K8S本身動手系列 - 2.4 - Service

時間 2019-12-13

標籤 k8s 本身動手系列 2.4 service 简体版

原文原文鏈接

前言

上個實驗2.3 – PV & PVC，咱們將wordpress+mysql的Deployment綁定PVC，併成功將mysql的數據保存才PV存儲捲上。可是mysql做爲數據庫應用，當水平擴展後，就是多個獨立的數據庫實例，數據彼此分離，致使應用在多個實例間的狀態不一致，那麼這個問題如何解決呢？java

答案就是將mysql與wordpress進行分離，咱們把wordpress看作一個支持水平擴展的無狀態應用，多個wordpress鏈接同一個mysql數據庫。node

那麼wordpress又如何找到對應的mysql數據庫呢？答案就是經過Servicemysql

場景

將wordpress與mysql分離成兩個Deployment，併爲mysql定義Service，wordpress經過ServiceName發現mysql的實例信息，mysql的Deployment使用PVC保存數據狀態，完成後wordpress能夠水平擴展爲多個實例，而且可以保證數據一致性git

本文實驗全部的源碼保存在： github.com/zrbcool/blo…github

實戰

對Deployment進行分離

先準備好PVC及PV

➜  lab07 git:(master) ✗ kubectl apply -f 01-1-mysql-pvc.yaml
persistentvolumeclaim/wordpress-mysql-pv-claim created
➜  lab07 git:(master) ✗ kubectl apply -f 01-2-mysql-pv.yaml 
persistentvolume/wordpress-mysql-pv-volume created
➜  lab07 git:(master) ✗ kubectl get pvc
NAME                       STATUS   VOLUME                      CAPACITY   ACCESS MODES   STORAGECLASS   AGE
wordpress-mysql-pv-claim   Bound    wordpress-mysql-pv-volume   2Gi        RWO                           15s
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爲mysql建立Deployment

➜  lab07 git:(master) ✗ cat 01-3-mysql-deployment.yaml 
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
 labels:
 app: wordpress
 type: mysql
 name: wordpress-mysql
spec:
 replicas: 1 
 selector:
 matchLabels:
 app: wordpress
 type: mysql
 template:
 metadata:
 labels:
 app: wordpress
 type: mysql
 spec:
 containers:
 - image: mysql:5.7.26
 imagePullPolicy: IfNotPresent
 name: mysql
 env:
 - name: MYSQL_ROOT_PASSWORD 
 value: "passw0rd"
 - name: MYSQL_DATABASE
 value: "wordpress"
 volumeMounts:
 - name: mysql-persistent-storage
 mountPath: /var/lib/mysql
 volumes:
 - name: mysql-persistent-storage
 persistentVolumeClaim:
 claimName: wordpress-mysql-pv-claim 
➜  lab07 git:(master) ✗ kubectl apply -f 01-3-mysql-deployment.yaml 
deployment.extensions/wordpress-mysql created
# 這裏能夠簡單測試一下
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爲mysql建立Service

➜  lab07 git:(master) ✗ cat 01-4-mysql-svc.yaml 
apiVersion: v1
kind: Service
metadata:
  name: wordpress-mysql-svc 
  labels:
    app: wordpress
    type: mysql
spec:
  ports:
  - port: 3306
    protocol: TCP
    targetPort: 3306
  selector:
    app: wordpress
    type: mysql
➜  lab07 git:(master) ✗ kubectl apply -f 01-4-mysql-svc.yaml 
service/wordpress-mysql-svc created
➜  lab07 git:(master) ✗ kubectl get svc -o wide
NAME                  TYPE        CLUSTER-IP    EXTERNAL-IP PORT(S) AGE SELECTOR wordpress-mysql-svc ClusterIP 10.98.45.79 <none> 3306/TCP 9s app=wordpress,type=mysql
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咱們來測試下這個Service是否work，sql

➜  lab07 git:(master) ✗ kubectl run -it --rm --image=mysql:5.7.26 --restart=Never mysql-client -- mysql -h wordpress-mysql-svc -ppassw0rd
If you don't see a command prompt, try pressing enter.

mysql> use wordpress
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> show tables;
+-----------------------+
| Tables_in_wordpress   |
+-----------------------+
| wp_commentmeta        |
| wp_comments           |
| wp_links              |
| wp_options            |
| wp_postmeta           |
| wp_posts              |
| wp_term_relationships |
| wp_term_taxonomy      |
| wp_termmeta           |
| wp_terms              |
| wp_usermeta           |
| wp_users              |
+-----------------------+
12 rows in set (0.00 sec)
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爲wordpress建立Deployment

➜  lab07 git:(master) ✗ cat 02-1-wordpress-deployment.yaml 
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  labels:
    app: wordpress
    type: wordpress
  name: wordpress-wp
spec:
  replicas: 1 
  selector:
    matchLabels:
      app: wordpress
      type: wordpress
  template:
    metadata:
      labels:
        app: wordpress
        type: wordpress
    spec:
      containers:
      - image: wordpress:latest
        imagePullPolicy: IfNotPresent
        name: wordpress
        env:
          - name: WORDPRESS_DB_HOST
            value: "wordpress-mysql-svc"
          - name: WORDPRESS_DB_USER
            value: "root"
          - name: WORDPRESS_DB_PASSWORD
            value: "passw0rd"
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須要注意到wordpress鏈接的數據庫信息已經再也不是127.0.0.1了，而是"wordpress-mysql-svc"，這樣wordpress的Pod就能夠經過ServiceName鏈接到mysql了，咱們來試試數據庫

➜  lab07 git:(master) ✗ kubectl apply -f 02-1-wordpress-deployment.yaml 
deployment.extensions/wordpress-wp created
ne>
➜  lab07 git:(master) ✗ kubectl get pods        
NAME                               READY   STATUS    RESTARTS   AGE
wordpress-mysql-66df4d4dd6-gwjsx   1/1     Running   0          19m
wordpress-wp-66ffcc84c5-tgbsc      1/1     Running   0          55s
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使用NodePort類型的Service暴露wordpress，咱們來測試一下：api

➜  lab07 git:(master) ✗ cat 02-2-wordpress-svc.yaml 
apiVersion: v1
kind: Service
metadata:
  name: wordpress-svc 
  labels:
    app: wordpress
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
    nodePort: 30611
  selector:
    app: wordpress
  type: NodePort
➜  lab07 git:(master) ✗ kubectl apply -f 02-2-wordpress-svc.yaml 
service/wordpress-svc created
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測試OK，能夠正常訪問，咱們來對wordpress的Pod進行擴容，app

➜  lab07 git:(master) ✗ kubectl scale --replicas=5 deploy/wordpress-wp
deployment.extensions/wordpress-wp scaled
➜  lab07 git:(master) ✗ kubectl get pods
NAME                               READY   STATUS    RESTARTS   AGE
wordpress-mysql-66df4d4dd6-gwjsx   1/1     Running   0          23m
wordpress-wp-66ffcc84c5-76tsh      1/1     Running   0          41s
wordpress-wp-66ffcc84c5-c4r4q      1/1     Running   0          41s
wordpress-wp-66ffcc84c5-qrv2r      1/1     Running   0          41s
wordpress-wp-66ffcc84c5-tgbsc      1/1     Running   0          5m24s
wordpress-wp-66ffcc84c5-w24sv      1/1     Running   0          41s
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屢次訪問網頁，發現已經狀態一致，全部請求均由一個數據庫處理，完成任務！ide

清除數據

➜  lab07 git:(master) ✗ kubectl delete -f .
persistentvolumeclaim "wordpress-mysql-pv-claim" deleted
persistentvolume "wordpress-mysql-pv-volume" deleted
deployment.extensions "wordpress-mysql" deleted
service "wordpress-mysql-svc" deleted
deployment.extensions "wordpress-wp" deleted
service "wordpress-svc" deleted
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