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Mysql主从日常管理任务主要包括两种:
查看复制状态
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: 0Master_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: 01 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: NULLCommand: 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: NULLCommand: Query Time: 0 State: init Info: show processlist2 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: NULLMaster_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: 01 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: NULLMaster_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: 01 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: 0Master_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: 01 row in set (0.00 sec)
查看复制状态，主从复制恢复正常.
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