调用 m.InstallAPIs 将扩展的 API Resources添加到路由中，在apiserver中即是以 /apis 开头的 resource；
// k8s.io/kubernetes/pkg/master/master.go:332 // New returns a new instance of Master from the given config. // Certain config fields will be set to a default value if unset. // Certain config fields must be specified, including: // KubeletClientConfig func (c completedConfig) New(delegationTarget genericapiserver.DelegationTarget) (*Master, error) { ... // 安装 LegacyAPI(core API) // install legacy rest storage if c.ExtraConfig.APIResourceConfigSource.VersionEnabled(apiv1.SchemeGroupVersion) { legacyRESTStorageProvider := corerest.LegacyRESTStorageProvider{ StorageFactory: c.ExtraConfig.StorageFactory, ProxyTransport: c.ExtraConfig.ProxyTransport, KubeletClientConfig: c.ExtraConfig.KubeletClientConfig, EventTTL: c.ExtraConfig.EventTTL, ServiceIPRange: c.ExtraConfig.ServiceIPRange, SecondaryServiceIPRange: c.ExtraConfig.SecondaryServiceIPRange, ServiceNodePortRange: c.ExtraConfig.ServiceNodePortRange, LoopbackClientConfig: c.GenericConfig.LoopbackClientConfig, ServiceAccountIssuer: c.ExtraConfig.ServiceAccountIssuer, ServiceAccountMaxExpiration: c.ExtraConfig.ServiceAccountMaxExpiration, APIAudiences: c.GenericConfig.Authentication.APIAudiences, } if err := m.InstallLegacyAPI(&c, c.GenericConfig.RESTOptionsGetter, legacyRESTStorageProvider); err != nil { return nil, err } } ... // 安装 APIs(named groups apis) if err := m.InstallAPIs(c.ExtraConfig.APIResourceConfigSource, c.GenericConfig.RESTOptionsGetter, restStorageProviders...); err != nil { return nil, err } ... return m, nil }整个kubeAPIServer提供了三类API Resource接口：
core group：主要在 /api/v1 下；
named groups：其 path 为 /apis/$GROUP/$VERSION；
系统状态的一些 API：如/metrics 、/version 等；
而API的URL大致以 /apis/{group}/{version}/namespaces/{namespace}/resource/{name} 组成，结构如下图所示：
kubeAPIServer会为每种API资源创建对应的RESTStorage，RESTStorage的目的是将每种资源的访问路径及其后端存储的操作对应起来：通过构造的REST Storage实现的接口判断该资源可以执行哪些操作（如：create、update等），将其对应的操作存入到action中，每一个操作对应一个标准的REST method，如create对应REST method为POST，而update对应REST method为PUT。最终根据actions数组依次遍历，对每一个操作添加一个handler(handler对应REST Storage实现的相关接口)，并注册到route，最终对外提供RESTful API，如下：
// m.GenericAPIServer.InstallLegacyAPIGroup --> s.installAPIResources --> apiGroupVersion.InstallREST --> installer.Install --> a.registerResourceHandlers // k8s.io/kubernetes/staging/src/k8s.io/apiserver/pkg/endpoints/installer.go:181 func (a *APIInstaller) registerResourceHandlers(path string, storage rest.Storage, ws *restful.WebService) (*metav1.APIResource, error) { ... // 1、判断该 resource 实现了哪些 REST 操作接口，以此来判断其支持的 verbs 以便为其添加路由 // what verbs are supported by the storage, used to know what verbs we support per path creater, isCreater := storage.(rest.Creater) namedCreater, isNamedCreater := storage.(rest.NamedCreater) lister, isLister := storage.(rest.Lister) getter, isGetter := storage.(rest.Getter) ... // 2、为 resource 添加对应的 actions(+根据是否支持 namespace) // Get the list of actions for the given scope. switch { case !namespaceScoped: // Handle non-namespace scoped resources like nodes. resourcePath := resource resourceParams := params itemPath := resourcePath + "/{name}" nameParams := append(params, nameParam) proxyParams := append(nameParams, pathParam) ... // Handler for standard REST verbs (GET, PUT, POST and DELETE). // Add actions at the resource path: /api/apiVersion/resource actions = appendIf(actions, action{"LIST", resourcePath, resourceParams, namer, false}, isLister) actions = appendIf(actions, action{"POST", resourcePath, resourceParams, namer, false}, isCreater) ... } ... // 3、从 rest.Storage 到 restful.Route 映射 // 为每个操作添加对应的 handler for _, action := range actions { ... switch action.Verb { ... case "POST": // Create a resource. var handler restful.RouteFunction // 4、初始化 handler if isNamedCreater { handler = restfulCreateNamedResource(namedCreater, reqScope, admit) } else { handler = restfulCreateResource(creater, reqScope, admit) } handler = metrics.InstrumentRouteFunc(action.Verb, group, version, resource, subresource, requestScope, metrics.APIServerComponent, handler) ... // 5、route 与 handler 进行绑定 route := ws.POST(action.Path).To(handler). Doc(doc). Param(ws.QueryParameter("pretty", "If 'true', then the output is pretty printed.")). Operation("create"+namespaced+kind+strings.Title(subresource)+operationSuffix). Produces(append(storageMeta.ProducesMIMETypes(action.Verb), mediaTypes...)...). Returns(http.StatusOK, "OK", producedObject). // TODO: in some cases, the API may return a v1.Status instead of the versioned object // but currently go-restful can't handle multiple different objects being returned. Returns(http.StatusCreated, "Created", producedObject). Returns(http.StatusAccepted, "Accepted", producedObject). Reads(defaultVersionedObject). Writes(producedObject) if err := AddObjectParams(ws, route, versionedCreateOptions); err != nil { return nil, err } addParams(route, action.Params) // 6、添加到路由中 routes = append(routes, route) case "DELETE": // Delete a resource. ... default: return nil, fmt.Errorf("unrecognized action verb: %s", action.Verb) } for _, route := range routes { route.Metadata(ROUTE_META_GVK, metav1.GroupVersionKind{ Group: reqScope.Kind.Group, Version: reqScope.Kind.Version, Kind: reqScope.Kind.Kind, }) route.Metadata(ROUTE_META_ACTION, strings.ToLower(action.Verb)) ws.Route(route) } // Note: update GetAuthorizerAttributes() when adding a custom handler. } ... }