Groupby Metrics

[GWphua]

Attempt at #18781 .

Description

Metrics Reporting via GroupByQueryMetrics

• Remove method signatures in codebase which rely on using PerQueryStats to retrieve metrics, and retrieve query stats via the GroupByQueryMetrics instead.
• Wrap a FinalizingResultsQueryRunner in a MetricsEmittingQueryRunner to emit the reported GroupByQueryMetrics.
• Update all method signatures in the codebase which rely on GroupByStatsProvider or PerQueryStats.
• Update GroupByStatsProvider Test.

Pass metrics via ResponseContext among the runners

• Passing groupBy metrics via ResponseContext, which collates and stores the information in the Sequence objects.

Why Response Context?

• In consideration of concurrency, QueryPlus may not have metrics, for example see GroupByMergingQueryRunner.
• It is also hard to create QueryMetrics objects in classes working on layers lower than the GroupByQueryQueryToolChest such as GroupByMergingQueryRunner, as creating the query metrics in a QueryPlus requires the toolChest.

Future Tasks

• Come up with new metric names, current metrics names clash with GroupByStatsMonitor. To be continued after agreeing about the logic of this PR with reviewers.
• Documentations on new metrics names.
• Documentation differentiating the use of GroupByStatsMonitor vs GroupByQueryMetrics.

Release note

Druid emits per-query GroupBy metrics by default.

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Key changed/added classes in this PR

Metrics-related classes

• GroupByQueryMetrics
• GroupByStatsProvider

Segment Walkers

• SinkQuerySegmentWalker
• ClientQuerySegmentWalker
• LocalQuerySegmentWalker
• ServerManager

Query Runner Level

• GroupByQueryQueryToolChest
• GroupByMergingQueryRunner
• GroupByRowProcessor
• GroupByResponseContextKeys
• ConcurrentGrouper
• SpillingGrouper
• LimitedTemporaryStorage

Others

• Test files
• Classes affected by method signature changes

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This PR has:

• [x] been self-reviewed.
• [ ] added documentation for new or modified features or behaviors.
• [x] a release note entry in the PR description.
• [x] added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• [x] added or updated version, license, or notice information in licenses.yaml
• [x] added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• [x] added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• [ ] added integration tests.
• [x] been tested in a test Druid cluster.