mysql 从数据库同步异常后，恢复同步

本人主要分享在mysql主从同步过程中，从数据库因为SQL命令执行异常导致该异常之后的sql都无法进行同步了。

先看从库同步状态

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: #主库ip
                  Master_User: th2class
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000017
          Read_Master_Log_Pos: 88974903
               Relay_Log_File: 1-relay-bin.000002
                Relay_Log_Pos: 88344166
        Relay_Master_Log_File: mysql-bin.000017
             Slave_IO_Running: Yes
            Slave_SQL_Running: No
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 1062
                   Last_Error: Error 'xxx错误信息xxxx'
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 88610079
              Relay_Log_Space: 88709562
              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: NULL
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 1062
               Last_SQL_Error: Error 'xxx错误信息xxxx'
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 5
                  Master_UUID: e9013703-6e44-11ea-ac83-fa163e2c1732
             Master_Info_File: /usr/local/mysql/var/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: 
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 200921 16:08:30
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 
                Auto_Position: 0
         Replicate_Rewrite_DB: 
                 Channel_Name: 
           Master_TLS_Version: 
1 row in set (0.00 sec)

这时看到 Slave_SQL_Running=No 说明sql是不再执行同步的了，然后发现了一个error，具体问题需要具体分析，这个时候恢复同步可以尝试两种方案

方案1

1. 先停止slave
   mysql>stop slave;

2. 跳过slave上的1个错误
   mysql>set global sql_slave_skip_counter=1;

3.在slave上手工插入一条数据(如果不是插入错误，例如是更新错误等自行执行)
mysql>insert into ...

4.启动slave
mysql>start slave;
既可恢复同步

方案2

方案2就比较粗暴了，在数据量跟用户量不大的时候使用比较合适，毕竟对数据库杀伤力比较大
首先去到主库执行

FLUSH TABLES WITH READ LOCK;

对库进行FTWRL，这个时候主库上了全局读锁
查看主库状态以及导出主库数据

mysql> show master status\G
*************************** 1. row ***************************
             File: mysql-bin.000017
         Position: 88970639
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set: 
1 row in set (0.00 sec)
 mysqldump --uroot -p  -A -B --master-data=2 --single-transaction  >>  /home/1.sql
#把导出来的sql文件通过scp或者其他路径传输到从服务器中

将刚导出来的sql导入到从库中

#注意这里已经是在从库的shell端口中了
source /home/1.sql;
stop slave;
reset slave;
#重新同步
change master to master_host='主机IP',master_user='master',master_password='master_pwd',master_log_file='mysql-bin.45451',master_log_pos=23415631;
slave start;

然后查看下同步状态 show slave status\G

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: #主库ip
                  Master_User: th2class
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000017
          Read_Master_Log_Pos: 88980289
               Relay_Log_File: 1-relay-bin.000002
                Relay_Log_Pos: 1552
        Relay_Master_Log_File: mysql-bin.000017
             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: 88980289
              Relay_Log_Space: 1755
              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: 5
                  Master_UUID: e9013703-6e44-11ea-ac83-fa163e2c1732
             Master_Info_File: /usr/local/mysql/var/master.info
                    SQL_Delay: 0
          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: 
                Auto_Position: 0
         Replicate_Rewrite_DB: 
                 Channel_Name: 
           Master_TLS_Version: 
1 row in set (0.00 sec)

看到
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
则表明重新同步生效

思路就是 在主库查看主库的状态 ，查看当前的 File: mysql-bin 与 Position ，然后马上导出sql文件，并将sql文件传输到从服务器，让从服务器的数据库导入该文件，然后执行重新同步操作（即停止同步，重置同步，执行重置同步命令，开启同步即可）