使用Mycat实现MySQL数据库的读写分离

摘要: Mycat可以让程序员只需要关心业务代码的编写，而不用担心数据库集群的读写分离，分库分表的数据分片逻辑的编写，只要直接连接Mycat就好

前提准备

1.一台CentOS机器

2.Mycat安装包 （http://www.mycat.io/）

安装使用

1.解压Mycat的安装包到/user/local/下



2.设置mycat的环境变量

vi /etc/profile



3.使配置文件立即生效

source /etc/profile

4.修改Mycat的配置文件

cd /usr/local/mycat/conf

vi schema.xml

<?xml version="1.0"?>
<!DOCTYPE mycat:schema SYSTEM "schema.dtd">
<mycat:schema xmlns:mycat="http://io.mycat/">

<!-- 定义MyCat的逻辑库 -->
<schema name="pcx_schema" checkSQLschema="false" sqlMaxLimit="100" dataNode="pcxNode"></schema>

<!-- 定义MyCat的数据节点 -->
<dataNode name="pcxNode" dataHost="dtHost" database="fs_shop" />

<!-- 定义数据主机dtHost，连接到MySQL读写分离集群 ,schema中的每一个dataHost中的host属性值必须唯一-->
<!-- dataHost实际上配置就是后台的数据库集群，一个datahost代表一个数据库集群 -->
<!-- balance="1"，全部的readHost与stand by writeHost参与select语句的负载均衡-->
<!-- writeType="0"，所有写操作发送到配置的第一个writeHost，这里就是我们的hostmaster，第一个挂了切到还生存的第二个writeHost-->
<dataHost name="dtHost" maxCon="500" minCon="20" balance="3"
dbType="mysql" dbDriver="native" switchType="1" slaveThreshold="100">
<!--心跳检测 -->
<heartbeat>show slave status</heartbeat>

<!--配置后台数据库的IP地址和端口号，还有账号密码 -->
<!--
<writeHost host="hostMaster" url="192.168.2.151:3306" user="root" password="123456" />
<readHost host="hostSlave" url="192.168.2.100:3306" user="root" password="123456" />
-->
<writeHost host="hostM1" url="192.168.2.151:3306" user="root" password="123456">		         <!-- can have multi read hosts -->
<readHost host="hostS2" url="192.168.2.152:3306" user="root" password="123456" />
</writeHost>
</dataHost>
</mycat:schema>

5.修改Mycat用户权限和系统变量

<?xml version="1.0" encoding="UTF-8"?>
<!-- - - Licensed under the Apache License, Version 2.0 (the "License");
- you may not use this file except in compliance with the License. - You
may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - - Unless required by applicable law or agreed to in writing, software -
distributed under the License is distributed on an "AS IS" BASIS, - WITHOUT
WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. - See the
License for the specific language governing permissions and - limitations
under the License. -->
<!DOCTYPE mycat:server SYSTEM "server.dtd">
<mycat:server xmlns:mycat="http://io.mycat/">
<system>
<property name="useSqlStat">0</property>  <!-- 1为开启实时统计、0为关闭 -->
<property name="useGlobleTableCheck">0</property>  <!-- 1为开启全加班一致性检测、0为关闭 -->

<property name="sequnceHandlerType">2</property>
<!--  <property name="useCompression">1</property>--> <!--1为开启mysql压缩协议-->
<!--  <property name="fakeMySQLVersion">5.6.20</property>--> <!--设置模拟的MySQL版本号-->
<!-- <property name="processorBufferChunk">40960</property> -->
<!--
<property name="processors">1</property>
<property name="processorExecutor">32</property>
-->
<!--默认为type 0: DirectByteBufferPool | type 1 ByteBufferArena-->
<property name="processorBufferPoolType">0</property>
<!--默认是65535 64K 用于sql解析时最大文本长度 -->
<!--<property name="maxStringLiteralLength">65535</property>-->
<!--<property name="sequnceHandlerType">0</property>-->
<!--<property name="backSocketNoDelay">1</property>-->
<!--<property name="frontSocketNoDelay">1</property>-->
<!--<property name="processorExecutor">16</property>-->
<!--
<property name="serverPort">8066</property> <property name="managerPort">9066</property>
<property name="idleTimeout">300000</property> <property name="bindIp">0.0.0.0</property>
<property name="frontWriteQueueSize">4096</property> <property name="processors">32</property> -->
<!--分布式事务开关，0为不过滤分布式事务，1为过滤分布式事务（如果分布式事务内只涉及全局表，则不过滤），2为不过滤分布式事务,但是记录分布式事务日志-->
<property name="handleDistributedTransactions">0</property>

<!--
off heap for merge/order/group/limit      1开启   0关闭
-->
<property name="useOffHeapForMerge">1</property>

<!--
单位为m
-->
<property name="memoryPageSize">1m</property>

<!--
单位为k
-->
<property name="spillsFileBufferSize">1k</property>

<property name="useStreamOutput">0</property>

<!--
单位为m
-->
<property name="systemReserveMemorySize">384m</property>

<!--是否采用zookeeper协调切换  -->
<property name="useZKSwitch">true</property>

</system>

<!-- 全局SQL防火墙设置 -->
<!--
<firewall>
<whitehost>
<host host="127.0.0.1" user="mycat"/>
<host host="127.0.0.2" user="mycat"/>
</whitehost>
<blacklist check="false">
</blacklist>
</firewall>
-->

<user name="root">
<property name="password">123456</property>
<property name="schemas">pcx_schema</property>

<!-- 表级 DML 权限设置 -->
<!--
<privileges check="false">
<schema name="TESTDB" dml="0110" >
<table name="tb01" dml="0000"></table>
<table name="tb02" dml="1111"></table>
</schema>
</privileges>
-->
</user>

<user name="user">
<property name="password">user</property>
<property name="schemas">pcx_schema</property>
<property name="readOnly">true</property>
</user>

</mycat:server>

6.启动

cd /usr/local/mycat/bin

./mycat start

ps：启动成功则有对应的端口（默认：8066），启动失败的可以到 logs 目录下进去日志的分析

7.修改项目的连接配置

我这里用的是spring boot：

spring.datasource.url = jdbc:mysql://192.168.2.151:8066/pcx_schema?useUnicode=true&characterEncoding=utf-8
spring.datasource.username = root
spring.datasource.password = 123456
spring.datasource.driverClassName = com.mysql.jdbc.Driver

8.检验是否正常使用

新增数据，



为了方便查看结果，所以两库之间没有做同步，可以看到，数据已经进写库，而页面和读库的数据一致