首页 > 编程语言 > 使用client-go工具调用kubernetes API接口的教程详解(v1.17版本)
2022
05-30

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

在这里插入图片描述

效果

运行完成后，可以直接获取k8s集群信息等

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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

在这里插入图片描述

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

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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

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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

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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

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创建一个deployment类型的nginx服务

vim deployment-create.go

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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

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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

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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

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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.

在这里插入图片描述

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