kubernetes CRD开发的示例分析

这篇文章主要介绍了kubernetes CRD开发的示例分析，具有一定借鉴价值，感兴趣的朋友可以参考下，希望大家阅读完这篇文章之后大有收获，下面让小编带着大家一起了解一下。

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/kubebuildercd kubebuildermake buildcp 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 tmpcurl -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/kubebuilderexport 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CRDmake run # 启动controller

然后我们就可以看到创建的CRD了

# kubectl get crdNAME                                           AGEvirtulmachines.infra.sealyun.com                  52m

来创建一个虚拟机：

# kubectl apply -f config/samples/# kubectl get virtulmachines.infra.sealyun.com NAME                   AGEvirtulmachine-sample   49m

看一眼yaml文件：

# cat config/samples/infra_v1_virtulmachine.yaml apiVersion: infra.sealyun.com/v1kind: VirtulMachinemetadata:  name: virtulmachine-samplespec:  # 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-controllermake 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: testdocker-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 binaryFROM golang:1.12.7 as builderWORKDIR /go/src/github.com/fanux/sealvm# Copy the Go Modules manifestsCOPY . . # BuildRUN 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:latestFROM golang:1.12.7WORKDIR /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-systemNAME                        DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGEsealvm-controller-manager   1         1         1            0           3mkubectl get svc -n sealvm-systemNAME                                        TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)    AGEsealvm-controller-manager-metrics-service   ClusterIP   10.98.71.199           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/v1kind: VirtulMachinemetadata:  name: virtulmachine-samplespec:  # 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/v1kind: VirtulMachinemetadata:  name: virtulmachine-samplespec:  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/v1kind: VirtulMachinemetadata:  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-5254bc16e436spec:      # 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=truetype 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}

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