在上一篇文章中，我们主要讨论了使用 operator-sdk 工具编写 Kubernetes Admission Webhook，并针对我们的自定义资源类型创建了我们的第一个 Mutating Admission Webhook。但是，这次我们将为 Deployment、Pod 等核心类型创建另一种类型的 Admission Webhook，称为“验证”，而不是自定义资源类型，因为我们可能并不总是有某种自定义资源类型。
一、Kubebuilder
此外，我们将使用“kubebuilder”来搭建项目模板。为什么？因为改变总是好的。我们在 Trendyol 的平台团队开发 webhook 时正在使用这种方法
Kubebuilder 是一个使用自定义资源定义 (CRD)构建 Kubernetes API 的框架。
与Ruby on Rails和SpringBoot等 Web 开发框架类似，Kubebuilder 提高了速度并降低了开发人员管理的复杂性，以便在 Go 中快速构建和发布 Kubernetes API。它建立在用于构建核心 Kubernetes API 的规范技术之上，以提供简单的抽象来减少样板文件和繁琐的工作。
正如我之前提到的，我们熟悉 Kubernetes Operator 模式中的这些工具，但这些工具也有助于创建 Kubernetes Admission Webhooks。
确实有很好的文档可以用来了解 kubebuilder，但是在这篇文章中，我们将重点关注“Webhook for Core Types”一书的特殊部分。前面我们也提到过，kubebuilder和 operator-sdk不支持核心类型的 webhook 脚手架，我们必须使用controler-runtime中的库来处理它。在控制器运行时有一个
现在，让我们进入Demo部分，这一次使用 kubebuilder工具来弄脏我们的手。
二、D版权声明：本文遵循 CC 4.0 BY-SA 版权协议，若要转载请务必附上原文出处链接及本声明，谢谢合作！ emo 实践
在这个Demo中，我们将根据我们标记为必需的标签来验证 Pod。如果 Pod 上存在必要的注解，那么我们允许创建 Pod，如果没有，我们不允许。
先决条件
- Minikube v1.18.1
- Kubebuilder v2.3.2
- kubectl v1.20.5
- go v1.16.3
我将在 macOS 环境中进行此Demo，因此，您可以使用macOS 的包管理器“brhttps://brew.sh/ew”来安装上述所有工具。
三、验证 Pod 的 AdmissionWebhook
由于我们使用的是 operator-sdk，因此我们可能熟悉 kubebuilder 命令。让我们为项目创建目录
$ mkdir -p pod-validatingwebhook
$ cd pod-validatingwebhook在使用 kubebuilder 初始化项目模板之前，我们应该首先创建 go模块：
$ go mod init pod-validatingwebhook
go: creating new go.mod: module pod-validationwebhook要初始化项目模板，我们应该运行以下命令：
$ kubebuilder init --domain developer.guy --license none --owner "developer-guy"
Writing scaffold for you to edit...
Get controller runtime:
$ go get sigs.k8s.io/[email protected]
Update go.mod:
$ go mod tidy
Running make:
$ make
go: creating new go.mod: module tmp
go get: added sigs.k8s.io/controller-tools v0.2.5
/Users/batuhan.apaydin/go/bin/controller-gen object:headerFile="hack/boilerplate.go.txt" paths="./..."
go fmt ./...
go vet ./...
go build -o bin/manager main.go
Next: define a resource with:
$ kubebuilder create api
# Look at the directory structure, you should see similar to the following
$ tree -L 2 .
.
├── Dockerfile
├── Makefile
├── PROJECT
├── bin
│ └── manager
├── config
│ ├── certmanager
│ ├── default
│ ├── manager
│ ├── prometheus
│ ├── rbac
│ └── webhook
├── go.mod
├── go.sum
├── hack
│ └── boilerplate.go.txt
└── main.go现在，我们已经准备好为 Pod 创建 ValidatingAdmissionWebhook，但让我们先创建一个 API。
$ kubebuilder create api — group core — version v1 — kind Pod — resource=false — controller=false ← be careful here we specified resource and controller creation as false here because we don’t need them.
Writing scaffold for you to edit…
Running make:
$ make
go: creating new go.mod: module tmp
go get: added sigs.k8s.io/controller-tools v0.2.5
/Users/batuhan.apaydin/go/bin/controller-gen object:headerFile=”hack/boilerplate.go.txt” paths=”./…”
Error: go [list -e -json -compiled=true -test=false -export=false -deps=true -find=false -tags ignore_autogenerated — ./…]: exit status 1: go: github.com/developer-guy/pod-validationwebhook: package k8s.io/api/core/v1 imported from implicitly required module; to add missing requirements, run:
go get k8s.io/api/core/[email protected]
# if you get the same error above , just get the dependency and run make again like the following:
$ go get k8s.io/api/core/[email protected]
$ make
go: creating new go.mod: module tmp
go get: added sigs.k8s.io/controller-tools v0.2.5
/Users/batuhan.apaydin/go/bin/controller-gen object:headerFile=”hack/boilerplate.go.txt” paths=”./…”
go fmt ./…
go vet ./…
go build -o bin/manager main.go之后，创建 ValidatingAdmissionWebhook。
# Remember here, programmatic-validation is for ValidatingAdmissionWebhook, and the --default for the Mutating one.
$ kubebuilder create webhook --group core --version v1 --kind Pod --programmatic-validation
Writing scaffold for you to edit...
api/v1/pod_webhook.go打开项目后，您应该注意到main.go和“api/v1/pod_webhook.go”文件中存在某种编译时错误。
因此，为了解决这个问题，我们将遵循我上面提到的 kubebuilder 书中的“Webhook for Core Types ”部分。
让我们用下面的代码来改变pod_webhook.go的内容，然后，我们将稍微解释一下代码。
package v1
import (
"context"
"fmt"
"net/http"
corev1 "k8s.io/api/core/v1"
"sigs.k8s.io/controller-runtime/pkg/client"
"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
)
// +kubebuilder:webhook:verbs=create;update,path=/validate-core-v1-pod,mutating=false,failurePolicy=fail,groups=core,resources=pods,versions=v1,name=vpod.kb.io
// podValidator validates Pods
type podValidator struct {
Client client.Client
decoder *admission.Decoder
}
func NewPodValidator(c client.Client) admission.Handler {
return &podValidator{Client: c}
}
// podValidator admits a pod if a specific annotation exists.
func (v *podValidator) Handle(ctx context.Context, req admission.Request) admission.Response {
pod := &corev1.Pod{}
err := v.decoder.Decode(req, pod)
if err != nil {
return admission.Errored(http.StatusBadRequest, err)
}
key := "example-mutating-admission-webhook"
anno, found := pod.Annotations[key]
if !found {
return admission.Denied(fmt.Sprintf("missing annotation %s", key))
}
if anno != "foo" {
return admission.Denied(fmt.Sprintf("annotation %s did not have value %q", key, "foo"))
}
return admission.Allowed("")
}
// podValidator implements admission.DecoderInjector.
// A decoder will be automatically injected.
// InjectDecoder injects the decoder.
func (v *podValidator) InjectDecoder(d *admission.Decoder) error {
v.decoder = d
return nil
}我们还需要做一件事。打开 main.go 文件并将 55 和 59 之间的行更改为以下内容以注册我们的 webhook 服务器。
pv := v1.NewPodValidator(mgr.GetClient())
mgr.GetWebhookServer().Register("/validate-core-v1-pod", &webhook.Admission{Handler: pv})
现在，我们从代码的角度准备好了。让我们继续部署 webhook。在构建和推送镜像之前，请从 Dockerfile 中删除#L15处的“COPY controllers/controllers/”，因为我们在这里没有使用控制器。
$ make docker-build docker-push IMG=devopps/pod-validationwebhook:v1
go: creating new go.mod: module tmp
go get: added sigs.k8s.io/controller-tools v0.2.5
/Users/batuhan.apaydin/go/bin/controller-gen object:headerFile="hack/boilerplate.go.txt" paths="./..."
go fmt ./...
go vet ./...
/Users/batuhan.apaydin/go/bin/controller-gen "crd:trivialVersions=true" rbac:roleName=manager-role webhook paths="./..." output:crd:artifacts:config=config/crd/bases
go test ./... -coverprofile cover.out
? github.com/developer-guy/pod-validationwebhook [no test files]
? github.com/developer-guy/pod-validationwebhook/api/v1 [no test files]
docker build . -t devopps/pod-validationwebhook:v1
[+] Building 24.2s (16/16) FINISHED
...
docker push devopps/pod-validationwebhook:v1
The push refers to repository [docker.io/devopps/pod-validationwebhook]
45ed4c050068: Pushed
417cb9b79ade: Pushed
v1: digest: sha256:63f3aaf383f34af74027802316f2c58ee750076c2b03046775ad39be818a80c3 size: 739一旦镜像推送成功，我们需要在进入部署部分之前做几件事，请删除config/default文件夹下的3和 9 webhookcainjection_patch.yaml之间的行，因为我们没有在这里创建 MutatingAdmissionWebhook，并删除来自同一目录下的kustomization.yaml的第 16行。另外，从config/rbac目录下的kustomization.yaml中删2行，一切就绪。
我们应该在这里做的最后一件事是启用和部署证书管理器，为了做到这一点，我们应该通过取消注释标记的部分和注释来编辑“config/default/kustomization.yaml” 文件。[WEBHOOK]和[CERTMANAGER]我们知道 kubebuilder 也使用 cert-manager 来管理我们的 webhook的 TLS 管理，所以，我们应该先在我们的集群中安装一个 cert-manager，让我们这样做。
$ minikube start
minikube v1.18.1 on Darwin 10.15.7
✨ Using the virtualbox driver based on user configuration
Starting control plane node minikube in cluster minikube
Creating virtualbox VM (CPUs=3, Memory=8192MB, Disk=20000MB) …
Preparing Kubernetes v1.20.2 on Docker 20.10.3 …
▪ Generating certificates and keys …
▪ Booting up control plane …
▪ Configuring RBAC rules …
Verifying Kubernetes components…
▪ Using image gcr.io/k8s-minikube/storage-provisioner:v4
Enabled addons: storage-provisioner, default-storageclass
Done! kubectl is now configured to use “minikube” cluster and “default” namespace by default
$ helm repo add jetstack https://charts.jetstack.io
"jetstack" has been added to your repositories
$ helm install \
cert-manager jetstack/cert-manager \
--namespace cert-manager \
--version v1.2.0 \
--create-namespace \
--set installCRDs=true
NAME: cert-manager
LAST DEPLOYED: Mon Apr 5 22:53:17 2021
NAMESPACE: cert-manager
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
cert-manager has been deployed successfully!
In order to begin issuing certificates, you will need to set up a ClusterIssuer
or Issuer resource (for example, by creating a 'letsencrypt-staging' issuer).
More information on the different types of issuers and how to configure them
can be found in our documentation:
https://cert-manager.io/docs/configuration/
For information on how to configure cert-manager to automatically provision
Certificates for Ingress resources, take a look at the `ingress-shim`
documentation:
https://cert-manager.io/docs/usage/ingress/
$ kubectl get pods --namespace cert-manager --watch
NAME READY STATUS RESTARTS AGE
cert-manager-85f9bbcd97-pqmnv 1/1 Running 0 3m46s
cert-manager-cainjector-74459fcc56-nnpjg 1/1 Running 0 3m46s
cert-manager-webhook-57d97ccc67-8vjff 1/1 Running 0 3m46s现在，我们已准备好部署 webhook。
$ make deploy IMG=devopps/pod-validationwebhook:v1
go: creating new go.mod: module tmp
go get: added sigs.k8s.io/controller-tools v0.2.5
/Users/batuhan.apaydin/go/bin/controller-gen “crd:trivialVersions=true” rbac:roleName=manager-role webhook paths=”./…” output:crd:artifacts:config=config/crd/bases
cd config/manager && kustomize edit set image controller=devopps/pod-validationwebhook:v1
kustomize build config/default | kubectl apply -f -
namespace/pod-validatingwebhook-system created
role.rbac.authorization.k8s.io/pod-validatingwebhook-leader-election-role created
clusterrole.rbac.authorization.k8s.io/pod-validatingwebhook-proxy-role created
Warning: rbac.authorization.k8s.io/v1beta1 ClusterRole is deprecated in v1.17+, unavailable in v1.22+; use rbac.authorization.k8s.io/v1 ClusterRole
clusterrole.rbac.authorization.k8s.io/pod-validatingwebhook-metrics-reader created
rolebinding.rbac.authorization.k8s.io/pod-validatingwebhook-leader-election-rolebinding created
clusterrolebinding.rbac.authorization.k8s.io/pod-validatingwebhook-manager-rolebinding created
clusterrolebinding.rbac.authorization.k8s.io/pod-validatingwebhook-proxy-rolebinding created
service/pod-validatingwebhook-controller-manager-metrics-service created
service/pod-validatingwebhook-webhook-service created
deployment.apps/pod-validatingwebhook-controller-manager created
certificate.cert-manager.io/pod-validatingwebhook-serving-cert created
issuer.cert-manager.io/pod-validatingwebhook-selfsigned-issuer created
Warning: admissionregistration.k8s.io/v1beta1 ValidatingWebhookConfiguration is deprecated in v1.16+, unavailable in v1.22+; use admissionregistration.k8s.io/v1 ValidatingWebhookConfiguration
validatingwebhookconfiguration.admissionregistration.k8s.io/pod-validatingwebhook-validating-webhook-configuration created耶！！！似乎一切正常，但让我们通过创建没有必需注释的 Pod 来测试 webhook。
# test with invalid Pod
$ kubectl run --generator=run-pod/v1 nginx --image=nginx
Found existing alias for “kubectl”. You should use: “k”
Alias tip: k run — generator=run-pod/v1 nginx — image=nginx
Flag — generator has been deprecated, has no effect and will be removed in the future.
Error from server (missing annotation example-mutating-admission-webhook): admission webhook “vpod.kb.io” denied the request: missing annotation example-mutating-admission-webhook
# test with valid Pod
$ kubectl run --generator=run-pod/v1 nginx --image=nginx --overrides='{ "apiVersion": "v1", "metadata": {"annotations": { "required-label":"foo" } } }'
Flag --generator has been deprecated, has no effect and will be removed in the future.
pod/nginx created现在，我们证明一切都如我们预期
参考文献
https://medium.com/trendyol-tech/getting-started-to-write-your-first-kubernetes-admission-webhook-part-2-48d0b0b1780e
你好，能否把完整的代码共享一下，按照你的步骤，总是部署不成功，最后提示如下错误
Error from server (InternalError): error when creating “deploy.yaml”: Internal error occurred: failed calling webhook “vpod.kb.io”: Post “https://pod-validatingwebhook-webhook-service.pod-validatingwebhook-system.svc:443/validate-core-v1-pod?timeout=10s”: EOF