kubernetes的api定义与装载

都有哪些api

kubectl api-versions可以看到集群支持的api：

$ kubectl api-versions
apps/v1beta1
authentication.k8s.io/v1beta1
authorization.k8s.io/v1beta1
autoscaling/v1
batch/v1
certificates.k8s.io/v1alpha1
extensions/v1beta1
policy/v1beta1
rbac.authorization.k8s.io/v1alpha1
storage.k8s.io/v1beta1
v1

这个可以通过kube-apiserver的--runtime-config来设置：

--runtime-config=/api=true,api/all=true,apis=true,apis/v1=true

api在哪里定义的？

api在pkg/api/和pkg/apis中定义, pkg/api目录中定义了pod等基础api，pkg/apis中定义的是扩展的api。

▾ api/
  ▸ annotations/
  ▸ endpoints/
  ▸ errors/
  ▸ events/
  ▸ install/
  ▸ meta/

▾ apis/
  ▸ abac/
  ▸ apps/
  ▸ authentication/
  ▸ authorization/
  ▸ autoscaling/
  ▸ batch/
  ▸ certificates/
  ▸ componentconfig/
  ▸ extensions/
  ▸ imagepolicy/
  ▸ meta/
  ▸ policy/
  ▸ rbac/
  ▸ settings/
  ▸ storage/

api是怎样被装载的？

如果你仔细查看api/和apis/的子目录，会发现很多都有一个名为install的目录（不是全部)。

这个目录中有一个名为install.go的文件，里面有这样一个init()函数：

func init() {
	Install(api.GroupFactoryRegistry, api.Registry, api.Scheme)
}

它调用的Install()函数，也在这个文件里实现：

func Install(groupFactoryRegistry announced.APIGroupFactoryRegistry, 
		registry *registered.APIRegistrationManager, scheme *runtime.Scheme) {
	...

Install()将完成api的装载，但是这个过程比较复杂，在下一节中分析。

问题是这些init()函数是什么时候给调用的？通过搜索、回溯代码发现了这个过程。

kube-apiserver的代码cmd/kube-apiserver/app/server.go:67中导入了名为master的package:

"k8s.io/kubernetes/pkg/master"

master的代码pkg/master/import_known_versions.go中导入了api/和apis/子目录中的install:

// These imports are the API groups the API server will support.
import (
    "fmt"
    "k8s.io/kubernetes/pkg/api"
    _ "k8s.io/kubernetes/pkg/api/install"
    _ "k8s.io/kubernetes/pkg/apis/apps/install"
    _ "k8s.io/kubernetes/pkg/apis/authentication/install"
    _ "k8s.io/kubernetes/pkg/apis/authorization/install"
    _ "k8s.io/kubernetes/pkg/apis/autoscaling/install"
    _ "k8s.io/kubernetes/pkg/apis/batch/install"
    _ "k8s.io/kubernetes/pkg/apis/certificates/install"
    _ "k8s.io/kubernetes/pkg/apis/componentconfig/install"
    _ "k8s.io/kubernetes/pkg/apis/extensions/install"
    _ "k8s.io/kubernetes/pkg/apis/imagepolicy/install"
    _ "k8s.io/kubernetes/pkg/apis/policy/install"
    _ "k8s.io/kubernetes/pkg/apis/rbac/install"
    _ "k8s.io/kubernetes/pkg/apis/settings/install"
    _ "k8s.io/kubernetes/pkg/apis/storage/install"
)
...

因此init()函数得以执行，完成api的装载。

api的装载过程

这里以”k8s.io/kubernetes/pkg/api/install”为例。

pkg/api/install/install.go中实现了init()函数，用来装载pkg/api目录下定义的资源：

// Package install installs the v1 monolithic api, making it available as an
// option to all of the API encoding/decoding machinery.
func init() {
    Install(api.GroupFactoryRegistry, api.Registry, api.Scheme)
}

// Install registers the API group and adds types to a scheme
func Install(groupFactoryRegistry announced.APIGroupFactoryRegistry, registry *registered.APIRegistrationManager, scheme *runtime.Scheme) {
    if err := announced.NewGroupMetaFactory(
        &announced.GroupMetaFactoryArgs{
            GroupName:                  api.GroupName,
            VersionPreferenceOrder:     []string{v1.SchemeGroupVersion.Version},
            ImportPrefix:               "k8s.io/kubernetes/pkg/api",
            AddInternalObjectsToScheme: api.AddToScheme,
            RootScopedKinds: sets.NewString(
                "Node",
                "Namespace",
                "PersistentVolume",
                "ComponentStatus",
            ),
            IgnoredKinds: sets.NewString(
                "ListOptions",
                "DeleteOptions",
                "Status",
                "PodLogOptions",
                "PodExecOptions",
                "PodAttachOptions",
                "PodPortForwardOptions",
                "PodProxyOptions",
                "NodeProxyOptions",
                "ServiceProxyOptions",
                "ThirdPartyResource",
                "ThirdPartyResourceData",
                "ThirdPartyResourceList",
            ),
        },
        announced.VersionToSchemeFunc{
            v1.SchemeGroupVersion.Version: v1.AddToScheme,
        },
    ).Announce(groupFactoryRegistry).RegisterAndEnable(registry, scheme); err != nil {
        panic(err)
    }
}

从Install()函数的实现中可以看到，Install的过程是通过announced.NewGroupMetaFactory()完成的:

announced.NewGroupMetaFactory().Annouce().RegisterAndEnable()

announced是"k8s.io/apimachinery/pkg/apimachinery/announced"。

通过走读代码，可以知道这里是将api的定义注册到了”k8s.io/kubernetes/pkg/api”中的GroupFactoryRegistry中:

var GroupFactoryRegistry = make(announced.APIGroupFactoryRegistry)

其它apis分组目录下的资源也注册到了这个GroupFactoryRegistry中。

有三个参数需要关注：

api.GroupName
api.AddToScheme
v1.SchemeGroupVersion.Version: v1.AddToScheme,

TODO：分析这个过程。

v1.AddToScheme

pkg/api/v1/register.go:

var (
    SchemeBuilder = runtime.NewSchemeBuilder(addKnownTypes, addDefaultingFuncs, addConversionFuncs, addFastPathConversionFuncs)
    AddToScheme   = SchemeBuilder.AddToScheme
)

AddToScheme是一个函数，它的作用就是调用SchemeBuilder中注册的函数：

func (sb *SchemeBuilder) AddToScheme(s *Scheme) error {
    for _, f := range *sb {
        if err := f(s); err != nil {
            return err
        }
    }
    return nil
}

也就是SchemeBuilder创建时传入的函数:

addKnownTypes, 
addDefaultingFuncs, 
addConversionFuncs, 
addFastPathConversionFuncs

api/v1中的addKnownTypes():

// Adds the list of known types to api.Scheme.
func addKnownTypes(scheme *runtime.Scheme) error {
    scheme.AddKnownTypes(SchemeGroupVersion,
        &Pod{},
        &PodList{},
        &PodStatusResult{},
        &PodTemplate{},
        &PodTemplateList{},
        &ReplicationController{},
        &ReplicationControllerList{},
        &Service{},
        &ServiceProxyOptions{},
        &ServiceList{},
        &Endpoints{},
        &EndpointsList{},
        &Node{},
        &NodeList{},
        &NodeProxyOptions{},
        &Binding{},
        &Event{},
        &EventList{},
        &List{},
...

参考

编程基础系统基础关注跟踪

Kubernetes Prometheus 超级账本

kubernetes