K8S本身动手系列 - 2.3 - PV & PVC

时间  2019-12-14
标签 k8s 本身 动手 系列 2.3 pvc 繁體版
原文   原文链接

前言

在实验2.2 – Deployment中，咱们将原来基于Pod部署的wordpress+mysql成功改形成基于Deployment部署，基于Deployment部署有不少好处，例如：支持滚动升级（Rolling Update），支持水平扩展。java

不过有个问题，就是当咱们的Deployment修改了，或者Pod删除重建了，数据也随之丢失了，这是咱们不但愿看到的，本篇文章咱们就来尝试一下基于PV & PVC保存数据状态的有状态应用。mysql

场景

对于单实例的有状态应用，咱们能够定义Deployment而且replicas只能为1，用指定PVC的方式关联到一个PV上，使用PV提供的状态存储功能。若是要启动多实例，那么Deployment就没法胜任这个任务，必须使用到咱们后面会讲到的StatefulSet+PVC Template的方式建立多实例对多PVC的模型。git

本文实验全部的源码保存在： github.com/zrbcool/blo…github

实战

PVC定义

➜  lab06 git:(master) ✗ cat 03-wordpress-pvc.yaml 
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
 name: wordpress-pv-claim
spec:
 accessModes:
 - ReadWriteOnce
 resources:
 requests:
 storage: 2Gi
复制代码

部署后查看状态sql

➜  lab06 git:(master) ✗ kubectl apply -f 03-wordpress-pvc.yaml
persistentvolumeclaim/wordpress-pv-claim created
➜  lab06 git:(master) ✗ kubectl get pvc
NAME                       STATUS    VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
wordpress-mysql-pv-claim   Pending                                                     4s
复制代码

发现PVC处于Pending状态，追查下缘由api

➜  lab06 git:(master) ✗ kubectl describe pvc/wordpress-mysql-pv-claim
Name:          wordpress-mysql-pv-claim
Namespace:     default
StorageClass:  
Status:        Pending
Volume:        
Labels:        <none>
Annotations:   kubectl.kubernetes.io/last-applied-configuration:
                 {"apiVersion":"v1","kind":"PersistentVolumeClaim","metadata":{"annotations":{},"name":"wordpress-mysql-pv-claim","namespace":"default"},"s...
Finalizers:    [kubernetes.io/pvc-protection]
Capacity:      
Access Modes:  
VolumeMode:    Filesystem
Events:
  Type       Reason         Age               From                         Message
  ----       ------         ----              ----                         -------
  Normal     FailedBinding  6s (x4 over 36s)  persistentvolume-controller  no persistent volumes available for this claim and no storage class is set
Mounted By:  <none>
复制代码

接下来咱们建立PVapp

PV定义

查看定义wordpress

➜  lab06 git:(master) ✗ cat 04-wordpress-pv.yaml 
kind: PersistentVolume
apiVersion: v1
metadata:
 name: wordpress-mysql-pv-volume
 labels:
 type: local
spec:
 capacity:
 storage: 2Gi
 accessModes:
 - ReadWriteOnce
 hostPath:
 path: "/data/pv/wordpress/mysql"
复制代码

该pv定义是基于hostPath的方式，因此咱们要在节点上提早建立好目录，以下：测试

➜  lab06 git:(master) ✗ mkdir -p /data/pv/wordpress/mysql

➜  lab06 git:(master) ✗ kubectl create -f 04-wordpress-pv.yaml 
persistentvolume/wordpress-mysql-pv-volume created
➜  lab06 git:(master) ✗ kubectl get pv
NAME                        CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                              STORAGECLASS   REASON   AGE
wordpress-mysql-pv-volume   2Gi        RWO            Retain           Bound    default/wordpress-mysql-pv-claim                           31s
➜  lab06 git:(master) ✗ kubectl get pvc
NAME                       STATUS   VOLUME                      CAPACITY   ACCESS MODES   STORAGECLASS   AGE
wordpress-mysql-pv-claim   Bound    wordpress-mysql-pv-volume   2Gi        RWO                           118s
复制代码

此时咱们以前定义的pvc也已经成功绑定了this

使Deployment使用该PVC

查看定义

➜  lab06 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"
 volumeMounts:
 - name: mysql-persistent-storage
 mountPath: /var/lib/mysql
 volumes:
 - name: mysql-persistent-storage
 persistentVolumeClaim:
 claimName: wordpress-mysql-pv-claim 
复制代码

执行更新并查看效果

➜  lab06 git:(master) ✗ kubectl apply -f 01-wordpress-mysql-deployment.yaml 
deployment.extensions/wordpress configured
➜  lab06 git:(master) ✗ kubectl get pod
NAME                         READY   STATUS    RESTARTS   AGE
wordpress-6cfd879fcd-9mlhb   2/2     Running   0          29s

➜  lab06 git:(master) ✗ ls -l /data/pv/wordpress/mysql/
total 188480
-rw-r----- 1 999 999       56 Jun 10 23:42 auto.cnf
-rw------- 1 999 999     1675 Jun 10 23:42 ca-key.pem
-rw-r--r-- 1 999 999     1107 Jun 10 23:42 ca.pem
...
drwxr-x--- 2 999 999    12288 Jun 10 23:42 sys
drwxr-x--- 2 999 999     4096 Jun 10 23:42 wordpress
复制代码

可见，Pod已经在/data/pv/wordpress/mysql/下产生数据了，接下来咱们来试一下配置数据后，删除Pod，使Deployment控制Pod重建，配置数据是否可以保存 经过下面命令删除Pod使其重建

➜  lab06 git:(master) ✗ kubectl get pod  
NAME                         READY   STATUS    RESTARTS   AGE
wordpress-6cfd879fcd-9mlhb   2/2     Running   0          7m34s
➜  lab06 git:(master) ✗ kubectl delete pod/wordpress-6cfd879fcd-9mlhb
pod "wordpress-6cfd879fcd-9mlhb" deleted
➜  lab06 git:(master) ✗ kubectl get pod                              
NAME                         READY   STATUS    RESTARTS   AGE
wordpress-6cfd879fcd-29qg9   2/2     Running   1          11s
复制代码

刷新网页，发布的测试文件还在，测试成功

新问题

查看官网说明：

意思是说，对于这个单实例的有状态Deployment不要对其进行扩容，同时当Deployment定义发生更新时也不能使用滚动更新，而应该先删除再建立，也就是strategy: type: Recreate 修改后的文件以下： 

➜  lab06 git:(master) ✗ cat 01-wordpress-mysql-deployment.yaml 
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  labels:
    app: wordpress
  name: wordpress
spec:
  strategy:
    type: Recreate
  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"
        volumeMounts:
        - name: mysql-persistent-storage
          mountPath: /var/lib/mysql
      volumes:
      - name: mysql-persistent-storage
        persistentVolumeClaim:
          claimName: wordpress-mysql-pv-claim
复制代码

清除数据

➜  lab06 git:(master) ✗ kubectl delete -f .
deployment.extensions "wordpress" deleted
service "wordpress-svc" deleted
persistentvolumeclaim "wordpress-mysql-pv-claim" deleted
persistentvolume "wordpress-mysql-pv-volume" deleted
复制代码
相关文章
相关标签/搜索
每日一句
    每一个你不满意的现在，都有一个你没有努力的曾经。
本站公众号
   欢迎关注本站公众号,获取更多信息
联系我们 最近搜索 最新文章 沪ICP备13005482号-10 MyBatis教程 SQL 教程 MySQL教程 Java 教程 Thymeleaf 教程 Hibernate教程 Spring教程 Redis教程