MySQL 5.6 已经支持延迟的流复制， 可设置备节点的延迟时间， 延迟复制是有意义的，例如防止主节点数据误删，查看数据库历史状态等。


重点：延迟复制实在原有的主从复制基础上、所以先要有主从复制的环境，然后配置延迟复制.  


一、 语法： 

CHANGE MASTER TO MASTER_DELAY = 30;---表示延迟30s

 备注：设置备节点延迟的时间，单位秒。


二、 配置延迟复制


登录从节点服务器进行设置：

root@localhost:mysql>stop slave;
Query OK, 0 rows affected (0.21 sec)
root@localhost:mysql>CHANGE MASTER TO MASTER_DELAY = 30;
Query OK, 0 rows affected (0.17 sec)
root@localhost:mysql>start slave;
Query OK, 0 rows affected (0.27 sec)


三、查看从节点状态

root@localhost:mysql>select * from slave_relay_log_info\G
*************************** 1. row ***************************
  Number_of_lines: 7
   Relay_log_name: ./db2-relay-bin.000007
    Relay_log_pos: 281
  Master_log_name: bin-log.000041
   Master_log_pos: 361
        Sql_delay: 30
Number_of_workers: 0
               Id: 1
1 row in set (0.00 sec)
root@localhost:mysql>show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.2.37
                  Master_User: rep1
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: bin-log.000040
          Read_Master_Log_Pos: 604
               Relay_Log_File: db2-relay-bin.000002
                Relay_Log_Pos: 281
        Relay_Master_Log_File: bin-log.000040
             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: 604
              Relay_Log_Space: 452
              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: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 1
                  Master_UUID: 0c130d47-22bb-11e4-aaaa-000c2986ac80
             Master_Info_File: mysql.slave_master_info
                    SQL_Delay: 30
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 
                Auto_Position: 0
1 row in set (0.00 sec)




四、主节点创建表测试

root@localhost:mysql>create table test_delay(id int4 primary key,
                     create_time datetime default current_timestamp); 
 Query OK, 0 rows affected (0.59 sec)
root@localhost:mysql>insert into test_delay (id) values(1);
 Query OK, 1 row affected (0.07 sec)

五、备节点查询

root@localhost:mysql>select * from test_delay;
Empty set (0.00 sec)
root@localhost:mysql>select * from test_delay;
Empty set (0.00 sec)
这时在备节点上还查不到表。


root@localhost:mysql>show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.2.37
                  Master_User: rep1
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: bin-log.000040
          Read_Master_Log_Pos: 1013
               Relay_Log_File: db2-relay-bin.000002
                Relay_Log_Pos: 281
        Relay_Master_Log_File: bin-log.000040
             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: 604
              Relay_Log_Space: 861
              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: 15
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 1
                  Master_UUID: 0c130d47-22bb-11e4-aaaa-000c2986ac80
             Master_Info_File: mysql.slave_master_info
                    SQL_Delay: 30
          SQL_Remaining_Delay: 14
      Slave_SQL_Running_State: Waiting until MASTER_DELAY seconds after master executed event
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 
                Auto_Position: 0
1 row in set (0.00 sec)

root@localhost:mysql>select * from test_delay;
+----+---------------------+
| id | create_time         |
+----+---------------------+
|  1 | 2014-12-12 14:38:47 |
+----+---------------------+
1 row in set (0.00 sec)


六、备注: 发现备节点在 30 秒后才能查到新建的表，这里有三个字段显示延迟的信息：

       SQL_Delay: 显示已设置的主备延迟的时间，单位秒;

       SQL_Remaining_Delay: 显示剩余的主备延迟时间，单位秒;

       Slave_SQL_Running_State: 表示 SQL thread 状态;