WL#10380: Group Replication: Monitoring improvements

Affects: Server-8.0   —   Status: Complete

This worklog goal is to improve Group Replication by introducing additional
columns in existing performance schema.
No existing table/column will be removed.
There will not be any change in names, data types or order for existing
tables and columns minimizing impact on customers.


We are not creating new performance_schema tables for Group Replication.
This worklog is related to extending existing GR performance schema tables
"replication_group_member" and "replication_group_member_stats" by appending
new columns at end, so previous column order is preserved.
Since we are extending existing GR P_S tables, we expect minimum to no impact
for existing customers.
Since we are extending existing GR P_S tables, we expect all things to remain
same w.r.t. compiling/enabling performance_schema, output of show variables
etc, other then display of new additional columns.


We need to show additional member related information like Role
(Primary or Secondary) and Version.
"replication_group_members" table shows information of all 
members(1 row/member), this needs to be maintained for new columns being added.


At present only information related to certification is shown in GR table
"replication_group_member_stats".
We need to extend table "replication_group_member_stats" to show statistics
of Applier, Local queue and related information that might help customers
for analysis.
Since some machines may be lagging, overloaded.., information of all members
should be visible from any group member machine.
At present customer can get stats information only by logging into local
member of which information is needed.