[IGNITE-14774] Add metrics for index pages loaded into memory

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 2.11
• Component/s: general
• Release Note: Added new metrics for monitoring the number of memory pages related to SQL indexes. These metrics can be made available through JMX and viewed as part of data region and cache group properties under the `InMemoryIndexPages` name.
• Ignite Flags: Release Notes Required
• Assignee: Aleksandr Polovtsev
• Reporter: Aleksandr Polovtsev
• Reviewer: Ivan Bessonov
• Created: 24/May/21 16:24
• Updated: 26/May/21 08:50
• Resolved: 26/May/21 08:50

Description

Expose the number of index pages currently loaded into memory on per-cache group and per-data region basis.

Implementation details

1. PageMetrics - an aggregation of all page-related metrics. At the moment of writing, contains the total number of pages and the number of index pages.
2. DataRegionMetricsImpl now contains page metrics related to every created cache group in a form of an immutable copy-on-write IntMap. It also contains an aggregation over these metrics that can be used as metrics for the whole data region.
3. Index pages allocation is tracked through the PageIO#initNewPage method, which can later be used to track other kinds of pages.
4. Index pages de-allocation is tracked in various places like replacing a page or adding it to a free list as I couldn’t find a single suitable place for this logic.

Issue Links

• links to: GitHub Pull Request #9125