kubernetes1.5.2--部署DNS服务

本文基于kubernetes 1.5.2版本编写

在kubernetes1.2之前，采用skydns+kube2dns+etcd的方式来部署dns。而从1.3开始，则部署方式有了一点儿变化，将skydns和kube2dns封装到了一个容器镜像中，放弃了etcd，而将dns解析直接放入到了内存之中，同时引入了dnsmasq，进一步利用其缓存。

使用DaemonSet方式部署，在每台宿主机上均有一个DNS服务。

使用http方式访问api server

cat skydns-rc.yaml
apiVersion: extensions/v1beta1
kind: DaemonSet
metadata:
  name: kube-dns
  namespace: kube-system
  labels:
    k8s-app: kube-dns
    kubernetes.io/cluster-service: "true"
spec:
  template:
    metadata:
      labels:
        k8s-app: kube-dns
      annotations:
        scheduler.alpha.kubernetes.io/critical-pod: ''
        scheduler.alpha.kubernetes.io/tolerations: '[{"key":"CriticalAddonsOnly", "operator":"Exists"}]'
    spec:
      containers:
      - name: kubedns
        image: docker.io/googlecontainer/kubedns-amd64:1.9
        imagePullPolicy: IfNotPresent
        resources:
          limits:
            memory: 170Mi
          requests:
            cpu: 100m
            memory: 70Mi
        livenessProbe:
          httpGet:
            path: /healthz-kubedns
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 60
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 5
        readinessProbe:
          httpGet:
            path: /readiness
            port: 8081
            scheme: HTTP
          initialDelaySeconds: 3
          timeoutSeconds: 5
        args:
        - --domain=lykops.net.
        #域名
        - --dns-port=10053
        - --config-map=kube-dns
        - --kube-master-url=http://192.168.20.128:8080
        - --v=0
        env:
        - name: PROMETHEUS_PORT
          value: "10055"
        ports:
        - containerPort: 10053
          name: dns-local
          protocol: UDP
        - containerPort: 10053
          name: dns-tcp-local
          protocol: TCP
        - containerPort: 10055
          name: metrics
          protocol: TCP
      - name: dnsmasq
        image: docker.io/googlecontainer/kube-dnsmasq-amd64:1.4.1
        imagePullPolicy: IfNotPresent
        livenessProbe:
          httpGet:
            path: /healthz-dnsmasq
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 60
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 5
        args:
        - --cache-size=1000
        - --no-resolv
        - --server=127.0.0.1#10053
        ports:
        - containerPort: 53
          name: dns
          protocol: UDP
        - containerPort: 53
          name: dns-tcp
          protocol: TCP
        resources:
          requests:
            cpu: 150m
            memory: 10Mi
      - name: dnsmasq-metrics
        image:  docker.io/googlecontainer/dnsmasq-metrics-amd64:1.0.1
        imagePullPolicy: IfNotPresent
        livenessProbe:
          httpGet:
            path: /metrics
            port: 10054
            scheme: HTTP
          initialDelaySeconds: 60
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 5
        args:
        - --v=2
        - --logtostderr
        ports:
        - containerPort: 10054
          name: metrics
          protocol: TCP
        resources:
          requests:
            memory: 10Mi
      - name: healthz
        image: docker.io/googlecontainer/exechealthz-amd64:1.2
        imagePullPolicy: IfNotPresent
        resources:
          limits:
            memory: 50Mi
          requests:
            cpu: 10m
            memory: 50Mi
        args:
        - --cmd=nslookup kubernetes.default.svc.lykops.net 127.0.0.1 >/dev/null
        - --url=/healthz-dnsmasq
        - --cmd=nslookup kubernetes.default.svc.lykops.net 127.0.0.1:10053 >/dev/null
        - --url=/healthz-kubedns
        - --port=8080
        - --quiet
        ports:
        - containerPort: 8080
          protocol: TCP
      dnsPolicy: Default

kubectl create -f skydns-rc.yaml

使用https方式访问apiserver接口

cat skydns-rc.yaml
......
        args:
        - --domain=lykops.net.
        - --dns-port=10053
        - --config-map=kube-dns
        - --kube-master-url=https://192.168.20.128:6443
        #这里修改为https
        - --kubecfg-file=/etc/kubernetes/kubelet-config
        #添加认证信息配置文件
        - --v=0
        #挂载认证需要的信息配置文件和证书
        volumeMounts:
        - name: config
          mountPath: /etc/kubernetes/kubelet-config
          readOnly: True
        - name: certs
          mountPath: /etc/ssl/kube
          readOnly: True
        env:
        - name: PROMETHEUS_PORT
          value: "10055"
      .......
      #挂载宿主机的信息配置文件和证书
      volumes:
      - name: certs
        hostPath:
          path: /etc/ssl/kube
      - name: config
        hostPath:
          path: /etc/kubernetes/kubelet-config
      dnsPolicy: Default

kubectl create -f skydns-rc.yaml

配置service

cat skydns-svc.yaml
apiVersion: v1
kind: Service
metadata:
  name: kube-dns
  namespace: kube-system
  labels:
    k8s-app: kube-dns
    kubernetes.io/cluster-service: "true"
    kubernetes.io/name: "KubeDNS"
spec:
  selector:
    k8s-app: kube-dns
  clusterIP: 172.17.114.114
  #固定IP地址
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
protocol: TCP

kubectl create -f skydns-svc.yaml

配置kubelet--实现服务发现

等待服务部署完成，在集群宿主机上执行telnet 172.17.114.114 53，能通表示部署完成

在客户端上执行修改/etc/kubernetes/kubelet

KUBELET_ARGS="--cluster-domain=lykops.net --cluster_dns=172.17.114.114"

重启服务

service kubelet restart