详解如何使用Rotate Master实现MySQL 多主复制的方法

use mysql;
CREATE TABLE `rotate_master` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`master_host` varchar(255) DEFAULT NULL comment 'master地址',
`master_port` int(10) unsigned DEFAULT NULL comment 'master端口' ,
`master_log_file` varchar(255) DEFAULT NULL ‘上次停止时的master-log文件',
`master_log_pos` int(10) unsigned DEFAULT NULL comment '上次停止时的master-log-pos',
`IS_Slave_Running` varchar(10) DEFAULT NULL comment '上次停止时主从是否有异常',
`in_use` tinyint(1) DEFAULT '0' comment '是否是当前正在同步的数据行',
`weight` int(11) NOT NULL DEFAULT '1' comment '该master的权重，即重复执行多少个时间片',
`repeated_times` int(11) NOT NULL DEFAULT '0' comment '当前已经重复执行的时间片数',
`LastExecuteTime` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP comment '上次执行的时间',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

insert into `rotate_master`
(`master_host`,`master_port`,`master_log_file`,`master_log_pos`,`in_use`,`weight`)
values
-- 1号master，权重=1，并设置为当前master
('192.168.0.1',3307,'mysqlbinlog.000542',4,1,1),
-- 2号master，权重=2
('192.168.0.2',3306,'mysqlbinlog.000702',64762429,0,2),
-- 3号master，权重=5
('192.168.0.3',3306,'mysqlbinlog.000646',22157422,0,5)

change master to master_host='192.168.0.1', master_port=3306,master_log_file='mysqlbinlog.000542',master_log_pos=4,master_user='repl',master_password='repl';
start slave;

DELIMITER $$
DROP PROCEDURE IF EXISTS `mysql`.`rotate_master`$$
CREATE DEFINER=`root`@`localhost` PROCEDURE `rotate_master`()
BEGIN
DECLARE _info text;
DECLARE _master_file varchar(255);
DECLARE _master_pos int unsigned;
DECLARE _master_host varchar(255);
DECLARE _master_port int unsigned;
DECLARE _is_slave_running varchar(10);
DECLARE _id int;
DECLARE _weight int;
DECLARE _repeated_times int;
select VARIABLE_VALUE from information_schema.GLOBAL_STATUS where VARIABLE_NAME = 'Slave_running' into _is_slave_running;
STOP SLAVE;
SELECT LOAD_FILE(@@relay_log_info_file) INTO _info;
SELECT
SUBSTRING_INDEX(SUBSTRING_INDEX(_info, '\n', 3), '\n', -1),
SUBSTRING_INDEX(SUBSTRING_INDEX(_info, '\n', 4), '\n', -1)
INTO _master_file, _master_pos;
UPDATE mysql.rotate_master SET `master_log_file` = _master_file, `master_log_pos` = _master_pos, id = LAST_INSERT_ID(id), `IS_Slave_Running` = _is_slave_running WHERE in_use = 1;
select weight,repeated_times into _weight,_repeated_times from mysql.rotate_master where in_use =1;
if(_weight <= _repeated_times)
THEN
SELECT
id,
master_host,
master_port,
master_log_file,
master_log_pos
INTO _id, _master_host, _master_port, _master_file, _master_pos
FROM rotate_master
ORDER BY id <= LAST_INSERT_ID(), id LIMIT 1;
SET @sql := CONCAT(
'CHANGE MASTER TO master_host=', QUOTE(_master_host),
', master_port=', _master_port,
', master_log_file=', QUOTE(_master_file),
', master_log_pos=', _master_pos
', master_user="repl"',
', master_password="repl"'
);
PREPARE myStmt FROM @sql;
EXECUTE myStmt;
UPDATE mysql.rotate_master SET in_use = 0,repeated_times=0 WHERE in_use = 1;
UPDATE mysql.rotate_master SET in_use = 1,repeated_times=1 WHERE id = _id;
ELSE
UPDATE mysql.rotate_master SET `repeated_times`=`repeated_times`+1 WHERE in_use = 1;
END IF;
START SLAVE;
END$$
DELIMITER ;

DELIMITER $$
CREATE EVENT `rotate_master` ON SCHEDULE EVERY 120 SECOND STARTS '2011-10-13 14:09:40' ON COMPLETION NOT PRESERVE ENABLE DO CALL mysql.rotate_master()$$
DELIMITER ;