Mysql主从日常管理任务主要包括两种:

  1. 查看复制状态

  2. 复制任务控制



一、查看复制状态


 要检查主从复制当前的状态,需要在从库服务器上执行语句:

  

show slave status

 执行结果如下所示:

 

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.200.20
                  Master_User: replica
                  Master_Port: 3306
                Connect_Retry: 10
              Master_Log_File: mysql-binlog.000017
          Read_Master_Log_Pos: 120
               Relay_Log_File: mysql-relaylog.000007
                Relay_Log_Pos: 286
        Relay_Master_Log_File: mysql-binlog.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: 120
              Relay_Log_Space: 624
              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: e84592e0-0e5b-11e4-a5d3-000c29e88022
             Master_Info_File: /usr/local/mysql/data/master.info
                    SQL_Delay: 0
          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)


查询结果报表中比较关键的几个字段:

Slave_IO_Status: 从服务器的IO状态。

Slave_IO_Runing: 从服务器IO线程是否正在运行,即从服务器是否正在读取主服务的二进制日志。

Slave_SQL_Running:从服务器SQL线程是否正在运行,即服务器是够正在执行中继日志中的事件.

Last_IO_Error,Last_SQL_Error: IO和SQL线程最新遇到的错误.

Seconds_Behind_Master:从服务器SQL线程处理中继日志的时间(秒),通常可以用来不精确性的评估主从

复制的延迟大小. 0 秒 意味着基本同步,数值越大意味着偏移量越大,同步延迟较高。

*_Log_*: 基本上都是和日志文件有关的信息,比如当前的二进制日志文件名称、位置等,都很容易理

解.



也可以在主服务器上查看当前已经连接的从服务器的状态,

包括以下语句:

show processlist
 show slave hosts

显示效果如下所示:

 

mysql> show processlist\G
*************************** 1. row ***************************
     Id: 1
   User: replica
   Host: 192.168.200.21:40781
     db: NULL
Command: Binlog Dump
   Time: 1929
  State: Master has sent all binlog to slave; waiting for binlog to be updated
   Info: NULL
*************************** 2. row ***************************
     Id: 2
   User: root
   Host: localhost
     db: NULL
Command: Query
   Time: 0
  State: init
   Info: show processlist
2 rows in set (0.00 sec)
mysql> show slave hosts;
+-----------+------+------+-----------+--------------------------------------+
| Server_id | Host | Port | Master_id | Slave_UUID                           |
+-----------+------+------+-----------+--------------------------------------+
|         2 |      | 3306 |         1 | 624856ee-1d1c-11e4-8605-000c29972cfa |
+-----------+------+------+-----------+--------------------------------------+
1 row in set (0.00 sec)

在主从复制过程中,是从服务器主动去主服务器获取二进制日志数据,因此从服务器控制复制过程,占

据主动地位,也因此在主服务器上查看Slave 状态时报表信息量很少.


二、复制任务控制


启停复制控制语句:

#启动复制
mysql> start slave;
#停止复制
mysql> stop slave;

"stop slave" 指令执行后,从服务器IO线程不再从主服务器读取二进制日志文件并写入到中继日志,

 SQL 线程也不再从中继日志读取事件并执行事件语句。如果想单独控制IO或者SQL线程,需要使用如

 下指令分别控制:


  

#停止IO线程
mysql> stop slave io_thread;
#停止SQL线程
mysql> stop slave sql_thread;

#分别启用IO和SQL线程:
mysql> start slave io_thread;
mysql> start slave sql_thread;


模拟控制线程并查看主从复制状态:


停止IO线程,并查看主从复制状态:

mysql> stop slave io_thread;
Query OK, 0 rows affected (0.09 sec)

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State:
                  Master_Host: 192.168.200.20
                  Master_User: replica
                  Master_Port: 3306
                Connect_Retry: 10
              Master_Log_File: mysql-binlog.000017
          Read_Master_Log_Pos: 120
               Relay_Log_File: mysql-relaylog.000007
                Relay_Log_Pos: 286
        Relay_Master_Log_File: mysql-binlog.000017
             Slave_IO_Running: No
            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: 120
              Relay_Log_Space: 624
              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: 0
               Last_SQL_Error:
  Replicate_Ignore_Server_Ids:
             Master_Server_Id: 1
                  Master_UUID: e84592e0-0e5b-11e4-a5d3-000c29e88022
             Master_Info_File: /usr/local/mysql/data/master.info
                    SQL_Delay: 0
          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)


可以看到Slave_IO_Status 状态值为No,而Slave_SQL_Status 状态值仍为 Yes.

Slave_IO_Status 也为空值了。


再停止SQL线程:

mysql> stop slave sql_thread;
Query OK, 0 rows affected (0.10 sec)

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State:
                  Master_Host: 192.168.200.20
                  Master_User: replica
                  Master_Port: 3306
                Connect_Retry: 10
              Master_Log_File: mysql-binlog.000017
          Read_Master_Log_Pos: 120
               Relay_Log_File: mysql-relaylog.000007
                Relay_Log_Pos: 286
        Relay_Master_Log_File: mysql-binlog.000017
             Slave_IO_Running: No
            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: 0
                   Last_Error:
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 120
              Relay_Log_Space: 624
              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: 0
               Last_SQL_Error:
  Replicate_Ignore_Server_Ids:
             Master_Server_Id: 1
                  Master_UUID: e84592e0-0e5b-11e4-a5d3-000c29e88022
             Master_Info_File: /usr/local/mysql/data/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:
               Master_SSL_Crl:
           Master_SSL_Crlpath:
           Retrieved_Gtid_Set:
            Executed_Gtid_Set:
                Auto_Position: 0
1 row in set (0.00 sec)


可以看到Slave_IO_Status 、Slave_SQL_Status 状态值全为 No.

再次执行"start slave" 或者分别执行"start slave io_thread"和"start slave sql_thread":

mysql> start  slave ;
mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.200.20
                  Master_User: replica
                  Master_Port: 3306
                Connect_Retry: 10
              Master_Log_File: mysql-binlog.000017
          Read_Master_Log_Pos: 120
               Relay_Log_File: mysql-relaylog.000008
                Relay_Log_Pos: 286
        Relay_Master_Log_File: mysql-binlog.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: 120
              Relay_Log_Space: 624
              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: e84592e0-0e5b-11e4-a5d3-000c29e88022
             Master_Info_File: /usr/local/mysql/data/master.info
                    SQL_Delay: 0
          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)


查看复制状态,主从复制恢复正常.