一文读懂 Kubernetes APIServer 原理 (7)

通过crd.UID以及crd.Name获取crdInfo，若不存在则创建对应的crdInfo(crdInfo, err := r.getOrCreateServingInfoFor(crd.UID, crd.Name))。crdInfo中包含了CRD定义以及该CRD对应Custom Resource的customresource.REST storage

customresource.REST storage由CR对应的Group(duyanghao.example.com)，Version(v1)，Kind(Student)，Resource(students)等创建完成，由于CR在Kubernetes代码中并没有具体结构体定义，所以这里会先初始化一个范型结构体Unstructured(用于保存所有类型的Custom Resource)，并对该结构体进行SetGroupVersionKind操作(设置具体Custom Resource Type)

从customresource.REST storage获取Unstructured结构体后会对其进行相应转换然后返回

// k8s.io/kubernetes/staging/src/k8s.io/apiextensions-apiserver/pkg/apiserver/customresource_handler.go:223 func (r *crdHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) { ctx := req.Context() requestInfo, ok := apirequest.RequestInfoFrom(ctx) ... crdName := requestInfo.Resource + "." + requestInfo.APIGroup crd, err := r.crdLister.Get(crdName) ... crdInfo, err := r.getOrCreateServingInfoFor(crd.UID, crd.Name) verb := strings.ToUpper(requestInfo.Verb) resource := requestInfo.Resource subresource := requestInfo.Subresource scope := metrics.CleanScope(requestInfo) ... switch { case subresource == "status" && subresources != nil && subresources.Status != nil: handlerFunc = r.serveStatus(w, req, requestInfo, crdInfo, terminating, supportedTypes) case subresource == "scale" && subresources != nil && subresources.Scale != nil: handlerFunc = r.serveScale(w, req, requestInfo, crdInfo, terminating, supportedTypes) case len(subresource) == 0: handlerFunc = r.serveResource(w, req, requestInfo, crdInfo, terminating, supportedTypes) default: responsewriters.ErrorNegotiated( apierrors.NewNotFound(schema.GroupResource{Group: requestInfo.APIGroup, Resource: requestInfo.Resource}, requestInfo.Name), Codecs, schema.GroupVersion{Group: requestInfo.APIGroup, Version: requestInfo.APIVersion}, w, req, ) } if handlerFunc != nil { handlerFunc = metrics.InstrumentHandlerFunc(verb, requestInfo.APIGroup, requestInfo.APIVersion, resource, subresource, scope, metrics.APIServerComponent, handlerFunc) handler := genericfilters.WithWaitGroup(handlerFunc, longRunningFilter, crdInfo.waitGroup) handler.ServeHTTP(w, req) return } }

更多代码原理详情，参考 kubernetes-reading-notes 。

Conclusion

本文从源码层面对Kubernetes apiserver进行了一个概览性总结，包括：aggregatorServer，kubeAPIServer，apiExtensionsServer以及bootstrap-controller等。通过阅读本文可以对apiserver内部原理有一个大致的理解，另外也有助于后续深入研究

Refs

kubernetes-reading-notes

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