kubernetes traefik ingress 安装及配置
Traefik是一款开源的反向代理与负载均衡工具。它最大的优点是能够与常见的微服务系统直接整合，可以实现自动化动态配置。目前支持Docker, Swarm, Mesos/Marathon, Mesos, Kubernetes, Consul, Etcd, Zookeeper, BoltDB, Rest API等等后端模型。
以下是架构图:
需要指出的是，ingress-controllers其实是kubernetes的一部分，ingress就是从kubernetes集群外访问集群的入口，将用户的URL请求转发到不同的service上。Ingress相当于nginx、apache等负载均衡方向代理服务器，其中还包括规则定义，即URL的路由信息，路由信息得的刷新由Ingress controller来提供。
Ingress Controller 实质上可以理解为是个监视器，Ingress Controller 通过不断地跟 kubernetes API 打交道，实时的感知后端 service、pod 等变化，比如新增和减少 pod，service 增加与减少等；当得到这些变化信息后，Ingress Controller 再结合下文的 Ingress 生成配置，然后更新反向代理负载均衡器，并刷新其配置，达到服务发现的作用。
1. 部署traefik
traefik的yaml文件可以从 https://github.com/containous/traefik/tree/master/examples/k8s 下载，无需修改可直接部署在kubernetes上。需要注意的是其提供了DaemonSet及deployment两种部署方式 ，我使用的是DaemonSet部署方式：
mkdir traefik
cd traefik/
wget https://raw.githubusercontent.com/containous/traefik/master/examples/k8s/traefik-rbac.yaml
wget https://raw.githubusercontent.com/containous/traefik/master/examples/k8s/traefik-ds.yaml
kubectl create -f traefik-ds.yaml
serviceaccount "traefik-ingress-controller" created
daemonset.extensions "traefik-ingress-controller" created
service "traefik-ingress-service" created
kubectl create -f traefik-rbac.yaml
clusterrole.rbac.authorization.k8s.io "traefik-ingress-controller" created
clusterrolebinding.rbac.authorization.k8s.io "traefik-ingress-controller" created
traefik有traefik-ingress-controller及traefik-web-ui两部分，后者为一个WEB的管理界面，可以使用traefik-ingress将其配置成集群外WEB访问.
wget https://raw.githubusercontent.com/containous/traefik/master/examples/k8s/ui.yaml
#修改host: traefik-ui.minikube改为你的域名
kubectl create -f ui.yaml
好了，现在可以用刚刚配置的域名来访问traefik web ui了。
2. traefik使用测试
编辑一个yaml文件：
vim nginx.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: nginx-router
namespace: test
spec:
replicas: 2
template:
metadata:
labels:
app: nginx-router
spec:
containers:
- name: nginx-router
image: 172.21.248.242/base/nginx
ports:
- containerPort: 80
---
kind: Service
apiVersion: v1
metadata:
name: nginx-router
namespace: test
spec:
selector:
app: nginx-router
ports:
- protocol: TCP
port: 80
targetPort: 80
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: nginx-router-ingress
namespace: test
annotations:
kubernetes.io/ingress.class: traefik
spec:
rules:
- host: "nginx.k8s.dev.huilog.com"
http:
paths:
- backend:
serviceName: nginx-router
servicePort: 80
# 创建部署及服务：
[root@bs-ops-test-docker-dev-01 dev]# kubectl create -f nginx.yaml
deployment.extensions "nginx-router" created
service "nginx-router" created
ingress.extensions "nginx-router-ingress" created
[root@bs-ops-test-docker-dev-01 dev]#
测试：
[root@bs-ops-test-docker-dev-01 dev]# kubectl -n=test get deploy -o wide
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
nginx-router 2 2 2 2 2d nginx-router 172.21.248.242/base/nginx app=nginx-router
[root@bs-ops-test-docker-dev-01 dev]# kubectl -n=test get pod -o wide | grep nginx-router
nginx-router-6d85cfb7cd-25mnb 1/1 Running 0 2d 10.244.2.16 bs-ops-test-docker-dev-03
nginx-router-6d85cfb7cd-2xhw6 1/1 Running 0 2d 10.244.1.3 bs-ops-test-docker-dev-02
[root@bs-ops-test-docker-dev-01 dev]# curl -x 172.21.251.111:80 http://nginx.k8s.dev.huilog.com
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
我们通过curl -x 172.21.251.111:80 http://nginx.k8s.dev.huilog.com 测试，可以看到是可以正常得到结果的。后面可以在Node的前端配置一台LB（nginx或硬件LB都可以），把这个域名配置到nginx上，后端发到k8s的traefik的节点上。 需要注意的是，在kubernetes前配置lb需要注意把host带过来，例如nginx配置一定要如下参数： proxy_set_header Host $host; 否则将会返回404的错误，原因是以IP去kubernetes访问，而不是域名,所以返回的是traefik默认的404页。
