my17_Mysql 主从切换

注意事项：

从库提升为主库read_only要设置为OFF
原主库改为从库后，read_only要设置ON
read_only=ON并不能对root生效，确保root不会进行数据写入
从主库进行 flush tables with read lock 开始，到主从切换完毕，数据库不能对外提供写服务；一直对外提供读服务

建立主从
***************************************************
grant replication slave on *.* to 'repl_user'@'192.168.%' identified by 'rootroot';
show master statusG;

CHANGE MASTER TO
MASTER_HOST='192.168.56.103',
MASTER_USER='repl_user',
MASTER_PASSWORD='rootroot',
MASTER_PORT=3302,
MASTER_LOG_FILE='mysql-bin.000001',
MASTER_LOG_POS=154,
MASTER_CONNECT_RETRY=10;

start slave;

主库加锁，锁定数据使之不再变化
***********************************

mysql -uautomng -p -h192.168.56.103 -P3302
use vodb;
call p_addtest(1000000); #使用过程插入数据以模拟业务数据，此处如果是使用root用户执行的，那么后面变为从库，仅仅使用read_only=OFF是无法中止该过程的

mysql -uroot -p -S /data/mysql/log/eee/mysql_eee.sock
flush logs;
flush tables with read lock;

确定从库与主库一致
**************************************
mysql> show full processlist;
+----+-------------+-----------+------+---------+------+---------------------------------------------+-----------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+-------------+-----------+------+---------+------+---------------------------------------------+-----------------------+
| 2 | root | localhost | NULL | Sleep | 6017 | | NULL |
| 3 | root | localhost | vodb | Query | 0 | starting | show full processlist |
| 42 | system user | | NULL | Connect | 172 | Waiting for master to send event | NULL |
| 43 | system user | | NULL | Connect | 0 | Waiting for dependent transaction to commit | NULL |
| 44 | system user | | NULL | Connect | 114 | Waiting for an event from Coordinator | NULL |
| 45 | system user | | NULL | Connect | 114 | System lock | NULL |
| 46 | system user | | NULL | Connect | 173 | Waiting for an event from Coordinator

从库要出现 Slave has read all relay log;
mysql> show full processlist;
+----+-------------+-----------+------+---------+------+--------------------------------------------------------+-----------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+-------------+-----------+------+---------+------+--------------------------------------------------------+-----------------------+
| 2 | root | localhost | NULL | Sleep | 6058 | | NULL |
| 3 | root | localhost | vodb | Query | 0 | starting | show full processlist |
| 42 | system user | | NULL | Connect | 213 | Waiting for master to send event | NULL |
| 43 | system user | | NULL | Connect | 1 | Slave has read all relay log; waiting for more updates | NULL |
| 44 | system user | | NULL | Connect | 79 | Waiting for an event from Coordinator

从库提升为主
*************************************************
reset master;
stop slave;
reset slave all;
grant replication slave on *.* to 'repl_user'@'192.168.56.%' identified by 'rootroot';
flush privileges;
set global read_only=OFF;
show master statusG;
*************************** 1. row ***************************
File: mysql-bin.000001
Position: 613

记下master status后，数据库就可以对外提供写服务了

原主库变成新从库
*************************************************
#如果root用户有业务，则直接关库，是防止一些未执行完的过程、触发器、JOB继续修改库，直接关闭一次，完全中断所有事务，包括root用户正在执行的事务；如果root没有业务使用，则不必关心此问题
#mysql> shutdown;
#mysqld_safe --defaults-file=/etc/my_eee.cnf --user=mysql &

set global read_only=ON;
reset master;

CHANGE MASTER TO
MASTER_HOST='192.168.56.102',
MASTER_USER='repl_user',
MASTER_PASSWORD='rootroot',
MASTER_PORT=3302,
MASTER_LOG_FILE='mysql-bin.000001',
MASTER_LOG_POS=613,
MASTER_CONNECT_RETRY=10;

start slave;