### k8s的服務發現插件---CoreDNS 服務發現需要解決的問題： 　　1、服務動態性強--容器在k8s中ip變化或遷移 　　2、更新發布頻繁--版本迭代快 　　3、支持自動伸縮--大促或流量高峰 我們為了解決pod地址變化的問題，我們之前部署了service資源，將pod地址通過service資源暴露的固定地址，來解決以上問題，那么，如何解決service資源名稱和service資源暴露出來的集群網絡IP做自動的對應呢，從而達到服務的自動發現呢？ 在k8s中，coredns就是為了解決以上問題。 從coredns開始，我們采用向k8s中交付容器的方式，來部署服務，并且使用聲明式的方式，來部署服務。 1、部署k8s的內網資源配置清單http服務 運維主機上，配置一個nginx虛擬主機，用以提供k8s統一的資源配置清單訪問入口 ``` cat /etc/nginx/conf.d/k8s-yaml.od.com.conf server { listen 80; server_name k8s-yaml.od.com; location / { autoindex on; default_type text/plain; root /data/k8s-yaml; } } ``` #### 加載nginx ``` nginx -t nginx -s reload ``` #### bind9添加A記錄 ``` vi /var/named/od.com.zone k8s-yaml A 10.4.7.200 systemctl restart named dig -t A k8s-yaml.od.com @10.4.7.11 +short 10.4.7.200 mkdir -p /data/k8s-yaml/coredns cd /data/k8s-yaml/coredns ``` #### 部署coredns 準備鏡像 ``` docker pull coredns/coredns:1.6.1 docker tag c0f6e815079e harbor.od.com/public/coredns:v1.6.1 docker push harbor.od.com/public/coredns:v1.6.1 ``` #### 準備資源配置清單 官方地址：https://github.com/kubernetes/kubernetes/blob/master/cluster/addons/dns/coredns/coredns.yaml.base 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 --- 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 ``` cm.yaml ``` apiVersion: v1 kind: ConfigMap metadata: name: coredns namespace: kube-system data: Corefile: | .:53 { errors log health ready kubernetes cluster.local 192.168.0.0/16 #service資源cluster地址 forward . 10.4.7.11 #上級DNS地址 cache 30 loop reload loadbalance } ``` dp.yaml ``` apiVersion: apps/v1 kind: Deployment metadata: name: coredns namespace: kube-system labels: k8s-app: coredns kubernetes.io/name: "CoreDNS" spec: replicas: 1 selector: matchLabels: k8s-app: coredns template: metadata: labels: k8s-app: coredns spec: priorityClassName: system-cluster-critical serviceAccountName: coredns containers: - name: coredns image: harbor.od.com/public/coredns:v1.6.1 args: - -conf - /etc/coredns/Corefile volumeMounts: - name: config-volume mountPath: /etc/coredns 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 dnsPolicy: Default volumes: - name: config-volume configMap: name: coredns items: - key: Corefile path: Corefile ``` svc.yaml ``` apiVersion: v1 kind: Service metadata: name: coredns namespace: kube-system labels: k8s-app: coredns kubernetes.io/cluster-service: "true" kubernetes.io/name: "CoreDNS" spec: selector: k8s-app: coredns clusterIP: 192.168.0.2 ports: - name: dns port: 53 protocol: UDP - name: dns-tcp port: 53 - name: metrics port: 9153 protocol: TCP ``` #### 創建查看 ``` kubectl apply -f http://k8s-yaml.od.com/coredns/rbac.yaml kubectl apply -f http://k8s-yaml.od.com/coredns/cm.yaml kubectl apply -f http://k8s-yaml.od.com/coredns/dp.yaml kubectl apply -f http://k8s-yaml.od.com/coredns/svc.yaml [root@hdss7-21 ~]# kubectl get all -n kube-system NAME READY STATUS RESTARTS AGE pod/coredns-594f5bd7bb-24d5b 1/1 Running 0 45s NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE service/coredns ClusterIP 192.168.0.2 <none> 53/UDP,53/TCP,9153/TCP 39s NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE deployment.apps/coredns 1 1 1 1 45s NAME DESIRED CURRENT READY AGE replicaset.apps/coredns-594f5bd7bb 1 1 1 45s ``` #### 驗證k8s-dns ``` [root@hdss7-21 ~]# dig -t A www.baidu.com @192.168.0.2 +short www.a.shifen.com. 180.101.49.12 180.101.49.11 ```