Mysql 主从数据库同步(centos篇)

环境:

主服务器:centos 5.2 mysql 5.1.35 源码 IP:192.168.1.22

从服务器:centos 5.2 mysql 5.1.35 源码  IP:192.168.1.33

配置:

一、主服务器

1.1、创建一个复制用户，具有replication slave 权限。

mysql>grant replication slave on *.* to 'repl'@'192.168.1.22' identified by 'repl';

1.2、编辑my.cnf文件

vi /etc/my.cnf
添加
server-id=1
并开启log-bin二进制日志文件
log-bin=mysql-bin

注:需要把默认的server-id=1去掉

1.3、启动mysql数据库

mysqld_safe --user=mysql &

1.4、设置读锁

mysql>flush tables with read lock;

1.5、得到binlog日志文件名和偏移量

mysql>show master status;

+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.0000010 |      106|              |                  |
+------------------+----------+--------------+------------------+

1.6、备份要同步的数据库

mysqldump test > test.sql

1.7、解锁

mysql>unlock tables;

二、从服务器

2.1、编辑my.cnf文件

vi /etc/my.cnf
添加
server-id=2

注:需要把默认的server-id=1去掉

2.2、启动从数据库

mysqld_safe --user=mysql &

2.3、对从数据库进行相应设置

mysql> change master to
        -> master_host='192.168.1.22'
        -> master_user='repl'
        -> master_password='repl'
        -> master_log_file='mysql-bin.0000010'
        -> master_log_pos=106;

2.4、启动从服务器slave线程

mysql>start slave;

执行show processlist命令显示以下进程:

mysql>show processlist\G
*************************** 2. row ***************************
         Id: 2
     User: system user
     Host:    
         db: NULL
Command: Connect
     Time: 2579
    State: Has read all relay log; waiting for the slave I/O thread to update it
     Info: NULL
表示slave已经连接上master，开始接受并执行日志

2.5、查看slave线程状态

mysql>show slave status;

*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.1.22

Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.0000010
          Read_Master_Log_Pos: 106
               Relay_Log_File: centos-relay-bin.000002
                Relay_Log_Pos: 529
        Relay_Master_Log_File: mysql-bin.0000010
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB:

Replicate_Ignore_DB:
           Replicate_Do_Table:
       Replicate_Ignore_Table:
      Replicate_Wild_Do_Table:
  Replicate_Wild_Ignore_Table:
                   Last_Errno: 0
                   Last_Error:
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 106
              Relay_Log_Space: 830
              Until_Condition: None
               Until_Log_File:
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File:
           Master_SSL_CA_Path:
              Master_SSL_Cert:
            Master_SSL_Cipher:
               Master_SSL_Key:
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error:
               Last_SQL_Errno: 0
               Last_SQL_Error:
1 row in set (0.00 sec)

验证是否配置正确

在从服务器上执行

show slave status\G;
Waiting for master to send event
Slave_IO_Running: Yes
Slave_SQL_Running: Yes

如以上二行同时为Yes 说明配置成功

测试

1、在主服务器test数据库中创建user表

mysql>use test;
mysql>create table user(id int);

2、在从服务器中查看user表

mysql>use test;
mysql> show tables like 'user';
+----------------------+
| Tables_in_test(user) |
+----------------------+
| user                 |    
+----------------------+
1 row in set (0.00 sec)

说明主从数据同步成功。

问题?

1.在从数据库中查看slave状态时出现

The slave I/O thread stops because master and slave have equal MySQL server ids; these ids must be different for replication to work (or the --replicate-same-server-id option must be used on slave but this does not always make sense; please check the manual before using it)

说明方从服务器里my.cnf中的server-id有相同的。

解决办法:

修改my.cnf里的server-id，并重启数据库服务。my.cnf文件默认有server-id=1

其它说明

主服务器my.cnf

#binlog-do-db=需要备份的数据库名，可写多行
#binlog-ignore-db=不需要备份的数据库名，可写多行
从服务器my.cnf

# replicate-do-db=test  需要备份的数据库名
# replicate-ignore-db=mysql 忽略的数据库
# master-connect-retry=60 如果从服务器发现主服务器断掉，重新连接的时间差(秒)

以下设置也可直接修改my.cnf配置文件

log-bin=mysql-bin
master-host=192.168.1.22

master-user=repl

master-password=repl
master-port=3306

主从服务器同步维护

由于各种原因，导致主从数据不一致，在负载低的时候，进行手动同步.

在主服务器上执行

mysql>flush tables with read lock;

Query OK,rows affected (0.01 sec)

mysql>show master status;

+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.0000011 |      260|              |                  |
+------------------+----------+--------------+------------------+

在从服务器上执行

先得到当前主服务器的二进制文件名和偏移量,执行命令使从服务器与主服务器同步

mysql>select master_pos_wait('mysql-bin.0000011','260');
+--------------------------------------------------+
| master_pos_wait('mysql-bin.0000011','260')            |
+--------------------------------------------------+
|  0                                                                   |   
+--------------------------------------------------+
1 row in set (0.01 sec)

同步完成后，在主服务器上执行解锁

mysql>unlock tables;

切换主从服务器

当主服务器出现故障时，可将从服务器当主服务器来使用.步骤如下:

1、保证所有从数据库都已经执行了relay log中的全部更新，在从服务器中执行

stop slave io_thread,用show processlist检查，查看状态是否是Has read all relay log,表示更新完成.

mysql>stop slave io_thread;
Query OK,0 affected (0.00 sec)
mysql>show processlist\G;

*************************** 2. row ***************************
     Id: 2
   User: system user
   Host:
     db: NULL
Command: Connect
   Time: 4757
  State: Has read all relay log; waiting for the slave I/O thread to update it
   Info: NULL

2、在从服务器上执行stop slave，reset master命令，重置成主数据库

mysql>stop slave;
Query OK,0 affected (0.00 sec)
mysql>reset master;
Query OK,0 affected (0.00 sec)

3、删除新的主服务器数据库目录中的master.info和relay-log.info文件，否则下次重启时还会按照从服务器来启动.