0、延时从库的使用场景

a、传统复制的痛点
只能帮我们解决物理损坏，很难解决逻辑损坏。
可以用备份解决，但是数据量很大，通过备份方式花费很长时间。
b、延时从库
主要是针对逻辑损坏等情况的发生

1、当前环境

10.0.0.100 master db01
10.0.0.101 slave db02
10.0.0.102 slave db03

2、配置延时从库

先需将10.0.0.101设置为延时从库

#此时是测试环境，所以我设置的延迟时间为60S，实际生产可根据情况自行设定
mysql> stop slave;
Query OK, 0 rows affected (0.00 sec)

mysql> change master to master_delay=60;
Query OK, 0 rows affected (0.01 sec)
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)
mysql> show slave status\G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 10.0.0.100
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000014
          Read_Master_Log_Pos: 27617
               Relay_Log_File: db02-relay-bin.000002
                Relay_Log_Pos: 414
        Relay_Master_Log_File: mysql-bin.000014
             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: 27617
              Relay_Log_Space: 620
              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: 100
                  Master_UUID: 93f12623-86ce-11eb-9689-000c29aec9e2
             Master_Info_File: /data/mysql/data/master.info
                    SQL_Delay: 60
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
           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: 1518e04e-8638-11eb-a908-000c29aec9e2:1-24,
8c88da03-86be-11eb-ac3c-000c29aec9e2:1-10,
93f12623-86ce-11eb-9689-000c29aec9e2:1-66
                Auto_Position: 1
         Replicate_Rewrite_DB: 
                 Channel_Name: 
           Master_TLS_Version: 
1 row in set (0.00 sec)