MySQL Proxy是一个处于你的client端和MySQL server端之间的简单程序，它可以监测、分析或改变它们的通信。它使用灵活，没有限制，常见的用途包括：负载平衡，故障、查询分析，查询过滤和修改等等。
MySQL Proxy就是这么一个中间层代理，简单的说，MySQL Proxy就是一个连接池，负责将前台应用的连接请求转发给后台的数据库，并且通过使用lua脚本，可以实现复杂的连接控制和过滤，从而实现读写分离和负载平衡。对于应用来说，MySQL Proxy是完全透明的，应用则只需要连接到MySQL Proxy的监听端口即可。当然，这样proxy机器可能成为单点失效，但完全可以使用多个proxy机器做为冗余，在应用服务器的连接池配置中配置到多个proxy的连接参数即可。
MySQL Proxy更强大的一项功能是实现“读写分离”，基本原理是让主数据库处理事务性查询，让从库处理SELECT查询。数据库复制被用来把事务性查询导致的变更同步到集群中的从库。
MySQL Proxy本身不支持读写分离，而是依赖Lua脚本进行扩展实现读写分离，它可以识别前端用户的sql语言并将写操作转发给主服务器，读操作转发给主服务器和从服务器或者只转发给从服务器
1、源码安装时，MySQL proxy的依赖关系：
libevent 1.x 或以上版本
lua 5.1.x或以上版本
glib2 2.6.0 或以上版本
pkg-config.
libtool 1.5或以上版本
MySQL 5.0.x 或以上版本
2、安装MySQL Proxy
# tar zxf mysql-proxy-0.8.2.tar.gz
# cd mysql-proxy-0.8.2
# ./configure
# make
# make check
如果管理员有密码，上面的步骤则需要使用如下格式进行：
# MYSQL_PASSWORD=root_pwd make check
# make install
默认情况下， mysql-proxy安装在/usr/local/sbin/mysql-proxy，而Lua示例脚本安装在/usr/local/share目录中。
3、配置指令
mysql proxy的各配置参数请参见官方文档，http://dev.mysql.com/doc/refman/5.6/en/mysql-proxy-configuration.html
使用rpm包在rhel6上安装mysql-proxy-0.8.2，其会提供配置文件及服务脚本，但没有提供读写分离的脚本。
/etc/sysconfig/mysql-proxy文件用于定义mysql-proxy的启动参数。
ADMIN_USER – the user for the proxy's admin interface. You can leave the default admin user.
ADMIN_PASSWORD – the password for the admin user in clear text. Change the default password for better security.
ADMIN_LUA_SCRIPT – the admin script in the Lua programming language. Without this script the admin interface cannot work. You can leave the default value.
PROXY_USER – the system user under which the proxy will work. By default it is mysql-proxy, and it's safe to leave it as is.
PROXY_OPTIONS – proxy options such as logging level, plugins, and Lua scripts to be loaded.
其中PROXY_OPTIONS是最常用的一个选项，用于定义mysql-proxy工作时的重要参数，例如：
PROXY_OPTIONS="--daemon --log-level=info --log-use-syslog --plugins=proxy --plugins=admin --proxy-backend-addresses=192.168.1.102:3306 --proxy-read-only-backend-addresses=192.168.1.105:3306 --proxy-lua-script=/usr/lib/mysql-proxy/lua/proxy/rw-splitting.lua"
四、安装配置mysql-proxy:
4.1 下载所需要的版本，这里的系统平台为rhel6.4 32位系统，因此就以mysql-proxy-0.8.3-linux-glibc2.3-x86-32bit.tar.gz为例。
# tar xf mysql-proxy-0.8.3-linux-glibc2.3-x86-32bit.tar.gz -C /usr/local
# cd /usr/local
# ln -sv mysql-proxy-0.8.3-linux-glibc2.3-x86-32bit mysql-proxy
添加代理用户
# useradd mysql-proxy
4.2 为mysql-proxy提供SysV服务脚本，内容如下所示
#vim /etc/rc.d/init.d/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 $"Starting $prog: "
daemon $prog $PROXY_OPTIONS --pid-file=$PROXY_PID --proxy-address="$PROXY_ADDRESS" --user=$PROXY_USER --admin-username="$ADMIN_USER" --admin-lua-script="$ADMIN_LUA_SCRIPT" --admin-password="$ADMIN_PASSWORD"
RETVAL=$?
echo
if [ $RETVAL -eq 0 ]; then
touch /var/lock/subsys/mysql-proxy
fi
}
stop() {
echo -n $"Stopping $prog: "
killproc -p $PROXY_PID -d 3 $prog
RETVAL=$?
echo
if [ $RETVAL -eq 0 ]; then
rm -f /var/lock/subsys/mysql-proxy
rm -f $PROXY_PID
fi
}
# See how we were called.
case "$1" in
start)
start
;;
stop)
stop
;;
restart)
stop
start
;;
condrestart|try-restart)
if status -p $PROXY_PIDFILE $prog >&/dev/null; then
stop
start
fi
;;
status)
status -p $PROXY_PID $prog
;;
*)
echo "Usage: $0 {start|stop|restart|reload|status|condrestart|try-restart}"
RETVAL=1
;;
esac
exit $RETVAL
将上述内容保存为/etc/rc.d/init.d/mysql-proxy，给予执行权限，而后加入到服务列表。
# chmod +x /etc/rc.d/init.d/mysql-proxy
# chkconfig --add mysql-proxy
4.3 为服务脚本提供配置文件（即启动时的参数配置文件）/etc/sysconfig/mysql-proxy，内容如下所示：
# 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"
其中最后一行，需要按实际场景进行修改，例如：
PROXY_OPTIONS="--daemon --log-level=info --log-use-syslog --plugins=proxy --plugins=admin --proxy-backend-addresses=172.16.100.6:3306 --proxy-read-only-backend-addresses=172.16.100.7:3306 --proxy-lua-script=/usr/local/mysql-proxy/share/doc/mysql-proxy/rw-splitting.lua"
其中的proxy-backend-addresses选项和proxy-read-only-backend-addresses选项均可重复使用多次，以实现指定多个读写服务器或只读服务器。
4.4 mysql-proxy的配置选项
mysql-proxy的配置选项大致可分为帮助选项、管理选项、代理选项及应用程序选项几类，下面一起去介绍它们。
--help
--help-admin
--help-proxy
--help-all ———— 以上四个选项均用于获取帮助信息；
--proxy-address=host:port ———— 代理服务监听的地址和端口；
--admin-address=host:port ———— 管理模块监听的地址和端口；
--proxy-backend-addresses=host:port ———— 后端mysql服务器的地址和端口；
--proxy-read-only-backend-addresses=host:port ———— 后端只读mysql服务器的地址和端口；
--proxy-lua-script=file_name ———— 完成mysql代理功能的Lua脚本；
--daemon ———— 以守护进程模式启动mysql-proxy；
--keepalive ———— 在mysql-proxy崩溃时尝试重启之；
--log-file=/path/to/log_file_name ———— 日志文件名称；
--log-level=level ———— 日志级别；
--log-use-syslog ———— 基于syslog记录日志；
--plugins=plugin,.. ———— 在mysql-proxy启动时加载的插件；
--user=user_name ———— 运行mysql-proxy进程的用户；
--defaults-file=/path/to/conf_file_name ———— 默认使用的配置文件路径；其配置段使用[mysql-proxy]标识；
--proxy-skip-profiling ———— 禁用profile；
--pid-file=/path/to/pid_file_name ———— 进程文件名；
5、复制如下内容建立admin.lua文件，将其保存至/usr/local/mysql-proxy/share/doc/mysql-proxy/目录中。
--[[ $%BEGINLICENSE%$
Copyright (c) 2007, 2012, Oracle and/or its affiliates. All rights reserved.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; version 2 of the
License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
02110-1301 USA
$%ENDLICENSE%$ --]]
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
6.1 管理功能测试
# mysql -uadmin -padmin -h172.16.100.107 --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
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql> SELECT * FROM backends;
+-------------+-------------------+-------+------+------+-------------------+
| backend_ndx | address | state | type | uuid | connected_clients |
+-------------+-------------------+-------+------+------+-------------------+
| 1 | 172.16.100.6:3306 | up | rw | NULL | 0 |
| 2 | 172.16.100.7:3306 | up | ro | NULL | 0 |
+-------------+-------------------+-------+------+------+-------------------+
2 rows in set (0.00 sec)
6.2 读写分离测试
# mysql -uroot -pmagedu.com -h172.16.100.107 --port=4040