Kubernetes 1.9集群使用traefik发布服务

在前文中介绍了在kubernetes 1.5.2集群环境中使用traefik进行服务发布。Traefik采用daemonset方式部署，连接api-server走的是http协议，也未配置rbac。本文将介绍在k8s 1.9版本中使用deployment方式部署traefik来进行服务发布。

在开始之前，需要先了解一下什么是RBAC。RBAC（基于角色的访问控制）使用 rbac.authorization.k8s.io  API 组来实现权限控制，RBAC 允许管理员通过 Kubernetes API 动态的配置权限策略。在 1.6 版本中 RBAC 还处于 Beat 阶段，如果想要开启 RBAC 授权模式需要在 apiserver 组件中指定 --authorization-mode=RBAC 选项。

在 RBAC API 的四个重要概念：
Role：是一系列的权限的集合，例如一个角色可以包含读取 Pod 的权限和列出 Pod 的权限
ClusterRole： 跟 Role 类似，但是可以在集群中到处使用（ Role 是 namespace 一级的）
RoloBinding：把角色映射到用户，从而让这些用户继承角色在 namespace 中的权限。
ClusterRoleBinding： 让用户继承 ClusterRole 在整个集群中的权限。

简单点说RBAC实现了在k8s集群中对api-server的鉴权，更多的RBAC知识点请查阅官方文档：https://kubernetes.io/docs/admin/authorization/rbac/

一、给集群的节点打上label
因为选择deployment方式部署，所以要给集群的节点打上label，后续选择nodeSelector指定traefik=proxy，副本数和集群节点数一致的时候，所有的节点上都会运行一个pod

# kubectl get nodes --show-labels
# kubectl label  node vm1 traefik=proxy
# kubectl label  node vm2 traefik=proxy
# kubectl get nodes --show-labels

二、准备yaml文件
1、rbac文件

# cat traefik-rbac.yaml 
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1beta1
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

在启用rbac的环境下，如果鉴权未配置清楚，则traefik pod会报错如下

E0226 00:15:27.729832 1 reflector.go:199] github.com/containous/traefik/vendor/k8s.io/client-go/tools/cache/reflector.go:94: Failed to list *v1.Service: services is forbidden: User "system:serviceaccount:kube-system:default" cannot list services at the cluster scope 
E0226 00:15:29.013298 1 reflector.go:199] github.com/containous/traefik/vendor/k8s.io/client-go/tools/cache/reflector.go:94: Failed to list *v1.Endpoints: endpoints is forbidden: User "system:serviceaccount:kube-system:default" cannot list endpoints at the cluster scope 
E0226 00:15:29.213354 1 reflector.go:199] github.com/containous/traefik/vendor/k8s.io/client-go/tools/cache/reflector.go:94: Failed to list *v1.Secret: secrets is forbidden: User "system:serviceaccount:kube-system:default" cannot list secrets at the cluster scope 
E0226 00:15:29.698574 1 reflector.go:199] github.com/containous/traefik/vendor/k8s.io/client-go/tools/cache/reflector.go:94: Failed to list *v1beta1.Ingress: ingresses.extensions is forbidden: User "system:serviceaccount:kube-system:default" cannot list ingresses.extensions at the cluster scope 
E0226 00:15:30.411837 1 reflector.go:199] github.com/containous/traefik/vendor/k8s.io/client-go/tools/cache/reflector.go:94: Failed to list *v1.Service: services is forbidden: User "system:serviceaccount:kube-system:default" cannot list services at the cluster scope 
E0226 00:15:31.912887 1 reflector.go:199] github.com/containous/traefik/vendor/k8s.io/client-go/tools/cache/reflector.go:94: Failed to list *v1.Endpoints: endpoints is forbidden: User "system:serviceaccount:kube-system:default" cannot list endpoints at the cluster scope 

2、traefik的deployment文件

# cat traefik-deployment.yaml   
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: traefik-ingress-controller
  namespace: kube-system
---
kind: Deployment
apiVersion: extensions/v1beta1
metadata:
  name: traefik-ingress-controller
  namespace: kube-system
  labels:
    k8s-app: traefik-ingress-lb
spec:
  replicas: 2
  selector:
    matchLabels:
      k8s-app: traefik-ingress-lb
  template:
    metadata:
      labels:
        k8s-app: traefik-ingress-lb
        name: traefik-ingress-lb
    spec:
      serviceAccountName: traefik-ingress-controller
      hostNetwork: true
      nodeSelector:
        traefik: proxy
      terminationGracePeriodSeconds: 60
      containers:
      - image: traefik
        name: traefik-ingress-lb
        ports:
        - name: web
          containerPort: 80
          hostPort: 80
        - name: admin
          containerPort: 8081
        args:
        - --web
        - --web.address=:8081
        - --kubernetes

3、traefik的service文件

# cat traefik-service.yaml
apiVersion: v1
kind: Service
metadata:
  name: traefik-web-ui
  namespace: kube-system
spec:
  selector:
    k8s-app: traefik-ingress-lb
  ports:
  - port: 80
    targetPort: 8081

4、通过yaml文件创建clusterrole、clusterrolebinding、deployment、serviceaccount、service

# ls
# kubectl create -f traefik-rbac.yaml 
# kubectl create -f traefik-deployment.yaml 
# kubectl create -f traefik-service.yaml 

# kubectl get pod -n kube-system
# kubectl get svc -n kube-system
# kubectl get svc 

可以看到集群中default namespace中存在一个frontend服务。kube-system namespace中存在nginx-test、traefik-web-ui、kubernetes-dashboard三个服务。我们后续将创建4个ingress

通过web-ui可以看到在两个节点上各运行了一个pod

三、通过yaml文件创建ingress

# cat ui.yaml 
apiVersion: v1
kind: Service
metadata:
  name: traefik-web-ui
  namespace: kube-system
spec:
  selector:
    k8s-app: traefik-ingress-lb
  ports:
  - port: 80
    targetPort: 8081
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: traefik-web-ui
  namespace: kube-system
  annotations:
    kubernetes.io/ingress.class: traefik
spec:
  rules:
  - host: traefik-ui
    http:
      paths:
      - backend:
          serviceName: traefik-web-ui
          servicePort: 80

# cat webui-ing.yaml                  
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: traefik-ingress
  namespace: kube-system
  annotations:
    kubernetes.io/ingress.class: traefik
spec:
  rules:
  - host: k8s.webui
    http:
      paths:
      - backend:
          serviceName: kubernetes-dashboard 
          servicePort: 443

# cat redis-ing.yaml 
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: traefik-ingress
  namespace: default
  annotations:
    kubernetes.io/ingress.class: traefik
spec:
  rules:
  - host: k8s.frontend
    http:
      paths:
      - backend:
          serviceName: frontend 
          servicePort: 80

# cat nginx-ing.yaml 
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: traefik-nginx-ingress
  namespace: kube-system
  annotations:
    kubernetes.io/ingress.class: traefik
spec:
  rules:
  - host: test.fjhb.cn
    http:
      paths:
      - backend:
          serviceName: nginx-test
          servicePort: 80

# kubectl create -f ui.yaml 
# kubectl create -f webui-ing.yaml 
# kubectl create -f redis-ing.yaml 
# kubectl get ingress 
# kubectl get ingress -n kube-system

三、验证
1、通过访问traefik service对应的nodeport端口，4个ingress配置都加载到了

2、修改测试机hosts文件，将4个域名的解析分配到两台节点上

3、浏览器访问测试

这里出现500错误的原因是，后端的kubernetes-dashboard配置的是https协议



可以在health页面看到http状态码的统计信息