扩展kubernetes两个最常用最需要掌握的东西：自定义资源CRD 和 adminsion webhook, 本文教你如何十分钟掌握CRD开发.
kubernetes允许用户自定义自己的资源对象，就如同deployment statefulset一样，这个应用非常广泛，比如prometheus opterator就自定义Prometheus对象，再加上一个自定义的controller监听到kubectl create Prometheus时就去创建Pod组成一个pormetheus集群。rook等等同理。
我需要用kubernetes调度虚拟机，所以这里自定义一个 VirtualMachine 类型
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kubebuilder
kubebuilder能帮我们节省大量工作，让开发CRD和adminsion webhook变得异常简单。
安装
通过源码安装：
git clone https://github.com/kubernetes-sigs/kubebuilder cd kubebuilder make build cp bin/kubebuilder $GOPATH/bin 或者下载二进制：
os=$(go env GOOS) arch=$(go env GOARCH) # download kubebuilder and extract it to tmp curl -sL https://go.kubebuilder.io/dl/2.0.0-beta.0/${os}/${arch} | tar -xz -C /tmp/ # move to a long-term location and put it on your path # (you'll need to set the KUBEBUILDER_ASSETS env var if you put it somewhere else) sudo mv /tmp/kubebuilder_2.0.0-beta.0_${os}_${arch} /usr/local/kubebuilder export PATH=$PATH:/usr/local/kubebuilder/bin 还需要装下kustomize 这可是个渲染yaml的神器，让helm颤抖。
go install sigs.k8s.io/kustomize/v3/cmd/kustomize 使用
注意你得先有个kubernetes集群，一步安装走你
创建CRD
kubebuilder init --domain sealyun.com --license apache2 --owner "fanux" kubebuilder create api --group infra --version v1 --kind VirtulMachine 安装CRD并启动controller
make install # 安装CRD make run # 启动controller 然后我们就可以看到创建的CRD了
# kubectl get crd NAME AGE virtulmachines.infra.sealyun.com 52m 来创建一个虚拟机：
# kubectl apply -f config/samples/ # kubectl get virtulmachines.infra.sealyun.com NAME AGE virtulmachine-sample 49m 看一眼yaml文件：
# cat config/samples/infra_v1_virtulmachine.yaml apiVersion: infra.sealyun.com/v1 kind: VirtulMachine metadata: name: virtulmachine-sample spec: # Add fields here foo: bar 这里仅仅是把yaml存到etcd里了，我们controller监听到创建事件时啥事也没干。
把controller部署到集群中
make docker-build docker-push IMG=fanux/infra-controller make deploy 我是连的远端的kubenetes, make docker-build时test过不去，没有etcd的bin文件，所以先把test关了。
修改Makefile:
# docker-build: test docker-build: Dockerfile里的gcr.io/distroless/static:latest 这个镜像你也可能拉不下来，随意改改就行，我改成了golang:1.12.7
也有可能构建时有些代码拉不下来，启用一下go mod vendor 把依赖打包进去
go mod vendor 如果你本地有些代码拉不下来，可以用proxy: export GOPROXY=https://goproxy.io
再改下Dockerfile, 注释掉download：
修改后：
# Build the manager binary FROM golang:1.12.7 as builder WORKDIR /go/src/github.com/fanux/sealvm # Copy the Go Modules manifests COPY . . # Build RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o manager main.go # Use distroless as minimal base image to package the manager binary # Refer to https://github.com/GoogleContainerTools/distroless for more details # FROM gcr.io/distroless/static:latest FROM golang:1.12.7 WORKDIR / COPY --from=builder /go/src/github.com/fanux/sealvm/manager . ENTRYPOINT ["/manager"] make deploy 时报错： Error: json: cannot unmarshal string into Go struct field Kustomization.patches of type types.Patch
把 config/default/kustomization.yaml 中的 patches: 改成 patchesStrategicMerge: 即可
kustomize build config/default 这个命令就渲染出了controller的yaml文件，可以体验下
看 你的controller已经跑起来了：
kubectl get deploy -n sealvm-system NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE sealvm-controller-manager 1 1 1 0 3m kubectl get svc -n sealvm-system NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE sealvm-controller-manager-metrics-service ClusterIP 10.98.71.199 <none> 8443/TCP 4m 开发
增加对象数据参数
看下config/samples下面的yaml文件：
apiVersion: infra.sealyun.com/v1 kind: VirtulMachine metadata: name: virtulmachine-sample spec: # Add fields here foo: bar 这里参数里有foo:bar， 那我们来加个虚拟CPU，内存信息：
直接api/v1/virtulmachine_types.go即可
// VirtulMachineSpec defines the desired state of VirtulMachine // 在这里加信息 type VirtulMachineSpec struct { // INSERT ADDITIONAL SPEC FIELDS - desired state of cluster // Important: Run "make" to regenerate code after modifying this file CPU string `json:"cpu"` // 这是我增加的 Memory string `json:"memory"` } // VirtulMachineStatus defines the observed state of VirtulMachine // 在这里加状态信息，比如虚拟机是启动状态，停止状态啥的 type VirtulMachineStatus struct { // INSERT ADDITIONAL STATUS FIELD - define observed state of cluster // Important: Run "make" to regenerate code after modifying this file } 然后make一下：
make && make install && make run 这时再去渲染一下controller的yaml就会发现CRD中已经带上CPU和内存信息了：
kustomize build config/default
properties: cpu: description: 'INSERT ADDITIONAL SPEC FIELDS - desired state of cluster Important: Run "make" to regenerate code after modifying this file' type: string memory: type: string 修改一下yaml:
apiVersion: infra.sealyun.com/v1 kind: VirtulMachine metadata: name: virtulmachine-sample spec: cpu: "1" memory: "2G" # kubectl apply -f config/samples virtulmachine.infra.sealyun.com "virtulmachine-sample" configured # kubectl get virtulmachines.infra.sealyun.com virtulmachine-sample -o yaml apiVersion: infra.sealyun.com/v1 kind: VirtulMachine metadata: annotations: kubectl.kubernetes.io/last-applied-configuration: | {"apiVersion":"infra.sealyun.com/v1","kind":"VirtulMachine","metadata":{"annotations":{},"name":"virtulmachine-sample","namespace":"default"},"spec":{"cpu":"1","memory":"2G"}} creationTimestamp: 2019-07-26T08:47:34Z generation: 2 name: virtulmachine-sample namespace: default resourceVersion: "14811698" selfLink: /apis/infra.sealyun.com/v1/namespaces/default/virtulmachines/virtulmachine-sample uid: 030e2b9a-af82-11e9-b63e-5254bc16e436 spec: # 新的CRD已生效 cpu: "1" memory: 2G Status 同理，就不再赘述了，比如我把status里加一个Create, 表示controller要去创建虚拟机了(主要一些控制层面的逻辑)，创建完了把状态改成Running
Reconcile 唯一需要实现的接口
controller把轮训与事件监听都封装在这一个接口里了.你不需要关心怎么事件监听的.
获取虚拟机信息
func (r *VirtulMachineReconciler) Reconcile(req ctrl.Request) (ctrl.Result, error) { ctx = context.Background() _ = r.Log.WithValues("virtulmachine", req.NamespacedName) vm := &v1.VirtulMachine{} if err := r.Get(ctx, req.NamespacedName, vm); err != nil { # 获取VM信息 log.Error(err, "unable to fetch vm") } else { fmt.Println(vm.Spec.CPU, vm.Spec.Memory) # 打印CPU内存信息 } return ctrl.Result{}, nil } make && make install && make run这个时候去创建一个虚拟机kubectl apply -f config/samples,日志里就会输出CPU内存了. List接口同理，我就不赘述了
r.List(ctx, &vms, client.InNamespace(req.Namespace), client.MatchingField(vmkey, req.Name)) 更新状态
在status结构体中加入状态字段：
type VirtulMachineStatus struct { Status string `json:"status"` } controller里去更新状态：
vm.Status.Status = "Running" if err := r.Status().Update(ctx, vm); err != nil { log.Error(err, "unable to update vm status") } 如果出现:the server could not find the requested resource 这个错误，那么在CRD结构体上需要加个注释 // +kubebuilder:subresource:status：
// +kubebuilder:subresource:status // +kubebuilder:object:root=true type VirtulMachine struct { metav1.TypeMeta `json:",inline"` metav1.ObjectMeta `json:"metadata,omitempty"` Spec VirtulMachineSpec `json:"spec,omitempty"` Status VirtulMachineStatus `json:"status,omitempty"` } 这样就好了
编译启动后再去apply发现状态已经变成running：
# kubectl get virtulmachines.infra.sealyun.com virtulmachine-sample -o yaml ... status: status: Running 删除
time.Sleep(time.Second * 10) if err := r.Delete(ctx, vm); err != nil { log.Error(err, "unable to delete vm ", "vm", vm) } 10s之后我们将GET不到
删除回收器 Finalizers
如果不使用Finalizers，kubectl delete 时直接就删了etcd数据，controller再想去拿CRD时已经拿不到了：
ERRO[0029] VirtulMachine.infra.sealyun.com "virtulmachine-sample" not foundunable to fetch vm source="virtulmachine_controller.go:48" 所以在创建时我们需要给CRD加上Finalizer:
vm.ObjectMeta.Finalizers = append(vm.ObjectMeta.Finalizers, "virtulmachine.infra.sealyun.com") 然后删除时就只会给CRD打上一个删除时间戳，供我们做后续处理, 处理完了我们删除掉Finalizers：
如果 DeleteionTimestamp不存在 如果没有Finalizers 加上Finalizers,并更新CRD 要不然，说明是要被删除的 如果存在Finalizers，删除Finalizers,并更新CRD 看个完整的代码示例：
if cronJob.ObjectMeta.DeletionTimestamp.IsZero() { if !containsString(cronJob.ObjectMeta.Finalizers, myFinalizerName) { cronJob.ObjectMeta.Finalizers = append(cronJob.ObjectMeta.Finalizers, myFinalizerName) if err := r.Update(context.Background(), cronJob); err != nil { return ctrl.Result{}, err } } } else { if containsString(cronJob.ObjectMeta.Finalizers, myFinalizerName) { if err := r.deleteExternalResources(cronJob); err != nil { return ctrl.Result{}, err } cronJob.ObjectMeta.Finalizers = removeString(cronJob.ObjectMeta.Finalizers, myFinalizerName) if err := r.Update(context.Background(), cronJob); err != nil { return ctrl.Result{}, err } } } 失败重试
假设我们A依赖B而B又后创建，那么在处理A CRD时直接返回失败即可，这样很快会重试
webhook
kuberentes有三种webhook,admission webhook, authorization webhook and CRD conversion webhook.
这里比如我们要给CRD设置一些默认值，又或者是用户创建时少填了一些参数，那么我们得禁止创建等等这些事。
使用webhook也非常的简单，只需给定义的结构体实现 Defaulter 和 Validator接口即可.
其它接口
Reconcile结构体聚合了Client接口，所以client的所有方法都是可以直接调用，大部分是对CRD object的相关操作
type Client interface { Reader Writer StatusClient } // Reader knows how to read and list Kubernetes objects. type Reader interface { // Get retrieves an obj for the given object key from the Kubernetes Cluster. // obj must be a struct pointer so that obj can be updated with the response // returned by the Server. Get(ctx context.Context, key ObjectKey, obj runtime.Object) error // List retrieves list of objects for a given namespace and list options. On a // successful call, Items field in the list will be populated with the // result returned from the server. List(ctx context.Context, list runtime.Object, opts ...ListOptionFunc) error } // Writer knows how to create, delete, and update Kubernetes objects. type Writer interface { // Create saves the object obj in the Kubernetes cluster. Create(ctx context.Context, obj runtime.Object, opts ...CreateOptionFunc) error // Delete deletes the given obj from Kubernetes cluster. Delete(ctx context.Context, obj runtime.Object, opts ...DeleteOptionFunc) error // Update updates the given obj in the Kubernetes cluster. obj must be a // struct pointer so that obj can be updated with the content returned by the Server. Update(ctx context.Context, obj runtime.Object, opts ...UpdateOptionFunc) error // Patch patches the given obj in the Kubernetes cluster. obj must be a // struct pointer so that obj can be updated with the content returned by the Server. Patch(ctx context.Context, obj runtime.Object, patch Patch, opts ...PatchOptionFunc) error } // StatusClient knows how to create a client which can update status subresource // for kubernetes objects. type StatusClient interface { Status() StatusWriter } 扫码关注sealyun
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