一、背景：

一开始的初衷是，想写一个脚本来监控服务器的高占用率进程并通过邮件发送给我，然后突发奇想，可以使用这种方式来备份我的数据库，开始动手！

二、设计思路：

通过编写Shell脚本，调用Linux的mail工具，MySQLDump的方式来保存数据库的sql文件，通过Mail工具添加到附件，最后发送到我的邮箱。

三、编写启动脚本

首先我们来编写一个启动脚本 为了方便以后的个性化配置，我们将脚本中的变量都提取到一个application.yml文件中，文件如下：

RUNTIME: 084900 
HOST: 172.16.1.2
USER: root
PORT: 3306
PASSWORD: 123456
DATABASE: dean
TARGETMAIL: deanmr@qq.com

接下来我们来写一下shell脚本，逻辑也很简单，当前时间与启动时间相同时，则调用sendmail函数发送邮件

#!/bin/bash

RUNTIME=$(cat ./application.yml | grep RUNTIME| awk '{print $2}')
HOST=$(cat ./application.yml | grep HOST| awk '{print $2}')
USER=$(cat ./application.yml | grep USER| awk '{print $2}')
PORT=$(cat ./application.yml | grep PORT| awk '{print $2}')
PASSWORD=$(cat ./application.yml | grep PASSWORD| awk '{print $2}')
DATABASE=$(cat ./application.yml | grep DATABASE| awk '{print $2}')
TARGETMAIL=$(cat ./application.yml | grep TARGETMAIL| awk '{print $2}')

function  sendmail(){
  echo -e "mysqlbak_$CURRENT_TIME" |mail -s "mysqlbak_$CURRENT_TIME" -a $DATABASE.sql $TARGETMAIL
  sleep 1
}
while true
do 
  CURRENT_TIME=$(date +%H%M%S)
  if [ $CURRENT_TIME = $RUNTIME ];then
    echo "starting bak mysql database"
    sendmail
    continue
  else
    echo $CURRENT_TIME
    sleep 1
  fi
done

四、构建镜像

因为我们最后要放到k8s平台上的，所以我们要构建一个镜像，在构建镜像之前，请先把application.yml demo.sh Dockerfile放在同一目录下 Dockerfile如下：PS:添加了mysql的客户端，邮件mail客户端

FROM centos
RUN mkdir /app && yum install -y mysql.x86_64 sendmail  mailx libreport-plugin-mailx 
WORKDIR /app
COPY demo.sh .
COPY application.yml .
CMD ["/bin/sh","demo.sh"]

使用docker build命令构建镜像,要记得加一下最后的点

docker build -t mysqlmail-bak:1.0.1 .

五、添加边车容器

边车容器(sidecar)：边车容器就是与主容器一起在一个pod中运行的容器，为业务容器赋能，共享一个网络空间，所以可以用127.0.0.1:3306连接主容器的数据库。

5.1 创建配置文件

为了方便调试，我把里面的shell脚本也挂载出来。创建两个configmap，分别对应容器内的配置文件与shell脚本，后面如果不需要调试可以取消mysqlshell的挂载。

apiVersion: v1
kind: ConfigMap
metadata:
  name: mysqlmail-conf
  namespace: dean
data:
  application.yml: | 
    RUNTIME: 105800
    HOST: 127.0.0.1
    USER: root
    PASSWORD: 123456
    DATABASE: dean
    TARGETMAIL: deanmr@qq.com
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: mysqlmail-shell
  namespace: dean
data:
  demo.sh: |
    #!/bin/bash
    RUNTIME=$(cat ./application.yml | grep RUNTIME| awk '{print $2}')
    HOST=$(cat ./application.yml | grep HOST| awk '{print $2}')
    USER=$(cat ./application.yml | grep USER| awk '{print $2}')
    PASSWORD=$(cat ./application.yml | grep PASSWORD| awk '{print $2}')
    DATABASE=$(cat ./application.yml | grep DATABASE| awk '{print $2}')
    TARGETMAIL=$(cat ./application.yml | grep TARGETMAIL| awk '{print $2}')    
    function  sendmail(){
      mysqldump -h$HOST  -u$USER -p$PASSWORD  --complete-insert --skip-add-drop-table  --column-statistics=0 --hex-blob $DATABASE  > $DATABASE.sql
      echo -e "mysqlbak_$CURRENT_TIME" |mail -s "mysqlbak_$CURRENT_TIME" -a $DATABASE.sql $TARGETMAIL
      sleep 1
    }
    while true
    do 
      CURRENT_TIME=$(date +%H%M%S)
      if [ $CURRENT_TIME = $RUNTIME ];then
        echo "starting bak mysql database"
        sendmail
        continue
      else
        echo $CURRENT_TIME
        sleep 1
      fi
    done

5.2 创建有状态服务部署文件

我们的deploy文件使用的是上篇文章中创建的mysql有状态服务的yaml

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: mysql
  namespace: dean
spec:
  serviceName: mysql-service
  selector:
    matchLabels:
      app: mysql
  replicas: 1
  template:
    metadata:
      labels:
        app: mysql
    spec:
      containers:
      - name: mysqlmail-bak
        imagePullPolicy: IfNotPresent
        image: mysqlmail-bak:1.0.1
        volumeMounts:
        - name: mysqlmail-conf
          mountPath: /app/application.yml
          subPath: application.yml
        - name: mysqlmail-shell
          mountPath: /app/demo.sh
          subPath: demo.sh
      - name: mysql-pod
        imagePullPolicy: IfNotPresent
        image: mysql:5.7
        env:
        - name: MYSQL_ROOT_PASSWORD
          value: "123456"
        ports:
        - containerPort: 3306
          name: msyql-listin
        volumeMounts:
        - name: mysql-data  
          mountPath: /var/lib/mysql
          subPath: mysql-data
        - name: mysql-conf
          mountPath: /etc/mysql/conf.d/my.cnf
          subPath: my.cnf
      volumes:
      - name: mysql-data
        hostPath:
          path: /data/mysql
      - name: mysql-conf
        configMap:
          name: mysql-conf
      - name: mysqlmail-conf
        configMap: 
          name: mysqlmail-conf
      - name: mysqlmail-shell
        configMap:
          name: mysqlmail-shell
---

apiVersion: v1
kind: Service
metadata:
  name: mysql-service
  namespace: dean
  labels:
    app: mysql
spec:
  ports:
  - targetPort: 3306
    port: 3306
  clusterIP: None
  selector:
     app: mysql

六、测试

我们上面给他定的时间是RUNTIME: 105800，上海时区也就是18点58分，我们来看一下效果 查看日志， 注意：当一个pod包含多个容器时，要使用 -c 参数指定查看哪个容器

[root@VM-24-15-centos solo]# kubectl logs -n solo mysql-0  -c mysqlmail-bak | grep mysql -C 5
105755
105756
105757
105758
105759
starting bak mysql database
mysqldump: [Warning] Using a password on the command line interface can be insecure.
105801
105802

从日志可以看到，邮件已经发送成功了！我们来去邮箱看一下，发现也已经成功了，至此我们的实验完美完成！