也可以执行如下语句创建该系统视图：
USE sys; DELIMITER $$ CREATE FUNCTION IFZERO(a INT, b INT) RETURNS INT DETERMINISTIC RETURN IF(a = 0, b, a)$$ CREATE FUNCTION LOCATE2(needle TEXT(10000), haystack TEXT(10000), offset INT) RETURNS INT DETERMINISTIC RETURN IFZERO(LOCATE(needle, haystack, offset), LENGTH(haystack) + 1)$$ CREATE FUNCTION GTID_NORMALIZE(g TEXT(10000)) RETURNS TEXT(10000) DETERMINISTIC RETURN GTID_SUBTRACT(g, '')$$ CREATE FUNCTION GTID_COUNT(gtid_set TEXT(10000)) RETURNS INT DETERMINISTIC BEGIN DECLARE result BIGINT DEFAULT 0; DECLARE colon_pos INT; DECLARE next_dash_pos INT; DECLARE next_colon_pos INT; DECLARE next_comma_pos INT; SET gtid_set = GTID_NORMALIZE(gtid_set); SET colon_pos = LOCATE2(':', gtid_set, 1); WHILE colon_pos != LENGTH(gtid_set) + 1 DO SET next_dash_pos = LOCATE2('-', gtid_set, colon_pos + 1); SET next_colon_pos = LOCATE2(':', gtid_set, colon_pos + 1); SET next_comma_pos = LOCATE2(',', gtid_set, colon_pos + 1); IF next_dash_pos < next_colon_pos AND next_dash_pos < next_comma_pos THEN SET result = result + SUBSTR(gtid_set, next_dash_pos + 1, LEAST(next_colon_pos, next_comma_pos) - (next_dash_pos + 1)) - SUBSTR(gtid_set, colon_pos + 1, next_dash_pos - (colon_pos + 1)) + 1; ELSE SET result = result + 1; END IF; SET colon_pos = next_colon_pos; END WHILE; RETURN result; END$$ CREATE FUNCTION gr_applier_queue_length() RETURNS INT DETERMINISTIC BEGIN RETURN (SELECT sys.gtid_count( GTID_SUBTRACT( (SELECT Received_transaction_set FROM performance_schema.replication_connection_status WHERE Channel_name = 'group_replication_applier' ), (SELECT @@global.GTID_EXECUTED) ))); END$$ CREATE FUNCTION gr_member_in_primary_partition() RETURNS VARCHAR(3) DETERMINISTIC BEGIN RETURN (SELECT IF( MEMBER_STATE='ONLINE' AND ((SELECT COUNT(*) FROM performance_schema.replication_group_members WHERE MEMBER_STATE != 'ONLINE') >= ((SELECT COUNT(*) FROM performance_schema.replication_group_members)/2) = 0), 'YES', 'NO' ) FROM performance_schema.replication_group_members JOIN performance_schema.replication_group_member_stats USING(member_id)); END$$ CREATE VIEW gr_member_routing_candidate_status AS SELECT sys.gr_member_in_primary_partition() as viable_candidate, IF( (SELECT (SELECT GROUP_CONCAT(variable_value) FROM performance_schema.global_variables WHERE variable_name IN ('read_only', 'super_read_only')) != 'OFF,OFF'), 'YES', 'NO') as read_only, sys.gr_applier_queue_length() as transactions_behind, Count_Transactions_in_queue as 'transactions_to_cert' from performance_schema.replication_group_member_stats;$$ DELIMITER ;视图创建后，可以查看该视图：
node1上：
mysql> select * from sys.gr_member_routing_candidate_status; +------------------+-----------+---------------------+----------------------+ | viable_candidate | read_only | transactions_behind | transactions_to_cert | +------------------+-----------+---------------------+----------------------+ | YES | NO | 0 | 0 | +------------------+-----------+---------------------+----------------------+node2上：
mysql> select * from sys.gr_member_routing_candidate_status; +------------------+-----------+---------------------+----------------------+ | viable_candidate | read_only | transactions_behind | transactions_to_cert | +------------------+-----------+---------------------+----------------------+ | YES | YES | 0 | 0 | +------------------+-----------+---------------------+----------------------+5.向mysql_group_replication_hostgroups中插入记录
delete from mysql_group_replication_hostgroups; insert into mysql_group_replication_hostgroups(writer_hostgroup,backup_writer_hostgroup,reader_hostgroup,offline_hostgroup,active,max_writers,writer_is_also_reader,max_transactions_behind) values(10,20,30,40,1,1,0,0); load mysql servers to runtime; save mysql servers to disk;上述配置中，我把writer_is_also_reader设置为false，让master只负责写操作。
admin> select * from mysql_group_replication_hostgroups\G *************************** 1. row *************************** writer_hostgroup: 10 backup_writer_hostgroup: 20 reader_hostgroup: 30 offline_hostgroup: 40 active: 1 max_writers: 1 writer_is_also_reader: 0 max_transactions_behind: 0 comment: NULL