通过 主从复制(Master-Slave)的方式来同步数据，再通过读写分离(MySQL-Proxy)来提升数据库的并发负载能力 。本文介绍mysql-proxy读写分离的实践。
原文地址：代码汇个人博客 http://www.codehui.net/info/65.html

我们先配置好mysql的主从复制，可以查看《mysql主从复制 简单实践》

mysql读写分离

测试的三台服务器都是centos7.6

mysql-proxy：192.168.73.128
主服务器： 192.168.73.130
从服务器： 192.168.73.131

mysql-proxy配置

只需要配置mysql-proxy服务器就可以了

1、下载 mysql-proxy

根据自己系统配置选择适合的版本，下载地址：https://downloads.mysql.com/archives/proxy/

wget https://cdn.mysql.com/archives/mysql-proxy/mysql-proxy-0.8.5-linux-glibc2.3-x86-64bit.tar.gz

2、配置mysql-proxy，创建主配置文件

tar zxvf mysql-proxy-0.8.5-linux-glibc2.3-x86-64bit.tar.gz
mv mysql-proxy-0.8.5-linux-glibc2.3-x86-64bit /usr/local/mysql-proxy
cd /usr/local/mysql-proxy
mkdir lua
cp share/doc/mysql-proxy/rw-splitting.lua ./lua #复制读写分离配置文件
cp share/doc/mysql-proxy/admin-sql.lua ./lua #复制管理脚本
vi /etc/mysql-proxy.cnf   #创建配置文件

# 注意这在写的时候把注释取了 不然会报错的
[mysql-proxy]
user=root #运行mysql-proxy用户
admin-username=root #主从mysql共有的用户
admin-password=123456 #用户的密码
proxy-address=192.168.73.128 #mysql-proxy运行ip和端口，不加端口，默认4040
proxy-read-only-backend-addresses=192.168.73.131 #指定后端从slave读取数据
proxy-backend-addresses=192.168.73.130 #指定后端主master写入数据
proxy-lua-script=/usr/local/mysql-proxy/lua/rw-splitting.lua #指定读写分离配置文件位置
admin-lua-script=/usr/local/mysql-proxy/lua/admin-sql.lua #指定管理脚本
log-file=/usr/local/mysql-proxy/logs/mysql-proxy.log #日志位置
log-level=info #定义log日志级别，由高到低分别有(error|warning|info|message|debug)
daemon=true    #以守护进程方式运行
keepalive=true #mysql-proxy崩溃时，尝试重启

保存退出！
chmod 660 /etc/mysql-porxy.cnf

3、修改读写分离配置文件

vi /usr/local/mysql-proxy/lua/rw-splitting.lua

if not proxy.global.config.rwsplit then
        proxy.global.config.rwsplit = {
                min_idle_connections = 1, #默认超过4个连接数时，才开始读写分离，改为1
                max_idle_connections = 1, #默认8，改为1

                is_debug = false
        }
end

4、启动mysql-proxy

/usr/local/mysql-proxy/bin/mysql-proxy --defaults-file=/etc/mysql-proxy.cnf

看下面报错了

[root@localhost www]# /usr/local/mysql-proxy/bin/mysql-proxy --defaults-file=/etc/mysql-proxy.cnf
2019-02-20 14:51:30: (critical) Key file contains key 'daemon' which has value that cannot be interpreted.
2019-02-20 14:51:30: (message) Initiating shutdown, requested from mysql-proxy-cli.c:367
2019-02-20 14:51:30: (message) shutting down normally, exit code is: 1

在mysql论坛找到了解决办法，/etc/mysql-proxy.cnf可能有非ASCII字符,删掉所有注释,启动成功了。:tw-1f602:

[mysql-proxy]
user=root
admin-username=root
admin-password=123456
proxy-address=192.168.73.128
proxy-read-only-backend-addresses=192.168.73.131
proxy-backend-addresses=192.168.73.130
proxy-lua-script=/usr/local/mysql-proxy/lua/rw-splitting.lua
admin-lua-script=/usr/local/mysql-proxy/lua/admin-sql.lua
log-file=/usr/local/mysql-proxy/logs/mysql-proxy.log
log-level=info
daemon=true
keepalive=true

查看启动情况，关闭可以使用killall -9 mysql-proxy

[root@localhost www]# netstat -tupln | grep 4000
tcp        0      0 192.168.73.128:4000     0.0.0.0:*               LISTEN      8061/mysql-proxy

5、测试读写分离

使用客户端连接mysql-proxy

mysql -u root -h 192.168.73.128 -P 4000 -p123456

我们在mysql-proxy中插入了两条数据，并且可以查看数据。

mysql> use codehui;
Database changed

mysql> create table proxy (id INT(11),name VARCHAR(255));
Query OK, 0 rows affected (0.06 sec)

mysql> insert into proxy values(001,'beijing');
Query OK, 1 row affected (0.02 sec)

mysql> insert into proxy values(002,'shanghai');
Query OK, 1 row affected (0.00 sec)

mysql> select * from proxy;
+------+----------+
| id   | name     |
+------+----------+
|    1 | beijing  |
|    2 | shanghai |
+------+----------+
2 rows in set (0.00 sec)

要怎么知道启用了读写分离呢？我们进入从服务器192.168.73.131，修改id为2的数据name值为xian。

mysql -u root -h 192.168.73.131 -p123456

mysql> use codehui;
Database changed

mysql> update proxy set name='xian' where id=2;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from proxy;
+------+---------+
| id   | name    |
+------+---------+
|    1 | beijing |
|    2 | xian    |
+------+---------+
2 rows in set (0.00 sec)

然后登陆mysql-proxy，查看到的数据是从服务器192.168.73.131的，说明读写分离成功。

mysql -u root -h 192.168.73.128 -P 4000 -p123456

mysql> use codehui;
Database changed

mysql> select * from proxy;
+------+---------+
| id   | name    |
+------+---------+
|    1 | beijing |
|    2 | xian    |
+------+---------+
2 rows in set (0.00 sec)