第十二章 Kubernetes的服务暴露插件--traefik
1、前言
- 之前部署的coredns实现了k8s的服务在集群内可以被自动发现，那么如何使得服务在k8s集群外被使用和访问呢？
使用nodeport星的Service:此方法只能使用iptables模型，无法使用kube-proxy的ipvs模型
使用Ingress资源（本教程使用）:Ingress只能调度并暴露7层应用，特指http和https协议 - 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就相当于nginx+一段GO语言的脚本；
常用的Ingress控制器的实现软件如下：
Ingress-nginx;
HAProxy;
Traefik;
2、部署Traefik（Ingress控制器）
2.1 准备traefik镜像
在10.4.7.200操作
[root@hdss7-200 ~]# docker pull traefik:v1.7.2-alpine
[root@hdss7-200 ~]# docker images|grep traefik
traefik v1.7.2-alpine add5fac61ae5 2 years ago 72.4MB
[root@hdss7-200 ~]# docker tag add5fac61ae5 harbor.od.com/public/traefik:v1.7.2
[root@hdss7-200 ~]# docker push harbor.od.com/public/traefik:v1.7.2
2.2 准备traefik资源配置清单
在10.4.7.200操作
创建清单目录
[root@hdss7-200 ~]# mkdir /data/k8s-yaml/traefik
[root@hdss7-200 ~]# cd /data/k8s-yaml/traefik/
创建rbac.yaml
[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
创建ds.yaml
注意：- --kubernetes.endpoint=https://10.4.7.10:7443
注意：hostPort最好是分别写两个，不然可能会出现8080web端口未被代理，导致最后访问traefik页面无法访问的情况，可以参考一下github上的配置https://github.com/traefik/traefik/blob/v1.7/examples/k8s/traefik-ds.yaml
[root@hdss7-200 traefik]# vim 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
#--------prometheus自动发现增加内容--------
annotations:
prometheus_io_scheme: "traefik"
prometheus_io_path: "/metrics"
prometheus_io_port: "8080"
#--------增加结束--------------------------
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
创建svc.yaml
[root@hdss7-200 traefik]# vim 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
创建ingress.yaml
[root@hdss7-200 traefik]# vim 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
2.3 依次执行创建资源
在其中一个运算节点操作
[root@hdss7-21 ~]# 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@hdss7-21 ~]# kubectl apply -f http://k8s-yaml.od.com/traefik/ds.yaml
daemonset.extensions/traefik-ingress created
[root@hdss7-21 ~]# kubectl apply -f http://k8s-yaml.od.com/traefik/svc.yaml
service/traefik-ingress-service created
[root@hdss7-21 ~]# kubectl apply -f http://k8s-yaml.od.com/traefik/ingress.yaml
ingress.extensions/traefik-web-ui created
如果出现容器起不来，报错如下：
(iptables failed: iptables --wait -t filter -A DOCKER ! -i docker0 -o docker0 -p tcp -d 172.7.22.4 --dport 80 -j ACCEPT: iptables: No chain/target/match by that name.
那么重启docker服务（所有运算节点），将之前的iptables规则加回来
[root@hdss7-22 ~]# systemctl restart docker
[root@hdss7-22 ~]# iptables-save |grep -i postrouting|grep docker0
-A POSTROUTING -s 172.7.22.0/24 ! -o docker0 -j MASQUERADE
-A POSTROUTING -s 172.7.22.0/24 ! -d 172.7.0.0/16 ! -o docker0 -j MASQUERADE
查看pod
[root@hdss7-21 ~]# kubectl get pod -n kube-system
NAME READY STATUS RESTARTS AGE
coredns-64f49f5655-smzzz 1/1 Running 1 22h
traefik-ingress-6xbxz 1/1 Running 0 22s
traefik-ingress-xdt5s 1/1 Running 0 12m
查看监听端口
[root@hdss7-21 ~]# netstat -anplt|grep 81
tcp 0 0 0.0.0.0:81 0.0.0.0:* LISTEN 31285/docker-proxy
tcp6 0 0 :::81 :::* LISTEN 31291/docker-proxy
查看service
[root@hdss7-21 ~]# kubectl get svc -o wide -n kube-system
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
coredns ClusterIP 192.168.0.2 <none> 53/UDP,53/TCP,9153/TCP 22h k8s-app=coredns
traefik-ingress-service ClusterIP 192.168.116.188 <none> 80/TCP,8080/TCP 17m k8s-app=traefik-ingress
查看ingress
[root@hdss7-21 ~]# kubectl get ingress -n kube-system
NAME HOSTS ADDRESS PORTS AGE
traefik-web-ui traefik.od.com 80 4s
3、配置反向代理
在10.4.7.11/12的代理节点部署，以10.4.7.11为例
[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;
}
}
[root@hdss7-11 ~]# nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
[root@hdss7-11 ~]# nginx -s reload
4、配置域名解析
在10.4.11DNS服务器上操作
[root@hdss7-11 ~]# vim /var/named/od.com.zone
$ORIGIN od.com.
$TTL 600 ; 10 minutes
@ IN SOA dns.od.com. dnsadmin.od.com. (
2020010504 ; serial
10800 ; refresh (3 hours)
900 ; retry (15 minutes)
604800 ; expire (1 week)
86400 ; minimum (1 day)
)
NS dns.od.com.
$TTL 60 ; 1 minute
dns A 10.4.7.11
harbor A 10.4.7.200
k8s-yaml A 10.4.7.200
traefik A 10.4.7.10
保存退出，重启服务
[root@hdss7-11 ~]# systemctl restart named
[root@hdss7-11 ~]# dig -t A traefik.od.com @10.4.7.11 +short
10.4.7.10
5、浏览器访问
http://traefik.od.com/dashboard/
6、问题排查
当访问http://traefik.od.com/dashboard/有问题时，我们应该从根源找起
首先，我们知道访问的traefik的web控制页面，这个服务时启动在容器中的，在ds.yaml配置中我们知道，容器（pod）端口是8080，我们去查看pod
[root@hdss7-21 ~]# kubectl get pod -o wide -n kube-system
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
coredns-64f49f5655-smzzz 1/1 Running 1 23h 172.7.21.3 hdss7-21.host.com <none> <none>
traefik-ingress-7pl4d 1/1 Running 0 18m 172.7.21.5 hdss7-21.host.com <none> <none>
traefik-ingress-ms7st 1/1 Running 0 18m 172.7.22.4 hdss7-22.host.com <none> <none>
查看service
[root@hdss7-21 ~]# kubectl get svc -o wide -n kube-system
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
coredns ClusterIP 192.168.0.2 <none> 53/UDP,53/TCP,9153/TCP 23h k8s-app=coredns
traefik-ingress-service ClusterIP 192.168.163.186 <none> 80/TCP,8080/TCP 19m k8s-app=traefik-ingress
查看ipvs规则
[root@hdss7-21 ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 192.168.0.1:443 nq
-> 10.4.7.21:6443 Masq 1 1 0
-> 10.4.7.22:6443 Masq 1 0 0
TCP 192.168.0.2:53 nq
-> 172.7.21.3:53 Masq 1 0 0
TCP 192.168.0.2:9153 nq
-> 172.7.21.3:9153 Masq 1 0 0
TCP 192.168.163.186:80 nq
-> 172.7.21.5:80 Masq 1 0 0
-> 172.7.22.4:80 Masq 1 0 0
TCP 192.168.163.186:8080 nq
-> 172.7.21.5:8080 Masq 1 0 0
-> 172.7.22.4:8080 Masq 1 0 0
TCP 192.168.191.8:80 nq
-> 172.7.21.4:80 Masq 1 0 0
TCP 192.168.196.123:80 nq
-> 172.7.22.2:80 Masq 1 0 0
UDP 192.168.0.2:53 nq
-> 172.7.21.3:53 Masq 1 0 0
从上面我们可以推断出service192.168.163.186:8080代理了pod172.7.21.5:8080和pod172.7.22.4:8080
我们首先看pod是否可以被访问，如下，说明是没有问题
[root@hdss7-21 ~]# curl 172.7.22.4:8080
<a href="/dashboard/">Found</a>.
在看service是否有问题，如下。也是ok的
[root@hdss7-21 ~]# curl 192.168.163.186:8080
<a href="/dashboard/">Found</a>.
查看在ds.yaml中可以知道，service的8080端口是被我们宿主机10.4.7.21和10.4.7.22的81端口代理的，如下
[root@hdss7-21 ~]# netstat -anplt|grep 81
tcp 0 0 0.0.0.0:81 0.0.0.0:* LISTEN 49252/docker-proxy
tcp6 0 0 :::81 :::* LISTEN 49258/docker-proxy
查看宿主机81是否可以被访问，无法访问是正常的，应为他直接访问的是容器的80端口
[root@hdss7-12 ~]# curl 10.4.7.21:81
404 page not found
再次最后一次nginx代理
在10.4.7.11和12中nginx的配置，我们知道10.4.7.21和22的81端口被server_name *.od.com代理，所以我们访问域名，如下，也是没有问题的
[root@hdss7-21 ~]# curl traefik.od.com
<a href="/dashboard/">Found</a>.
那么最后我们的外网是否可以访问呢，在我们的物理主机上查看DNS解析是否生效，如下，也是没问题的
按照上面的思路一步步排查，都没有问题的话，就可以成功访问traefik页面了
