mysql主从配置

　　在应对数据库压力的时候，选择读写分离是比较常用的手段，下面将总结一下，如何配置读库和写库，以及读写不同步的时候如何去保持同步。在这里，我们将写库称为主库，读库称为从库

主从库的基本配置

1、主库的配置：

    a、分配权限　　

grant replication slave on *.* to 'repl_90'@'192.168.90.90' identified by 'sina_sport';

　　

　b、修改主库配置文件

        server-id       = 91003306  #保持唯一即可
        log-bin         = mysql-bin
        relay-log       = mysql-relay-bin
        binlog-ignore-db=information_schema
        binlog-ignore-db=cluster
        binlog-ignore-db=mysql    

   c、重启主库服务

2、从库的配置    

　a、修改从库配置文件　　

        server-id       = 890091     #保持唯一即可
        log-bin         = mysql-bin
        relay-log       = mysql-relay-bin

   

　 b、重启从库服务
        
    
    c、执行主从同步sql

        mysql>CHANGE MASTER TO
                MASTER_HOST='192.168.90.91',
                MASTER_USER='repl_90',
                MASTER_PASSWORD='sk_sport',
                MASTER_PORT=3306,
                MASTER_LOG_FILE='mysql-bin.000001',
                MASTER_LOG_POS=98,
                MASTER_CONNECT_RETRY=10; #可不填写
        
        mysql>start slave;

　　        其中，MASTER_LOG_FILE和MASTER_LOG_POS 在主库中执行show master status可以看到
                
3、验证服务
   

mysql> show processlist;
+----+---------+----------------------+------+-------------+--------+-----------------------------------------------------------------------+------------------+
| Id | User    | Host                 | db   | Command     | Time   | State                                                                 | Info             |
+----+---------+----------------------+------+-------------+--------+-----------------------------------------------------------------------+------------------+
|  6 | repl_90 | X.X.X.X:54004 | NULL | Binlog Dump | 245837 | Master has sent all binlog to slave; waiting for binlog to be updated | NULL             |
|  7 | repl_90 | X.X.X.X:33431 | NULL | Binlog Dump | 245716 | Master has sent all binlog to slave; waiting for binlog to be updated | NULL             |
| 86 | root    | localhost            | NULL | Query       |      0 | NULL                                                                  | show processlist |
+----+---------+----------------------+------+-------------+--------+-----------------------------------------------------------------------+------------------+

其中X.X.X.X是从库的IP地址或者域名

主从不同步的处理办法

1、从库执行停止从库

mysql> slave stop;      

2、查看主库binlog

mysql> flush logs;
mysql> show master status;
+------------------+----------+--------------+----------------------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB                 |
+------------------+----------+--------------+----------------------------------+
| mysql-bin.000025 |    14628 |              | information_schema,cluster,mysql |
+------------------+----------+--------------+----------------------------------+

3、从库执行，保持同步

mysql> CHANGE MASTER TO MASTER_HOST='x.x.x.x',
            MASTER_USER='user',
            MASTER_PASSWORD='password',
            MASTER_LOG_FILE=' mysql-bin.000025',
            MASTER_LOG_POS=14628; 
mysql> START SLAVE;