K8S本身动手系列 - 2.2 - Deployment

前言

前面的文章，咱们使用Pod完成了wordpress+mysql的部署，并将两个容器放在了一个Pod当中，本篇文章，咱们将使用Deployment完成前面的部署工做

本文实验全部的源码保存在： github.com/zrbcool/blo…

实战

查看deployment定义

➜  lab05 git:(master) ✗ cat 01-wordpress-mysql-deployment.yaml 
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  labels:
    app: wordpress
  name: wordpress
spec:
  replicas: 1
  selector:
    matchLabels:
      app: wordpress
  template:
    metadata:
      labels:
        app: wordpress 
    spec:
      containers:
      - image: wordpress:latest
        imagePullPolicy: IfNotPresent
        name: wordpress
        env:
          - name: WORDPRESS_DB_HOST
            value: "127.0.0.1"
          - name: WORDPRESS_DB_USER
            value: "root"
          - name: WORDPRESS_DB_PASSWORD
            value: "passw0rd"
      - image: mysql:5.7.26
        imagePullPolicy: IfNotPresent
        name: mysql
        env:
          - name: MYSQL_ROOT_PASSWORD 
            value: "passw0rd"
          - name: MYSQL_DATABASE
            value: "wordpress"
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执行部署操做

➜  lab05 git:(master) ✗ kubectl apply -f 01-wordpress-mysql-deployment.yaml 
deployment.extensions/wordpress created
➜  lab05 git:(master) ✗ kubectl apply -f 02-wordpress-svc.yaml 
service/wordpress-svc created

➜  lab05 git:(master) ✗ kubectl get deploy -o wide
NAME        READY   UP-TO-DATE   AVAILABLE   AGE     CONTAINERS        IMAGES                          SELECTOR
wordpress   1/1     1            1           2m15s   wordpress,mysql   wordpress:latest,mysql:5.7.26   app=wordpress
➜  lab05 git:(master) ✗ kubectl get pod -o wide
NAME                         READY   STATUS    RESTARTS   AGE     IP            NODE       NOMINATED NODE   READINESS GATES
wordpress-5844bb9d6b-dbfb4   2/2     Running   0          2m23s   10.244.0.62   worker01   <none>           <none>
➜  lab05 git:(master) ✗ kubectl get svc -o wide
NAME            TYPE        CLUSTER-IP     EXTERNAL-IP PORT(S) AGE SELECTOR wordpress-svc NodePort 10.98.150.68 <none> 80:30611/TCP 2m23s app=wordpress
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访问咱们的服务，

Deployment扩缩容尝试

修改咱们的deployment定义，将replicas修改成2，查看效果

➜  lab05 git:(master) ✗ kubectl get deploy -o wide
NAME        READY   UP-TO-DATE   AVAILABLE   AGE     CONTAINERS        IMAGES                          SELECTOR
wordpress   2/2     2            2           7m43s   wordpress,mysql   wordpress:latest,mysql:5.7.26   app=wordpress
➜  lab05 git:(master) ✗ kubectl get pod -o wide
NAME                         READY   STATUS    RESTARTS   AGE     IP            NODE       NOMINATED NODE   READINESS GATES
wordpress-5844bb9d6b-dbfb4   2/2     Running   0          7m47s   10.244.0.62   worker01   <none>           <none>
wordpress-5844bb9d6b-ttkvm   2/2     Running   0          11s     10.244.0.63   worker01   <none>           <none>
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屡次访问网页，发现网页进入了网站初始化界面，初始化网站为mywebsite2，发现网站常常在website1与website2间切换，这是由于咱们的两个副本从应用到数据库彻底是相同的两份，而Service负载均衡，会分配请求到两套实例上，可是mysql是有状态应用，就形成了咱们使用上的问题。

问题如何解决

实际上，Deployment就是用来部署无状态应用的，它期待你的副本之间是没有区别的，那么在咱们的场景下，mysql使用Deployment来部署就不是一个好的实践，咱们这里只是学习使用，后续咱们会用StatefulSet来部署有状态应用解决当前这个问题。