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

目录

• 说明
• 效果
• 实现
• 1、拉取工具源码
• 2、创建目录结构
• 查询代码实例
• 创建deployment资源
• 更新deployment类型服务
• 删除deployment类型服务

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.

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