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: -
# 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
# 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=
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  ]; then
        touch /var/lock/subsys/mysql-proxy
    fi
}
stop() {
    echo -n $"Stopping $prog: "
    killproc -p $PROXY_PID -d  $prog
    RETVAL=$?
    echo
    if [ $RETVAL -eq  ]; 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=
        ;;
esac
exit $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-proxy
ADMIN_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) , , 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  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.,  Franklin St, Fifth Floor, Boston, MA
 -  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()
 
        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 = , #proxy.global.backends do
                        local states = {
                                "unknown",
                                "up",
                                "down"
                        }
                        local types = {
                                "unknown",
                                "rw",
                                "ro"
                        }
                        local b = proxy.global.backends[i]
 
                        rows[#rows + ] = {
                                i,
                                b.dst.name,          -- configured backend address
                                states[b.state + ], -- the C-id is pushed down starting at
                                types[b.type + ],   -- the C-id is pushed down starting at
                                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 + ] = { "SELECT * FROM help", "shows this help" }
                rows[#rows + ] = { "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

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. --port=
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. --port=
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is
Server version: 5.0.-agent-admin
Copyright (c) , , 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.
mysql> select * from backends;
+-------------+--------------------+---------+------+------+-------------------+
| backend_ndx | address            | state   | type | uuid | connected_clients |
+-------------+--------------------+---------+------+------+-------------------+
|            | 192.168.1.200: | up      | rw   | NULL |                  |
|            | 192.168.1.202: | up      | ro   | NULL |                  |
+-------------+--------------------+---------+------+------+-------------------+
 

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