SHOW VARIABLES LIKE 'server_id';
Variable_name	Value
server_id	1
SHOW INSTANCES;
instance_name	status
mysqld1	online
mysqld2	offline
SET mysqld1.server_id = 11;
server_id =11
server_id           = 2
SHOW VARIABLES LIKE 'server_id';
Variable_name	Value
server_id	1
SET mysqld2.server_id = 12;
server_id =11
server_id =12
FLUSH INSTANCES;
server_id =11
server_id =12
SHOW VARIABLES LIKE 'server_id';
Variable_name	Value
server_id	1