使用client-go工具调用kubernetes API接口的教程详解(v1.17版本)

说明

可以调取k8s API 接口的工具有很多，这里我就介绍下client-go

gitlab上client-go项目地址: https://github.com/kubernetes/client-go  

这个工具是由kubernetes官方指定维护的，大家可以放心使用

效果

运行完成后，可以直接获取k8s集群信息等

实现

1、拉取工具源码

注意事项：https://github.com/kubernetes/client-go/blob/master/INSTALL.md

总结：一定要拉取跟集群对应版本的工具源码，比如我这里集群是1.17版本，那我就拉取17版本

go get k8s.io/client-go@v0.17.0

我是1.17版本的集群，所有依赖文件放在这了，可以直接使用client-go k8s1.17 api

2、创建目录结构

集群的角色配置文件（默认在/root/.kube/config）
kube/config

查询代码实例

查询pod信息

查看ferry命名空间下pod的信息，pod名字、pod的IP

vim kube-api.go

package main

import (
"fmt"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"

"k8s.io/client-go/kubernetes"

"k8s.io/client-go/tools/clientcmd"
)

func main() {

config, err := clientcmd.BuildConfigFromFlags("", "kube/config")
if err != nil {
panic(err)
}
client, _ := kubernetes.NewForConfig(config)
pods ,err := client.CoreV1().Pods("ferry").List(metav1.ListOptions{})
if err != nil {
fmt.Println(err)
return
}

for _,v := range  pods.Items {
fmt.Printf(" 命名空间是：％v\n pod名字：％v\n IP：％v\n\n",v.Namespace,v.Name,v.Status.PodIP)
}
}

自动关联依赖

go mod tidy

运行结果

$ go run kube-api.go

 命名空间是：ferry
 pod名字：ferry-backend-7949596679-h8lxb
 IP：10.42.1.14

 命名空间是：ferry
 pod名字：ferry-mysql-8db8d49f7-6psbv
 IP：10.42.1.11

查询一个pod是否在一个命名空间下

https://github.com/kubernetes/client-go/blob/master/examples/in-cluster-client-configuration/main.go
每3秒检查下nginx-74959fc858-cp48w是否在default命名空间下

package main

import (
"context"
"fmt"
"k8s.io/apimachinery/pkg/api/errors"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/tools/clientcmd"
"time"
)

func main() {

config, err := clientcmd.BuildConfigFromFlags("", "kube/config")
if err != nil {
panic(err)
}
clientset, err := kubernetes.NewForConfig(config)
if err != nil {
panic(err.Error())
}
for {
// get pods in all the namespaces by omitting namespace
// Or specify namespace to get pods in particular namespace
pods, err := clientset.CoreV1().Pods("").List(context.TODO(), metav1.ListOptions{})
if err != nil {
panic(err.Error())
}
fmt.Printf("There are ％d pods in the cluster\n", len(pods.Items))

// Examples for error handling:
// - Use helper functions e.g. errors.IsNotFound()
// - And/or cast to StatusError and use its properties like e.g. ErrStatus.Message
_, err = clientset.CoreV1().Pods("default").Get(context.TODO(), "nginx-74959fc858-cp48w", metav1.GetOptions{})
if errors.IsNotFound(err) {
fmt.Printf("Pod nginx-74959fc858-cp48w not found in default namespace\n")
} else if statusError, isStatus := err.(*errors.StatusError); isStatus {
fmt.Printf("Error getting pod ％v\n", statusError.ErrStatus.Message)
} else if err != nil {
panic(err.Error())
} else {
fmt.Printf("Found nginx-74959fc858-cp48w pod in default namespace\n")
}

time.Sleep(3 * time.Second)
}
}

运行结果

$ go run kube-api.go
There are 22 pods in the cluster
Found nginx-74959fc858-cp48w pod in default namespace
There are 22 pods in the cluster
Found nginx-74959fc858-cp48w pod in default namespace
There are 22 pods in the cluster
Found nginx-74959fc858-cp48w pod in default namespace
There are 23 pods in the cluster
Found nginx-74959fc858-cp48w pod in default namespace
There are 22 pods in the cluster
Found nginx-74959fc858-cp48w pod in default namespace
There are 22 pods in the cluster
Found nginx-74959fc858-cp48w pod in default namespace
There are 21 pods in the cluster
\\在集群种手动删除了这个pod
Pod nginx-74959fc858-cp48w not found in default namespace
There are 21 pods in the cluster
Pod nginx-74959fc858-cp48w not found in default namespace

查询deployment服务类型信息

查询default命名空间下的deployment服务信息，服务名字、服务副本数

package main

import (
"fmt"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"

"k8s.io/client-go/kubernetes"

"k8s.io/client-go/tools/clientcmd"
)

func main() {

config, err := clientcmd.BuildConfigFromFlags("", "kube/config")
if err != nil {
panic(err)
}
client, _ := kubernetes.NewForConfig(config)
deploymentList, err := client.AppsV1().Deployments("default").List(metav1.ListOptions{})
if err != nil {
fmt.Println(err)
return
}

for _,v := range deploymentList.Items {
fmt.Printf(" 命名空间是：％v\n deployment服务名字：％v\n 副本个数：％v\n\n",v.Namespace,v.Name,v.Status.Replicas)
}

}

运行结果

$ go run kube-api.go
 命名空间是：default
 deployment服务名字：nginx
 副本个数：2

创建deployment资源

https://github.com/kubernetes/client-go/blob/master/examples/create-update-delete-deployment/main.go

复制一个config文件到当前目录下

创建一个deployment类型的nginx服务

vim deployment-create.go

package main

import (
"context"
"flag"
"fmt"

"path/filepath"

appsv1 "k8s.io/api/apps/v1"
apiv1 "k8s.io/api/core/v1"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/tools/clientcmd"
"k8s.io/client-go/util/homedir"
//
// Uncomment to load all auth plugins
// _ "k8s.io/client-go/plugin/pkg/client/auth"
//
// Or uncomment to load specific auth plugins
// _ "k8s.io/client-go/plugin/pkg/client/auth/azure"
// _ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
// _ "k8s.io/client-go/plugin/pkg/client/auth/oidc"
// _ "k8s.io/client-go/plugin/pkg/client/auth/openstack"
)

func main() {
var kubeconfig *string
if home := homedir.HomeDir(); home != "" {
kubeconfig = flag.String("kubeconfig", filepath.Join("config"), "(optional) absolute path to the kubeconfig file")
} else {
kubeconfig = flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
}
flag.Parse()

config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
if err != nil {
panic(err)
}
clientset, err := kubernetes.NewForConfig(config)
if err != nil {
panic(err)
}

deploymentsClient := clientset.AppsV1().Deployments(apiv1.NamespaceDefault)

deployment := &appsv1.Deployment{
ObjectMeta: metav1.ObjectMeta{
Name: "nginx-deployment",
},
Spec: appsv1.DeploymentSpec{
Replicas: int32Ptr(2),
Selector: &metav1.LabelSelector{
MatchLabels: map[string]string{
"app": "nginx",
},
},
Template: apiv1.PodTemplateSpec{
ObjectMeta: metav1.ObjectMeta{
Labels: map[string]string{
"app": "nginx",
},
},
Spec: apiv1.PodSpec{
Containers: []apiv1.Container{
{
Name:  "web",
Image: "nginx:1.12",
Ports: []apiv1.ContainerPort{
{
Name:          "http",
Protocol:      apiv1.ProtocolTCP,
ContainerPort: 80,
},
},
},
},
},
},
},
}

// Create Deployment
fmt.Println("Creating deployment nginx...")
result, err := deploymentsClient.Create(context.TODO(), deployment, metav1.CreateOptions{})
if err != nil {
panic(err)
}
fmt.Printf("Created deployment ％q.\n", result.GetObjectMeta().GetName())

}

运行结果

$ go run deployment-create.go
Creating deployment nginx...
Created deployment "nginx-deployment".

更新deployment类型服务

https://github.com/kubernetes/client-go/blob/master/examples/create-update-delete-deployment/main.go
更改服务的副本数，由上一步创建的2修改成1，并修改镜像由nginx1.12–>nginx1.13

package main

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

apiv1 "k8s.io/api/core/v1"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/tools/clientcmd"
"k8s.io/client-go/util/homedir"
"k8s.io/client-go/util/retry"
//
// Uncomment to load all auth plugins
// _ "k8s.io/client-go/plugin/pkg/client/auth"
//
// Or uncomment to load specific auth plugins
// _ "k8s.io/client-go/plugin/pkg/client/auth/azure"
// _ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
// _ "k8s.io/client-go/plugin/pkg/client/auth/oidc"
// _ "k8s.io/client-go/plugin/pkg/client/auth/openstack"
)

func main() {
var kubeconfig *string
if home := homedir.HomeDir(); home != "" {
kubeconfig = flag.String("kubeconfig", filepath.Join("config"), "(optional) absolute path to the kubeconfig file")
} else {
kubeconfig = flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
}
flag.Parse()

config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
if err != nil {
panic(err)
}
clientset, err := kubernetes.NewForConfig(config)
if err != nil {
panic(err)
}

deploymentsClient := clientset.AppsV1().Deployments(apiv1.NamespaceDefault)

retryErr := retry.RetryOnConflict(retry.DefaultRetry, func() error {
// Retrieve the latest version of Deployment before attempting update
// RetryOnConflict uses exponential backoff to avoid exhausting the apiserver
result, getErr := deploymentsClient.Get(context.TODO(), "nginx-deployment", metav1.GetOptions{})
if getErr != nil {
panic(fmt.Errorf("Failed to get latest version of Deployment: ％v", getErr))
}

result.Spec.Replicas = int32Ptr(1)                           // reduce replica count
result.Spec.Template.Spec.Containers[0].Image = "nginx:1.13" // change nginx version
_, updateErr := deploymentsClient.Update(context.TODO(), result, metav1.UpdateOptions{})
return updateErr
})
if retryErr != nil {
panic(fmt.Errorf("Update failed: ％v", retryErr))
}
fmt.Println("Updated deployment nginx")

}
func int32Ptr(i int32) *int32 { return &i }

运行结果

$ go run deployment-update.go
Updated deployment nginx

删除deployment类型服务

删除上面创建的nginx-deployment资源，删除之前添加了确认语句

package main

import (
"bufio"
"context"
"flag"
"fmt"
"os"
"path/filepath"

apiv1 "k8s.io/api/core/v1"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/tools/clientcmd"
"k8s.io/client-go/util/homedir"
//
// Uncomment to load all auth plugins
// _ "k8s.io/client-go/plugin/pkg/client/auth"
//
// Or uncomment to load specific auth plugins
// _ "k8s.io/client-go/plugin/pkg/client/auth/azure"
// _ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
// _ "k8s.io/client-go/plugin/pkg/client/auth/oidc"
// _ "k8s.io/client-go/plugin/pkg/client/auth/openstack"
)

func main() {
var kubeconfig *string
if home := homedir.HomeDir(); home != "" {
kubeconfig = flag.String("kubeconfig", filepath.Join( "config"), "(optional) absolute path to the kubeconfig file")
} else {
kubeconfig = flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
}
flag.Parse()

config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
if err != nil {
panic(err)
}
clientset, err := kubernetes.NewForConfig(config)
if err != nil {
panic(err)
}

deploymentsClient := clientset.AppsV1().Deployments(apiv1.NamespaceDefault)

prompt()
fmt.Println("Deleting deployment nginx...")
deletePolicy := metav1.DeletePropagationForeground
if err := deploymentsClient.Delete(context.TODO(), "nginx-deployment", metav1.DeleteOptions{
PropagationPolicy: &deletePolicy,
}); err != nil {
panic(err)
}
fmt.Println("Deleted deployment.")
}

func prompt() {
fmt.Printf("-> Press Return key to continue, will delete!")
scanner := bufio.NewScanner(os.Stdin)
for scanner.Scan() {
break
}
if err := scanner.Err(); err != nil {
panic(err)
}
fmt.Println()
}

func int32Ptr(i int32) *int32 { return &i }

运行结果

$ go run deployment-delete.go
-> Press Return key to continue, will delete! 这里点击回车后继续删除资源

Deleting deployment nginx...
Deleted deployment.

来源：https://blog.csdn.net/zhanremo3062/article/details/119888687