Kubernetes Ingress 学习

Kubernetes 中暴露服务的方式有三种

  • Loadbalancer 这种方式往往需要云供应商支持,或者本地F5等设备支持
  • NodePort 这种方式调用方通过NodeIP:NodePort 的方式访问服务,无法应对Pod发生迁移时的场景
  • Ingress Ingress是Kubernetes中的一种资源,通过这种资源提供了外部访问内部服务的通路,实现上是通过一个Pod加NodePort来实现的。通过Ingress,方便我们自己定义负载均衡。现在有很多种的Ingress支持,本文主要介绍Nginx的方案。

Kubernetes社区和Nginx公司都发布了一款叫做Nginx-ingress的Controller,它们之间的不同可以参考 Difference between two nginx-ingress 本文基于 Nginx-ingress Controller 做的实验。版本为 1.3.0。

Kubernetes 社区方案

安装

[root@devops-101 ~]# kubectl apply -f  https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/mandatory.yaml
namespace/ingress-nginx created
configmap/nginx-configuration created
serviceaccount/nginx-ingress-serviceaccount created
clusterrole.rbac.authorization.k8s.io/nginx-ingress-clusterrole created
role.rbac.authorization.k8s.io/nginx-ingress-role created
rolebinding.rbac.authorization.k8s.io/nginx-ingress-role-nisa-binding created
clusterrolebinding.rbac.authorization.k8s.io/nginx-ingress-clusterrole-nisa-binding created
deployment.extensions/nginx-ingress-controller created
[root@devops-101 ~]# kubectl get pods --all-namespaces -l app.kubernetes.io/name=ingress-nginx --watch
NAMESPACE NAME READY STATUS RESTARTS AGE
ingress-nginx nginx-ingress-controller-664f488479-pr87w 0/1 ContainerCreating 0 5s
ingress-nginx nginx-ingress-controller-664f488479-pr87w 0/1 Running 0 11s
ingress-nginx nginx-ingress-controller-664f488479-pr87w 1/1 Running 0 16s
[root@devops-101 ~]# kubectl get all -n ingress-nginx
NAME READY STATUS RESTARTS AGE
pod/nginx-ingress-controller-664f488479-pr87w 1/1 Running 0 2m NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
deployment.apps/nginx-ingress-controller 1 1 1 1 2m NAME DESIRED CURRENT READY AGE
replicaset.apps/nginx-ingress-controller-664f488479 1 1 1 2m

安装文件mandatory,需要增加hostNetwork属性,否则访问的时候总是有问题。

配置tomcat和httpd

从我的Github上下载tomcat-deploy\httpd-deploy\tomcat-service\httpd-service几个文件,并分别部署。

再下载tomcat-ingress.yaml文件,进行部署。

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: tomcat-ingress
# namespace: nginx-ingress
annotations:
nginx.ingress.kubernetes.io/rewrite-target: /
spec:
rules:
- host: ingressweb.com
http:
paths:
- path: /
backend:
serviceName: tomcat-service
servicePort: 8080
- path: /httpd
backend:
serviceName: httpd-service
servicePort: 80

验证

上面的例子中,我配置的域名为 ingressweb.com ,在本地修改host,指向ingress-controller运行的节点,通过浏览器访问 http://ingressweb.com 可以看到 tomcat 的界面,通过 http://ingressweb.com/httpd 可以看到httpd的It Works!界面。

Kubernetes Ingress 学习

Nginxinc 的方案

看一下Nginx Ingress Controller的示意图

Kubernetes Ingress 学习

Nginx Ingress Controller 支持的功能

  • 暴露服务,一般有两种方式,通过不同的主机名(如 serviceA.com,serviceB.com)或者通过不同的URL(如 /serviceA 和 /serviceB)。
  • 配置SSL支持
  • TCP负载均衡
  • Url 重写

安装

首先需要有一个可以正常运行的Kubernetes环境,如果还没有,可以参考我的安装步骤 kubeadm安装kubernetes V1.11.1 集群

[root@devops-101 ~]# kubectl apply -f ingress-install.yaml
namespace/nginx-ingress created
serviceaccount/nginx-ingress created
secret/default-server-secret created
configmap/nginx-config created
clusterrole.rbac.authorization.k8s.io/nginx-ingress configured
clusterrolebinding.rbac.authorization.k8s.io/nginx-ingress configured
deployment.extensions/nginx-ingress created
[root@devops-101 ~]# kubectl get pods -n nginx-ingress
NAME READY STATUS RESTARTS AGE
nginx-ingress-767cc6477f-flj2f 1/1 Running 5 4m

实例

没有规则配置的时候,对于所有的请求默认都返回404状态。

[root@devops-101 ~]# kubectl apply -f cafe-example.yaml
deployment.extensions/coffee created
service/coffee-svc created
deployment.extensions/tea created
service/tea-svc created
secret/cafe-secret created
ingress.extensions/cafe-ingress created
[root@devops-101 ~]# IC_IP=192.168.0.102
[root@devops-101 ~]# IC_HTTPS_PORT=31586
[root@devops-101 ~]# curl --resolve cafe.example.com:$IC_HTTPS_PORT:$IC_IP https://cafe.example.com:$IC_HTTPS_PORT/tea --insecure
Server address: 172.16.1.138:80
Server name: tea-7d57856c44-jxpvt
Date: 22/Oct/2018:11:37:47 +0000
URI: /tea
Request ID: 796e79e0280a27743cb682b8e893d6e9

Kubernetes Ingress 学习

参考资料

  1. Kubernetes ingress controller
  2. Github nginx ingress
  3. Difference between two nginx-ingress
  4. Kubernetes的负载均衡问题
  5. 初试Kubernetes暴露服务类型之Nginx Ingress
  6. Kubernetes Nginx Ingress
  7. Kubernetes Nginx Ingress教程
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