Aggregation
API Aggregation 允許在不修改 Kubernetes 核心代碼的同時擴展 Kubernetes API，即將第三方服務註冊到 Kubernetes API 中，這樣就可以通過 Kubernetes API 來訪問外部服務。
備註：另外一種擴展 Kubernetes API 的方法是使用 CustomResourceDefinition (CRD)。
何時使用 Aggregation
Your API is Declarative.
Your API does not fit the Declarative model.
You want your new types to be readable and writable using kubectl.
kubectl support is not required
You want to view your new types in a Kubernetes UI, such as dashboard, alongside built-in types.
Kubernetes UI support is not required.
You are developing a new API.
You already have a program that serves your API and works well.
You are willing to accept the format restriction that Kubernetes puts on REST resource paths, such as API Groups and Namespaces. (See the API Overview.)
You need to have specific REST paths to be compatible with an already defined REST API.
Your resources are naturally scoped to a cluster or to namespaces of a cluster.
Cluster or namespace scoped resources are a poor fit; you need control over the specifics of resource paths.
You want to reuse Kubernetes API support features.
You don’t need those features.
開啓 API Aggregation
kube-apiserver 增加以下配置
--requestheader-client-ca-file=<path to aggregator CA cert>
--requestheader-allowed-names=aggregator
--requestheader-extra-headers-prefix=X-Remote-Extra-
--requestheader-group-headers=X-Remote-Group
--requestheader-username-headers=X-Remote-User
--proxy-client-cert-file=<path to aggregator proxy cert>
--proxy-client-key-file=<path to aggregator proxy key>如果 kube-proxy 沒有在 Master 上面運行，還需要配置
--enable-aggregator-routing=true創建擴展 API
確保開啓 APIService API（默認開啓，可用
kubectl get apiservice命令驗證）創建 RBAC 規則
創建一個 namespace，用來運行擴展的 API 服務
創建 CA 和證書，用於 https
創建一個存儲證書的 secret
創建一個部署擴展 API 服務的 deployment，並使用上一步的 secret 配置證書，開啓 https 服務
創建一個 ClusterRole 和 ClusterRoleBinding
創建一個非 namespace 的 apiservice，注意設置
spec.caBundle運行
kubectl get <resource-name>，正常應該返回No resources found.
可以使用 apiserver-builder 工具自動化上面的步驟。
# 初始化項目
$ cd GOPATH/src/github.com/my-org/my-project
$ apiserver-boot init repo --domain <your-domain>
$ apiserver-boot init glide
# 創建資源
$ apiserver-boot create group version resource --group <group> --version <version> --kind <Kind>
# 編譯
$ apiserver-boot build executables
$ apiserver-boot build docs
# 本地運行
$ apiserver-boot run local
# 集群運行
$ apiserver-boot run in-cluster --name nameofservicetorun --namespace default --image gcr.io/myrepo/myimage:mytag
$ kubectl create -f sample/<type>.yaml示例
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