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[K8S系列五]Ingress与Ingress Controller

发布时间 2023-10-18 02:00:11作者: MaxBruce

原文：https://www.jianshu.com/p/cd7ebd6876c9

1.为什么要有Ingress

前一篇文章[K8S系列四] K8S核心组件与核心概念(Pod、Deployment、Service)中提到了NodePort类型Service，但是NodePort类型Service有如下缺点：
1.一个端口只能一个服务使用，根据端口划分服务，需要提前规划好（可用端口范围：30000~32767）
2.只支持4层负载均衡设备(Service基于IPTABLE实现)，不能实现7层的负载。7层与4层简单理解就是7层最常见就是应用层的http，也就是url；4层是传输层，为tcp/udp端口。

2.Ingress与Ingress Controller

Ingress是自kubernetes1.1版本后引入的资源类型，在这个资源中我们可以去配置我们的服务路由规则，但是要真正去实现识别这个 Ingress 并提供代理路由功能，还需要安装一个对应的控制器Ingress controller才能实现。
Ingress controller是以一种插件的形式提供，有多种实现，例如官方维护的Ingress NGINX。Ingress controller 是部署在Kubernetes之上的Docker容器。它的Docker镜像包含一个像Nginx或HAProxy的负载均衡器和一个控制器守护进程。控制器守护程序从Kubernetes接收所需的Ingress配置。它会生成一个Nginx或HAProxy配置文件，并重新启动负载平衡器进程以使更改生效。换句话说，Ingress controller是由Kubernetes管理的负载均衡器。

3.示例

3.1 Ingress Nginx安装

如果是在公有云上安装Ingress Nginx，可以根据Installation Guide选择合适的安装方式。公有云有完善的网络负载均衡，类型可以选择LoadBalancer。
但这里是通过kubeadm自行搭建的K8S集群，所以选择Bare-Metal方式。类型为NodePort，在集群上开一个端口(范围为：30000-32767)，用于简单测试。

# kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/controller-v1.2.0/deploy/static/provider/baremetal/deploy.yaml

# kubectl get svc -o wide -n ingress-nginx
NAME                                 TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)                      AGE     SELECTOR
default-http-backend                 ClusterIP   10.111.34.218   <none>        80/TCP                       3h40m   app.kubernetes.io/name=default-http-backend,app.kubernetes.io/part-of=ingress-nginx
ingress-nginx-controller             NodePort    10.108.187.49   <none>        80:30434/TCP,443:30609/TCP   178m    app.kubernetes.io/component=controller,app.kubernetes.io/instance=ingress-nginx,app.kubernetes.io/name=ingress-nginx
ingress-nginx-controller-admission   ClusterIP   10.102.128.23   <none>        443/TCP                      178m    app.kubernetes.io/component=controller,app.kubernetes.io/instance=ingress-nginx,app.kubernetes.io/name=ingress-nginx
3.2 配置ingress

需要注意从1.16开始，部分api发生变化，所以请根具体使用的版本，调整配置。具体请参考根据Deprecated APIs Removed In 1.16: Here’s What You Need To Know。
这里配置域名为foo.mydomain.com，代理的两个Service为nginx-clusterip和whoami-cluster。nginx-clusterip和whoami-cluster的yaml配置请参考附录1和2

#ingress.yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: nginx-ingress
spec:
  ingressClassName: nginx
  rules:
  - host: foo.mydomain.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: nginx-clusterip
            port:
              number: 8080
      - path: /whoami
        pathType: Prefix
        backend:
          service:
            name: whoami-clusterip
            port:
              number: 8080

# kubectl apply -f ingress.yaml

# kubectl get svc -o wide -n ingress-nginx
NAME                                 TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)                      AGE     SELECTOR
default-http-backend                 ClusterIP   10.111.34.218   <none>        80/TCP                       5h15m   app.kubernetes.io/name=default-http-backend,app.kubernetes.io/part-of=ingress-nginx
ingress-nginx-controller             NodePort    10.108.187.49   <none>        80:30434/TCP,443:30609/TCP   4h33m   app.kubernetes.io/component=controller,app.kubernetes.io/instance=ingress-nginx,app.kubernetes.io/name=ingress-nginx
ingress-nginx-controller-admission   ClusterIP   10.102.128.23   <none>        443/TCP                      4h33m   app.kubernetes.io/component=controller,app.kubernetes.io/instance=ingress-nginx,app.kubernetes.io/name=ingress-nginx

# kubectl get ingress
NAME            CLASS   HOSTS              ADDRESS        PORTS   AGE
nginx-ingress   nginx   foo.mydomain.com   192.168.0.62   80      3h47m

# kubectl describe ingress nginx-ingress
Name:             nginx-ingress
Labels:           <none>
Namespace:        default
Address:          192.168.0.62
Default backend:  default-http-backend:80 (<error: endpoints "default-http-backend" not found>)
Rules:
  Host              Path  Backends
  ----              ----  --------
  foo.mydomain.com
                    /         nginx-clusterip:8080 (10.244.190.84:80,10.244.190.85:80,10.244.190.86:80 + 1 more...)
                    /whoami   whoami-clusterip:8080 (10.244.190.88:8000,10.244.80.211:8000,10.244.80.212:8000)
Annotations:        <none>
Events:
  Type    Reason  Age                  From                      Message
  ----    ------  ----                 ----                      -------
  Normal  Sync    47m (x8 over 3h48m)  nginx-ingress-controller  Scheduled for sync
3.3 测试

在集群外服务器的/etc/hosts中增加一条记录192.168.0.61 foo.mydomain.com。
分别访问foo.mydomain.com:30434和foo.mydomain.com:30434/whoami，可以看到nginx-clusterip和whoami-clusterip的返回结果。

# curl foo.mydomain.com:30434
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

# curl foo.mydomain.com:30434/whoami
I'm whoami-deployment-8886867c8-67d4f

附录

1.nginx-clutserip.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80

-------
apiVersion: v1
kind: Service
metadata:
  name: nginx-clusterip
spec:
  selector:
    app: nginx
  ports:
    - protocol: TCP
      port: 8080
      targetPort: 80
  type: ClusterIP
2. whoami-clutserip.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: whoami-deployment
  labels:
    app: whoami
spec:
  replicas: 3
  selector:
    matchLabels:
      app: whoami
  template:
    metadata:
      labels:
        app: whoami
    spec:
      containers:
      - name: whoami
        image: jwilder/whoami
        ports:
        - containerPort: 8000

-------------
apiVersion: v1
kind: Service
metadata:
  name: whoami-clusterip
spec:
  selector:
    app: whoami
  ports:
    - protocol: TCP
      port: 8080
      targetPort: 8000
  type: ClusterIP


作者：925781609
链接：https://www.jianshu.com/p/cd7ebd6876c9
来源：简书
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