MySQL双向同步热备设置以及同步错误的处理


环境

A: 192.168.0.1
B: 192.168.0.2

其中A上已经有数据库在服务，需要在B上搭建一个备库，并且和A实现双向同步。


设置
授权复制用户
即分别在A，B上增加一个用户让彼此访问

A:
grant replication slave,file on *.* to 'backup'@'192.168.0.2' identified by '123456';

B:
grant replication slave,file on *.* to 'backup'@'192.168.0.1' identified by '123456';

检测通过backup这个用户能够访问彼此的MySQL。

配置文件设置
B:

[mysqld]
# 省略...
# replication settings
# A 192.168.0.1
# B 192.168.0.2
server-id=2
log-bin=/home/mysql/log/mysql-bin
# 因为是双向，自动增加的id会有冲突，把步长改为2 初始设为2
auto_increment_increment=2
auto_increment_offset=2
# master设置
master-host=192.168.0.1
master-user=backup
master-pass=123456
master-port=3306
master-connect-retry=30
# 设置需要复制的库
replicate-do-db=your_db1
replicate-do-db=your_db2

# 省略...

A:

[mysqld]
# 省略...
# replication settings
# A 192.168.0.1
# B 192.168.0.2
server-id=1
log-bin=/home/mysql/log/mysql-bin
# 因为是双向，自动增加的id会有冲突，把步长改为2 初始设为1
auto_increment_increment=2
auto_increment_offset=1
# master设置
master-host=192.168.0.2
master-user=backup
master-pass=123456
master-port=3306
master-connect-retry=30
# 设置需要复制的库
replicate-do-db=your_db1
replicate-do-db=your_db2

# 省略...

同步现有数据
停止A数据库的操作，把A中的数据用mysqldump或者直接拷贝文件的方法复制到B，确保B正常。

设置并检查同步
启动A和B上的的MySQL

检查master status:

A:

mysql> show master status;
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000004 |  8937501 |              |                  |
+------------------+----------+--------------+------------------+
1 row in set (0.00 sec)

B:

mysql> show master status;
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000019 |      597 |              |                  |
+------------------+----------+--------------+------------------+
1 row in set (0.00 sec)

检查slave status:

A:

mysql> show slave status\G
*************************** 1. row ***************************
             Slave_IO_State: Waiting for master to send event
                Master_Host: 192.168.0.2
                Master_User: backup
                Master_Port: 3306
              Connect_Retry: 60
            Master_Log_File: mysql-bin.000019
        Read_Master_Log_Pos: 597
             Relay_Log_File: mysqld-relay-bin.000005
              Relay_Log_Pos: 429
      Relay_Master_Log_File: mysql-bin.000019
           Slave_IO_Running: Yes
          Slave_SQL_Running: Yes
            Replicate_Do_DB: your_db1,your_db2
        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: 597
            Relay_Log_Space: 429
            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
1 row in set (0.00 sec)

B:

mysql> show slave status\G
*************************** 1. row ***************************
             Slave_IO_State: Waiting for master to send event
                Master_Host: 192.168.0.1
                Master_User: backup
                Master_Port: 3306
              Connect_Retry: 30
            Master_Log_File: mysql-bin.000004
        Read_Master_Log_Pos: 9914005
             Relay_Log_File: mysqld-relay-bin.000008
              Relay_Log_Pos: 9914142
      Relay_Master_Log_File: mysql-bin.000004
           Slave_IO_Running: Yes
          Slave_SQL_Running: Yes
            Replicate_Do_DB: your_db1,your_db2
        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: 9914005
            Relay_Log_Space: 9914142
            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
1 row in set (0.00 sec)

需要特别注意的是这两行：

           Slave_IO_Running: Yes
          Slave_SQL_Running: Yes

必须都是Yes，否则同步不成功。

分别在A和B上做操作，看同步是否生效；

复制不成功的解决方法
一开始我设置从A复制到B时出现了错误

           Slave_IO_Running: No
          Slave_SQL_Running: Yes

mysqld.log里面：

121217 17:43:39 [ERROR] Error reading packet from server: error reading log entry ( server_errno=1236)
121217 17:43:39 [ERROR] Got fatal error 1236: 'error reading log entry' from master when reading data from binary log

这时我用CHANGE MASTER命令重新指定master：

停止A的MySQL操作，查看master状态:

A:

mysql> show master status;
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000003 |    98    |              |                  |
+------------------+----------+--------------+------------------+
1 row in set (0.00 sec)

记住上面的File和Position数值

在B上用CHANGE MASTER命令重新指定master:

mysql> slave stop;
mysql> change master to master_host='192.168.0.1',master_user='backup',master_password='123456', master_log_file='mysql-bin.000003',master_log_pos=98;
mysql> slave start;

此时检查B上的slave status, 发现已经OK：

           Slave_IO_Running: Yes
          Slave_SQL_Running: Yes