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