MySQL Bugs: #85747: Documentation on MTS statistics

Bug #85747	Documentation on MTS statistics
Submitted:	31 Mar 2017 16:12	Modified:	7 Aug 2020 14:18
Reporter:	Juan Arruti	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Replication	Severity:	S3 (Non-critical)
Version:	5.7, 5.7.18	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
Hi,

I didn't find information in MySQL reference manual about MTS statistics, I had to look into source code in order to get more information about them. Please add information to manual to get a better understanding about the meaning of each statistic and information about how to disable statistics messages from error log.

Thanks

How to repeat:
When using a multi-threaded slave, slave_parallel_workers greater than 0, and log_warnings > 1 or log_error_verbosity > 2, statistics from MTS are shown almost every 120 seconds in error log file, as follows:

2017-03-31T00:48:32.305882Z 2 [Note] Multi-threaded slave statistics for channel '': seconds elapsed = 19364; events assigned = 124929; worker queues filled over overrun level = 0; waited due a Worker queue full = 0; waited due the total size = 0; waited at clock conflicts = 0 waited (count) when Workers occupied = 0 waited when Workers occupied = 0

2017-03-31T00:56:40.471525Z 2 [Note] Multi-threaded slave statistics for channel '': seconds elapsed = 488; events assigned = 139265; worker queues filled over overrun level = 0; waited due a Worker queue full = 0; waited due the total size = 0; waited at clock conflicts = 0 waited (count) when Workers occupied = 0 waited when Workers occupied = 0

Hello Juan Arruti,

Thank you for the report and feedback.
Verifying as code bug after discussing internally with Developer.

Thanks,
Umesh

Bug #88251 marked as duplicate of this one

Posted by developer:
 
Documentation added to:
https://dev.mysql.com/doc/refman/5.6/en/replication-implementation-details.html
https://dev.mysql.com/doc/refman/5.7/en/replication-implementation-details.html
https://dev.mysql.com/doc/refman/8.0/en/replication-implementation-details.html
The statistics are in a subtopic of this main topic.