MySQL Proxy 实现MySQLDB 读写分离

一、简述

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。

二、对MariaDB做主从复制

关于如何对MariaDB做主从复制，请移步本人博客MariaDB 主从复制 

三、安装

   1.可以通过rpm安装，其会提供配置文件及服务脚本，但是没有读写分享脚本

 2.通过编译安装

①、源码安装时，MySQL proxy的依赖关系：    

           libevent 1.x or higher (1.3b or later is preferred).

           lua 5.1.x or higher.

           glib2 2.6.0 or higher.

           pkg-config.

           libtool 1.5 or higher.

           MySQL 5.0.x or higher developer files.

       ②、下载源码包，编译安装

# 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.通过通用二进制格式安装

①、下载解压。这里的系统平台为rhel6.5 64位系统

[root@httpweb ~]# wget http://mirror.sohu.com/mysql/MySQL-Proxy/mysql-proxy-0.8.4-linux-el6-x86-64bit.tar.gz[root@httpweb ~]# tar xf mysql-proxy-0.8.4-linux-el6-x86-64bit.tar.gz[root@httpweb ~]# mv mysql-proxy-0.8.4-linux-el6-x86-64bit /usr/local/mysql-proxy

②、添加代理用户

[root@httpweb mysql-proxy]# useradd mysql-proxy

 ③、为mysql-proxy提供SysV服务脚本

#!/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/functionsprog="/usr/local/mysql-proxy/bin/mysql-proxy"# Source networking configuration.if [ -f /etc/sysconfig/network ]; then	. /etc/sysconfig/networkfi# 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.pidPROXY_USER="mysql-proxy"# Source mysql-proxy configuration.if [ -f /etc/sysconfig/mysql-proxy ]; then	. /etc/sysconfig/mysql-proxyfiRETVAL=0start() {	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		;;esacexit $RETVAL

将上述内容保存为/etc/init.d/mysql-proxy，给予执行权限，而后添加至服务列表

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

④、为服务脚本提供配置文件/etc/sysconfig/mysql-proxy

#Options for mysql-proxyADMIN_USER="firefox"ADMIN_PASSWORD="firefox"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=192.168.1.200:3306 --proxy-read-only-backend-addresses=192.168.1.202:3306 --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。

⑤、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； 

⑥、提供admin.lua文件，将其保存至/usr/local/mysql-proxy/share/mysql-proxy/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 02110-1301USA $%ENDLICENSE%$ --]]function set_error(errmsg)	proxy.response = {		type = proxy.MYSQLD_PACKET_ERR,		errmsg = errmsg or "error"	}endfunction 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_RESULTend

 ⑦、测试

启动服务；

service mysql-proxy start

管理功能测试      

可以看到4041端口和3306端口以及处于监听状态

我们在主服务器上授予201数据库写的权限

MariaDB [(none)]>grant all on *.* to 'firefox'@'192.168.1.201' identified by 'firefox';MariaDB [(none)]> flush privileges;[root@httpweb mysql-proxy]# mysql -ufirefox -pfirefox -h192.168.1.201 --port=3306我们可以看到我们在mysql-proxy的可以登录数据库了

查看是否配置成功   

[root@httpweb ~]# mysql -ufirefox -pfirefox -h192.168.1.201 --port=4041Welcome to the MySQL monitor.Commands end with ; or /g.Your MySQL connection id is 1Server version: 5.0.99-agent-adminCopyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.mysql> select * from backends;+-------------+--------------------+---------+------+------+-------------------+| backend_ndx | address| state | type | uuid | connected_clients |+-------------+--------------------+---------+------+------+-------------------+| 1 | 192.168.1.200:3306 | up| rw | NULL | 0 || 2 | 192.168.1.202:3306 | up| ro | NULL | 0 |+-------------+--------------------+---------+------+------+-------------------+

我们的程序就可以实现真正意义上的读写分离了，大功告成，由于本人水平有限，请各位大神多多批评指正