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