generation int64)
	GetSelfLink() string
	SetSelfLink(selfLink string)
	GetCreationTimestamp() Time
	SetCreationTimestamp(timestamp Time)
	GetDeletionTimestamp() *Time
	SetDeletionTimestamp(timestamp *Time)
	GetDeletionGracePeriodSeconds() *int64
	SetDeletionGracePeriodSeconds(*int64)
	GetLabels() map[string]string
	SetLabels(labels map[string]string)
	GetAnnotations() map[string]string
	SetAnnotations(annotations map[string]string)
	GetFinalizers() []string
	SetFinalizers(finalizers []string)
	GetOwnerReferences() []OwnerReference
	SetOwnerReferences([]OwnerReference)
	GetClusterName() string
	SetClusterName(clusterName string)
	GetManagedFields() []ManagedFieldsEntry
	SetManagedFields(managedFields []ManagedFieldsEntry)
}

// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/meta.go
//
type ObjectMetaAccessor interface {
	GetObjectMeta() Object
}

// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/types.go
//
// ListMeta describes metadata that synthetic resources must have, including lists and
// various status objects. A resource may have only one of {ObjectMeta, ListMeta}.
type ListMeta struct {
	// selfLink is a URL representing this object.
	// Populated by the system.
	// Read-only.
	SelfLink string `json:"selfLink,omitempty" protobuf:"bytes,1,opt,name=selfLink"`

	// String that identifies the server's internal version of this object that
	// can be used by clients to determine when objects have changed.
	// Value must be treated as opaque by clients and passed unmodified back to the server.
	// Populated by the system.
	// Read-only.
	ResourceVersion string `json:"resourceVersion,omitempty" protobuf:"bytes,2,opt,name=resourceVersion"`

	// continue may be set if the user set a limit on the number of items returned, and indicates that
	// the server has more data available. The value is opaque and may be used to issue another request
	// to the endpoint that served this list to retrieve the next set of available objects. Continuing a
	// consistent list may not be possible if the server configuration has changed or more than a few
	// minutes have passed. The resourceVersion field returned when using this continue value will be
	// identical to the value in the first response, unless you have received this token from an error
	// message.
	Continue string `json:"continue,omitempty" protobuf:"bytes,3,opt,name=continue"`

	// remainingItemCount is the number of subsequent items in the list which are not included in this
	// list response. If the list request contained label or field selectors, then the number of
	// remaining items is unknown and the field will be left unset and omitted during serialization.
	// If the list is complete (either because it is not chunking or because this is the last chunk),
	// then there are no more remaining items and this field will be left unset and omitted during
	// serialization.
	// Servers older than v1.15 do not set this field.
	// The intended use of the remainingItemCount is *estimating* the size of a collection. Clients
	// should not rely on the remainingItemCount to be set or to be exact.
	RemainingItemCount *int64 `json:"remainingItemCount,omitempty" protobuf:"bytes,4,opt,name=remainingItemCount"`
}

// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/meta.go
//
// ListInterface lets you work with list metadata from any of the versioned or
// internal API objects. Attempting to set or retrieve a field on an object that does
// not support that field will be a no-op and return a default value.
type ListInterface interface {
	GetResourceVersion() string
	SetResourceVersion(version string)
	GetSelfLink() string
	SetSelfLink(selfLink string)
	GetContinue() string
	SetContinue(c string)
	GetRemainingItemCount() *int64
	SetRemainingItemCount(c *int64)
}

// source code from https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/meta.go
//
// ListMetaAccessor retrieves the list interface from an object
type ListMetaAccessor interface {
	GetListMeta() ListInterface
}

// source code from: https://github.com/kubernetes/apimachinery/blob/master/pkg/runtime/interfaces.go
//
// Object interface must be supported by all API types registered with Scheme. Since objects in a scheme are
// expected to be serialized to the wire, the interface an Object must provide to the Scheme allows
// serializers to set the kind, version, and group the object is represented as. An Object may choose
// to return a no-op ObjectKindAccessor in cases where it is not expected to be serialized.
type Object interface {
    // used to access type metadata(GVK)
    GetObjectKind() schema.ObjectKind
    // DeepCopyObject needed to implemented by each kubernetes API type definition,
    // usually by automatically generated code.
    DeepCopyObject() Object
}

// source code from: https://github.com/kubernetes/apimachinery/blob/master/pkg/api/meta/meta.go
//
// Accessor takes an arbitrary object pointer and returns meta.Interface.
// obj must be a pointer to an API type. An error is returned if the minimum
// required fields are missing. Fields that are not required return the default
// value and are a no-op if set.
func Accessor(obj interface{}) (metav1.Object, error) {
	switch t := obj.(type) {
	case metav1.Object:
		return t, nil
	case metav1.ObjectMetaAccessor:
		if m := t.GetObjectMeta(); m != nil {
			return m, nil
		}
		return nil, errNotObject
	default:
		return nil, errNotObject
	}
}

// source code from https://github.com/kubernetes/api/blob/master/core/v1/zz_generated.deepcopy.go
//
// DeepCopyObject is an autogenerated deepcopy function, copying the receiver, creating a new runtime.Object.
func (in *ConfigMap) DeepCopyObject() runtime.Object {
	if c := in.DeepCopy(); c != nil {
		return c
	}
	return nil
}

type Pod struct {
	metav1.TypeMeta `json:",inline"`
	metav1.ObjectMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"`
	Spec PodSpec `json:"spec,omitempty" protobuf:"bytes,2,opt,name=spec"`
	Status PodStatus `json:"status,omitempty" protobuf:"bytes,3,opt,name=status"`
}

type k8sUnstructuredObject struct {
	Object map[string]interface{}
}

// soure code from: https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/unstructured/unstructured.go
//
type Unstructured struct {
	// Object is a JSON compatible map with string, float, int, bool, []interface{}, or
	// map[string]interface{} children.
	Object map[string]interface{}
}

import (
    "k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
    "k8s.io/apimachinery/pkg/runtime/serializer/yaml"
)

var manifest = `
apiVersion: v1
kind: pod
metadata:
  name: web
spec:
  ...
`
// convert yaml to unstructured
objs := &unstructured.Unstructured{}
dec := yaml.NewDecodingSerializer(unstructured.UnstructuredJSONScheme)
dec.Decode([]byte(manifest), nil, obj)

labels := obj.GetLabels()
labels["owner"]="xxx"
obj.SetLabels(labels)

dynamicClient.Resource().Namespace(namespace).Create(context.TODO(), obj, metav1.CreateOptions{})

import "k8s.io/client-go/kubernetes"

clientset, err := kubernetes.NewForConfig(config)

pod := &Corev1.Pod{}
pod.Name = "web"
pod.Spec = pod.PodSpec{
	...
}

clientset.CoreV1().Pods(apiv1.NamespaceDefault).Create(pod)

import "k8s.io/client-go/dynamic"

client, _ := dynamic.NewForConfig(config)
podGVR := schema.GroupVersionResource{Group: "core", Version: "v1", Resource: "pods"}

pod := &unstructured.Unstructured{
	Object: map[string]interface{}{
		"apiVersion": "v1",
		"kind":       "Pod",
		"metadata": map[string]interface{}{
			"name": "web",
		},
		"spec": map[string]interface{}{
			"serviceAccount": "default",
			...
		}
	}
}

client.Resource(podGVR).Namespace(namespace).Create(context.TODO(), pod, metav1.CreateOptions{})

POST /api/v1/namespaces/{namespace}/pods/{name}

// source code from: https://github.com/kubernetes/apimachinery/blob/master/pkg/runtime/converter.go
//
// UnstructuredConverter is an interface for converting between interface{}
// and map[string]interface representation.
type UnstructuredConverter interface {
	ToUnstructured(obj interface{}) (map[string]interface{}, error)
	FromUnstructured(u map[string]interface{}, obj interface{}) error
}