Kubernetes----HeadLess类型的Service
作者:redrose2100   类别:    日期:2022-05-23 14:26:32    阅读:1448 次   消耗积分:0 分

一、Headless类型Service简介

在某些场景下,开发人员可能不想使用Service提供的负载均衡功能,而希望自己来控制负载均衡策略,针对这种情况,Kubernetes提供了Headless Service,这类Service不会分配ClusterIP,如果想要访问Service,只能通过service的域名进行查询

二、环境准备

编写deployment.yaml文件,内容如下:

  1. apiVersion: v1
  2. kind: Namespace
  3. metadata:
  4. name: dev
  5. ---
  6. apiVersion: apps/v1
  7. kind: Deployment
  8. metadata:
  9. name: pc-deployment
  10. namespace: dev
  11. spec:
  12. replicas: 3
  13. selector:
  14. matchLabels:
  15. app: nginx-pod
  16. template:
  17. metadata:
  18. labels:
  19. app: nginx-pod
  20. spec:
  21. containers:
  22. - name: nginx
  23. image: nginx:1.17.1
  24. ports:
  25. - containerPort: 80

然后使用如下命令创建资源

  1. [root@master service]# kubectl apply -f deployment.yaml
  2. namespace/dev created
  3. deployment.apps/pc-deployment created
  4. [root@master service]#

查看创建的资源如下:

  1. [root@master service]# kubectl get deploy,pod -n dev -o wide
  2. NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
  3. deployment.apps/pc-deployment 3/3 3 3 17m nginx nginx:1.17.1 app=nginx-pod
  4. NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
  5. pod/pc-deployment-5ffc5bf56c-mqwst 1/1 Running 0 17m 10.244.2.191 node2 <none> <none>
  6. pod/pc-deployment-5ffc5bf56c-qbznm 1/1 Running 0 17m 10.244.1.53 node1 <none> <none>
  7. pod/pc-deployment-5ffc5bf56c-zxnsx 1/1 Running 0 17m 10.244.2.190 node2 <none> <none>
  8. [root@master service]#

三、创建Headless类型的Service

编辑headless.yaml文件,内容如下:

  1. apiVersion: v1
  2. kind: Service
  3. metadata:
  4. name: service-headless
  5. namespace: dev
  6. spec:
  7. selector:
  8. app: nginx-pod
  9. clusterIP: None
  10. type: ClusterIP
  11. ports:
  12. - port: 80
  13. targetPort: 80

使用如下命令创建服务

  1. [root@master service]# kubectl apply -f headless.yaml
  2. service/service-headless created
  3. [root@master service]#

查看创建的资源

  1. [root@master service]# kubectl get service,deployment,pod -n dev -o wide
  2. NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
  3. service/service-headless ClusterIP None <none> 80/TCP 99s app=nginx-pod
  4. NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
  5. deployment.apps/pc-deployment 3/3 3 3 8m50s nginx nginx:1.17.1 app=nginx-pod
  6. NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
  7. pod/pc-deployment-5ffc5bf56c-mqwst 1/1 Running 0 8m50s 10.244.2.191 node2 <none> <none>
  8. pod/pc-deployment-5ffc5bf56c-qbznm 1/1 Running 0 8m50s 10.244.1.53 node1 <none> <none>
  9. pod/pc-deployment-5ffc5bf56c-zxnsx 1/1 Running 0 8m50s 10.244.2.190 node2 <none> <none>
  10. [root@master service]#

此时服务因为没有ClusterIP,所以此时不能使用ip去访问了,只能使用域名访问了,即 service-headless.dev.svc.cluster.local,这里面格式是

  1. [service的名字].[命名空间].svc.cluster.local

首先登录pod查看域名解析

  1. [root@master service]# kubectl exec -it pod/pc-deployment-5ffc5bf56c-mqwst -n dev /bin/bash
  2. kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
  3. root@pc-deployment-5ffc5bf56c-9bg6w:/#
  4. root@pc-deployment-5ffc5bf56c-9bg6w:/# cat /etc/resolv.conf
  5. nameserver 10.96.0.10
  6. search dev.svc.cluster.local svc.cluster.local cluster.local
  7. options ndots:5
  8. root@pc-deployment-5ffc5bf56c-9bg6w:/#

然后查看域名解析,具体查看域名的命令如下

  1. [root@master service]# dig @10.96.0.10 service-headless.dev.svc.cluster.local
  2. ; <<>> DiG 9.11.4-P2-RedHat-9.11.4-26.P2.el7_9.9 <<>> @10.96.0.10 service-headless.dev.svc.cluster.local
  3. ; (1 server found)
  4. ;; global options: +cmd
  5. ;; Got answer:
  6. ;; WARNING: .local is reserved for Multicast DNS
  7. ;; You are currently testing what happens when an mDNS query is leaked to DNS
  8. ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 62573
  9. ;; flags: qr aa rd; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
  10. ;; WARNING: recursion requested but not available
  11. ;; OPT PSEUDOSECTION:
  12. ; EDNS: version: 0, flags:; udp: 4096
  13. ;; QUESTION SECTION:
  14. ;service-headless.dev.svc.cluster.local. IN A
  15. ;; ANSWER SECTION:
  16. service-headless.dev.svc.cluster.local. 30 IN A 10.244.2.190
  17. service-headless.dev.svc.cluster.local. 30 IN A 10.244.1.53
  18. service-headless.dev.svc.cluster.local. 30 IN A 10.244.2.191
  19. ;; Query time: 0 msec
  20. ;; SERVER: 10.96.0.10#53(10.96.0.10)
  21. ;; WHEN: Mon Apr 04 11:57:01 CST 2022
  22. ;; MSG SIZE rcvd: 229
  23. [root@master service]#
始终坚持开源开放共享精神,同时感谢您的充电鼓励和支持!
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