change master 'master1' to 
master_port=MYPORT_1, 
master_host='127.0.0.1', 
master_user='root';
start slave 'master1';
set default_master_connection = 'master1';
include/wait_for_slave_to_start.inc
drop table if exists t1;
create table t1 (i int) engine=MyISAM;
mysqld-relay-bin-master1.000001
mysqld-relay-bin-master1.000002
mysqld-relay-bin-master1.index
show relaylog events in 'mysqld-relay-bin-master1.000002';
Log_name	Pos	Event_type	Server_id	End_log_pos	Info
mysqld-relay-bin-master1.000002	4	Format_desc	3	248	Server version
mysqld-relay-bin-master1.000002	248	Rotate	1	0	master-bin.000001;pos=4
mysqld-relay-bin-master1.000002	292	Format_desc	1	248	Server version
mysqld-relay-bin-master1.000002	536	Gtid_list	1	273	[]
mysqld-relay-bin-master1.000002	561	Binlog_checkpoint	1	313	master-bin.000001
mysqld-relay-bin-master1.000002	601	Gtid	1	351	GTID 0-1-1
mysqld-relay-bin-master1.000002	639	Query	1	465	use `test`; DROP TABLE IF EXISTS `t1` /* generated by server */
mysqld-relay-bin-master1.000002	753	Gtid	1	503	GTID 0-1-2
mysqld-relay-bin-master1.000002	791	Query	1	603	use `test`; create table t1 (i int) engine=MyISAM
show relaylog events;
Log_name	Pos	Event_type	Server_id	End_log_pos	Info
mysqld-relay-bin-master1.000001	4	Format_desc	3	248	Server version
mysqld-relay-bin-master1.000001	248	Rotate	3	306	mysqld-relay-bin-master1.000002;pos=4
drop table t1;
include/reset_master_slave.inc
include/reset_master_slave.inc