MySQL主从切换

1、查看从库数据库状态：
mysql> show processlist;
+----+-------------+-----------------+--------+---------+-------+-----------------------------------------------------------------------------+------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+-------------+-----------------+--------+---------+-------+-----------------------------------------------------------------------------+------------------+
| 2 | root | 127.0.0.1:59012 | sakila | Query | 0 | NULL | show processlist |
| 3 | system user | | NULL | Connect | 17618 | Waiting for master to send event | NULL |
| 4 | system user | | NULL | Connect | 17305 | Slave has read all relay log; waiting for the slave I/O thread to update it | NULL |
+----+-------------+-----------------+--------+---------+-------+-----------------------------------------------------------------------------+------------------+
3 rows in set (0.00 sec)

mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 172.16.33.143
Master_User: master
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql.000003
Read_Master_Log_Pos: 3296928
Relay_Log_File: slave-relay-bin.000002
Relay_Log_Pos: 3296845
Relay_Master_Log_File: mysql.000003
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB: test
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: 3296928
Relay_Log_Space: 3297001
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
1 row in set (0.00 sec)

mysql> show processlist;
+----+--------+---------------------+--------+-------------+-------+-----------------------------------------------------------------------+------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+--------+---------------------+--------+-------------+-------+-----------------------------------------------------------------------+------------------+
| 1 | root | 127.0.0.1:33623 | sakila | Query | 0 | NULL | show processlist |
| 2 | master | 172.16.33.144:48988 | NULL | Binlog Dump | 17455 | Master has sent all binlog to slave; waiting for binlog to be updated | NULL |
+----+--------+---------------------+--------+-------------+-------+-----------------------------------------------------------------------+------------------+
2 rows in set (0.00 sec)

mysql> show master status;
+--------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+--------------+----------+--------------+------------------+
| mysql.000003 | 3296928 | | |
+--------------+----------+--------------+------------------+
1 row in set (0.00 sec)

2、修改配置文件：
主库：read_only = 1
从库：#read_only = 1

3、操作从库：
mysql> show processlist;
+----+-------------+-----------------+--------+---------+-------+-----------------------------------------------------------------------------+------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+-------------+-----------------+--------+---------+-------+-----------------------------------------------------------------------------+------------------+
| 2 | root | 127.0.0.1:59012 | sakila | Query | 0 | NULL | show processlist |
| 3 | system user | | NULL | Connect | 17770 | Waiting for master to send event | NULL |
| 4 | system user | | NULL | Connect | 17457 | Slave has read all relay log; waiting for the slave I/O thread to update it | NULL |
+----+-------------+-----------------+--------+---------+-------+-----------------------------------------------------------------------------+------------------+
3 rows in set (0.00 sec)

mysql> stop slave io_thread;
Query OK, 0 rows affected (0.00 sec)

mysql> show processlist;
+----+-------------+-----------------+--------+---------+-------+-----------------------------------------------------------------------------+------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+-------------+-----------------+--------+---------+-------+-----------------------------------------------------------------------------+------------------+
| 2 | root | 127.0.0.1:59012 | sakila | Query | 0 | NULL | show processlist |
| 4 | system user | | NULL | Connect | 17526 | Slave has read all relay log; waiting for the slave I/O thread to update it | NULL |
+----+-------------+-----------------+--------+---------+-------+-----------------------------------------------------------------------------+------------------+
2 rows in set (0.00 sec)

确认从库的状态为：Slave has read all relay log

mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State:
Master_Host: 172.16.33.143
Master_User: master
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql.000003
Read_Master_Log_Pos: 3296928
Relay_Log_File: slave-relay-bin.000002
Relay_Log_Pos: 3296845
Relay_Master_Log_File: mysql.000003
Slave_IO_Running: No
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB: test
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: 3296928
Relay_Log_Space: 3297001
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
1 row in set (0.00 sec)

4、查看主库状态：
mysql> show master status;
+--------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+--------------+----------+--------------+------------------+
| mysql.000003 | 3296928 | | |
+--------------+----------+--------------+------------------+
1 row in set (0.00 sec)

5、主从切换，从库变主库：
mysql> slave stop;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> reset master;
Query OK, 0 rows affected (0.02 sec)

mysql> reset slave;
Query OK, 0 rows affected (0.00 sec)

mysql> show master status;
+--------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+--------------+----------+--------------+------------------+
| mysql.000001 | 107 | | |
+--------------+----------+--------------+------------------+
1 row in set (0.00 sec)

6、主从切换，主库变从库：
mysql> reset master;
Query OK, 0 rows affected (0.02 sec)

mysql> reset slave;
Query OK, 0 rows affected (0.00 sec)

mysql> change master to master_host='172.16.33.144',master_port=3306,master_user='master',master_password='123456',master_log_file=' mysql-bin.000001',master_log_pos=107;
Query OK, 0 rows affected (0.04 sec)

7、重启主从：
[root@yoon ~]# service mysqld restart
Shutting down MySQL. SUCCESS!
Starting MySQL.. SUCCESS!

8、查看主从是否正常：
主库：
show processlist;
show master status;

从库：
show processlist;
start slave;
show slave status\G