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

k8s核心概念Ingress

 

 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
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