Bug #102706 Update group replication docs replication configuration requirements
Submitted: 23 Feb 15:02 Modified: 24 Feb 13:45
Reporter: Eduardo Ortega Email Updates:
Status: Verified Impact on me:
None 
Category:MySQL Server: Documentation Severity:S3 (Non-critical)
Version:8.0.21, 8.0.23 OS:Any
Assigned to: CPU Architecture:Any

[23 Feb 15:02] Eduardo Ortega
Description:
Hi:

group replication fails to start when slave_preserve_commit_order = 0 and slave_parallel_workers > 1. This is the error in the error log:

2021-02-23T14:50:07.755573Z 5092442 [Warning] [MY-011682] [Repl] Plugin group_replication reported: 'Group Replication requires slave-preserve-commit-order to be set to ON when using more than 1 applier threads.'

However, the docs don't seem to reflect this requirements, at least neither here:

https://dev.mysql.com/doc/refman/8.0/en/group-replication-configuring-instances.html

nor here:

https://dev.mysql.com/doc/refman/8.0/en/group-replication-limitations.html

How to repeat:
1. Create replication group.

2. stop group_replication  in a member

3. Set slave_preserve_commit_order=0 and slave_parallel_workers=10 on the member

4. start group_replication.

5. See error on the error log.

6. Profit :D

Suggested fix:
Update the docs to reflect the configuration requirement
[24 Feb 13:45] MySQL Verification Team
Hello Eduardo,

Thank you for the report and feedback.
Verified as described.

regards,
Umesh
[24 Feb 13:47] MySQL Verification Team
MySQL Server 8.0.23 test results

Attachment: 102706_8.0.23.results (application/octet-stream, text), 15.70 KiB.

[24 Feb 13:48] MySQL Verification Team
Changing the category to Docs