16、Kubernetes - 实战：Ingress 控制器
一、环境安装
参考
二、Ingress介绍
1 基本概念
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，Ingress Controller 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**。
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
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；
查看Ingress官方帮助
kubectl explain ingress
KIND: Ingress
VERSION: networking.k8s.io/v1
DESCRIPTION:
Ingress is a collection of rules that allow inbound connections to reach
the endpoints defined by a backend. An Ingress can be configured to give
services externally-reachable urls, load balance traffic, terminate SSL,
offer name based virtual hosting etc.
FIELDS:
apiVersion <string>
APIVersion defines the versioned schema of this representation of an
object. Servers should convert recognized schemas to the latest internal
value, and may reject unrecognized values. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources
kind <string>
Kind is a string value representing the REST resource this object
represents. Servers may infer this from the endpoint the client submits
requests to. Cannot be updated. In CamelCase. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds
metadata <Object>
Standard object's metadata. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
spec <Object>
Spec is the desired state of the Ingress. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status
status <Object>
Status is the current state of the Ingress. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status
三、Ingress使用
1 创建yml文件
tomcat-nginx.yml
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
2 创建service和deploy实例
kubectl create -f tomcat-nginx.yml
3 查看service服务
kubectl get svc -n dev
4 创建Ingress HTTP 代理
ingress-http.yml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: ingress-http
namespace: dev
spec:
rules:
- host: nginx.example.com
http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: nginx-service svc 中配置的名字
port:
number: 80 svc 中配置的端口
- host: tomcat.example.com
http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: tomcat-service
port:
number: 8080
kubectl create -f ingress-http.yml
5 查看 Ingress
kubectl get ing -n dev
