乐趣区

kubernetes-CRD如此简单

jiezi

原文地址

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
<!–more–>

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

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
}

探讨可加 QQ 群：98488045

退出移动版