Collect information about variables from P_S

[Sveta Smirnova]

Currently pt-stalk collects information from SHOW GLOBAL VARIABLES output, but this statement and tables in Information Schema are deprecated and will be replaced with Performance Schema. Also in version 8.0 there will be possibility to know where one or another global variable originated from which is very helpful for troubleshooting.

Please add P_S support to pt-stalk and collect variables information from it. You may use queries:

select * from performance_schema.variables_by_thread order by thread_id, variable_name;
select * from performance_schema.user_variables_by_thread order by thread_id, variable_name;
select * from performance_schema.status_by_thread order by thread_id, variable_name; (performance_schema_max_thread_instances must be -1 or very big)

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PT-833