✨
client-goさわってみた
自己紹介
都内SaaS 企業でSRE エンジニア ２年目のFujihara Akitoです。
週一程度簡単なmemo書を残したいと思っています。
client-go とは？
client-go とは k8aとやりとりするgoのpackageで、k8s api-serverへのアクセスに利用されます。
client-goを構成する機能
- Reflector: API serverからリソースの変更を検知して、DeltaFIFO queueに反映させる
- Informer: API serverからリソースの変更を検知して、Objectの変更を監視する
- Indexer: local cacheを保持しており、Controller内で使うListerはこのcacheから取り出す
- ClientSet: API serverとのやりとりをする
clientsetからpodを取得してみる
podlists.go
package main
import (
"context"
"fmt"
"path/filepath"
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"
)
func main() {
defaultKubeConfigPath := filepath.Join(homedir.HomeDir(), ".kube", "config")
config, _ := clientcmd.BuildConfigFromFlags("", defaultKubeConfigPath)
clientset, _ := kubernetes.NewForConfig(config)
pods, _ := clientset.CoreV1().Pods("").List(context.Background(), metav1.ListOptions{})
fmt.Println("NAMESPACE\tNAME")
for _, pod := range pods.Items {
fmt.Printf("%s\t%s\n", pod.GetNamespace(), pod.GetName())
}
}
command
❯ kind create cluster
❯ go run ./podlist.go
NAMESPACE NAME
kube-system coredns-787d4945fb-4j8h2
kube-system coredns-787d4945fb-h4qwt
kube-system etcd-kind-control-plane
kube-system kindnet-7424d
kube-system kube-apiserver-kind-control-plane
kube-system kube-controller-manager-kind-control-plane
kube-system kube-proxy-fq44p
kube-system kube-scheduler-kind-control-plane
local-path-storage local-path-provisioner-75f5b54ffd-blg54
informerでpodの変更を監視してみる
informer.go
package main
import (
"log"
"path/filepath"
"time"
"k8s.io/apimachinery/pkg/util/wait"
"k8s.io/client-go/informers"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/tools/cache"
"k8s.io/client-go/tools/clientcmd"
"k8s.io/client-go/util/homedir"
)
func main() {
KubeConfigPath := filepath.Join(homedir.HomeDir(), ".kube", "config")
config, _ := clientcmd.BuildConfigFromFlags("", KubeConfigPath)
clientset, _ := kubernetes.NewForConfig(config)
informerFactory := informers.NewSharedInformerFactory(clientset, time.Second*30)
podInformer := informerFactory.Core().V1().Pods()
podInformer.Informer().AddEventHandler(
cache.ResourceEventHandlerFuncs{
AddFunc: AddFuncPod,
UpdateFunc: UpdateFuncPod,
DeleteFunc: DeleteFuncPod,
},
)
StopCh := make(chan struct{})
informerFactory.Start(wait.NeverStop)
go wait.Until(func() {
log.Println("------- running --------")
}, time.Second*10, StopCh)
<-StopCh
}
func AddFuncPod(obj interface{}) {
if pod_name, err := cache.MetaNamespaceKeyFunc(obj); err != nil {
log.Printf("Error Get Pod Obj: %s\n", err.Error())
} else {
log.Println("AddFunc Pod:", pod_name)
}
}
func UpdateFuncPod(old, new interface{}) {
if pod_name, err := cache.MetaNamespaceKeyFunc(new); err != nil {
log.Printf("Error Get Pod Obj: %s\n", err.Error())
} else {
log.Println("UpdateFunc Pod:", pod_name)
}
}
func DeleteFuncPod(obj interface{}) {
if pod_name, err := cache.MetaNamespaceKeyFunc(obj); err != nil {
log.Printf("Error Get Pod Obj: %s\n", err.Error())
} else {
log.Println("DeleteFunc Pod:", pod_name)
}
}
command
❯ kind create cluster
❯ go run ./informer.go
2023/08/03 01:49:39 ------- running --------
2023/08/03 01:49:39 AddFunc Pod: kube-system/etcd-kind-control-plane
2023/08/03 01:49:39 AddFunc Pod: kube-system/kube-controller-manager-kind-control-plane
2023/08/03 01:49:39 AddFunc Pod: kube-system/kube-scheduler-kind-control-plane
2023/08/03 01:49:39 AddFunc Pod: local-path-storage/local-path-provisioner-75f5b54ffd-blg54
2023/08/03 01:49:39 AddFunc Pod: kube-system/kube-apiserver-kind-control-plane
2023/08/03 01:49:39 AddFunc Pod: kube-system/kindnet-7424d
2023/08/03 01:49:39 AddFunc Pod: kube-system/kube-proxy-fq44p
2023/08/03 01:49:39 AddFunc Pod: kube-system/coredns-787d4945fb-h4qwt
2023/08/03 01:49:39 AddFunc Pod: kube-system/coredns-787d4945fb-4j8h2
2023/08/03 01:49:49 ------- running --------
2023/08/03 01:49:59 ------- running --------
2023/08/03 01:50:09 ------- running --------
2023/08/03 01:50:09 UpdateFunc Pod: kube-system/kube-controller-manager-kind-control-plane
2023/08/03 01:50:09 UpdateFunc Pod: kube-system/kube-scheduler-kind-control-plane
2023/08/03 01:50:09 UpdateFunc Pod: local-path-storage/local-path-provisioner-75f5b54ffd-blg54
2023/08/03 01:50:09 UpdateFunc Pod: kube-system/kindnet-7424d
2023/08/03 01:50:09 UpdateFunc Pod: kube-system/coredns-787d4945fb-h4qwt
2023/08/03 01:50:09 UpdateFunc Pod: kube-system/coredns-787d4945fb-4j8h2
2023/08/03 01:50:09 UpdateFunc Pod: kube-system/etcd-kind-control-plane
2023/08/03 01:50:09 UpdateFunc Pod: kube-system/kube-apiserver-kind-control-plane
2023/08/03 01:50:09 UpdateFunc Pod: kube-system/kube-proxy-fq44p
2023/08/03 01:50:19 ------- running --------
・・・・・・
2023/08/03 01:53:49 ------- running --------
2023/08/03 01:53:56 AddFunc Pod: default/nginx
・・・・
2023/08/03 01:55:10 DeleteFunc Pod: default/nginx
2023/08/03 01:55:19 ------- running --------
別でcommandを実行
❯ kubectl run nginx --image=nginx
pod/nginx created
❯ kubectl delete pod nginx
pod "nginx" deleted
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