18.服务发现-CoreDNS

╰半夏微凉° 2022-10-05 14:55 151阅读 0赞

### 18.服务发现-CoreDNS ###

> 本节将通过向k8s内部署容器的方式来交付CoreDNS服务

#### 一、获取CoreDNS ####

二进制包：[https://github.com/coredns/coredns/releases][https_github.com_coredns_coredns_releases]  
使用容器部署CoreDNS：[https://registry.hub.docker.com/r/coredns/coredns/tags?page=1&ordering=last\_updated][https_registry.hub.docker.com_r_coredns_coredns_tags_page_1_ordering_last_updated]  
`docker pull coredns/coredns:1.8.3`

#### 二、资源配置清单 ####

> 参考：[https://github.com/kubernetes/kubernetes/blob/v1.17.16/cluster/addons/dns/coredns/coredns.yaml.base][https_github.com_kubernetes_kubernetes_blob_v1.17.16_cluster_addons_dns_coredns_coredns.yaml.base]

资源配置清单文件创建到node200:/data/k8s-yaml

##### 1. RBAC #####

coredns\_rbac.yaml

apiVersion: v1
    kind: ServiceAccount
    metadata:
      name: coredns
      namespace: kube-system
      labels:
          kubernetes.io/cluster-service: "true"
          addonmanager.kubernetes.io/mode: Reconcile
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRole
    metadata:
      labels:
        kubernetes.io/bootstrapping: rbac-defaults
        addonmanager.kubernetes.io/mode: Reconcile
      name: system:coredns
    rules:
    - apiGroups:
      - ""
      resources:
      - endpoints
      - services
      - pods
      - namespaces
      verbs:
      - list
      - watch
    - apiGroups:
      - ""
      resources:
      - nodes
      verbs:
      - get
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRoleBinding
    metadata:
      annotations:
        rbac.authorization.kubernetes.io/autoupdate: "true"
      labels:
        kubernetes.io/bootstrapping: rbac-defaults
        addonmanager.kubernetes.io/mode: EnsureExists
      name: system:coredns
    roleRef:
      apiGroup: rbac.authorization.k8s.io
      kind: ClusterRole
      name: system:coredns
    subjects:
    - kind: ServiceAccount
      name: coredns
      namespace: kube-system

##### 2. ConfigMap #####

coredns\_configmap.yaml

apiVersion: v1
    kind: ConfigMap
    metadata:
      name: coredns
      namespace: kube-system
      labels:
          addonmanager.kubernetes.io/mode: EnsureExists
    data:
      Corefile: |
        .:53 {
            errors
            health {
                lameduck 5s
            }
            ready
            kubernetes cluster.local in-addr.arpa ip6.arpa {        # cluster.local 集群域名
                pods insecure
                fallthrough in-addr.arpa ip6.arpa
                ttl 30
            }
            prometheus :9153
            forward . /etc/resolv.conf
            cache 30
            loop
            reload
            loadbalance
        }

修改`forward . 172.10.10.11`可以将coredns的上级dns指定为我们之前搭建的bind9，这样容器内就能同步bind9的dns内容了

##### 3. Deployment #####

coredns\_dp.yaml

apiVersion: apps/v1
    kind: Deployment
    metadata:
      name: coredns
      namespace: kube-system
      labels:
        k8s-app: kube-dns
        kubernetes.io/cluster-service: "true"
        addonmanager.kubernetes.io/mode: Reconcile
        kubernetes.io/name: "CoreDNS"
    spec:
      # replicas: not specified here:
      # 1. In order to make Addon Manager do not reconcile this replicas parameter.
      # 2. Default is 1.
      # 3. Will be tuned in real time if DNS horizontal auto-scaling is turned on.
      strategy:
        type: RollingUpdate
        rollingUpdate:
          maxUnavailable: 1
      selector:
        matchLabels:
          k8s-app: kube-dns
      template:
        metadata:
          labels:
            k8s-app: kube-dns
          annotations:
            seccomp.security.alpha.kubernetes.io/pod: 'docker/default'
        spec:
          priorityClassName: system-cluster-critical
          serviceAccountName: coredns
          tolerations:
            - key: "CriticalAddonsOnly"
              operator: "Exists"
          nodeSelector:
            beta.kubernetes.io/os: linux
          containers:
          - name: coredns
            image: harbor.hzwod.com/k8s/coredns:1.6.5
            imagePullPolicy: IfNotPresent
            resources:
              limits:
                memory:  128Mi            # 内存限制
              requests:
                cpu: 100m
                memory: 70Mi
            args: [ "-conf", "/etc/coredns/Corefile" ]
            volumeMounts:
            - name: config-volume
              mountPath: /etc/coredns
              readOnly: true
            ports:
            - containerPort: 53
              name: dns
              protocol: UDP
            - containerPort: 53
              name: dns-tcp
              protocol: TCP
            - containerPort: 9153
              name: metrics
              protocol: TCP
            livenessProbe:
              httpGet:
                path: /health
                port: 8080
                scheme: HTTP
              initialDelaySeconds: 60
              timeoutSeconds: 5
              successThreshold: 1
              failureThreshold: 5
            readinessProbe:
              httpGet:
                path: /ready
                port: 8181
                scheme: HTTP
            securityContext:
              allowPrivilegeEscalation: false
              capabilities:
                add:
                - NET_BIND_SERVICE
                drop:
                - all
              readOnlyRootFilesystem: true
          dnsPolicy: Default
          volumes:
            - name: config-volume
              configMap:
                name: coredns
                items:
                - key: Corefile
                  path: Corefile

##### 4.Service #####

coredns\_service.yaml

apiVersion: v1
    kind: Service
    metadata:
      name: kube-dns
      namespace: kube-system
      annotations:
        prometheus.io/port: "9153"
        prometheus.io/scrape: "true"
      labels:
        k8s-app: kube-dns
        kubernetes.io/cluster-service: "true"
        addonmanager.kubernetes.io/mode: Reconcile
        kubernetes.io/name: "CoreDNS"
    spec:
      selector:
        k8s-app: kube-dns
      clusterIP: 192.168.0.2        # dns在集群中的ip
      ports:
      - name: dns
        port: 53
        protocol: UDP
      - name: dns-tcp
        port: 53
        protocol: TCP
      - name: metrics
        port: 9153
        protocol: TCP

`clusterIP: 192.168.0.2`指定coredns暴露svc的ip, 此ip要和 kubelet 启动参数`--cluster-dns 192.168.0.2`对应上

#### 三.交付coredns ####

上述文件拷贝到`node200:/data/k8s-yaml`目录下

node21或node22上应用上述资源

kubectl apply -f http://k8s-yaml.hzwod.com/coredns_rbac.yaml
    kubectl apply -f http://k8s-yaml.hzwod.com/coredns_configmap.yaml
    kubectl apply -f http://k8s-yaml.hzwod.com/coredns_dp.yaml
    kubectl apply -f http://k8s-yaml.hzwod.com/coredns_service.yaml

查看效果

[root@node21 ~]# kubectl get all -n kube-system 
    NAME                           READY   STATUS    RESTARTS   AGE
    pod/coredns-786565dc55-qpwpd   1/1     Running   0          <invalid>
    NAME               TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)                  AGE
    service/kube-dns   ClusterIP   192.168.0.2   <none>        53/UDP,53/TCP,9153/TCP   65m
    NAME                      READY   UP-TO-DATE   AVAILABLE   AGE
    deployment.apps/coredns   1/1     1            1           99m
    NAME                                 DESIRED   CURRENT   READY   AGE
    replicaset.apps/coredns-786565dc55   1         1         1       99m
    [root@node21 ~]# dig -t A nginx-dp.hzwns.svc.cluster.local. @192.168.0.2 +short
    192.168.182.94

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzE5NjU1NDA1_size_16_color_FFFFFF_t_70]

留下一个问题，看上图服务端nginx收到的数据包源地址不是容器ip，这个问题如何解决？

[https_github.com_coredns_coredns_releases]: https://github.com/coredns/coredns/releases
[https_registry.hub.docker.com_r_coredns_coredns_tags_page_1_ordering_last_updated]: https://registry.hub.docker.com/r/coredns/coredns/tags?page=1&ordering=last_updated
[https_github.com_kubernetes_kubernetes_blob_v1.17.16_cluster_addons_dns_coredns_coredns.yaml.base]: https://github.com/kubernetes/kubernetes/blob/v1.17.16/cluster/addons/dns/coredns/coredns.yaml.base
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzE5NjU1NDA1_size_16_color_FFFFFF_t_70]: /images/20221005/9548c71260a849f1aaec99126cf799b6.png