k8s核心概念Ingress

1.  什么是 Ingress

　　通常情况下，service和pod的IP仅可在集群内部访问。集群外部的请求需要通过负载均衡转发到service在Node上暴露的NodePort上，然后再由kube-proxy将其转发给相关的Pod。

        而Ingress就是为进入集群的请求提供路由规则的集合，如下图所示

  internet
        |
   [ Ingress ]
   --|-----|--
   [ Services ]

    Ingress可以给service提供集群外部访问的URL、负载均衡、SSL终止、HTTP路由等。为了配置这些Ingress规则，集群管理员需要部署一个Ingress controller，它监听Ingress和service的变化，并根据规则配置负载均衡并提供访问入口。

　　一个 Ingress controller 是能将一个特定的负载均衡器和 Kubernetes 整合在一起的软件。开源的 NGINX 和 NGINX Plus 有相应的 Ingress controller，GitHub 仓库（https://github.com/nginxinc/kubernetes-ingress)。我自己理解Ingress Controller 实际上是将nginx 和 kubernetes做了一个整合，使得nginx 可以拿到kubernetes 的service 信息，我们启动一个ingressController 之后，在编写对应的rule 即可实现转发以及负载均衡。

　　可以理解为ingress 是对service进行代理，我们不需要知道service 对pods 暴露的端口等信息，pods 重启service 暴露的端口改变等对于应用无感，应用只和ingress 大交道。

2. 和pod 的关系

　　ingress 和 pod 通过service 进行关联，ingress 作为统一入口，由service 关联一组pod。

3. Ingress 工作流程

　　ingress 作为统一的入口，根据请求路径不同转发到后端不同服务。

4. 使用ingress：

1. 部署ingress controller

2. 创建ingress 规则

5. 部署测试

　　选择官方维护nginx 控制器，实现部署。简单的实现基于不同的域名转发到不同的service。效果如下：

1. 创建nginx 应用，使用service 对外暴露端口

kubectl create deployment nginx --image=nginx
kubectl expose deployment nginx --port=80 --type=NodePort

查看svc 以及 相关信息：

[root@k8smaster1 ~]# kubectl get svc -o wide
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE   SELECTOR
kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP        8d    <none>
nginx        NodePort    10.109.175.64   <none>        80:32503/TCP   32m   app=nginx

　　接下来从windows， 通过任何k8s 节点的32503 端口即可访问到nginx。

2. 创建tomcat服务, 并且使用service 对其暴露端口

[root@k8smaster1 ~]# kubectl create deployment tomcat --image=tomcat:8.0.15-jre8
deployment.apps/tomcat created
[root@k8smaster1 ~]# kubectl get pods
NAME                     READY   STATUS    RESTARTS   AGE
nginx-f89759699-vkf7d    1/1     Running   1          59m
tomcat-58767d5b5-f5qwj   1/1     Running   0          8s
[root@k8smaster1 ~]# kubectl expose deployment tomcat --port=8080 --type=NodePort
service/tomcat exposed
[root@k8smaster1 ~]# kubectl get svc -o wide
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE   SELECTOR
kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP          8d    <none>
nginx        NodePort    10.109.175.64   <none>        80:32503/TCP     59m   app=nginx
tomcat       NodePort    10.100.178.25   <none>        8080:30158/TCP   6s    app=tomcat

 3. 最后service 暴露后的效果如下： 可以从外部通过k8s任意的节点IP+端口访问到指定服务

 

 4. 创建ingress controller

(1) 创建ingress-controller.yaml

apiVersion: v1
kind: Namespace
metadata:
  name: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

---

kind: ConfigMap
apiVersion: v1
metadata:
  name: nginx-configuration
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

---
kind: ConfigMap
apiVersion: v1
metadata:
  name: tcp-services
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

---
kind: ConfigMap
apiVersion: v1
metadata:
  name: udp-services
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: nginx-ingress-serviceaccount
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: nginx-ingress-clusterrole
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
rules:
  - apiGroups:
      - ""
    resources:
      - configmaps
      - endpoints
      - nodes
      - pods
      - secrets
    verbs:
      - list
      - watch
  - apiGroups:
      - ""
    resources:
      - nodes
    verbs:
      - get
  - apiGroups:
      - ""
    resources:
      - services
    verbs:
      - get
      - list
      - watch
  - apiGroups:
      - ""
    resources:
      - events
    verbs:
      - create
      - patch
  - apiGroups:
      - "extensions"
      - "networking.k8s.io"
    resources:
      - ingresses
    verbs:
      - get
      - list
      - watch
  - apiGroups:
      - "extensions"
      - "networking.k8s.io"
    resources:
      - ingresses/status
    verbs:
      - update

---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: Role
metadata:
  name: nginx-ingress-role
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
rules:
  - apiGroups:
      - ""
    resources:
      - configmaps
      - pods
      - secrets
      - namespaces
    verbs:
      - get
  - apiGroups:
      - ""
    resources:
      - configmaps
    resourceNames:
      # Defaults to "<election-id>-<ingress-class>"
      # Here: "<ingress-controller-leader>-<nginx>"
      # This has to be adapted if you change either parameter
      # when launching the nginx-ingress-controller.
      - "ingress-controller-leader-nginx"
    verbs:
      - get
      - update
  - apiGroups:
      - ""
    resources:
      - configmaps
    verbs:
      - create
  - apiGroups:
      - ""
    resources:
      - endpoints
    verbs:
      - get

---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: RoleBinding
metadata:
  name: nginx-ingress-role-nisa-binding
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: nginx-ingress-role
subjects:
  - kind: ServiceAccount
    name: nginx-ingress-serviceaccount
    namespace: ingress-nginx

---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: nginx-ingress-clusterrole-nisa-binding
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: nginx-ingress-clusterrole
subjects:
  - kind: ServiceAccount
    name: nginx-ingress-serviceaccount
    namespace: ingress-nginx

---

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-ingress-controller
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: ingress-nginx
      app.kubernetes.io/part-of: ingress-nginx
  template:
    metadata:
      labels:
        app.kubernetes.io/name: ingress-nginx
        app.kubernetes.io/part-of: ingress-nginx
      annotations:
        prometheus.io/port: "10254"
        prometheus.io/scrape: "true"
    spec:
      hostNetwork: true
      # wait up to five minutes for the drain of connections
      terminationGracePeriodSeconds: 300
      serviceAccountName: nginx-ingress-serviceaccount
      nodeSelector:
        kubernetes.io/os: linux
      containers:
        - name: nginx-ingress-controller
          image: lizhenliang/nginx-ingress-controller:0.30.0
          args:
            - /nginx-ingress-controller
            - --configmap=$(POD_NAMESPACE)/nginx-configuration
            - --tcp-services-configmap=$(POD_NAMESPACE)/tcp-services
            - --udp-services-configmap=$(POD_NAMESPACE)/udp-services
            - --publish-service=$(POD_NAMESPACE)/ingress-nginx
            - --annotations-prefix=nginx.ingress.kubernetes.io
          securityContext:
            allowPrivilegeEscalation: true
            capabilities:
              drop:
                - ALL
              add:
                - NET_BIND_SERVICE
            # www-data -> 101
            runAsUser: 101
          env:
            - name: POD_NAME
              valueFrom:
                fieldRef:
                  fieldPath: metadata.name
            - name: POD_NAMESPACE
              valueFrom:
                fieldRef:
                  fieldPath: metadata.namespace
          ports:
            - name: http
              containerPort: 80
              protocol: TCP
            - name: https
              containerPort: 443
              protocol: TCP
          livenessProbe:
            failureThreshold: 3
            httpGet:
              path: /healthz
              port: 10254
              scheme: HTTP
            initialDelaySeconds: 10
            periodSeconds: 10
            successThreshold: 1
            timeoutSeconds: 10
          readinessProbe:
            failureThreshold: 3
            httpGet:
              path: /healthz
              port: 10254
              scheme: HTTP
            periodSeconds: 10
            successThreshold: 1
            timeoutSeconds: 10
          lifecycle:
            preStop:
              exec:
                command:
                  - /wait-shutdown

---

apiVersion: v1
kind: LimitRange
metadata:
  name: ingress-nginx
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
spec:
  limits:
  - min:
      memory: 90Mi
      cpu: 100m
    type: Container

(2) 创建相关资源

[root@k8smaster1 ~]# kubectl apply -f ingress-controller.yaml 
namespace/ingress-nginx created
configmap/nginx-configuration created
configmap/tcp-services created
configmap/udp-services 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.apps/nginx-ingress-controller created
limitrange/ingress-nginx created
[root@k8smaster1 ~]# kubectl get all -o wide -n ingress-nginx
NAME                                           READY   STATUS              RESTARTS   AGE   IP               NODE       NOMINATED NODE   READINESS GATES
pod/nginx-ingress-controller-766fb9f77-tksqp   0/1     ContainerCreating   0          36s   192.168.13.105   k8snode2   <none>           <none>

NAME                                       READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS                 IMAGES                                        SELECTOR
deployment.apps/nginx-ingress-controller   0/1     1            0           36s   nginx-ingress-controller   lizhenliang/nginx-ingress-controller:0.30.0   app.kubernetes.io/name=ingress-nginx,app.kubernetes.io/part-of=ingress-nginx

NAME                                                 DESIRED   CURRENT   READY   AGE   CONTAINERS                 IMAGES                                        SELECTOR
replicaset.apps/nginx-ingress-controller-766fb9f77   1         1         0       36s   nginx-ingress-controller   lizhenliang/nginx-ingress-controller:0.30.0   app.kubernetes.io/name=ingress-nginx,app.kubernetes.io/part-of=ingress-nginx,pod-template-hash=766fb9f77

(3) 到k8snode2 节点查看nginx 监听的端口， nginx-controller 实际是启动了一个nginx

[root@k8snode2 ~]# netstat -nltp | grep 80
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      5852/nginx: master  
tcp6       0      0 :::80                   :::*                    LISTEN      5852/nginx: master  
[root@k8snode2 ~]# netstat -nltp | grep 443
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN      5852/nginx: master  
tcp6       0      0 :::443                  :::*                    LISTEN      5852/nginx: master 

5. 编写ingress 规则

(1) 编写 ingress-rule.yaml

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: example-ingress
spec:
  rules:
  - host: nginx.ingredemo.com
    http:
      paths:
      - path: /
        backend:
          serviceName: nginx
          servicePort: 80
  - host: tomcat.ingredemo.com
    http:
      paths:
      - path: /
        backend:
          serviceName: tomcat
          servicePort: 8080          

(2) 执行创建并且查看

[root@k8smaster1 ~]# kubectl apply -f ingress-rule.yaml 
ingress.networking.k8s.io/example-ingress configured
[root@k8smaster1 ~]# kubectl get ing -o wide
NAME              CLASS    HOSTS                                      ADDRESS   PORTS   AGE
example-ingress   <none>   nginx.ingredemo.com,tomcat.ingredemo.com             80      15h
[root@k8smaster1 ~]# kubectl describe ing example-ingress
Name:             example-ingress
Namespace:        default
Address:          
Default backend:  default-http-backend:80 (<error: endpoints "default-http-backend" not found>)
Rules:
  Host                  Path  Backends
  ----                  ----  --------
  nginx.ingredemo.com   
                        /   nginx:80 (10.244.1.89:80)
  tomcat.ingredemo.com  
                        /        tomcat:8080 (10.244.1.92:8080)
Annotations:            Events:  <none>

6. 测试：

(1) windows 下面配置虚拟的域名:

C:\Windows\System32\drivers\etc\hosts 文件增加如下配置， 注意IP 是自己nginx-controller 所在的节点

192.168.13.105    nginx.ingredemo.com
192.168.13.105    tomcat.ingredemo.com

(2) 访问测试：根据不同域名可以访问到不同的服务

补充： ingress 也可以根据不同的路径分配到不同的service 

例如：

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: test
spec:
  rules:
  - host: foo.bar.com
    http:
      paths:
      - path: /foo
        backend:
          serviceName: s1
          servicePort: 80
      - path: /bar
        backend:
          serviceName: s2
          servicePort: 80

　　上面表示如下结果：

foo.bar.com -> 178.91.123.132 -> / foo    s1:80
                                 / bar    s2:80