Kubernetes-Service

Service

一种访问Pod的策略，其他的Pod可以通过这个Service访问到这个Service代理的Pod。

apiVersion: v1
kind: Service
metadata:
  labels:
    app: nginx
  name: nginx
  namespace: default
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: nginx
  sessionAffinity: None
  type: ClusterIP

Service类型：

• ClusterIP：集群内部使用，默认使用
• NodePort：在所有安装了kube-proxy的节点上打开一个端口，此端口可以代理至后端Pod，然后集群外部可以使用节点的IP地址和NodePort的端口号访问到集群Pod的服务。NodePort默认端口访问：30000-32767
• LoadBalance：会用云提供商的负载均衡器公开服务。
• ExternalName: 通过返回定义的CNAME别名

代理k8s外部服务

apiVersion: v1
kind: Service
metadata:
  labels:
    app: nginx-svc-external
  name: nginx-svc-external
spec:
  ports:
  - name: http
    port: 80
    protocol: TCP
    targetPort: 80
  sessionAffinity: None
  type: ClusterIP
---
apiVersion: v1
kind: Endpoints
metadata:
  labels:
    app: nginx-svc-external
  name: nginx-svc-external
  namespace: default
subsets:
- addresses:
  - ip: 220.181.38.251
  ports:
  - name: http
    port: 80
    protocol: TCP

要确保Endpoints和Service的name和labels名字相同，还有port的名字、端口、协议相同才能匹配

$ kubectl get ep
NAME                 ENDPOINTS                             AGE
nginx                172.16.107.204:80,172.16.169.139:80   4h22m
nginx-svc-external   220.181.38.251:80                     8m20s
$ kubectl get svc
NAME                 TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
nginx                ClusterIP   10.0.0.252   <none>        80/TCP    4h22m
nginx-svc-external   ClusterIP   10.0.0.105   <none>        80/TCP    8m29s

Pod访问service名称或者ClusterIP，测试service能否正常代理外部的百度地址

$ curl baidu.com -I
HTTP/1.1 200 OK
Date: Wed, 12 Jan 2022 05:49:19 GMT
Server: Apache
Last-Modified: Tue, 12 Jan 2010 13:48:00 GMT
ETag: "51-47cf7e6ee8400"
Accept-Ranges: bytes
Content-Length: 81
Cache-Control: max-age=86400
Expires: Thu, 13 Jan 2022 05:49:19 GMT
Connection: Keep-Alive
Content-Type: text/html

$ curl 10.0.0.105 -I
HTTP/1.1 200 OK
Date: Wed, 12 Jan 2022 05:49:07 GMT
Server: Apache
Last-Modified: Tue, 12 Jan 2010 13:48:00 GMT
ETag: "51-47cf7e6ee8400"
Accept-Ranges: bytes
Content-Length: 81
Cache-Control: max-age=86400
Expires: Thu, 13 Jan 2022 05:49:07 GMT
Connection: Keep-Alive
Content-Type: text/html