MGR_ERROR 3092 (HY000): DROP DATABASE failed;

• start group_replication;时报以下错:

ERROR 3092 (HY000): DROP DATABASE failed; some tables may have been dropped but the database directory remains. The GTID has not been added to GTID_EXECUTED and the statement was not written to the binary log. Fix this as follows: (1) remove all files from the database directory %-.192s; (2) SET GTID_NEXT='%-.192s'; (3) DROP DATABASE `%-.192s`.

• error.log报错提示:

2018-08-23T11:46:54.344944+08:00 5 [Note] 'CHANGE MASTER TO FOR CHANNEL 'group_replication_applier' executed'. Previous state master_host='<NULL>', master_port= 0, master_log_file='', master_log_pos= 4, master_bind=''. New state master_host='<NULL>', master_port= 0, master_log_file='', master_log_pos= 4, master_bind=''.
2018-08-23T11:46:54.350004+08:00 3 [Note] Plugin group_replication reported: 'Group Replication applier module successfully initialized!'
2018-08-23T11:46:54.350028+08:00 8 [Note] Slave SQL thread for channel 'group_replication_applier' initialized, starting replication in log 'FIRST' at position 0, relay log './relay-bin-group_replication_applier.000006' position: 4
2018-08-23T11:46:54.350033+08:00 3 [Note] Plugin group_replication reported: 'auto_increment_increment is set to 7'
2018-08-23T11:46:54.350065+08:00 3 [Note] Plugin group_replication reported: 'auto_increment_offset is set to 1'
2018-08-23T11:46:54.370338+08:00 0 [Note] Plugin group_replication reported: 'XCom protocol version: 3'
2018-08-23T11:46:54.370366+08:00 0 [Note] Plugin group_replication reported: 'XCom initialized and ready to accept incoming connections on port 23507'
2018-08-23T11:46:56.444399+08:00 0 [ERROR] Plugin group_replication reported: 'The member is configured with a lower_case_table_names option value '4227861216' different from the group '1'. The member will now exit the group. If there is existing data on member, it may be incompatible with group if created with a lower_case_table_names value different from the group.'
2018-08-23T11:46:56.444466+08:00 0 [Note] Plugin group_replication reported: 'Group membership changed to db211:3507, db210:3507,  on view 15349902199191235:13.'
2018-08-23T11:46:56.444474+08:00 3 [Note] Plugin group_replication reported: 'Going to wait for view modification'
2018-08-23T11:46:59.799625+08:00 0 [Note] Plugin group_replication reported: 'Group membership changed: This member has left the group.'
2018-08-23T11:47:04.799833+08:00 3 [Note] Plugin group_replication reported: 'auto_increment_increment is reset to 1'
2018-08-23T11:47:04.799870+08:00 3 [Note] Plugin group_replication reported: 'auto_increment_offset is reset to 1'
2018-08-23T11:47:04.800069+08:00 8 [Note] Error reading relay log event for channel 'group_replication_applier': slave SQL thread was killed
2018-08-23T11:47:04.800339+08:00 5 [Note] Plugin group_replication reported: 'The group replication applier thread was killed'

• 原因分析:
  
  ***1.查看节点间:lower_case_table_names 参数值都为1 ***
  
  2.查看节点间版本发现当前节点版本为5.7.20-log,而其他节点为5.7.23
• 解决办法将本节点版本升级为:5.7.23,问题解决;