k8s restful API 结构分析

k8s的api-server组件负责提供restful api访问端点, 并且将数据持久化到etcd server中. 那么k8s是如何组织它的restful api的?

一, namespaced resources

所谓的namespaced resources,就是这个resource是从属于某个namespace的, 也就是说它不是cluster-scoped的资源. 比如pod, deployment, service都属于namespaced resource. 那么我们看一下如何请求一个namespaced resources.

http://localhost:8080/api/v1/namespaces/default/pods/test-pod

可以看出, 该restful api的组织形式是:

api	api版本	namespaces	所属的namespace	资源种类	所请求的资源名称
api	v1	namespaces	default	pods	test-pod

这里api version如果是v1的话,表示这是一个很稳定的版本了, 以后不会有大的修改,并且当前版本所支持的所有特性以后都会兼容. 而如果版本号是v1alpha1, v1beta1之类的,则不保证其稳定性.

二, non-namespaced resources

http://localhost:8080/apis/rbac.authorization.k8s.io/v1/clusterroles/test-clusterrole

这里可以观察到它clusterrole与pod不同, apis表示这是一个非核心api. rbac.authorization.k8s.io指代的是api-group, 另外它没有namespaces字段, 其他与namespaced resources类似.不再赘述.

三, non-resource url

这类资源和pod, clusterrole都不同. 例如

http://localhost:8080/healthz/etcd

这就是用来确认etcd服务是不是健康的.它不属于任何namespace,也不属于任何api版本.

总结, k8s的REST API的设计结构为:

[api/apis] /  api-group                           / api-version /  namespaces / namespace-name / resource-kind / resource-name

apis          /   rbac.authorization.k8s.io /  v1              /  namespaces / default                  /  roles              /  test-role

所有的api结构都可以通过访问相关断点来获取信息, 最低一层为api-server的地址, 访问结果如下:

{
  "paths": [
    "/api",
    "/api/v1",
    "/apis",
    "/apis/",
    "/apis/admissionregistration.k8s.io",
    "/apis/admissionregistration.k8s.io/v1beta1",
    "/apis/apiextensions.k8s.io",
    "/apis/apiextensions.k8s.io/v1beta1",
    "/apis/apiregistration.k8s.io",
    "/apis/apiregistration.k8s.io/v1",
    "/apis/apiregistration.k8s.io/v1beta1",
    "/apis/apps",
    "/apis/apps/v1",
    "/apis/apps/v1beta1",
    "/apis/apps/v1beta2",
    "/apis/authentication.k8s.io",
    "/apis/authentication.k8s.io/v1",
    "/apis/authentication.k8s.io/v1beta1",
    "/apis/authorization.k8s.io",
    "/apis/authorization.k8s.io/v1",
    "/apis/authorization.k8s.io/v1beta1",
    "/apis/autoscaling",
    "/apis/autoscaling/v1",
    "/apis/autoscaling/v2beta1",
    "/apis/autoscaling/v2beta2",
    "/apis/batch",
    "/apis/batch/v1",
    "/apis/batch/v1beta1",
    "/apis/certificates.k8s.io",
    "/apis/certificates.k8s.io/v1beta1",
    "/apis/coordination.k8s.io",
    "/apis/coordination.k8s.io/v1beta1",
    "/apis/events.k8s.io",
    "/apis/events.k8s.io/v1beta1",
    "/apis/extensions",
    "/apis/extensions/v1beta1",
    "/apis/networking.k8s.io",
    "/apis/networking.k8s.io/v1",
    "/apis/policy",
    "/apis/policy/v1beta1",
    "/apis/rbac.authorization.k8s.io",
    "/apis/rbac.authorization.k8s.io/v1",
    "/apis/rbac.authorization.k8s.io/v1beta1",
    "/apis/scheduling.k8s.io",
    "/apis/scheduling.k8s.io/v1beta1",
    "/apis/storage.k8s.io",
    "/apis/storage.k8s.io/v1",
    "/apis/storage.k8s.io/v1beta1",
    "/healthz",
    "/healthz/autoregister-completion",
    "/healthz/etcd",
    "/healthz/log",
    "/healthz/ping",
    "/healthz/poststarthook/apiservice-openapi-controller",
    "/healthz/poststarthook/apiservice-registration-controller",
    "/healthz/poststarthook/apiservice-status-available-controller",
    "/healthz/poststarthook/bootstrap-controller",
    "/healthz/poststarthook/ca-registration",
    "/healthz/poststarthook/generic-apiserver-start-informers",
    "/healthz/poststarthook/kube-apiserver-autoregistration",
    "/healthz/poststarthook/rbac/bootstrap-roles",
    "/healthz/poststarthook/scheduling/bootstrap-system-priority-classes",
    "/healthz/poststarthook/start-apiextensions-controllers",
    "/healthz/poststarthook/start-apiextensions-informers",
    "/healthz/poststarthook/start-kube-aggregator-informers",
    "/healthz/poststarthook/start-kube-apiserver-admission-initializer",
    "/healthz/poststarthook/start-kube-apiserver-informers",
    "/logs",
    "/metrics",
    "/openapi/v2",
    "/swagger-2.0.0.json",
    "/swagger-2.0.0.pb-v1",
    "/swagger-2.0.0.pb-v1.gz",
    "/swagger.json",
    "/swaggerapi",
    "/version"
  ]
}