--- blogpost: true date: Oct 14, 2020 author: JeffreyGuan location: BJ category: Kubernetes tags: kubernetes, client-go, restclient, k8s源码分析 language: English --- # client-go系列之3---restclient的使用 摘要：介绍如何使用client-go中的restclient，可以结合“系列之1”来看。 ![](https://gitee.com/double12gzh/wiki-pictures/raw/master/2020-10-13-client-go-kubeconfig/0.png) ## 0. 背景 > 个人主页: https://gzh.readthedocs.io > > 关注容器技术、关注`Kubernetes`。问题或建议，请公众号留言。 首先我通过`kind`创建了一个6节点的集群，本文章中所有的操作都是在这个集群中进行的。 通过本文的讲解，希望您能了解如何使用client-go中的RESTClient来对资源进行操作，这里我只是举了最简单的例子---pod资源获取。 文中用到的软件的版本如下： * kind ```bash [root@xxx-wsl ~/client-go-example] kind version kind v0.9.0 go1.15.2 linux/amd64 ``` ## 1. 环境准备 通过kind创建多节点的k8s集群: 3个master节点 + 3个worker节点 ```bash [root@xxx-wsl ~/init_kind_clusters] kind create cluster --config=init_cluster.yaml Creating cluster "kind" ... ✓ Ensuring node image (kindest/node:v1.19.1) 🖼 ✓ Preparing nodes 📦 📦 📦 📦 📦 📦 ✓ Configuring the external load balancer ⚖️ ✓ Writing configuration 📜 ✓ Starting control-plane 🕹️ ✓ Installing CNI 🔌 ✓ Installing StorageClass 💾 ✓ Joining more control-plane nodes 🎮 ✓ Joining worker nodes 🚜 Set kubectl context to "kind-kind" You can now use your cluster with: kubectl cluster-info --context kind-kind Not sure what to do next? 😅 Check out https://kind.sigs.k8s.io/docs/user/quick-start/ ``` 其中`init_cluster.yaml`内容如下： ```yaml [root@xxx-wsl ~/init_kind_clusters] cat init_cluster.yaml # a cluster with 3 control-plane nodes and 3 workers kind: Cluster apiVersion: kind.x-k8s.io/v1alpha4 nodes: - role: control-plane - role: control-plane - role: control-plane - role: worker - role: worker - role: worker ``` ## 2. RestClient使用示例 这段代码的作用：从namespace为`kube-system`中获取所有的`pod`并输出到屏幕 `main.go` ```go package main import ( "context" "fmt" corev1 "k8s.io/api/core/v1" metav1 "k8s.io/apimachinery/pkg/apis/meta/v1" "k8s.io/client-go/kubernetes/scheme" "k8s.io/client-go/rest" "k8s.io/client-go/tools/clientcmd" ) func main() { fmt.Println("Prepare config object.") // 加载k8s配置文件，生成Config对象 config, err := clientcmd.BuildConfigFromFlags("", "/root/.kube/config") if err != nil { panic(err) } config.APIPath = "api" config.GroupVersion = &corev1.SchemeGroupVersion config.NegotiatedSerializer = scheme.Codecs fmt.Println("Init RESTClient.") // 定义RestClient，用于与k8s API server进行交互 restClient, err := rest.RESTClientFor(config) if err != nil { panic(err) } fmt.Println("Get Pods in cluster.") // 获取pod列表。这里只会从namespace为"kube-system"中获取指定的资源(pods) result := &corev1.PodList{} if err := restClient. Get(). Namespace("kube-system"). Resource("pods"). VersionedParams(&metav1.ListOptions{Limit: 500}, scheme.ParameterCodec). Do(context.TODO()). Into(result); err != nil { panic(err) } fmt.Println("Print all listed pods.") // 打印所有获取到的pods资源，输出到标准输出 for _, d := range result.Items { fmt.Printf("NAMESPACE: %v NAME: %v \t STATUS: %v \n", d.Namespace, d.Name, d.Status.Phase) } } ``` `go.mod` ```bash module main go 1.15 require ( github.com/go-logr/logr v0.2.1 // indirect github.com/google/gofuzz v1.2.0 // indirect github.com/imdario/mergo v0.3.11 // indirect golang.org/x/crypto v0.0.0-20201002170205-7f63de1d35b0 // indirect golang.org/x/net v0.0.0-20201010224723-4f7140c49acb // indirect golang.org/x/oauth2 v0.0.0-20200902213428-5d25da1a8d43 // indirect golang.org/x/sys v0.0.0-20201009025420-dfb3f7c4e634 // indirect golang.org/x/time v0.0.0-20200630173020-3af7569d3a1e // indirect k8s.io/api v0.19.2 k8s.io/apimachinery v0.19.2 //k8s.io/client-go v11.0.0+incompatible // k8s.io/client-go v11.0.0+incompatible k8s.io/klog v1.0.0 // indirect k8s.io/klog/v2 v2.3.0 // indirect k8s.io/utils v0.0.0-20201005171033-6301aaf42dc7 // indirect ) require k8s.io/client-go v0.19.2 ``` ## 3. 输出结果 ```bash [root@xxx-wsl ~/client-go-example] go run main.go Prepare config object. Init RESTClient. Get Pods in cluster. Print all listed pods. NAMESPACE: kube-system NAME: coredns-f9fd979d6-rhzfd STATUS: Running NAMESPACE: kube-system NAME: coredns-f9fd979d6-whrj2 STATUS: Running NAMESPACE: kube-system NAME: etcd-kind-control-plane STATUS: Running NAMESPACE: kube-system NAME: etcd-kind-control-plane2 STATUS: Running NAMESPACE: kube-system NAME: etcd-kind-control-plane3 STATUS: Running NAMESPACE: kube-system NAME: kindnet-bpsfl STATUS: Running NAMESPACE: kube-system NAME: kindnet-ks6zv STATUS: Running NAMESPACE: kube-system NAME: kindnet-pm6zl STATUS: Running NAMESPACE: kube-system NAME: kindnet-qfhqt STATUS: Running NAMESPACE: kube-system NAME: kindnet-s7qqn STATUS: Running NAMESPACE: kube-system NAME: kindnet-trk5l STATUS: Running NAMESPACE: kube-system NAME: kube-apiserver-kind-control-plane STATUS: Running NAMESPACE: kube-system NAME: kube-apiserver-kind-control-plane2 STATUS: Running NAMESPACE: kube-system NAME: kube-apiserver-kind-control-plane3 STATUS: Running NAMESPACE: kube-system NAME: kube-controller-manager-kind-control-plane STATUS: Running NAMESPACE: kube-system NAME: kube-controller-manager-kind-control-plane2 STATUS: Running NAMESPACE: kube-system NAME: kube-controller-manager-kind-control-plane3 STATUS: Running NAMESPACE: kube-system NAME: kube-proxy-7gz67 STATUS: Running NAMESPACE: kube-system NAME: kube-proxy-bvbkk STATUS: Running NAMESPACE: kube-system NAME: kube-proxy-clf72 STATUS: Running NAMESPACE: kube-system NAME: kube-proxy-d8zpb STATUS: Running NAMESPACE: kube-system NAME: kube-proxy-dsmsj STATUS: Running NAMESPACE: kube-system NAME: kube-proxy-fplkk STATUS: Running NAMESPACE: kube-system NAME: kube-scheduler-kind-control-plane STATUS: Running NAMESPACE: kube-system NAME: kube-scheduler-kind-control-plane2 STATUS: Running NAMESPACE: kube-system NAME: kube-scheduler-kind-control-plane3 STATUS: Running ```