K8s ❉ Service-Ingress详解

一 介绍

Service对集群之外暴露服务的主要方式有两种：NotePort和LoadBalancer，但是这两种方式，都有一定的缺点：

• NodePort方式的缺点是会占用很多集群机器的端口，那么当集群服务变多的时候，这个缺点就愈发明显
• LB方式的缺点是每个service需要一个LB，浪费、麻烦，并且需要kubernetes之外设备的支持

基于这种现状，kubernetes提供了Ingress资源对象，Ingress只需要一个NodePort或者一个LB就可以满足暴露多个Service的需求。

1 工作机制

        实际上，Ingress相当于一个7层的负载均衡器，是kubernetes对反向代理的一个抽象，它的工作原理类似于Nginx，可以理解成在Ingress里建立诸多映射规则，IngressController通过监听这些配置规则并转化成Nginx的反向代理配置，然后对外部提供服务。在这里有两个核心概念：

• ingress：kubernetes中的一个对象，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，根据配置的规则来实现请求转发，实现方式有很多，比如Nginx, Contour, Haproxy等等

2 工作原理

1. 用户编写Ingress规则，说明哪个域名对应kubernetes集群中的哪个Service
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控制器会将生成的Nginx配置写入到一个运行着的Nginx服务中，并动态更新
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 Ingress使用

1 环境准备

搭建 ingress 环境

# 创建⽂件夹
[root@k8s-master01 ~]# mkdir ingress-controller
[root@k8s-master01 ~]# cd ingress-controller/
# 获取ingress-nginx，本次案例使⽤的是0.30版本
[root@k8s-master01 ingress-controller]# wget
https://raw.githubusercontent.com/kubernetes/ingress-nginx/nginx-
0.30.0/deploy/static/mandatory.yaml
[root@k8s-master01 ingress-controller]# wget
https://raw.githubusercontent.com/kubernetes/ingress-nginx/nginx-
0.30.0/deploy/static/provider/baremetal/service-nodeport.yaml
# 修改mandatory.yaml⽂件中的仓库
# 修改quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.30.0
# 为quay-mirror.qiniu.com/kubernetes-ingress-controller/nginx-ingress-controller:0.30.0
# 创建ingress-nginx
[root@k8s-master01 ingress-controller]# kubectl apply -f ./
# 查看ingress-nginx
[root@k8s-master01 ingress-controller]# kubectl get pod -n ingress-nginx
NAME                                         READY STATUS     RESTARTS AGE
pod/nginx-ingress-controller-fbf967dd5-4qpbp 1/1   Running    0        12h
# 查看service
[root@k8s-master01 ingress-controller]# kubectl get svc -n ingress-nginx
NAME            TYPE     CLUSTER-IP     EXTERNAL-IP     PORT(S)                     AGE
ingress-nginx   NodePort 10.98.75.163   <none>          80:32240/TCP,443:31335/TCP  11h

2 准备service和pod

为了后面的实验方便，创建如下图所示的模型

# 创建tomcat-nginx.yaml
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

 

# 创建
[root@k8s-master01 ~]# kubectl create -f tomcat-nginx.yaml
# 查看
[root@k8s-master01 ~]# kubectl get svc -n dev
NAME             TYPE         CLUSTER-IP EXTERNAL-IP PORT(S)      AGE
nginx-service    ClusterIP     None      <none>      80/TCP       48s
tomcat-service   ClusterIP     None      <none>      8080/TCP     48s

3 Http代理

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



# 创建
[root@k8s-master01 ~]# kubectl create -f ingress-http.yaml
ingress.extensions/ingress-http created
# 查看
[root@k8s-master01 ~]# kubectl get ing ingress-http -n dev
NAME         HOSTS                                     ADDRESS PORTS  AGE
ingress-http nginx.itheima.com,tomcat.itheima.com              80     22s
# 查看详情
[root@k8s-master01 ~]# kubectl describe ing ingress-http -n dev
...
Rules:
Host Path Backends
---- ---- --------
nginx.itheima.com / nginx-service:80 (10.244.1.96:80,10.244.1.97:80,10.244.2.112:80)
tomcat.itheima.com / tomcat- service:8080(10.244.1.94:8080,10.244.1.95:8080,10.244.2.111:8080)
...
# 接下来,在本地电脑上配置host⽂件,解析上面的两个域名到192.168.109.100(master)上
# 然后,就可以分别访问tomcat.itheima.com:32240 和 nginx.itheima.com:32240 查看效果了

4 Https代理

创建证书

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

# 创建ingress-https.yaml
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: ingress-https
  namespace: dev
spec:
  tls:
  - hosts:
  - nginx.itheima.com
  - tomcat.itheima.com
    secretName: tls-secret # 指定秘钥
  rules:
  - host: nginx.itheima.com
    http:
      paths:
      - path: /
    backend:
      serviceName: nginx-service
      servicePort: 80
  - host: tomcat.itheima.com
    http:
 paths:
 - path: /
   backend:
     serviceName: tomcat-service
     servicePort: 8080

# 创建
[root@k8s-master01 ~]# kubectl create -f ingress-https.yaml
ingress.extensions/ingress-https created
# 查看
[root@k8s-master01 ~]# kubectl get ing ingress-https -n dev
NAME             HOSTS                                 ADDRESS              PORTS     AGE
ingress-https    nginx.itheima.com,tomcat.itheima.com  10.104.184.38 80,    443       2m42s
# 查看详情
[root@k8s-master01 ~]# kubectl describe ing ingress-https -n dev
...
TLS:
 tls-secret terminates nginx.itheima.com,tomcat.itheima.com
Rules:
Host Path Backends
---- ---- --------
nginx.itheima.com / nginx-service:80 (10.244.1.97:80,10.244.1.98:80,10.244.2.119:80)
tomcat.itheima.com / tomcat-service:8080(10.244.1.99:8080,10.244.2.117:8080,10.244.2.120:8080)
...
# 下面可以通过浏览器访问https://nginx.itheima.com:31335 和 https://tomcat.itheima.com:31335来查看了