mycat实现mysql读写分离

1、mycat的下载地址 https://github.com/MyCATApache/Mycat-download
这里下载的版本是Mycat-server-1.4-release-20151019230038-win.tar.gz
解压即可

2、需要配置JDK的环境变量；然后修改conf文件夹下的wrapper.conf文件的：

# Java Application
wrapper.java.command=E:\Programs\Java\jdk1.8.0_31\bin
wrapper.working.dir=..

3、修改server.xml文件：

<mycat:server xmlns:mycat="http://org.opencloudb/">
    <system>
    <property name="defaultSqlParser">druidparserproperty>
       
    
    
        
        
        
        
        
        
        
    system>
    <user name="root">
        <property name="password">rootproperty>
        <property name="schemas">qsproperty>
    user>

    <user name="user">
        <property name="password">userproperty>
        <property name="schemas">qsproperty>
        <property name="readOnly">trueproperty>
    user>
    
    

mycat:server>

注：qs必须和schema.xml的schemas对应；此处的user root 和user 指的是mycat的用户名；可以通过>mysql -uroot -proot -hlocalhost -P8066 -Dqs 登录查询。

4、修改schema.xml文件：

<mycat:schema xmlns:mycat="http://org.opencloudb/">

    <schema name="qs" checkSQLschema="false" sqlMaxLimit="100" dataNode="dn1">
    schema>

    <dataNode name="dn1" dataHost="localhost1" database="db1" />


    <dataHost name="localhost1" maxCon="1000" minCon="10" balance="3" writeType="0" dbType="mysql" dbDriver="native" switchType="2" slaveThreshold="100">
        <heartbeat>select user()heartbeat>

        <writeHost host="hostM1" url="192.168.1.56:3306" user="root" password="root">

        <readHost host="hostS1" url="192.168.0.83:3306" user="root" password="root" />
        writeHost>

    dataHost>

mycat:schema>

没有涉及到分库配置比较简单；database=”db1” db1是两台mysql服务器中都存在的数据库(因为两个数据库已经配置好主从复制，所以数据一样的)。
注：192.168.1.56 和 192.168.0.83 在已经配置好mysql主从复制的情况下，然后通过mycat的读写分离来实现读取数据库只在192.168.0.83，写入数据库只在192.168.1.56。

balance 属性
负载均衡类型，目前的取值有 3 种：
1. balance=”0”, 不开启读写分离机制，所有读操作都发送到当前可用的 writeHost 上。
2. balance=”1”，全部的 readHost 与 stand by writeHost 参与 select 语句的负载均衡，简单的说，当双
主双从模式(M1->S1，M2->S2，并且 M1 与 M2 互为主备)，正常情况下，M2,S1,S2 都参与 select 语句的负载
均衡。
3. balance=”2”，所有读操作都随机的在 writeHost、readhost 上分发。
4. balance=”3”，所有读请求随机的分发到 wiriterHost 对应的 readhost 执行，writerHost 不负担读压
力，注意 balance=3 只在 1.4 及其以后版本有，1.3 没有。

writeType 属性
负载均衡类型，目前的取值有 3 种：
1. writeType=”0”, 所有操作发送到配置的第一个 writeHost，第一个挂了切到还生存的第二个
writeHost，重新启动后已切换后的为准，切换记录在配置文件中:dnindex.properties .
2. writeType=”1”，所有写操作都随机发送到配置的 writeHost，1.5 以后废弃不推荐。

switchType 属性
- 0 表示不自动切换
- 1 默讣值，自动切换
- 2 基于 MySQL 主从同步的状态决定是否切换

根据主从延时切换：
1.4 开始支持 MySQL 主从复制状态绑定的读写分离机制，让读更加安全可靠，配置如下：
MyCAT 心跳检查语句配置为 show slave status ，dataHost 上定义两个新属性： switchType=”2” 于
slaveThreshold=”100”，此时意味着开启 MySQL 主从复制状态绑定的读写分离于切换机制，Mycat 心跳机制
通过检测 show slave status 中的 “Seconds_Behind_Master”, “Slave_IO_Running”,
“Slave_SQL_Running” 三个字段来确定当前主从同步的状态以及 Seconds_Behind_Master 主从复制时延，
当 Seconds_Behind_Master>slaveThreshold 时，读写分离筛选器会过滤掉此 Slave 机器，防止读到很久之前
的旧数捤，而当主节点宕机后，切换逻辑会检查 Slave 上的 Seconds_Behind_Master 是否为 0，为 0 时则
表示主从同步，可以安全切换，否则不会切换。

read测试 mycat和192.168.0.83一致：

C:\Program Files\MySQL\MySQL Server 5.7\bin>mysql -uroot -proot -hlocalhost -P8066 -Dqs
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 12
Server version: 5.5.8-mycat-1.4-release-20151019230038 MyCat Server (OpenCloundDB)

Copyright (c) 2000, 2016, 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.

Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the current input statement.

mysql> select * from test1;
+—-+——+
| id | name |
+—-+——+
| 1 | 8383 |
+—-+——+
1 row in set (0.00 sec)

C:\Program Files\MySQL\MySQL Server 5.7\bin>mysql -uroot -proot -h192.168.0.83 -P3306 -Ddb1
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 411
Server version: 5.7.13-log MySQL Community Server (GPL)

Copyright (c) 2000, 2016, 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.

Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the current input statement.

mysql> select * from test1;
+—-+——+
| id | name |
+—-+——+
| 1 | 8383 |
+—-+——+
1 row in set (0.00 sec)

测试写入(已关闭mysql主从复制功能)：
C:\Program Files\MySQL\MySQL Server 5.7\bin>mysql -uroot -proot -hlocalhost -P8066 -Dqs
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 13
Server version: 5.5.8-mycat-1.4-release-20151019230038 MyCat Server (OpenCloundDB)

Copyright (c) 2000, 2016, 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.

Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the current input statement.

mysql> insert test1 values(2,’localhost’);
Query OK, 1 row affected (0.01 sec)

mysql> select * from test1;
+—-+——+
| id | name |
+—-+——+
| 1 | 8383 |
+—-+——+
1 row in set (0.00 sec)

C:\Program Files\MySQL\MySQL Server 5.7\bin>mysql -uroot -proot -h192.168.0.83 -P3306 -Ddb1
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 412
Server version: 5.7.13-log MySQL Community Server (GPL)

Copyright (c) 2000, 2016, 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.

Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the current input statement.

mysql> select * from test1;
+—-+——+
| id | name |
+—-+——+
| 1 | 8383 |
+—-+——+
1 row in set (0.00 sec)

C:\Program Files\MySQL\MySQL Server 5.7\bin>mysql -uroot -proot -h192.168.1.56 -P3306 -Ddb1
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 784
Server version: 5.7.13-log MySQL Community Server (GPL)

Copyright (c) 2000, 2016, 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.

Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the current input statement.

mysql> select * from test1;
+—-+————-+
| id | name |
+—-+————-+
| 1 | 5656565656 |
| 2 | localhost |
+—-+————-+
2 rows in set (0.00 sec)