MaxScale是maridb开发的一个mysql数据中间件，其配置简单，能够实现读写分离，并且可以根据主从状态实现写库的自动切换，本篇文章重点为大家讲解一下Linux下使用MaxScale实现数据库读写分离。
操作系统:CentOS Linux release 7.3.1611 (Core)
数据库:MariaDB-10.2.6-linux-glibc_214-x86_64
MaxScale服务器:10.200.10.55
主服务器:172.16.8.56
从服务器:172.16.8.57
从服务器:172.16.8.58
1.maxscale的安装方式有很多，例如源码安装、rpm、二进制构建等，我选择二进制进行安装。
根据场景需要下载相对应的版本，下载地址；https://mariadb.com/downloads/maxscale
[root@localhost ~]# groupadd maxscale
[root@localhost ~]# useradd -g maxscale maxscale
[root@localhost ~]# cd /usr/local
[root@localhost local]# wget https://downloads.mariadb.com/MaxScale/2.1.3/centos/7server/x86_64/maxscale-2.1.3.centos.7.tar.gz
[root@localhost local]# tar zxvf maxscale-2.1.3.centos.7.tar.gz
[root@localhost local]# ln -s maxscale-2.1.3.centos.7 maxscale
[root@localhost local]# cd maxscale
[root@zhu56 maxscale]# chown -R maxscale var建议创建软连接，这样有助于以后的版本升级及后期维护。
2.首次安装maxscale需要创建日志相关目录
[root@localhost ~]# mkdir /var/log/maxscale
[root@localhost ~]# mkdir /var/lib/maxscale
[root@localhost ~]# mkdir /var/run/maxscale
[root@localhost ~]# mkdir /var/cache/maxscale3.以下目录必须具备maxscala用户权限
[root@localhost ~]# chown maxscale /var/log/maxscale
[root@localhost ~]# chown maxscale /var/lib/maxscale
[root@localhost ~]# chown maxscale /var/run/maxscale
[root@localhost ~]# chown maxscale /var/cache/maxscale4.为了能让Maxscale能顺利启动，还需要创建配置文件，在Maxscale目录下有配置文件模板拷贝到etc下即可。
[root@localhost ~]# cp /usr/local/maxscale/etc/maxscale.cnf.template /etc/maxscale.cnf5.在修改配置文件之前，需要在主服务器上创建一个用户并给予授权，而这个用户用于MySQL监控、路由功能
MariaDB [(none)]> create user 'jiankongdb'@'%' identified by 'jiankong123';
MariaDB [(none)]> grant SELECT on mysql.user to 'jiankongdb'@'%';
MariaDB [(none)]> GRANT SELECT ON mysql.db TO 'jiankongdb'@'%';
MariaDB [(none)]> GRANT SELECT ON mysql.tables_priv TO 'jiankongdb'@'%';
MariaDB [(none)]> GRANT SHOW DATABASES ON *.* TO 'jiankongdb'@'%';
MariaDB [(none)]> grant REPLICATION CLIENT on *.* to 'jiankongdb'@'%';
MariaDB [(none)]> GRANT replication slave, replication client,SELECT ON *.* TO jiankongdb@'%';
6.查看授权情况
MariaDB [(none)]> SHOW GRANTS FOR'jiankong'@'%';
7.接下来就开始修改maxscale.cnf配置文件，否则无法启动。
[root@localhost ~]# vim /etc/maxscale.cnf
# MaxScale documentation on GitHub:
# https://github.com/mariadb-corporation/MaxScale/blob/2.1/Documentation/Documentation-Contents.md
# Global parameters
#
# Complete list of configuration options:
# https://github.com/mariadb-corporation/MaxScale/blob/2.1/Documentation/Getting-Started/Configuration-Guide.md
#全局配置
[maxscale]
threads=1
# Server definitions
#
# Set the address of the server to the network
# address of a MySQL server.
#
[server1]
type=server
address=172.16.8.56
port=3306
protocol=MySQLBackend
serv_weight=1
[server2]
type=server
address=172.16.8.57
port=3306
protocol=MySQLBackend
serv_weight=3
[server3]
type=server
address=172.16.8.58
port=3306
protocol=MySQLBackend
serv_weight=3
# Monitor for the servers
#
# This will keep MaxScale aware of the state of the servers.
# MySQL Monitor documentation:
# https://github.com/mariadb-corporation/MaxScale/blob/2.1/Documentation/Monitors/MySQL-Monitor.md
#MariaDB状态监控
[MySQL Monitor]
type=monitor
module=mysqlmon
servers=server1,server2,server3
user=jiankong
passwd=jiankong123
monitor_interval=10000
detect_stale_master=true #即使从全挂掉,保证主担任读写
# Service definitions
#
# Service Definition for a read-only service and
# a read/write splitting service.
#
# ReadConnRoute documentation:
# https://github.com/mariadb-corporation/MaxScale/blob/2.1/Documentation/Routers/ReadConnRoute.md
#读
[Read-Only Service]
type=service
router=readconnroute
servers=server1,server2,server3
user=jiankong
passwd=jiankong123
router_options=slave
enable_root_user=1 #允许root用户登录执行
weightby=serv_weight #主从权重
# ReadWriteSplit documentation:
# https://github.com/mariadb-corporation/MaxScale/blob/2.1/Documentation/Routers/ReadWriteSplit.md
#写
[Read-Write Service]
type=service
router=readwritesplit
servers=server1,server2,server3
user=jiankong
passwd=jiankong123
max_slave_connections=100%
use_sql_variables_in=master #保证会话的一致性
enable_root_user=1 #允许root登录
max_slave_replication_lag=3600 #允许从超出主的同步时间,超出则不路由
# This service enables the use of the MaxAdmin interface
# MaxScale administration guide:
# https://github.com/mariadb-corporation/MaxScale/blob/2.1/Documentation/Reference/MaxAdmin.md
[MaxAdmin Service]
type=service
router=cli
# Listener definitions for the services
#
# These listeners represent the ports the
# services will listen on.
#
[Read-Only Listener]
type=listener
service=Read-Only Service
protocol=MySQLClient
port=4008
[Read-Write Listener]
type=listener
service=Read-Write Service
protocol=MySQLClient
port=4006
[MaxAdmin Listener]
type=listener
service=MaxAdmin Service
protocol=maxscaled
socket=default
保存并退出。 8.下面创建启动脚本
[root@localhost ~]# cp /usr/local/maxscale-2.1.3.centos.7/share/maxscale.service /usr/lib/systemd/system/
[root@localhost ~]# vim /usr/lib/systemd/system/maxscale.service9.修改maxscale.service中的ExecStart=///bin/maxscale为ExecStart=/usr/local/maxscale/bin/maxscale
[root@localhost ~]# chmod 755 /usr/lib/systemd/system/maxscale.service
[root@localhost ~]# systemctl enable maxscale
[root@localhost ~]# systemctl daemon-reload
[root@localhost ~]# systemctl start maxscale10.添加变量值
[root@localhost ~]# vi /etc/profile //最后一行添加以下内容保存退出！
PATH=$PATH:/usr/local/maxscale/bin
export PATH
[root@localhost ~]# source /etc/profile //使其变量立即生效11.接下来就可以使用MaxAdmin进行管理。MaxAdmin是一个简单的客户端管理界面，可用于与MariaDB MaxScale服务器进行交互，可以显示MariaDB MaxScale内部的统计信息状态以及对MariaDB MaxScale操作的控制。详情： https://mariadb.com/kb/en/mariadb-enterprise/maxadmin-admin-interface/
[root@localhost ~]# maxadmin //回车
MaxScale> list servers
Servers.
---------------+--------------+-------+-------------+-----------------
Server | Address | Port | Connections | Status
---------------+--------------+-------+-------------+-----------------
server1 | 172.16.8.56 | 3306 | 0 | Master, Running
server2 | 172.16.8.57 | 3306 | 0 | Slave, Running
server2 | 172.16.8.58 | 3306 | 0 | Slave, Running
---------------+--------------+-------+-------------+-----------------
12.至此MaxScale已经配置完成。现在就可以使用客户端连接Maxscale服务器端 端口为4006。
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