client-go系列之3---restclient的使用
0. 背景
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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
[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
[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：
[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
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
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
[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
4. 调用分析
简略调用图
详细调用图(图片较大，请耐心等待加载，或者从这里下载到本地)
