一、创建两个service
[root@master69 kubernetes]# kubectl create -f hl95-notary/hl95-notary-namespace.yaml [root@master69 kubernetes]# kubectl create -f hl95-notary/hl95-notary-api-deployment.yaml [root@master69 kubernetes]# kubectl create -f hl95-notary/hl95-notary-api-service.yaml
[root@master69 kubernetes]# kubectl create -f nginx-demo/nginx-demo-deployment.yaml
[root@master69 kubernetes]# kubectl create -f nginx-demo/nginx-demo-service.yaml
二、查看service
[root@master69 hl95-notary]# kubectl get svc -n default -o wide NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 3d16h <none> nginx-demo-service NodePort 10.100.213.139 <none> 81:30001/TCP 95m app=nginx-k8s-demo
[root@master69 hl95-notary]# kubectl get svc -n hl95-notary -o wide NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR hl95-notary-api-service NodePort 10.104.120.54 <none> 8079:8079/TCP 59m app=hl95-notary-api
可以看到nginx-demo-service位于default命名空间，IP为10.100.213.139
hl95-notary-api-service位于hl95-notary命名空间，ip为10.104.120.54
三、进入nginx-demo-service后端的一个pod中
[root@redis-01 kubernetes]# kubectl exec -it nginx-demo-deployment-59fbc48594-8gns5 /bin/bash
通过服务名称:端口 来访问服务
root@nginx-demo-deployment-59fbc48594-8gns5:/# curl nginx-demo-service:81 <!DOCTYPE html> <html> <head> <title>Welcome to nginx!</title> <style> body { 35em; margin: 0 auto; font-family: Tahoma, Verdana, Arial, sans-serif; } </style> </head> <body> <h1>Welcome to nginx!</h1> <p>If you see this page, the nginx web server is successfully installed and working. Further configuration is required.</p> <p>For online documentation and support please refer to <a href="http://nginx.org/">nginx.org</a>.<br/> Commercial support is available at <a href="http://nginx.com/">nginx.com</a>.</p> <p><em>Thank you for using nginx.</em></p> </body> </html> root@nginx-demo-deployment-59fbc48594-8gns5:/#
访问成功，为什么通过服务名称就能直接访问接口呢？我们查看/etc/resolv.conf，这个域名解析文件
root@nginx-demo-deployment-59fbc48594-8gns5:/# cat /etc/resolv.conf nameserver 10.96.0.10 search default.svc.master69.kubernetes.blockchain.hl95.com svc.master69.kubernetes.blockchain.hl95.com master69.kubernetes.blockchain.hl95.com hlqxt options ndots:5
nameserver：dns服务器地址，10.96.0.10正是kube-dns服务的地址
[root@master69 hl95-notary]# kubectl get svc -n kube-system NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kube-dns ClusterIP 10.96.0.10 <none> 53/UDP,53/TCP,9153/TCP 3d16h
也就是说，pod内的域名访问是通过kube-dns服务来解析的
search:字段，之所以能够通过Service名称和Namespace就能访问Service，就是因为search配置的规则。在解析域名时会自动拼接成完整域名去查询DNS。
如果不带namespace，则默认为dedault
我们直接在nginx的pod里访问另外一个service看看
root@nginx-demo-deployment-59fbc48594-8gns5:/# ping hl95-notary-api-service ping: unknown host
发现未知的主机，报错，说明这个域名是不能解析的，是因为hl95-notary-api-service这个服务在另外一个namespace里，所以需要带上namespace才可以访问
root@nginx-demo-deployment-59fbc48594-8gns5:/# ping hl95-notary-api-service.hl95-notary PING hl95-notary-api-service.hl95-notary.svc.master69.kubernetes.blockchain.hl95.com (10.104.120.54): 56 data bytes 64 bytes from 10.104.120.54: icmp_seq=0 ttl=64 time=0.085 ms 64 bytes from 10.104.120.54: icmp_seq=1 ttl=64 time=0.097 ms
root@nginx-demo-deployment-59fbc48594-8gns5:/# curl hl95-notary-api-service.hl95-notary:8079 {"timestamp":1610504965410,"status":404,"error":"Not Found","message":"No message available","path":"/"}root@nginx-demo-deployment-59fbc48594-8gns5:/#
通过service.namesapce.port成功访问
同样在hl95-notary-api-service后端的pod里也需要加上nginx-demo-service.default才可以访问nginx服务
bash-5.0# ping nginx-demo-service ping: bad address 'nginx-demo-service' bash-5.0# ping nginx-demo-service.default PING nginx-demo-service.default (10.100.213.139): 56 data bytes 64 bytes from 10.100.213.139: seq=0 ttl=64 time=0.093 ms 64 bytes from 10.100.213.139: seq=1 ttl=64 time=0.174 ms
bash-5.0# curl nginx-demo-service.default:81 <!DOCTYPE html> <html> <head> <title>Welcome to nginx!</title> <style> body { 35em; margin: 0 auto; font-family: Tahoma, Verdana, Arial, sans-serif; } </style> </head> <body> <h1>Welcome to nginx!</h1> <p>If you see this page, the nginx web server is successfully installed and working. Further configuration is required.</p> <p>For online documentation and support please refer to <a href="http://nginx.org/">nginx.org</a>.<br/> Commercial support is available at <a href="http://nginx.com/">nginx.com</a>.</p> <p><em>Thank you for using nginx.</em></p> </body> </html> bash-5.0#
如果服务之间是不通的namesapce空间下的，那么在服务之间相互访问，则必须使用service.namesapce来访问，不能直接使用service来访问了。