18-ExternalName类型和endpoint实现K8S集群外部服务映射
一、ExternalName类型实现K8S集群外部服务映射
1.编写资源清单
[root@master231 service]# cat 04-svc-ExternalName.yaml
apiVersion: v1
kind: Service
metadata:
name: svc-externalname
spec:
# externalName: www.baidu.com
externalName: www.cnblogs.com
type: ExternalName
2.创建资源
[root@master231 service]# kubectl apply -f 04-svc-ExternalName.yaml
service/svc-externalname created
[root@master231 service]# kubectl get -f 04-svc-ExternalName.yaml
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
svc-externalname ExternalName <none> www.cnblogs.com <none> 3s
3.使用 dig 工具查询集群中svc-externalname的DNS 解析结果
[root@master231 service]# dig @10.200.0.10 svc-externalname.default.svc.oldboyedu.com +short
www.cnblogs.com.
118.31.180.41
101.37.225.65
[root@master231 service]# ping www.cnblogs.com -c 3
PING www.cnblogs.com (118.31.180.41) 56(84) bytes of data.
64 bytes from 118.31.180.41 (118.31.180.41): icmp_seq=1 ttl=128 time=26.9 ms
64 bytes from 118.31.180.41 (118.31.180.41): icmp_seq=2 ttl=128 time=26.7 ms
64 bytes from 118.31.180.41 (118.31.180.41): icmp_seq=3 ttl=128 time=26.9 ms
--- www.cnblogs.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2005ms
rtt min/avg/max/mdev = 26.724/26.839/26.931/0.086 ms
#dig到的dns与ping得到的dns相同，如果不同可能是网站本身做了CDN加速
4.使用缺陷
使用ExternalName实现外部服务映射需要单独配置DNS服务，因为涉及到了其他技术栈，学习成本高，不经常使用。通常使用endpoint来实现。
二、endpoints实现K8S集群外部服务映射
1.什么是endpoints
endpoints简称ep，表示端点的意思，用户存储一个或多个IP地址及端口列表。
除了ExternalName外的svc类型，在创建时都会创建一个同名称的ep资源。
当svc删除时会自动删除该ep。
我们如果想要将局域网内部的某个服务器的服务映射到K8S集群内部的某个svc，我们的思路可以先创建一个ep，而后创建一个同名称的svc与之关联即可。
2.验证svc对应的ep关系
2.1 查看svc的全部信息
[root@master231 service]# kubectl get svc -A
NAMESPACE NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
calico-apiserver calico-api ClusterIP 10.200.87.86 <none> 443/TCP 2d4h
calico-system calico-kube-controllers-metrics ClusterIP None <none> 9094/TCP 2d4h
calico-system calico-typha ClusterIP 10.200.43.178 <none> 5473/TCP 2d4h
default baidu ExternalName <none> www.cnblogs.com <none> 10m
default kubernetes ClusterIP 10.200.0.1 <none> 443/TCP 2d4h
default rc-xiuxian ClusterIP 10.200.196.245 <none> 80/TCP 24h
default svc-externalname ExternalName <none> www.cnblogs.com <none> 8m51s
default svc-wp-lb LoadBalancer 10.200.229.158 10.0.0.151 80:30130/TCP 40m
default svc-xiuxian ClusterIP 10.200.25.148 <none> 90/TCP 24h
default svc-xiuxian-nodeport NodePort 10.200.21.38 <none> 90:30090/TCP 22h
kube-system kube-dns ClusterIP 10.200.0.10 <none> 53/UDP,53/TCP,9153/TCP 2d4h
metallb-system metallb-webhook-service ClusterIP 10.200.27.157 <none> 443/TCP 3h59m
oldboyedu svc-db ClusterIP 10.200.86.142 <none> 3306/TCP 40m
oldboyedu svc-xiuxian-lb LoadBalancer 10.200.150.228 10.0.0.150 90:30120/TCP 3h52m
2.2 查看endpoint的全部信息
[root@master231 service]# kubectl get endpoints -A
NAMESPACE NAME ENDPOINTS AGE
calico-apiserver calico-api 10.100.140.67:5443,10.100.203.144:5443 2d4h
calico-system calico-kube-controllers-metrics 10.100.160.134:9094 2d4h
calico-system calico-typha 10.0.0.232:5473,10.0.0.233:5473 2d4h
default kubernetes 10.0.0.231:6443 2d4h
default rc-xiuxian <none> 24h
default svc-wp-lb 10.100.140.127:80 39m
default svc-xiuxian <none> 24h
default svc-xiuxian-nodeport <none> 22h
kube-system kube-dns 10.100.160.133:53,10.100.160.135:53,10.100.160.133:53 + 3 more... 2d4h
metallb-system metallb-webhook-service 10.100.203.160:9443 3h58m
oldboyedu svc-db 10.100.203.169:3306 39m
oldboyedu svc-xiuxian-lb 10.100.140.119:80,10.100.140.120:80,10.100.203.161:80 + 2 more... 3h51m
2.3 得出结论
我们对比两张表来看，只有当svc类型为ExternalName时，不会自动创建一个endpoint资源
2.4 查看详细信息
#选择一个svc类型为非ExternalName查看详细信息，时创建了ep资源的，endpoint已经列出所有准备好的（Ready）Pod 的 IP 地址
[root@master231 service]# kubectl -n oldboyedu describe svc svc-xiuxian-lb
Name: svc-xiuxian-lb
Namespace: oldboyedu
Labels: <none>
Annotations: metallb.io/ip-allocated-from-pool: linux96
Selector: version=v1
Type: LoadBalancer
IP Family Policy: SingleStack
IP Families: IPv4
IP: 10.200.150.228
IPs: 10.200.150.228
LoadBalancer Ingress: 10.0.0.150
Port: <unset> 90/TCP
TargetPort: 80/TCP
NodePort: <unset> 30120/TCP
Endpoints: 10.100.140.119:80,10.100.140.120:80,10.100.203.161:80 + 2 more...
Session Affinity: None
External Traffic Policy: Cluster
Events: <none>
#查看该pod的详细ep信息
[root@master231 service]# kubectl -n oldboyedu describe ep svc-xiuxian-lb
Name: svc-xiuxian-lb
Namespace: oldboyedu
Labels: <none>
Annotations: endpoints.kubernetes.io/last-change-trigger-time: 2025-04-09T04:00:15Z
Subsets:
Addresses: 10.100.140.119,10.100.140.120,10.100.203.161,10.100.203.162,10.100.203.164
NotReadyAddresses: <none>
Ports:
Name Port Protocol
---- ---- --------
<unset> 80 TCP
Events: <none>
3.ep实战案例
3.1 在K8S集群外部部署MySQL数据库
[root@harbor250.oldboyedu.com ~]# docker run -d --name mysql-server --network host -e MYSQL_DATABASE=wordpress -e MYSQL_ALLOW_EMPTY_PASSWORD=yes -e MYSQL_USER=admin -e MYSQL_PASSWORD=yinzhengjie harbor250.oldboyedu.com/oldboyedu-wp/mysql:8.0.36-oracle --character-set-server=utf8 --collation-server=utf8_bin --default-authentication-plugin=mysql_native_password
[root@harbor250.oldboyedu.com ~]# ss -ntl | grep 3306
LISTEN 0 70 *:33060 *:*
LISTEN 0 151 *:3306 *:*
[root@harbor250.oldboyedu.com ~]# docker exec -it mysql-server mysql wordpress
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 8.0.36 MySQL Community Server - GPL
Copyright (c) 2000, 2024, Oracle and/or its affiliates.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> SHOW TABLES;
Empty set (0.00 sec)
mysql>
3.2 编写资源清单
[root@master231 endpoints]# cat 01-ep-svc-deploy.yaml
apiVersion: v1
#设置资源类型为ep，资源名称为ep-db
kind: Endpoints
metadata:
name: ep-db
subsets:
- addresses:
#获取10.0.0.250外部服务器的mysql服务
- ip: 10.0.0.250
ports:
- port: 3306
---
#使用默认的svc类型，
apiVersion: v1
kind: Service
#使用ep资源向服务器内部暴露端口
metadata:
name: ep-db
spec:
type: ClusterIP
ports:
- port: 3306
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: deploy-wp
namespace: default
spec:
replicas: 1
selector:
matchLabels:
apps: wp
template:
metadata:
labels:
apps: wp
spec:
containers:
- image: harbor250.oldboyedu.com/oldboyedu-wp/wordpress:6.7.1-php8.1-apache
name: wp
env:
- name: WORDPRESS_DB_HOST
# 指定数据库服务的来源为ep-db
value: ep-db
- name: WORDPRESS_DB_NAME
value: wordpress
- name: WORDPRESS_DB_USER
value: admin
- name: WORDPRESS_DB_PASSWORD
value: yinzhengjie
---
apiVersion: v1
kind: Service
metadata:
name: svc-wp-lb
namespace: default
spec:
type: LoadBalancer
ports:
- port: 80
selector:
apps: wp
[root@master231 endpoints]# kubectl apply -f 01-ep-svc-deploy.yaml
endpoints/ep-db created
service/ep-db created
deployment.apps/deploy-wp created
[root@master231 endpoints]# kubectl get -f 01-ep-svc-deploy.yaml
NAME ENDPOINTS AGE
endpoints/ep-db 10.0.0.250:3306 4s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/ep-db ClusterIP 10.200.2.2 <none> 3306/TCP 4s
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/deploy-wp 1/1 1 1 4s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/svc-wp-lb LoadBalancer 10.200.77.193 10.0.0.151 80:32203/TCP 4s
[root@master231 endpoints]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
deploy-wp-6666c4477c-5zc8q 1/1 Running 0 60s 10.100.140.66 worker233 <none> <none>
3.3 测试验证
在网页安装好WordPress，查看数据库
[root@harbor250.oldboyedu.com ~]# docker exec -it mysql-server mysql wordpress
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 8.0.36 MySQL Community Server - GPL
Copyright (c) 2000, 2024, Oracle and/or its affiliates.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
mysql> SHOW TABLES;
+-----------------------+
| Tables_in_wordpress |
+-----------------------+
| wp_commentmeta |
| wp_comments |
| wp_links |
| wp_options |
| wp_postmeta |
| wp_posts |
| wp_term_relationships |
| wp_term_taxonomy |
| wp_termmeta |
| wp_terms |
| wp_usermeta |
| wp_users |
+-----------------------+
12 rows in set (0.00 sec)
mysql>
本文来自博客园，作者：丁志岩，转载请注明原文链接：https://www.cnblogs.com/dezyan/p/18817404
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