基于 Kubernetes v1.14.0 之 CoreDNS部署

1、部署容器前说明：

1.1、如果没有特殊指明，本文档的所有操作均在 k8s-operation 节点上执行；

kuberntes 自带插件的 manifests yaml 文件使用 gcr.io 的 docker registry，国内被墙，需要手动替换为其它 registry 地址；

1.2、由于k8s-master 没有部署容器服务于路由服务，但是k8s-master 又要访问容器网络跟k8s集群网络，1、在上级路由器写入静态路由让其能访问容器网络与k8s集群网络。2、在k8s-master 服务器写入静态路由。 以k8s-master 服务器写入静态路由为例：

ip route add 10.48.0.0/12 via 192.168.31.252
ip route add 10.64.0.0/16 via 192.168.31.252
加入重启服务器自动写入路由：
vim /etc/rc.local
chmod +x /etc/rc.local
192.168.31.252 为k8s-vip ip 由于vip ip安装了容器服务与路由服务
上级路由器写入让外面访问整个容器网络建议也写vip ip 这样坏掉一台第二台可以直接接管所以的配置可以不用更换

1.3、配置k8s-vip 与k8s-ingress 不参与调度

kubectl cordon k8s-vip-01
kubectl cordon k8s-vip-02
kubectl cordon k8s-ingress-01
kubectl cordon k8s-ingress-02

2、CoreDNS 准备

cd /apps/work/k8s/kubernetes
tar -xvf  kubernetes-src.tar.gz 
cd cluster/addons/dns/coredns

3、修改CoreDNS 配置

export CLUSTER_DNS_DOMAIN="niuke.local"
export CLUSTER_DNS_SVC_IP="10.64.0.2"
sed -i -e "s/__PILLAR__DNS__DOMAIN__/${CLUSTER_DNS_DOMAIN}/" -e "s/__PILLAR__DNS__SERVER__/${CLUSTER_DNS_SVC_IP}/" coredns.yaml
vi coredns.yaml
替换成
 image: coredns/coredns
 删除 loop 

4、coredns.yaml

# __MACHINE_GENERATED_WARNING__

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
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: coredns
  namespace: kube-system
  labels:
      addonmanager.kubernetes.io/mode: EnsureExists
data:
  Corefile: |
    .:53 {
        errors
        health
        kubernetes niuke.local in-addr.arpa ip6.arpa {
            pods insecure
            upstream
            fallthrough in-addr.arpa ip6.arpa
        }
        prometheus :9153
        forward . /etc/resolv.conf
        cache 30
        reload
        loadbalance
    }
---
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.
  replicas: 3
  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: coredns/coredns
        imagePullPolicy: IfNotPresent
        resources:
          limits:
            memory: 170Mi
          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: /health
            port: 8080
            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
---
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: 10.64.0.2
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
    protocol: TCP
  - name: metrics
    port: 9153
    protocol: TCP

5、创建CoreDNS 自动横向扩容基于请求数 后期执行

vi  hpa-coredns.yaml
apiVersion: autoscaling/v2beta1
kind: HorizontalPodAutoscaler
metadata:
  name: coredns
  namespace: kube-system
spec:
  scaleTargetRef:
    apiVersion: extensions/v1beta1
    kind: Deployment
    name: coredns
  minReplicas: 3
  maxReplicas: 10
  metrics:
  - type: Pods
    pods:
      metricName: coredns_dns_request_count
      targetAverageValue: 1000

6、创建CoreDNS 服务

kubectl create -f coredns.yaml

7、检查CoreDNS 功能

kubectl get all -n kube-system
[root@jenkins coredns]# kubectl get all -n kube-system
NAME                                           READY   STATUS    RESTARTS   AGE
pod/coredns-6cbf85dbc6-hcqd7                   1/1     Running   1          47d
pod/coredns-6cbf85dbc6-rdcww                   1/1     Running   0          2d18h
pod/coredns-6cbf85dbc6-wcqmd                   1/1     Running   0          32d
NAME                           TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)                  AGE
service/kube-dns               ClusterIP   10.64.0.2       <none>        53/UDP,53/TCP,9153/TCP   47d
NAME                                       READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/coredns                    3/3     3            3           47d
NAME                                                 DESIRED   CURRENT   READY   AGE
replicaset.apps/coredns-6cbf85dbc6                   3         3         3       47d
NAME                                          REFERENCE            TARGETS   MINPODS   MAXPODS   REPLICAS   AGE
horizontalpodautoscaler.autoscaling/coredns   Deployment/coredns   11%/80%   2         10        3          53d

新建一个 Deployment
kubectl run myip --image=cloudnativelabs/whats-my-ip --replicas=3 --port=8080
export 该 Deployment, 生成 myip 服务：
kubectl expose deployment myip --port=8080 --target-port=8080 --type=NodePort
kubectl get pod -o wide
kubectl get services --all-namespaces
说明：k8s-vip 主要提供以后监控，等内部访问，主要基于dns+nginx 对外提供业务暴露访问
修改k8s-vip /etc/resolv.conf
options ndots:5
; generated by /usr/sbin/dhclient-script
nameserver 10.64.0.2
search kube-system.svc.niuke.local svc.niuke.local niuke.local

安装 yum install -y bind-utils
测试CoreDNS 服务是否正常

[root@nginx-1 src]# dig @10.64.0.2 www.baid.com

; <<>> DiG 9.9.4-RedHat-9.9.4-73.el7_6 <<>> @10.64.0.2 www.baid.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 9443
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;www.baid.com.                  IN      A

;; ANSWER SECTION:
www.baid.com.           30      IN      A       47.254.33.193

;; Query time: 38 msec
;; SERVER: 10.64.0.2#53(10.64.0.2)
;; WHEN: Tue Jun 11 10:04:17 CST 2019
;; MSG SIZE  rcvd: 69

查询刚刚建立myip 服务是否能解析
[root@nginx-1 src]# dig @10.64.0.2 myip.default.svc.niuke.local

; <<>> DiG 9.9.4-RedHat-9.9.4-73.el7_6 <<>> @10.64.0.2 myip.default.svc.niuke.local
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 62331
;; flags: qr rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;myip.default.svc.niuke.local.  IN      A

;; ANSWER SECTION:
myip.default.svc.niuke.local. 1 IN      A       10.64.160.236

;; Query time: 1 msec
;; SERVER: 10.64.0.2#53(10.64.0.2)
;; WHEN: Tue Jun 11 10:06:13 CST 2019
;; MSG SIZE  rcvd: 101

curl myip.default.svc.niuke.local:8080
[root@nginx-1 src]# curl myip.default.svc.niuke.local:8080
HOSTNAME:myip-7ddc5b85f4-6h47f IP:10.65.1.250
[root@nginx-1 src]# curl myip.default.svc.niuke.local:8080
HOSTNAME:myip-7ddc5b85f4-69jlx IP:10.65.4.243
[root@nginx-1 src]# curl myip.default.svc.niuke.local:8080
HOSTNAME:myip-7ddc5b85f4-9wxd4 IP:10.65.3.149
解析正常也能正常访问

下一篇： Kubernetes 生产环境安装部署 基于 Kubernetes v1.14.0 之 kubernetes-dashboard部署