K8S核心外掛-ingress(服務暴露)控制器-traefik

1 K8S兩種服務暴露方法

前面通過coredns在k8s叢集內部做了serviceNAME和serviceIP之間的自動對映,使得不需要記錄service的IP地址,只需要通過serviceNAME就能訪問POD
但是在K8S叢集外部,顯然是不能通過serviceNAME或serviceIP來解析服務的
要在K8S叢集外部來訪問叢集內部的資源,需要用到服務暴露功能

1.1 K8S常用的兩種服務暴露方法

1. 使用NodePort型的Service
   nodeport型的service原理相當於埠對映，將容器內的埠對映到宿主機上的某個埠。
   K8S叢集不能使用ipvs的方式排程,必須使用iptables,且只支援rr模式

2. 使用Ingress資源
   Ingress是K8S API標準資源之一,也是核心資源
   是一組基於域名和URL路徑的規則,把使用者的請求轉發至指定的service資源
   可以將叢集外部的請求流量,轉發至叢集內部,從而實現'服務暴露'

1.2 Ingress控制器是什麼

可以理解為一個簡化版本的nginx
Ingress控制器是能夠為Ingress資源健康某套接字,然後根據ingress規則匹配機制路由排程流量的一個元件
只能工作在七層網路下，建議暴露http, https可以使用前端nginx來做證書方面的解除安裝

我們使用的ingress控制器為Traefik

traefik：GITHUB官方地址

2 部署traefik

同樣的,現在7.200完成docker映象拉取和配置清單建立,然後再到任意master節點執行配置清單

2.1 準備docker映象

docker pull traefik:v1.7.2-alpine
docker tag  traefik:v1.7.2-alpine harbor.zq.com/public/traefik:v1.7.2
docker push harbor.zq.com/public/traefik:v1.7.2

2.2 建立資源清單

mkdir -p /data/k8s-yaml/traefik

2.2.1 rbac授權清單

cat >/data/k8s-yaml/traefik/rbac.yaml <<EOF
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
EOF
 

2.2.2 delepoly資源清單

cat >/data/k8s-yaml/traefik/ds.yaml <<EOF
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
    spec:
      serviceAccountName: traefik-ingress-controller
      terminationGracePeriodSeconds: 60
      containers:
      - image: harbor.zq.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
EOF

2.2.3 service清單

cat >/data/k8s-yaml/traefik/svc.yaml <<EOF
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
EOF

2.2.4 ingress清單

cat >/data/k8s-yaml/traefik/ingress.yaml <<EOF
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: traefik-web-ui
  namespace: kube-system
  annotations:
    kubernetes.io/ingress.class: traefik
spec:
  rules:
  - host: traefik.zq.com
    http:
      paths:
      - path: /
        backend:
          serviceName: traefik-ingress-service
          servicePort: 8080
EOF

2.3 建立資源

2.3.1 任意節點上建立資源

kubectl create -f http://k8s-yaml.zq.com/traefik/rbac.yaml
kubectl create -f http://k8s-yaml.zq.com/traefik/ds.yaml
kubectl create -f http://k8s-yaml.zq.com/traefik/svc.yaml
kubectl create -f http://k8s-yaml.zq.com/traefik/ingress.yaml

2.3.2 在前端nginx上做反向代理

在7.11和7.12上,都做反向代理,將泛域名的解析都轉發到traefik上去

cat >/etc/nginx/conf.d/zq.com.conf <<'EOF'
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 *.zq.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;
    }
}
EOF

# 重啟nginx服務
nginx -t
nginx -s reload

2.3.3 在bind9中新增域名解析

需要將traefik 服務的解析記錄新增的DNS解析中,注意是繫結到VIP上

vi /var/named/zq.com.zone
........
traefik            A    10.4.7.10

注意前滾serial編號

重啟named服務

systemctl restart named

#dig驗證解析結果
[root@hdss7-11 ~]# dig -t A traefik.zq.com +short
10.4.7.10

2.3.4 在叢集外訪問驗證

在叢集外,訪問http://traefik.zq.com,如果能正常顯示web頁面.說明我們已經暴露服務成功