Ingress和Egress的解析

Ingress介绍

     每个Service都要有一个负载均衡服务,所以这个做法实际上既浪费成本又高.作为用户,更希望看到Kubernetes为我内置一个全局的负载均衡器.然后,通过我访问的 URL,把请求转发给不同的后端 Service.这种全局的,为了代理不同后端Service而设置的负载均衡服务,就是Kubernetes里的Ingress服务

    所以Ingress的功能其实很容易理解:所谓 Ingress,就是 Service 的Service

    Ingress和Service的区别:

         Ingress负载均衡的后端应用是由众多Service组成的集合  本质是一个7层调度器(通过url,http,https协议进行调度)

         Servie负载均衡的后端应用是由众多Pod组成的集合         本质是一个4层调度器(iptables,ipvs进行IP包转发)

    使用Kubernetes的Ingress来创建一个统一的负载均衡器,从而实现当用户访问不同的域名时,能够访问到不同的Deployment

    最值得我们关注的,是 rules 字段.在 Kubernetes 里 这个字段叫作:IngressRule

    IngressRule的Key就叫做:host.它必须是一个标准的域名格式(Fully Qualified Domain Name)的字符串,而不能是IP地址

    而host 字段定义的值,就是这个Ingress的入口.这也就意味着,当用户访问 cafe.example.com 的时候,实际上访问到的是这个Ingress对象.这样Kubernetes 就能使用IngressRule来对你的请求进行下一步转发 

      

 Ingress Contronl控制器

       Ingress Controller会根据你定义的Ingress对象,提供对应的代理能力.目前,业界常用的各种反向代理项目Nginx、HAProxy、Envoy、Traefik 等都已经为Kubernetes专门维护了对应的Ingress Controller

      一个Nginx Ingress Controller为你提供的服务,其实是一个可以根据Ingress对象和被代理后端Service的变化,来自动进行更新的Nginx负载均衡器

      Ingress只能工作在七层,而 Service只能工作在四层.所以当你想要在k8s里为应用进行TLS配置等HTTP相关的操作时都必须通过Ingress来进行

      Ingress Controller是一个拥有运行七层调度的应用程序的Pod(比如运行一个NGINX的服务的Pod)    nginx pod通过url映射来把请求代理不同的Pod

      外部用戶跟Ingress Controller管理的Pod采用https协议进行通信 Ingress Controller管理的Pod跟被它代理的其它Pod采用http协议通信 

      Ingress Controller管理的Pod实现了https会话卸载器的功能

      Ingress资源
           1.首先通过无头service动态关联符合标签选择器选择的后端Pod
           2.Ingress动态的把service关联的pod地址注入到前端配置upstream中  同时触发主程序重新加载最新的配置文件

      pod变化 >  service变化  >  Ingress变化 >  Ingress Control注入配置
           1.Pod的数量或者IP发生变化的时候通过selector选择Pod的service会自动更新 

           2.因为Service是无头service类型 所以访问service的时候获取的不是VIP而是service被代理的Pod地址集合

           3.Ingress资源通过Service资源的变化自动维护提供upstream的后端Pod集合

           4.Ingress自动更新配置文件 通知nginx主进程重载最新的配置文件

    

      

 Ingress部署实例

     1.部署一个Ingress Control 比如nginx的Pod 

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:
      # 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: quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.28.0
          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: 
  - default:
    min:    
      memory: 90Mi
      cpu: 100m
    type: Container

     

  2.部署nodeport的service用来为ingress-controller的pod提供访问入口接入集群外部流量

apiVersion: v1
kind: Service
metadata:
  name: ingress-nginx
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
spec:
  type: NodePort
  ports:
    - name: http
      port: 80
      targetPort: 80
      protocol: TCP
    - name: https
      port: 443
      targetPort: 443
      protocol: TCP
  selector:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

---

   

   

  3.定义Pod和service 并通过selector把service和pod关联起来

      Ingress Control的pod中nginx有多少组upstream就需要定义多少个headless service来关联不同的pod 

     

apiVersion: apps/v1
kind: Deployment
metadata:
  name: coffee
spec:
  replicas: 2
  selector:
    matchLabels:
      app: coffee
  template:
    metadata:
      labels:
        app: coffee
    spec:
      containers:
      - name: coffee
        image: nginxdemos/hello:plain-text
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: coffee-svc
spec:
  ports:
  - port: 80
    targetPort: 80
    protocol: TCP
    name: http
  selector:
    app: coffee
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: tea
spec:
  replicas: 3
  selector:
    matchLabels:
      app: tea
  template:
    metadata:
      labels:
        app: tea
    spec:
      containers:
      - name: tea
        image: nginxdemos/hello:plain-text
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: tea-svc
  labels:
spec:
  ports:
  - port: 80
    targetPort: 80
    protocol: TCP
    name: http
  selector:
    app: tea

   4.定义一个Ingress资源关联servie

   

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: cafe-ingress
  namespace: default
  annotations:
    kubernetes.io/ingress.class: "nginx"
spec:
  rules:
  - host: yxh.example.com
    http:
      paths:
      - path: /tea
        backend:
          serviceName: tea-svc
          servicePort: 80
      - path: /coffee
        backend:
          serviceName: coffee-svc
          servicePort: 80

   5.配置DNS解析

      IngressRule的Key,就叫做:host.它必须是一个标准的域名格式(Fully Qualified Domain Name)的字符串而不能是IP地址 修改hosts

    

  6.测试负载效果

       集群外客户端通过访问nodeport的serive端口->Ingress Control(nginx) ->读取最新nginx.conf找Pod(根据不同的url转发到不同的Pod) -> Pod