MySQL读写分离是指让master处理写操作，让slave处理读操作，非常适用于读操作量比较大的场景，可减轻master的压力。
使用mysql-proxy实现mysql的读写分离，mysql-proxy实际上是作为后端mysql主从服务器的代理，它直接接受客户端的请求，对SQL语句进行分析，判断出是读操作还是写操作，然后分发至对应的mysql服务器上。

环境准备：

三台主机：
192.168.20.10 master
192.168.20.11 slave
192.168.20.12 proxy

第一：192.168.20.10、11两台mysql搭建主从复制架构。
第二、在proxy机器上安装配置mysql-proxy，实现master/slave架构读写分离。
1、下载mysql-proxy-0.8.5-linux-el6-x86-64bit.tar.gz
2、安装mysql-proxy
[root@proxy install]# tar zxvf mysql-proxy-0.8.5-linux-el6-x86-64bit.tar.gz
mysql-proxy-0.8.5-linux-el6-x86-64bit/
mysql-proxy-0.8.5-linux-el6-x86-64bit/bin/
......
[root@proxy install]# mv mysql-proxy-0.8.5-linux-el6-x86-64bit /usr/local/
[root@proxy local]# ln -s mysql-proxy-0.8.5-linux-el6-x86-64bit/ mysql-proxy
[root@proxy local]# useradd -r mysql-proxy
[root@proxy local]# id mysql-proxy
uid=493(mysql-proxy) gid=486(mysql-proxy) groups=486(mysql-proxy)

3、添加mysql-proxy自启动
[root@proxy local]# cd /etc/init.d/
[root@proxy init.d]# vi mysql-proxy

!/bin/bash

mysql-proxy This script starts and stops the mysql-proxy daemon

chkconfig: - 78 30

processname: mysql-proxy

description: mysql-proxy is a proxy daemon for mysql

Source function library.

. /etc/rc.d/init.d/functions
prog="/usr/local/mysql-proxy/bin/mysql-proxy"

Source networking configuration.

if [ -f /etc/sysconfig/network ]; then
. /etc/sysconfig/network
fi

Check that networking is up.

[ ${NETWORKING} = "no" ] && exit 0

Set default mysql-proxy configuration.

ADMIN_USER="admin"
ADMIN_PASSWD="admin"
ADMIN_LUA_SCRIPT="/usr/local/mysql-proxy/share/doc/mysql-proxy/admin.lua"
PROXY_OPTIONS="--daemon"
PROXY_PID=/var/run/mysql-proxy.pid
PROXY_USER="mysql-proxy"

Source mysql-proxy configuration.

if [ -f /etc/sysconfig/mysql-proxy ]; then
. /etc/sysconfig/mysql-proxy
fi
RETVAL=0
start() {
echo -n prog: "
daemon PROXY_OPTIONS --pid-file=PROXY_ADDRESS" --user=ADMIN_USER" --admin-lua-script="ADMIN_PASSWORD"
RETVAL=RETVAL -eq 0 ]; then
touch /var/lock/subsys/mysql-proxy
fi
}
stop() {
echo -n prog: "
killproc -p prog
RETVAL=RETVAL -eq 0 ]; then
rm -f /var/lock/subsys/mysql-proxy
rm -f $PROXY_PID
fi
}

See how we were called.

case "PROXY_PIDFILE PROXY_PID 0 {start|stop|restart|reload|status|condrestart|try-restart}"
RETVAL=1
;;
esac
exit $RETVAL

[root@proxy init.d]# chmod +x /etc/init.d/mysql-proxy
[root@proxy init.d]# chkconfig --add mysql-proxy
[root@proxy init.d]# vim /etc/sysconfig/mysql-proxy

Options for mysql-proxy

ADMIN_USER="admin"
ADMIN_PASSWORD="admin"
ADMIN_ADDRESS=""
ADMIN_LUA_SCRIPT="/usr/local/mysql-proxy/share/doc/mysql-proxy/admin.lua"
PROXY_ADDRESS=""
PROXY_USER="mysql-proxy"
PROXY_OPTIONS="--daemon --log-level=info --log-use-syslog --plugins=proxy --plugins=admin --proxy-backend-addresses=192.168.20.10:3306 --proxy-read-only-backend-addresses=192.168.20.11:3306 --proxy-lua-script=/usr/local/mysql-proxy/share/doc/mysql-proxy/rw-splitting.lua"

[root@proxy init.d]# vim /usr/local/mysql-proxy/share/doc/mysql-proxy/admin.lua
function set_error(errmsg)
proxy.response = {
type = proxy.MYSQLD_PACKET_ERR,
errmsg = errmsg or "error"
}
end
function read_query(packet)
if packet:byte() ~= proxy.COM_QUERY then
set_error("[admin] we only handle text-based queries (COM_QUERY)")
return proxy.PROXY_SEND_RESULT
end
local query = packet:sub(2)
local rows = { }
local fields = { }
if query:lower() == "select * from backends" then
fields = {
{ name = "backend_ndx",
type = proxy.MYSQL_TYPE_LONG },
{ name = "address",
type = proxy.MYSQL_TYPE_STRING },
{ name = "state",
type = proxy.MYSQL_TYPE_STRING },
{ name = "type",
type = proxy.MYSQL_TYPE_STRING },
{ name = "uuid",
type = proxy.MYSQL_TYPE_STRING },
{ name = "connected_clients",
type = proxy.MYSQL_TYPE_LONG },
}

for i = 1, #proxy.global.backends do
local states = {
"unknown",
"up",
"down"
}
local types = {
"unknown",
"rw",
"ro"
}
local b = proxy.global.backends[i]

rows[#rows + 1] = {
i,
b.dst.name, -- configured backend address
states[b.state + 1], -- the C-id is pushed down starting at 0
types[b.type + 1], -- the C-id is pushed down starting at 0
b.uuid, -- the MySQL Server's UUID if it is managed
b.connected_clients -- currently connected clients
}
end
elseif query:lower() == "select * from help" then
fields = {
{ name = "command",
type = proxy.MYSQL_TYPE_STRING },
{ name = "description",
type = proxy.MYSQL_TYPE_STRING },
}
rows[#rows + 1] = { "SELECT * FROM help", "shows this help" }
rows[#rows + 1] = { "SELECT * FROM backends", "lists the backends and their state" }
else
set_error("use 'SELECT * FROM help' to see the supported commands")
return proxy.PROXY_SEND_RESULT
end

proxy.response = {
type = proxy.MYSQLD_PACKET_OK,
resultset = {
fields = fields,
rows = rows
}
}
return proxy.PROXY_SEND_RESULT
end

4、启动proxy服务：
[root@proxy bin]# service mysql-proxy start
Starting /usr/local/mysql-proxy/bin/mysql-proxy: [ OK ]

[root@proxy bin]# ss -nalp|grep mysql
LISTEN 0 128 *:4041 : users:(("mysql-proxy",28520,11))
LISTEN 0 128 *:3306 : users:(("mysql-proxy",28520,10))

[root@proxy bin]# mysql -uadmin -padmin -h192.168.20.12 --port=4041
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 1
Server version: 5.0.99-agent-admin
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
mysql> SELECT * FROM backends;
+-------------+-----------------+---------+------+------+-------------------+
| backend_ndx | address | state | type | uuid | connected_clients |
+-------------+-----------------+---------+------+------+-------------------+
| 1 | 192.168.20.10:3306 | unknown | rw | NULL | 0 |
| 2 | 192.168.20.11:3306 | unknown | ro | NULL | 0 |
+-------------+-----------------+---------+------+------+-------------------+
2 rows in set (0.00 sec)
配置完成。

第三、测试
[root@master ~]# su – mysql
-bash-4.1$ mysql -uroot -p12345
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 22
Server version: 5.6.37-log MySQL Community Server (GPL)
Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
mysql>
mysql>
mysql> GRANT ALL ON . TO 'alex'@'192.168.20.%' IDENTIFIED BY '123456';
Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)

mysql>

主从机器上：
tcpdump -i eth0 -nn -XX ip dst 192.168.20.10 and tcp dst port 3306
tcpdump -i eth0 -nn -XX ip dst 192.168.20.11 and tcp dst port 3306
进行抓包观察。

PROXY机器上操作：
[root@proxy bin]# mysql -ualex -p123456 -h192.168.20.12 --port=3306 （这个地方连接3306）
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 26
Server version: 5.6.37-log MySQL Community Server (GPL)
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql>create database alex;
mysql>use mysql;
mysql>select * from user G

[root@proxy ~]# mysql -uadmin -padmin -h192.168.20.12 --port=4041
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 1
Server version: 5.0.99-agent-admin

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> SELECT * FROM backends;
+-------------+-----------------+-------+------+------+-------------------+
| backend_ndx | address | state | type | uuid | connected_clients |
+-------------+-----------------+-------+------+------+-------------------+
| 1 | 192.168.20.10:3306 | up | rw | NULL | 0 |
| 2 | 192.168.20.11:3306 | up | ro | NULL | 0 |
+-------------+-----------------+-------+------+------+-------------------+
2 rows in set (0.00 sec)

成功实现读写分离。

作者：crpp0902
来源：CSDN
原文：https://blog.csdn.net/crpp0902/article/details/76085155
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