【云原生 • Kubernetes】kubernetes 核心技术 - Ingress

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一、前言

在以往的操作过程中，我们都是将某端口号对外暴露，然后再使用 IP+端口号 进行访问服务，这是通过 Service 中的 NodePort 实现的。

但是 NodePort 有着明显的缺陷：NodePort 会在每一个 node 节点都启用一个端口，也就是说在集群中的任何一个 node 节点中，使用节点 IP + 端口号都能访问到该服务；每个端口只能使用一次，每个端口也只对应一个应用。而在实际的项目当中，其实都是使用 域名 访问的，根据不同的域名跳转到不同的端口服务中。

Ingress 的应用正是专门用于弥补 NodePort 的这些缺陷。

二、Ingress 和 pod 有什么关系

首先，Ingress 和 pod 是通过 Service 进行关联的，将 Ingress 作为一个统一的访问入口，访问由 Service 关联的一组 pod，如下示意图：

三、使用 Ingress 对外暴露应用

1. 创建应用并使用 NodePort 暴露端口

第一步：创建 nginx 应用，使用 NodePort 对外暴露端口；

[root@master ~]# kubectl create deployment web --image=nginx
deployment.apps/web created
[root@master ~]# 

查看 pod 可以看到我们创建的 web；

第二步：对外暴露一个端口，如下 32153 即为暴露端口；

[root@master ~]# kubectl expose deployment web --port=80 --target-port=80 --type=NodePort
service/web exposed
#查看
[root@master ~]# kubectl get svc
NAME             TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
kubernetes       ClusterIP   10.96.0.1       <none>        443/TCP        44d
myweb1           NodePort    10.104.70.36    <none>        80:30619/TCP   14d
ui-weave-scope   NodePort    10.110.235.39   <none>        80:31772/TCP   15d
web              NodePort    10.96.191.100   <none>        80:32153/TCP   23s
[root@master ~]# 

此时，在任一 node 节点通过 节点IP+32153 就可以访问到 web 容器中的应用服务，为了避免这个问题，所以 接下来我们开始添加 Ingress。

2. 应用 Ingress

(1) 部署 Ingress Controller

Ingress Controller 是一个反向代理程序，负责解析 Ingress 的反向代理规则，以 Pod 的形式运行，监控 api-server 的 ingress 端口后的 backend services，如果 Ingress 有增删改的变动，所有的 Ingress Controller 都会及时更新自己相应的转发规则，当 Ingress Controller 收到请求后就会根据这些规则将请求转发到对应的 Service。

Ingress Controller 并不是 k8s 集群内置的，所以需要我们手动下载部署。

第一步：vi 创建 yaml 文件 ingress-controller.yaml，添加以下内容；

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 "-"
      # Here: "-"
      # 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

第二步：执行该文件；

[root@master ~]# kubectl apply -f ingress-controller.yaml

(2) 创建 Ingress 规则

创建 Ingress 规则的目的就是要找到访问的内容。

第一步：vi 创建 yaml 文件 ingress.yaml，添加以下内容；

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: example-ingress
spec:
  rules:
  #通过以下域名访问
  - host: example.ingredemo.com
    http:
      paths:
      - path: /
        backend:
          #服务名称，我们之前创建的web
          serviceName: web
          servicePort: 80

第二步：执行该文件；

[root@master ~]# kubectl apply -f ingress.yaml 
ingress.networking.k8s.io/example-ingress created
[root@master ~]# 

Ingress 规则创建完成。

(3) 在 Windows 系统的 hosts 文件添加域名访问规则

系统中的 hosts 文件默认在 C:\Windows\System32\drivers\etc 目录下；

编辑该文件；

设置完成后，就可以使用域名来访问我们集群中的服务了。