GO 获取 K8S api 服务器健康状态

Question

我有一个 golang 程序，我需要向K8S API server status (livez) api 添加一个新调用以获取运行状况。

https://kubernetes.io/docs/reference/using-api/health-checks/

程序应该在api服务器的同一个集群上运行并且需要获得/livez状态，我试图在client-go lib中找到这个API但没有找到实现它的方法...

https://github.com/kubernetes/client-go

有没有办法从运行在 API 服务器运行的同一个集群上的 Go 程序中做到这一点？

Answer 1

更新（最终答案）

附加

OP 要求我修改我的答案以显示“微调”或“特定”服务帐户的配置，而不使用集群管理员..

据我所知，默认情况下，每个 pod 都具有从 /healthz 读取的权限。例如，下面的CronJob 完全不使用ServiceAccount 就可以正常工作：

# cronjob
apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: is-healthz-ok-no-svc
spec:
  schedule: "*/5 * * * *" # at every fifth minute
  jobTemplate:
    spec:
      template:
        spec:
######### serviceAccountName: health-reader-sa
          containers:
            - name: is-healthz-ok-no-svc
              image: oze4/is-healthz-ok:latest
          restartPolicy: OnFailure

原创

我继续为此写了一个概念证明。 You can find the full repo here，但代码如下。

main.go

package main

import (
    "os"
    "errors"
    "fmt"

    "k8s.io/client-go/kubernetes"
    "k8s.io/client-go/rest"
)

func main() {
    client, err := newInClusterClient()
    if err != nil {
        panic(err.Error())
    }

    path := "/healthz"
    content, err := client.Discovery().RESTClient().Get().AbsPath(path).DoRaw()
    if err != nil {
        fmt.Printf("ErrorBadRequst : %s\n", err.Error())
        os.Exit(1)
    }

    contentStr := string(content)
    if contentStr != "ok" {
        fmt.Printf("ErrorNotOk : response != 'ok' : %s\n", contentStr)
        os.Exit(1)
    }

    fmt.Printf("Success : ok!")
    os.Exit(0)
}

func newInClusterClient() (*kubernetes.Clientset, error) {
    config, err := rest.InClusterConfig()
    if err != nil {
        return &kubernetes.Clientset{}, errors.New("Failed loading client config")
    }
    clientset, err := kubernetes.NewForConfig(config)
    if err != nil {
        return &kubernetes.Clientset{}, errors.New("Failed getting clientset")
    }
    return clientset, nil
}

码头文件

FROM golang:latest
RUN mkdir /app
ADD . /app
WORKDIR /app
RUN go build -o main .
CMD ["/app/main"]

deploy.yaml

（作为 CronJob）

# cronjob
apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: is-healthz-ok
spec:
  schedule: "*/5 * * * *" # at every fifth minute
  jobTemplate:
    spec:
      template:
        spec:
          serviceAccountName: is-healthz-ok
          containers:
            - name: is-healthz-ok
              image: oze4/is-healthz-ok:latest
          restartPolicy: OnFailure
---
# service account
apiVersion: v1
kind: ServiceAccount
metadata:
  name: is-healthz-ok
  namespace: default
---
# cluster role binding
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: is-healthz-ok
subjects:
  - kind: ServiceAccount
    name: is-healthz-ok
    namespace: default
roleRef:
  kind: ClusterRole
  ##########################################################################
  # Instead of assigning cluster-admin you can create your own ClusterRole #
  # I used cluster-admin because this is a homelab                         #
  ##########################################################################
  name: cluster-admin
  apiGroup: rbac.authorization.k8s.io
---

截图

成功的 CronJob 运行

---

更新 1

OP 询问如何部署“in-cluster-client-config”，所以我提供了一个示例部署（我正在使用的）..

你可以找到repo here

示例部署（我使用的是 CronJob，但它可以是任何东西）：

cronjob.yaml

apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: remove-terminating-namespaces-cronjob
spec:
  schedule: "0 */1 * * *" # at minute 0 of each hour aka once per hour
  #successfulJobsHistoryLimit: 0
  #failedJobsHistoryLimit: 0
  jobTemplate:
    spec:
      template:
        spec:
          serviceAccountName: svc-remove-terminating-namespaces
          containers:
          - name: remove-terminating-namespaces
            image: oze4/service.remove-terminating-namespaces:latest
          restartPolicy: OnFailure

rbac.yaml

apiVersion: v1
kind: ServiceAccount
metadata:
  name: svc-remove-terminating-namespaces
  namespace: default
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: crb-namespace-reader-writer
subjects:
- kind: ServiceAccount
  name: svc-remove-terminating-namespaces
  namespace: default
roleRef:
  kind: ClusterRole
  ##########################################################################
  # Instead of assigning cluster-admin you can create your own ClusterRole #
  # I used cluster-admin because this is a homelab                         #
  ##########################################################################
  name: cluster-admin
  apiGroup: rbac.authorization.k8s.io
---

---

原答案

听起来您正在寻找的是来自 client-go 的“in-cluster-client-config”。

请务必记住，当使用“in-cluster-client-config”时，Go 代码中的 API 调用会使用“that”pod 的服务帐户。只是想确保您使用有权读取“/livez”的帐户进行测试。

我测试了以下代码，我能够获得“livez”状态..

package main

import (
    "errors"
    "flag"
    "fmt"
    "path/filepath"

    "k8s.io/client-go/kubernetes"
    "k8s.io/client-go/tools/clientcmd"
    "k8s.io/client-go/rest"
    "k8s.io/client-go/util/homedir"
)

func main() {
    // I find it easiest to use "out-of-cluster" for tetsing
    // client, err := newOutOfClusterClient()

    client, err := newInClusterClient()
    if err != nil {
        panic(err.Error())
    }

    livez := "/livez"
    content, _ := client.Discovery().RESTClient().Get().AbsPath(livez).DoRaw()

    fmt.Println(string(content))
}

func newInClusterClient() (*kubernetes.Clientset, error) {
    config, err := rest.InClusterConfig()
    if err != nil {
        return &kubernetes.Clientset{}, errors.New("Failed loading client config")
    }
    clientset, err := kubernetes.NewForConfig(config)
    if err != nil {
        return &kubernetes.Clientset{}, errors.New("Failed getting clientset")
    }
    return clientset, nil
}

// I find it easiest to use "out-of-cluster" for tetsing
func newOutOfClusterClient() (*kubernetes.Clientset, error) {
    var kubeconfig *string
    if home := homedir.HomeDir(); home != "" {
        kubeconfig = flag.String("kubeconfig", filepath.Join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
    } else {
        kubeconfig = flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
    }
    flag.Parse()

    // use the current context in kubeconfig
    config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
    if err != nil {
        return nil, err
    }

    // create the clientset
    client, err := kubernetes.NewForConfig(config)
    if err != nil {
        return nil, err
    }

    return client, nil
}