构建API Server的详细步骤

func CreateServerChain(runOptions *options.ServerRunOptions, stopCh <-chan struct{}) (*genericapiserver.GenericAPIServer, error) {

// api server的config结构

kubeAPIServerConfig, sharedInformers, versionedInformers, insecureServingOptions, serviceResolver, err := CreateKubeAPIServerConfig(runOptions, nodeTunneler, proxyTransport)

if err != nil {

return nil, err

}

// extension server的config结构

apiExtensionsConfig, err := createAPIExtensionsConfig(*kubeAPIServerConfig.GenericConfig, versionedInformers, runOptions)

if err != nil {

return nil, err

}

// 1. 创建api extensions server

apiExtensionsServer, err := createAPIExtensionsServer(apiExtensionsConfig, genericapiserver.EmptyDelegate)

if err != nil {

return nil, err

}

// 2. 创建api server，delegate到extensions server上（注意，第二个参数）

kubeAPIServer, err := CreateKubeAPIServer(kubeAPIServerConfig, apiExtensionsServer.GenericAPIServer, sharedInformers, versionedInformers)

if err != nil {

return nil, err

}

.....

// otherwise go down the normal path of standing the aggregator up in front of the API server

// this wires up openapi

kubeAPIServer.GenericAPIServer.PrepareRun()

// This will wire up openapi for extension api server

apiExtensionsServer.GenericAPIServer.PrepareRun()

....

// 3. 创建aggregator server, delegate到api server上

aggregatorServer, err := createAggregatorServer(aggregatorConfig, kubeAPIServer.GenericAPIServer, apiExtensionsServer.Informers)

if err != nil {

// we don't need special handling for innerStopCh because the aggregator server doesn't create any go routines

return nil, err

}

....

return aggregatorServer.GenericAPIServer, nil

}

func CreateKubeAPIServer(kubeAPIServerConfig *master.Config, delegateAPIServer genericapiserver.DelegationTarget, sharedInformers informers.SharedInformerFactory, versionedInformers clientgoinformers.SharedInformerFactory) (*master.Master, error) {

kubeAPIServer, err := kubeAPIServerConfig.Complete(versionedInformers).New(delegateAPIServer)

if err != nil {

return nil, err

}

kubeAPIServer.GenericAPIServer.AddPostStartHook("start-kube-apiserver-informers", func(context genericapiserver.PostStartHookContext) error {

sharedInformers.Start(context.StopCh)

return nil

})

return kubeAPIServer, nil

}

// kubeAPIServerConfig.Complete(versionedInformers).New(delegateAPIServer)中的New方法如下所示：

func (c completedConfig) New(delegationTarget genericapiserver.DelegationTarget) (*Master, error) {

...

// 通过Config创建APIServer对应的GenericAPIServer对象

s, err := c.GenericConfig.New("kube-apiserver", delegationTarget)

if err != nil {

return nil, err

}

....

m := &Master{

GenericAPIServer: s,

}

// 将所有REST资源（Pods/Deployments）的Storage接口实现类都install到master内含的GenericAPIServer上

restStorageProviders := []RESTStorageProvider{

authenticationrest.RESTStorageProvider{Authenticator: c.GenericConfig.Authenticator},

authorizationrest.RESTStorageProvider{Authorizer: c.GenericConfig.Authorizer, RuleResolver: c.GenericConfig.RuleResolver},

autoscalingrest.RESTStorageProvider{},

batchrest.RESTStorageProvider{},

certificatesrest.RESTStorageProvider{},

extensionsrest.RESTStorageProvider{},

networkingrest.RESTStorageProvider{},

policyrest.RESTStorageProvider{},

rbacrest.RESTStorageProvider{Authorizer: c.GenericConfig.Authorizer},

schedulingrest.RESTStorageProvider{},

settingsrest.RESTStorageProvider{},

storagerest.RESTStorageProvider{},

// keep apps after extensions so legacy clients resolve the extensions versions of shared resource names.

// See https://github.com/kubernetes/kubernetes/issues/42392

appsrest.RESTStorageProvider{},

admissionregistrationrest.RESTStorageProvider{},

}

m.InstallAPIs(c.ExtraConfig.APIResourceConfigSource, c.GenericConfig.RESTOptionsGetter, restStorageProviders...)

...

return m, nil

}