K8S不負責任介紹

Kubernetes (或簡稱K8s) 是一套高成熟度的開源軟體系統
用於管理容器化的工作或服務，由 Google 於 2014 年對外發佈。

K8S有以下幾個優點~

可以跑在任何地方
開源軟體系統
確保持續提供服務
設定副本與負載平衡
滾動更新

環境準備

一個或多個 Master
一個或多個 Worker Nodes
Kubeadm安裝K8S
安裝Docker

不負責任K8S圖解

這是一個最陽春的K8S集群，有一個Master和兩個Node

k8scluster

以下是K8S集群內元件的介紹

kubectl: 負責在機器上運行內容，屬於最基礎的組件。
API Server: 負責將東西放入etcd，並管裡身分驗證。例如:誰可以將什麼東西放入etcd?
Controller Manager: 分配Pod在哪個node上運行，運行幾個，就像調度員一樣。
etcd: K8S的大腦，所有的狀態都儲存在etcd。
kubelet: 和master連接，告訴Docker去run container。
Proxy: 將請求轉發到正確的容器。
Scheduler: 依照你希望的配置份配Pod的位置，若沒設訂，Scheduler會幫你安排。
Pod: K8S元件最小單位，Node內可以有很多Pod，Pod內可有很多Container。

當我們在Master節點下kubectl create -f xxxx.yaml 指令，K8S就會開始動作，變成如下圖

k8scluster2

K8S-Ingress 介紹

當你想要將佈署在K8S上的服務對外開放時，需要在yaml檔裡設定Service的Type

ClusterIP: 預設的Service type，會給你的Service一組只有K8S集群內部可連的IP。
NodePort: 給你的Service一組預設範圍在30000-32767的port，讓Service可以透過NodeIP+port訪問。
LoadBalancer: 給你的Service一組外部IP，此type僅限於雲服務可用。例如AWS、GCP

但是在本地的VM，不適用LoadBalancer，如果想要將自己剛建立好的POD對外發佈讓別人可以連，只能用NodePort嗎?這樣每次都要用NodeIP:Port才能連，很不方便也暴露很多不必要的資訊，所以～

k8scluster2
圖片連結https://medium.com/google-cloud/ - Kubernetes NodePort vs LoadBalancer vs Ingress? When should I use what?

顧名思義，ingress就是一個進入點，他在service前就先設定好該連去哪個service，扮演著smart router的角色。

來設定自己的Ingress吧

step1. 需先創一個default-backend.yaml

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: default-http-backend
  labels:
    k8s-app: default-http-backend
  namespace: kube-system
spec:
  replicas: 1
  template:
    metadata:
      labels:
        k8s-app: default-http-backend
    spec:
      terminationGracePeriodSeconds: 60
      containers:
      - name: default-http-backend
        # Any image is permissable as long as:
        # 1. It serves a 404 page at /
        # 2. It serves 200 on a /healthz endpoint
        image: gcr.io/google_containers/defaultbackend:1.0
        livenessProbe:
          httpGet:
            path: /healthz
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 30
          timeoutSeconds: 5
        ports:
        - containerPort: 8080
        resources:
          limits:
            cpu: 10m
            memory: 20Mi
          requests:
            cpu: 10m
            memory: 20Mi
---
apiVersion: v1
kind: Service
metadata:
  name: default-http-backend
  namespace: kube-system
  labels:
    k8s-app: default-http-backend
spec:
  ports:
  - port: 80
    targetPort: 8080
  selector:
    k8s-app: default-http-backend

kubectl create -f default-backend.yaml

———-我是分隔線———-

step2. 設定ingress的ServiceAccount
創一個nginx-ingress-controller-role.yaml

apiVersion: v1
kind: ServiceAccount
metadata:
  name: nginx
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: nginx-role
rules:
- apiGroups:
  - ""
  - "extensions"
  resources:
  - configmaps
  - secrets
  - endpoints
  - ingresses
  - nodes
  - pods
  verbs:
  - list
  - watch
- apiGroups:
  - ""
  resources:
  - services
  verbs:
  - list
  - watch
  - get
  - update
- apiGroups:
  - "extensions"
  resources:
  - ingresses
  verbs:
  - get
- apiGroups:
  - ""
  resources:
  - events
  verbs:
  - create
- apiGroups:
  - "extensions"
  resources:
  - ingresses/status
  verbs:
  - update
- apiGroups:
  - ""
  resources:
  - configmaps
  verbs:
  - get
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: nginx-role
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: nginx-role
subjects:
- kind: ServiceAccount
  name: nginx
  namespace: kube-system

kubectl create -f nginx-ingress-controller-role.yaml -n kube-system

———-我是分隔線———-

step3. 設定ingress的configmap
創一個nginx-ingress-controller-config-map.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: nginx-ingress-controller-conf
  labels:
    app: k8s-app
data:
  enable-vts-status: 'true'

kubectl create -f nginx-ingress-controller-config-map.yaml -n kube-system

———-我是分隔線———-

step4. Run一個nginx的deployment
建一個nginx-ingress-controller.yaml

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: nginx-ingress-controller
  labels:
    k8s-app: nginx-ingress-controller
spec:
  replicas: 1
  selector:
    matchLabels:
      k8s-app: nginx-ingress-controller
  template:
    metadata:
      labels:
        k8s-app: nginx-ingress-controller
    spec:
      # hostNetwork makes it possible to use ipv6 and to preserve the source IP correctly regardless of docker configuration
      # however, it is not a hard dependency of the nginx-ingress-controller itself and it may cause issues if port 10254 already is taken on the host
      # that said, since hostPort is broken on CNI (https://github.com/kubernetes/kubernetes/issues/31307) we have to use hostNetwork where CNI is used
      # like with kubeadm
      hostNetwork: true
      terminationGracePeriodSeconds: 60
      serviceAccount: nginx
      serviceAccountName: nginx
      containers:
      - image: quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.12.0
        name: nginx-ingress-controller
        readinessProbe:
          httpGet:
            path: /healthz
            port: 10254
            scheme: HTTP
        livenessProbe:
          httpGet:
            path: /healthz
            port: 10254
            scheme: HTTP
          initialDelaySeconds: 10
          timeoutSeconds: 1
        ports:
        - containerPort: 80
          hostPort: 80
        - containerPort: 443
          hostPort: 443
        env:
          - name: POD_NAME
            valueFrom:
              fieldRef:
                fieldPath: metadata.name
          - name: POD_NAMESPACE
            valueFrom:
              fieldRef:
                fieldPath: metadata.namespace
        args:
        - /nginx-ingress-controller
        - --default-backend-service=$(POD_NAMESPACE)/default-http-backend
        - --configmap=\$(POD_NAMESPACE)/nginx-ingress-controller-conf

kubectl create -f nginx-ingress-controller.yaml -n kube-system

———-我是分隔線———-

step5. 可以來設定ingress囉~
創一個nginx-ingress.yaml

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: nginx-ingress
spec:
  rules:
  - host: test.rita.com #你要設定啥都可以
    http:
      paths:
      - backend:
          serviceName: nginx-ingress
          servicePort: 18080
        path: /nginx_status

kubectl create -f nginx-ingress.yaml -n kube-system

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step6. 用kubectl get po -o wide -n kube-system
看一下你的nginx-ingress-controller是Run在哪一台，把那台的IP和剛才設定的ingress網址加到本機host
k8scluster2
所以host就設定↓
10.9.18.146 test.rita.com

———-我是分隔線———-

來測試一下是不是連的到default backend~~

成功惹~

快去試試吧!!