[kubernetes] Go client

개요

• GitHub
• 예제는 해당 클러스터의 파드로 기동된다고 가정
  • config 설정이 따로 필요 없음
  • 외부 클러스터에 대한 예제

Dockerfile

• FROM golang:1.21.3 AS build
  WORKDIR /work
  COPY go.mod go.sum ./
  RUN go mod download
  COPY ./ ./
  RUN CGO_ENABLED=0 GOOS=linux go build -o main ./main.go
      
  FROM alpine/curl
  COPY --from=build /work/main /usr/bin/.
  ENTRYPOINT ["main"]
  

yaml

•     ---
      apiVersion: rbac.authorization.k8s.io/v1
      kind: ClusterRole
      metadata:
        name: test-api
      rules:
      - apiGroups:
        - ""
        resources:
        - nodes
        - services
        - namespaces
        - pods
        - endpoints
        - persistentvolumeclaims
        - persistentvolumes
        verbs:
        - create
        - get
        - list
        - update
        - delete
          
      ---
      kind: ClusterRoleBinding
      apiVersion: rbac.authorization.k8s.io/v1
      metadata:
        name: test-api
      subjects:
      - kind: ServiceAccount
        name: test-api
        namespace: test
        apiGroup: ""
      roleRef:
        kind: ClusterRole
        name: test-api
        apiGroup: rbac.authorization.k8s.io
          
      ---
      apiVersion: v1
      kind: ServiceAccount
      metadata:
        name: test-api
        namespace: test
          
      ---
      apiVersion: apps/v1
      #kind: Deployment
      kind: StatefulSet
      metadata:
        name: test-api
        namespace: test
      spec:
        replicas: 1
        selector:
          matchLabels:
            app: test-api
        template:
          metadata:
            annotations:
            labels:
              app: test-api
          spec:
            serviceAccountName: test-api
            containers:
              - name: test-api
                image: xxx.xxx.xxx.xxx:xxxx/test-api:0.0.0.1
                imagePullPolicy: Always
                ports:
                  - name: http
                    containerPort: 10000
                    protocol: TCP
            tolerations:
              - key: node-role.kubernetes.io/master
                operator: Exists
                effect: NoSchedule
              - key: node.kubernetes.io/not-ready
                operator: Exists
                effect: NoSchedule
  

예제 - 파드 리스트 가져오기

• 코드

  •  package main
            
     import (
         "context"
         "time"
            
         metaV1 "k8s.io/apimachinery/pkg/apis/meta/v1"
         "k8s.io/client-go/kubernetes"
         "k8s.io/client-go/rest"
     )
            
     func main() {
         config, err := rest.InClusterConfig()
         if err != nil {
             panic(err)
         }
         clientset, err := kubernetes.NewForConfig(config)
         if err != nil {
             panic(err)
         }
         for {
             pods, err := clientset.CoreV1().Pods("").List(context.TODO(), metaV1.ListOptions{})
             if err != nil {
                 println(err)
                 continue
             }
            
             println("pod count :", len(pods.Items))
            
             time.Sleep(10 * time.Second)
         }
     }
    

• 실행 결과

  •  # kubectl logs -f test-api-0 -n test
     pod count : 28
    

예제 - 서비스 생성/삭제

• 코드

  •  package main
            
     import (
     	"context"
            
     	coreV1 "k8s.io/api/core/v1"
     	"k8s.io/apimachinery/pkg/api/errors"
     	metaV1 "k8s.io/apimachinery/pkg/apis/meta/v1"
     	"k8s.io/apimachinery/pkg/util/intstr"
     	"k8s.io/client-go/kubernetes"
     	"k8s.io/client-go/rest"
     )
            
     func main() {
     	config, err := rest.InClusterConfig()
     	if err != nil {
     		panic(err)
     	}
     	clientset, err := kubernetes.NewForConfig(config)
     	if err != nil {
     		panic(err)
     	}
            
     	name := "service-test"
     	namespace := "test"
            
     	if err := clientset.CoreV1().Services(namespace).Delete(context.TODO(), name, metaV1.DeleteOptions{}); err != nil && errors.IsNotFound(err) == false {
     		panic(err)
     	}
            
     	service := &coreV1.Service{
     		ObjectMeta: metaV1.ObjectMeta{
     			Name:      name,
     			Namespace: namespace,
     			Labels: map[string]string{
     				"app": name,
     			},
     		},
     		Spec: coreV1.ServiceSpec{
     			Ports: []coreV1.ServicePort{
     				coreV1.ServicePort{
     					Name:       "metrics",
     					Protocol:   coreV1.ProtocolTCP,
     					Port:       9610,
     					TargetPort: intstr.IntOrString{Type: intstr.Int, IntVal: 9610},
     				},
     			},
     			Type: coreV1.ServiceTypeClusterIP,
     		},
     	}
            
     	if _, err := clientset.CoreV1().Services(namespace).Create(context.TODO(), service, metaV1.CreateOptions{}); err != nil {
     		panic(err)
     	}
            
     	println("create")
     }
    

• 실행 결과

  •  # kubectl logs -f test-api-0 -n test
     create
    

예제 - 엔드포인트 생성/삭제

• 코드

  •  package main
            
     import (
     	"context"
     	coreV1 "k8s.io/api/core/v1"
     	"k8s.io/apimachinery/pkg/api/errors"
     	metaV1 "k8s.io/apimachinery/pkg/apis/meta/v1"
     	"k8s.io/client-go/kubernetes"
     	"k8s.io/client-go/rest"
     )
            
     func main() {
     	config, err := rest.InClusterConfig()
     	if err != nil {
     		panic(err)
     	}
     	clientset, err := kubernetes.NewForConfig(config)
     	if err != nil {
     		panic(err)
     	}
            
     	name := "endpoints-test"
     	namespace := "test"
     	ip := "192.168.1.111"
            
     	if err := clientset.CoreV1().Endpoints(namespace).Delete(context.TODO(), name, metaV1.DeleteOptions{}); err != nil && errors.IsNotFound(err) == false {
     		panic(err)
     	}
            
     	endpoints := &coreV1.Endpoints{
     		ObjectMeta: metaV1.ObjectMeta{
     			Name:      name,
     			Namespace: namespace,
     			Labels: map[string]string{
     				"app": name,
     			},
     		},
     		Subsets: []coreV1.EndpointSubset{
     			coreV1.EndpointSubset{
     				Addresses: []coreV1.EndpointAddress{
     					coreV1.EndpointAddress{
     						IP: ip,
     					},
     				},
     				Ports: []coreV1.EndpointPort{
     					coreV1.EndpointPort{
     						Name:     "metrics",
     						Port:     9610,
     						Protocol: coreV1.ProtocolTCP,
     					},
     				},
     			},
     		},
     	}
            
     	if _, err := clientset.CoreV1().Endpoints(namespace).Create(context.TODO(), endpoints, metaV1.CreateOptions{}); err != nil {
     		panic(err)
     	}
            
     	println("create")
     }
    

• 실행 결과

  •  # kubectl logs -f test-api-0 -n test
     create