k8s之服务暴露

k8s的服务暴露

k8s的dns实现了服务在集群“内”被自动发现，那如何是的服务在k8s集群”外“被使用和访问呢？

使用nodePort型的Service
- 注意：无法使用kube-proxy的ipvs模型，只能使用iptables模型
使用ingress资源
- 注意：ingress只能调度并暴露7层应用，特指http和https协议
  - 不建议https用ingress
  那https协议来了怎么办呢？
  
  在L7层负载均衡上做证书卸载

ingress是k8s API的标准资源类型之一，也是一种核心资源，它其实就是一组基于域名和URL路径，把用户的请求转发至指定Service资源的规则

可以将集群外部的请求流量，转发至集群内部，从而实现“服务暴露”

ingress控制器是能够为ingress资源监听某套接字，然后根据ingress规则匹配机制路由调度流量的一个组件。

说白了，ingress没啥神秘的，就是个简化版的nginx+一段go脚本而已

常用的ingress控制器的实现软件

Ingress-nginx
HAProxy
Traefik

部署traefik

在hdss7-200操作

[root@hdss7-200 coredns]# pwd
/data/k8s-yaml/coredns
[root@hdss7-200 coredns]# cd ..
[root@hdss7-200 k8s-yaml]# mkdir traefik
[root@hdss7-200 k8s-yaml]# cd traefik/

[traefik地址][https://github.com/containous/traefik]

建议使用1.7.2版本就可以了

[root@hdss7-200 traefik]# docker pull traefik:v1.7.2-alpine
[root@hdss7-200 traefik]# docker images | grep traefik
traefik         v1.7.2-alpine              add5fac61ae5        22 months ago       72.4MB

[root@hdss7-200 traefik]# docker tag add5fac61ae5 harbor.od.com/public/traefik:v1.7.2
[root@hdss7-200 traefik]# docker push !$
docker push harbor.od.com/public/traefik:v1.7.2

[root@hdss7-200 traefik]# vim rbac.yaml

apiVersion: v1
kind: ServiceAccount
metadata:
  name: traefik-ingress-controller
  namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: traefik-ingress-controller
rules:
  - apiGroups:
      - ""
    resources:
      - services
      - endpoints
      - secrets
    verbs:
      - get
      - list
      - watch
  - apiGroups:
      - extensions
    resources:
      - ingresses
    verbs:
      - get
      - list
      - watch
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: traefik-ingress-controller
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: traefik-ingress-controller
subjects:
- kind: ServiceAccount
  name: traefik-ingress-controller
  namespace: kube-system

svc.yaml

kind: Service
apiVersion: v1
metadata:
  name: traefik-ingress-service
  namespace: kube-system
spec:
  selector:
    k8s-app: traefik-ingress
  ports:
    - protocol: TCP
      port: 80
      name: controller
    - protocol: TCP
      port: 8080
      name: admin-web

ds.yaml

apiVersion: extensions/v1beta1
kind: DaemonSet
metadata:
  name: traefik-ingress
  namespace: kube-system
  labels:
    k8s-app: traefik-ingress
spec:
  template:
    metadata:
      labels:
        k8s-app: traefik-ingress
        name: traefik-ingress
    spec:
      serviceAccountName: traefik-ingress-controller
      terminationGracePeriodSeconds: 60
      containers:
      - image: harbor.od.com/public/traefik:v1.7.2
        name: traefik-ingress
        ports:
        - name: controller
          containerPort: 80
          hostPort: 81
        - name: admin-web
          containerPort: 8080
        securityContext:
          capabilities:
            drop:
            - ALL
            add:
            - NET_BIND_SERVICE
        args:
        - --api
        - --kubernetes
        - --logLevel=INFO
        - --insecureskipverify=true
        - --kubernetes.endpoint=https://10.4.7.10:7443
        - --accesslog
        - --accesslog.filepath=/var/log/traefik_access.log
        - --traefiklog
        - --traefiklog.filepath=/var/log/traefik.log
        - --metrics.prometheus

ingress.yaml

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: traefik-web-ui
  namespace: kube-system
  annotations:
    kubernetes.io/ingress.class: traefik
spec:
  rules:
  - host: traefik.od.com
    http:
      paths:
	  - path: /
        backend:
          serviceName: traefik-ingress-service
          servicePort: 8080

    - name: controller
      containerPort: 80
      hostPort: 81
把docker的80端口映射到宿主机的81端口

ingress控制器是能够为ingress资源监听某套接字(暴露的端口），然后根据ingress规则匹配机制路由调度流量的一个组件。

创建对应的资源

[root@hdss7-22 ~]# kubectl apply -f http://k8s-yaml.od.com/traefik/rbac.yaml
serviceaccount/traefik-ingress-controller created
clusterrole.rbac.authorization.k8s.io/traefik-ingress-controller created
clusterrolebinding.rbac.authorization.k8s.io/traefik-ingress-controller created

[root@hdss7-22 ~]# kubectl apply -f http://k8s-yaml.od.com/traefik/ds.yaml
daemonset.extensions/traefik-ingress created

[root@hdss7-22 ~]# kubectl apply -f http://k8s-yaml.od.com/traefik/svc.yaml
service/traefik-ingress-service created

[root@hdss7-22 ~]# kubectl apply -f http://k8s-yaml.od.com/traefik/ingress.yaml

[root@hdss7-22 ~]# kubectl apply -f http://k8s-yaml.od.com/traefik/ingress.yaml
ingress.extensions/traefik-web-ui created

[root@hdss7-22 ~]# kubectl get pods -n kube-system
NAME                       READY   STATUS    RESTARTS   AGE
coredns-6b6c4f9648-ttfg8   1/1     Running   0          11h
traefik-ingress-fnrbg      0/1     Running   0          58s
traefik-ingress-kxm8t      0/1     Running   0          33s

如果一直启动不起来，尝试重启docker服务

[root@hdss7-22 ~]# systemctl restart docker.service
[root@hdss7-21 ~]# systemctl restart docker.service

再次查看

[root@hdss7-22 ~]# kubectl get pods -n kube-system
NAME                       READY   STATUS    RESTARTS   AGE
coredns-6b6c4f9648-ttfg8   1/1     Running   0          11h
traefik-ingress-fnrbg      1/1     Running   0          58s
traefik-ingress-kxm8t      1/1     Running   0          33s

netstat -luntp | grep 81

在hdss7-11和hdss7-12上操作，配置反向代理

注意：nginx的优先级是详细的优先于泛的。

[root@hdss7-11 ~]# vim /etc/nginx/conf.d/od.com.conf

upstream default_backend_traefik {
    server 10.4.7.21:81    max_fails=3 fail_timeout=10s;
    server 10.4.7.22:81    max_fails=3 fail_timeout=10s;
}
server {
    server_name *.od.com;
  
    location / {
        proxy_pass http://default_backend_traefik;
        proxy_set_header Host       $http_host;
        proxy_set_header x-forwarded-for $proxy_add_x_forwarded_for;
    }
}

81是ingress controller端口

server_name ，泛域名匹配，泛域名流量调度

上面这个配置的意思就是，凡是走*.od.com业务域的流量，没差别的提交给server，抛给了ingress controller，然后交给了ingress service，最终，ingress service交给了traefik ingress service，它又是怎么找到pod的呢？通过node-selector找到k8s-app: traefik-ingress，然后找到对应的k8s-app的标签

svc.yaml

  selector:
    k8s-app: traefik-ingress

ds.yaml

      labels:
        k8s-app: traefik-ingress

再次参考图

kube service就是由kube-proxy这个组件承载的。

回到正题，经过这样配置之后，nginx可以永远不用再动了，nginx七层代理就干这件事。如果还需要调度七层流量规则怎么办？你只需要声明ingress配置文件，七层调度全部交给ingress来干了。

修改dns解析

               2020080104; serial
traefik          A 10.4.7.10

traefik这里要指向vip的地址

重启相关服务

[root@hdss7-12 ~]# systemctl restart named
[root@hdss7-12 ~]# nginx -s reload

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