在Kubernetes上使用Traefik
本节内容：[*]Traefik介绍
[*]部署测试用的两个服务
[*]Role Based Access Control configuration (Kubernetes 1.6+ only)
[*]部署Traefik
[*]部署 Ingress
[*]部署Traefik UI
[*]访问测试
[*]健康检查
一、Traefik介绍
traefik 是一个前端负载均衡器，对于微服务架构尤其是 kubernetes 等编排工具具有良好的支持；同 nginx 等相比，traefik 能够自动感知后端容器变化，从而实现自动服务发现。
由于微服务架构以及 Docker 技术和 kubernetes 编排工具最近几年才开始逐渐流行，所以一开始的反向代理服务器比如 nginx、apache 并未提供其支持，毕竟他们也不是先知；所以才会出现 Ingress Controller 这种东西来做 kubernetes 和前端负载均衡器如 nginx 之间做衔接；即 Ingress Controller 的存在就是为了能跟 kubernetes 交互，又能写 nginx 配置，还能>https://images2017.cnblogs.com/blog/1132141/201712/1132141-20171201174425086-1635667337.png
二、部署测试用的两个服务
部署两个服务nginx1-7和nginx1-8，后面用Traefik去负载这两个服务：
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apiVersion: v1
kind: Service
metadata:
name: frontend
spec:
ports:
- port: 80
targetPort: 80
selector:
app: nginx1-7
---
apiVersion: apps/v1beta1
kind: Deployment
metadata:
name: nginx1-7-deployment
spec:
replicas: 2
template:
metadata:
labels:
app: nginx1-7
spec:
containers:
- name: nginx
image: nginx:1.7.9
ports:
- containerPort: 80
nginx1-7.yaml
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apiVersion: v1
kind: Service
metadata:
name: my-nginx
spec:
ports:
- port: 80
targetPort: 80
selector:
app: nginx1-8
---
apiVersion: apps/v1beta1
kind: Deployment
metadata:
name: nginx1-8-deployment
spec:
replicas: 2
template:
metadata:
labels:
app: nginx1-8
spec:
containers:
- name: nginx
image: nginx:1.8
ports:
- containerPort: 80
nginx1-8.yaml 运行两个服务：
# kubectl create -f nginx1-7.yaml
service
"frontend" created
deployment
"nginx1-7-deployment" created
# kubectl create
-f nginx1-8.yaml
service
"my-nginx" created
deployment
"nginx1-8-deployment" created
三、Role Based Access Control configuration (Kubernetes 1.6+ only)
我这里部署的是1.6.0集群，开启了RBAC，授权需要使用角色和绑定角色。
# pwd
/opt/traefik
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# vim ingress-rbac.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
name: ingress
namespace: kube-system
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
name: ingress
subjects:
- kind: ServiceAccount
name: ingress
namespace: kube-system
roleRef:
kind: ClusterRole
name: cluster-admin
apiGroup: rbac.authorization.k8s.io
ingress-rbac.yaml
四、部署Traefik
# pwd
/opt/traefik
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# vim traefik-deploy.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: traefik-ingress-lb
namespace: kube-system
labels:
k8s-app: traefik-ingress-lb
spec:
template:
metadata:
labels:
k8s-app: traefik-ingress-lb
name: traefik-ingress-lb
spec:
terminationGracePeriodSeconds: 60
hostNetwork: true
restartPolicy: Always
serviceAccountName: ingress
containers:
- image: traefik
name: traefik-ingress-lb
resources:
limits:
cpu: 200m
memory: 30Mi
requests:
cpu: 100m
memory: 20Mi
ports:
- name: http
containerPort: 80
hostPort: 80
- name: admin
containerPort: 8580
hostPort: 8580
args:
- --web
- --web.address=:8580
- --kubernetes
traefik-deploy.yaml 其中 traefik 监听 node 的 80 和 8580 端口，80 提供正常服务，8580 是其自带的 UI 界面，原本默认是 8080，因为环境里端口冲突了，所以这里临时改一下。
【注意】：这里用的是Deploy类型，没有限定该pod运行在哪个主机上。
五、部署 Ingress
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# cat traefik.yaml
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: traefik-ingress
namespace: default
spec:
rules:
- host: traefik.nginx.io
http:
paths:
- path: /
backend:
serviceName: my-nginx
servicePort: 80
- host: traefik.frontend.io
http:
paths:
- path: /
backend:
serviceName: frontend
servicePort: 80
traefik.yaml 其中的backend中要配置default namespace中启动的service名字，如果你没有配置namespace名字，默认使用default namespace，如果你在其他namespace中创建服务想要暴露到kubernetes集群外部，可以创建新的ingress.yaml文件，同时在文件中指定该namespace，其他配置与上面的文件格式相同。path就是URL地址后的路径，如traefik.frontend.io/path，service将会接受path这个路径，host最好使用service-name.filed1.filed2.domain-name这种类似主机名称的命名方式，方便区分服务。
根据实际环境中部署的service的名字和端口自行修改，有新service增加时，修改该文件后可以使用kubectl replace -f traefik.yaml来更新。
六、部署Traefik UI
traefik 本身还提供了一套 UI 供我们使用，其同样以 Ingress 方式暴露，只需要创建一下即可。
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# cat traefik-ui-service.yaml
apiVersion: v1
kind: Service
metadata:
name: traefik-web-ui
namespace: kube-system
spec:
selector:
k8s-app: traefik-ingress-lb
ports:
- name: web
port: 80
targetPort: 8580
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: traefik-web-ui
namespace: kube-system
spec:
rules:
- host: traefik-ui.local
http:
paths:
- path: /
backend:
serviceName: traefik-web-ui
servicePort: web
traefik-ui-service.yaml 最后一起创建：
# kubectl create -f .
serviceaccount
"ingress" created
clusterrolebinding
"ingress" created
deployment
"traefik-ingress-lb" created
service
"traefik-web-ui" created
ingress
"traefik-web-ui" created
ingress
"traefik-ingress" created
七、访问测试
查看traefik pod被分配到了哪台主机上：
# kubectl get pods -n kube-system -l k8s-app=traefik-ingress-lb -o wide
NAME READY STATUS RESTARTS AGE IP NODE
traefik
-ingress-lb-4237248072-1dg9n 1/1 Running 0 2m 172.16.7.152 172.16.7.152
浏览器输入http://172.16.7.152:8580/，将可以看到dashboard。
https://images2017.cnblogs.com/blog/1132141/201712/1132141-20171201211637792-1781116602.png
左侧黄色部分部分列出的是所有的rule，右侧绿色部分是所有的backend。
在Kubernetes集群的任意一个节点上执行。假如现在我要访问nginx的"/"路径。
curl -H Host:traefik.nginx.io http://172.16.7.152/
如果需要在kubernetes集群以外访问就需要设置DNS，或者修改本机的hosts文件。
172.16.7.152 traefik.nginx.io
172.16.7.152 traefik.frontend.io
所有访问这些地址的流量都会发送给172.16.7.152这台主机，就是我们启动traefik的主机。
Traefik会解析http请求header里的Host参数将流量转发给Ingress配置里的相应service。
修改hosts后就就可以在kubernetes集群外访问以上两个service。
八、健康检查
关于健康检查，测试可以使用 kubernetes 的 Liveness Probe 实现，如果 Liveness Probe检查失败，则 traefik 会自动移除该 pod。
【示例】：我们定义一个 test-health 的 deployment，健康检查方式是 cat /tmp/health，容器启动 2 分钟后会删掉这个文件，模拟健康检查失败。
test-health的deployment：
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# cat test-health-deploy.yaml
apiVersion: v1
kind: Deployment
apiVersion: extensions/v1beta1
metadata:
name: test
namespace: default
labels:
test: alpine
spec:
replicas: 1
selector:
matchLabels:
test: alpine
template:
metadata:
labels:
test: alpine
name: test
spec:
containers:
- image: mritd/alpine:3.4
name: alpine
resources:
limits:
cpu: 200m
memory: 30Mi
requests:
cpu: 100m
memory: 20Mi
ports:
- name: http
containerPort: 80
args:
command:
- "bash"
- "-c"
- "echo ok > /tmp/health;sleep 120;rm -f /tmp/health"
livenessProbe:
exec:
command:
- cat
- /tmp/health
initialDelaySeconds: 20
test-health-deploy.yaml test-health 的 service：
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# vim test-health-service.yaml
apiVersion: v1
kind: Service
metadata:
name: test
labels:
name: test
spec:
ports:
- port: 8123
targetPort: 80
selector:
name: test
test-health-service.yaml test-health的 Ingress：
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# vim test-health-ingress.yaml
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: test
spec:
rules:
- host: test.com
http:
paths:
- path: /
backend:
serviceName: test
servicePort: 8123
test-health-ingress.yaml 全部创建好以后，进入 traefik ui 界面，可以观察到每隔 2 分钟健康检查失败后，kubernetes 重建 pod，同时 traefik 会从后端列表中移除这个 pod。
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