kubernetes上的服务发现-CoreDNS配置

电玩女神 2022-01-23 14:13 211阅读 0赞

**1.当前已经开启ipvs的kube-proxy，集群DNS的IP为10.0.0.2**

下载coredns项目的kubernetes
    wget https://github.com/coredns/deployment/archive/master.zip
    unzip master.zip
    
    因为项目使用了jq命令，需要安装jq程序
    由于jq来源于epel，因此需要安装扩展的yum仓库
    rpm -ivh http://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
    yum -y install jq
    yum -y install conntrack-tools
    
    上面下载master.zip解压缩至deployment-master文件夹
    cd deployment-master/kubernetes
    ./deploy.sh -h #查看部署帮助
    [root@master kubernetes]# ./deploy.sh -h
    usage: ./deploy.sh [ -r REVERSE-CIDR ] [ -i DNS-IP ] [ -d CLUSTER-DOMAIN ] [ -t YAML-TEMPLATE ]
    
        -r : Define a reverse zone for the given CIDR. You may specifcy this option more
             than once to add multiple reverse zones. If no reverse CIDRs are defined,
             then the default is to handle all reverse zones (i.e. in-addr.arpa and ip6.arpa)
        -i : Specify the cluster DNS IP address. If not specificed, the IP address of
             the existing "kube-dns" service is used, if present.
        -s : Skips the translation of kube-dns configmap to the corresponding CoreDNS Corefile configuration.

**2.修改每台node上的 kubelet 启动参数**

> ![image.png][]

**3.创建coredns 和svc**

./deploy.sh -r 10.0.0.0/24 -i 10.0.0.2 -d cluster.local | kubectl apply -f -

> ![format_png][]  
> 创建成功

**4.验证coreDNS是否正常工作**

[root@master yaml]# cat busybox.yaml 
    apiVersion: v1
    kind: Pod
    metadata:
      name: busybox
      namespace: default
    spec:
      containers:
      - name: busybox
        image: busybox:1.28
        command:
          - sleep
          - "3600"
        imagePullPolicy: IfNotPresent
      restartPolicy: Always

**5.创建Busybox pod**

> ![format_png 1][]

**6.busybox的resolv.conf内容**

[root@master yaml]# kubectl exec busybox cat /etc/resolv.conf
    nameserver 10.0.0.2
    search default.svc.cluster.local. svc.cluster.local. cluster.local.
    options ndots:5
    [root@master yaml]# kubectl get pod
    NAME                                            READY     STATUS    RESTARTS   AGE
    busybox                                         1/1       Running   0          54m
    memory-tomcat-deployment-75c49974b5-swvpl       1/1       Running   1          8h
    memory-tomcat-deployment-75c49974b5-z49tv       1/1       Running   1          8h
    nginx-deployment-966857787-65mtm                1/1       Running   0          1h
    nginx-deployment-966857787-99l7s                1/1       Running   0          1h
    quizii-tomcat-deployment-54cd6ffb5c-lpbn6       1/1       Running   0          1h

**7.在busybox 的pod里解析kubernetes.default 的IP地址**

[root@master kubernetes]# kubectl exec -ti busybox -- nslookup kubernetes.default
    Server:    10.0.0.2
    Address 1: 10.0.0.2 kube-dns.kube-system.svc.cluster.local
    
    Name:      kubernetes.default
    Address 1: 10.0.0.1 kubernetes.default.svc.cluster.local

**8.在busybox 的pod里解析外部IP地址 ，按照前文coreDNS的配置，是通过pod所在node上的/etc/resolv.conf 来代理解析的**

[root@master kubernetes]# kubectl exec -ti busybox -- nslookup www.sina.com.cn
    Server:    10.0.0.2
    Address 1: 10.0.0.2 kube-dns.kube-system.svc.cluster.local
    
    Name:      www.sina.com.cn
    Address 1: 219.238.4.9

**9.在busybox 的pod里解析创建的服务**

[root@master kubernetes]# kubectl get svc
    NAME                    TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)          AGE
    kubernetes              ClusterIP   10.0.0.1     <none>        443/TCP          12d
    memory-tomcat-svc       NodePort    10.0.0.101   <none>        8082:32000/TCP   10d
    nginx-svc               NodePort    10.0.0.13    <none>        8080:30000/TCP   3h
    quizii-tomcat-svc       NodePort    10.0.0.66    <none>        8081:31000/TCP   1h
    usercenter-tomcat-svc   NodePort    10.0.0.112   <none>        8083:33000/TCP   1h
    [root@master kubernetes]# kubectl exec -ti busybox -- nslookup usercenter-tomcat-svc
    Server:    10.0.0.2
    Address 1: 10.0.0.2 kube-dns.kube-system.svc.cluster.local
    
    Name:      usercenter-tomcat-svc
    Address 1: 10.0.0.112 usercenter-tomcat-svc.default.svc.cluster.local
    [root@master kubernetes]# kubectl exec -ti busybox -- nslookup quizii-tomcat-svc
    Server:    10.0.0.2
    Address 1: 10.0.0.2 kube-dns.kube-system.svc.cluster.local
    
    Name:      quizii-tomcat-svc
    Address 1: 10.0.0.66 quizii-tomcat-svc.default.svc.cluster.local

**总结：通过以上例子可见，coredns工作正常。在我们创建的Kubernetes 1.12.3 cluster中，coredns既可以管理新生成的service的域名，又可以解析出外部域名**

[image.png]: /images/20220123/1b867c996eaa413fa372cb8d65bf0d90.png
[format_png]: /images/20220123/d359d5e9620841eea80caaeffbdcdcbd.png
[format_png 1]: /images/20220123/2a44950e4c8a45ac95ec2ce6ebbac93d.png