#yyds干货盘点#kubernetes入门基础-Ingress的概念与使用

Posted 2022-02-18 极客开发者

一、相关概念

• NodePort方式的缺点是会占用很多集群的端口，那么集群服务器变多的时候，这个缺点愈发明显
• LoadBalancer的缺点是每个Service需要一个LoadBalancer，浪费、麻烦，并且需要k8s之外的设备支持

基于这两种现状，k8s提供了Ingress资源对象，Ingress值需要一个NodePort或者一个LoadBalancer就可以满足暴露多个Service的需求。工作机制大致如下图所示

• Ingress：k8s中的一个抽象，作用是定义请求如何转发到Service的规则
• Ingress controller：具体实现反向代理及负载均衡的程序，对Ingress定义的规则进行解析，根据配置规则来实现转发，实现方式有很多种，比如nginx、Controller、Haproxy等等

Ingress（以Nginx为例）的工作原理如下：

• 1. 用户编写Ingress规则，说明哪个域名对应k8s集群的哪个Seivice
• 2. Ingress控制器动态感知Ingress服务规则的变化，然后生成一段对应的Nginx反向代理配置
• 3. Ingress控制器将会生成的Nginx配置写入到一个运行着的Nginx服务中，并且动态更新
• 4. 到此为止，其实真正在工作的就是一个Nginx了，内部配置了用户定义的请求转发规则

二、创建Ingress

1.创建Ingress Controller

将以下两个资源清单文件保存到服务器

# 创建目录
mkdir ingress-controller
# 进入资源目录
cd ingress-controller
# mandatory
wget https://github.com/kubernetes/ingress-nginx/blob/nginx-0.30.0/deploy/static/mandatory.yaml
# service-nodeport文件
wget https://raw.githubusercontent.com/kubernetes/ingress-nginx/nginx-0.30.0/deploy/static/provider/baremetal/service-nodeport.yaml

执行kubectl创建资源命令

kubectl apply -f ./

2. 查看Ingress Controller

查看Pod：kubectl get pods -n ingress-nginx，返回以下内容

NAME                                        READY   STATUS    RESTARTS   AGE
nginx-ingress-controller-5bb8fb4bb6-qnbdv   1/1     Running   0          3m23s

查看Service：kubectl get svc -n ingress-nginx，返回以下内容

NAME            TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)                      AGE
ingress-nginx   NodePort   10.99.166.208   <none>        80:30796/TCP,443:31737/TCP   5m22s

3. 创建Deployment和Service

创建3个Nginx和3个tomcat应用和对应的两个Service，创建tomcat-nginx.yaml文件，添加以下内容：

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  namespace: dev
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx-pod
  template:
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
      - name: nginx
        image: nginx:1.17.1
        ports:
        - containerPort: 80

---

apiVersion: apps/v1
kind: Deployment
metadata:
  name: tomcat-deployment
  namespace: dev
spec:
  replicas: 3
  selector:
    matchLabels:
      app: tomcat-pod
  template:
    metadata:
      labels:
        app: tomcat-pod
    spec:
      containers:
      - name: tomcat
        image: tomcat:8.5-jre10-slim
        ports:
        - containerPort: 8080

---

apiVersion: v1
kind: Service
metadata:
  name: nginx-service
  namespace: dev
spec:
  selector:
    app: nginx-pod
  clusterIP: None
  type: ClusterIP
  ports:
  - port: 80
    targetPort: 80

---

apiVersion: v1
kind: Service
metadata:
  name: tomcat-service
  namespace: dev
spec:
  selector:
    app: tomcat-pod
  clusterIP: None
  type: ClusterIP
  ports:
  - port: 8080
    targetPort: 8080

4. 创建ingress-http

创建ingress-http.yaml，添加以下内容

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: ingress-http
  namespace: dev
spec:
  rules:
  - host: nginx.jkdev.cn
    http:
      paths:
      - path: /
        backend:
          serviceName: nginx-service
          servicePort: 80
  - host: tomcat.jkdev.cn
    http:
      paths:
      - path: /
        backend:
          serviceName: tomcat-service
          servicePort: 8080

使用以下命令进行创建

kubectl create -f ingress-http.yaml

创建之后使用以下命令查看

kubectl get ingress -n dev
# 或
kubectl get ing -n dev

或使用以下命令指定ingress名称查看

kubectl get ingress ingress-http -n dev
# 或
kubectl get ing ingress-http -n dev

或使用kubectl describe ingress -n dev指令查看详细信息，返回以下详细内容

Name:             ingress-http
Namespace:        dev
Address:          10.99.166.208
Default backend:  default-http-backend:80 (<error: endpoints "default-http-backend" not found>)
Rules:
  Host             Path  Backends
  ----             ----  --------
  nginx.jkdev.cn   
                   /   nginx-service:80 (10.244.1.20:80,10.244.1.21:80,10.244.1.24:80)
  tomcat.jkdev.cn  
                   /   tomcat-service:8080 (10.244.1.22:8080,10.244.1.23:8080,10.244.1.25:8080)
Annotations:       <none>
Events:
  Type    Reason  Age   From                      Message
  ----    ------  ----  ----                      -------
  Normal  CREATE  21m   nginx-ingress-controller  Ingress dev/ingress-http
  Normal  UPDATE  21m   nginx-ingress-controller  Ingress dev/ingress-http

5. 创建ingress-https

生成ssl证书以及密钥

# 生成证书
openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 -keyout tls.key -out tls.crt -subj "/C=CN/ST=GZ/O=nginx/CN=jkdev.cn"
# 创建密钥
kubectl create secret tls tls-secret --key tls.key --cert tls.crt

添加ingress-https.yaml，添加以下内容

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: ingress-https
  namespace: dev
spec:
  tls:
  - hosts:
    - nginx.jkdev.cn
    - tomcat.jkdev.cn
    secretName: tls-secret # 指定密钥，必须和创建的密钥名称一致
  rules:
  - host: nginx.jkdev.cn
    http:
      paths:
      - path: /
        backend:
          serviceName: nginx-service
          servicePort: 80
  - host: tomcat.jkdev.cn
    http:
      paths:
      - path: /
        backend:
          serviceName: tomcat-service
          servicePort: 8080

三、Nginx转发到k8s

使用Nginx将来自外网的请求转发给k8s集群

upstream default_backend_traefix 
  server 10.99.166.208:80 max_fails=3 fail_timeout=10s;


server
  listen 80;
  server_name *.jkdev.cn;

  location / 
    proxy_pass http://default_backend_traefix;
    proxy_set_header Host $http_host;
    proxy_set_header x-forwarded-for $proxy_add_x_forwarded_for;