Bug #100052 install group_replication will write error log
Submitted: 1 Jul 0:45 Modified: 20 Jul 8:59
Reporter: phoenix Zhang (OCA) Email Updates:
Status: Not a Bug Impact on me:
None 
Category:MySQL Server: Group Replication Severity:S3 (Non-critical)
Version:8.0.18, 8.0.20 OS:Any
Assigned to: CPU Architecture:Any
Tags: group_replication

[1 Jul 0:45] phoenix Zhang
Description:
if without any group_replication config in my.cnf, when install group_replication, it will success, while, still write error log.

How to repeat:
The basedir my.cnf 

[mysqld]
basedir=/usr/local/mysql
datadir=/usr/local/mysql/data
socket=/usr/local/mysql/data/mysql.sock
user=mysql
port=3306

server-id=1
binlog-checksum=NONE
enforce-gtid-consistency
gtid-mode=ON

After init the mysql server, connect:
mysql> install plugin group_replication soname 'group_replication.so';
Query OK, 0 rows affected (0.01 sec)

It install success, while, error log found:
[ERROR] [MY-011685] [Repl] Plugin group_replication reported: 'The group name option is mandatory'
[ERROR] [MY-011660] [Repl] Plugin group_replication reported: 'Unable to start Group Replication on

Suggested fix:
The group_replication_start_on_boot=on is default, and group_replication_group_name is default empty.

When install plugin, maybe cause group_replication_start_on_boot is on, it will try to start group_replication. However, this error-log is not friendly. It should not write such error log when just install plugin.
[1 Jul 11:39] MySQL Verification Team
Hello phoenix Zhang!

Thank you for the report.

regards,
Umesh
[20 Jul 8:59] Erlend Dahl
According to the Group Replication team, this is the expected behaviour.