MariaDB九之基于mysql-porxy实现读写分离

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http://wangfeng7399.blog.51cto.com/3518031/1394509

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/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/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="wangfeng7399"
ADMIN_PASSWORD="wangfeng7399"
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
 02110-1301  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

       ⑦、测试

           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 'wangfeng7399'@'192.168.1.201' identified by 'wangfeng7399';
MariaDB [(none)]> flush privileges;

[root@httpweb mysql-proxy]# mysql -uwangfeng7399 -pwangfeng7399 -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 -uwangfeng7399 -pwangfeng7399 -h192.168.1.201 --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.
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