kfaraz opened a new pull request, #17935:
URL: https://github.com/apache/druid/pull/17935
### Description
#17653 added a `HeapMemorySegmentMetadataCache` for used segments and
pending segments on the Overlord.
This cache is similar to `SqlSegmentsMetadataManager` in the sense that both
of them periodically poll the metadata
store and keep used segments in memory.
But the `HeapMemorySegmentMetadataCache` offers a performance advantage
since it polls only updated
segments from the metadata store, thus reducing the time it takes the
service to sync with the metadata store.
This patch:
- Allows use of segment metadata cache on the Coordinator to improve poll
times
- Reorganizes `SqlSegmentsMetadataManager`and
`IndexerSQLMetadataStorageCoordinator` to reduce code
duplication and avoid functionality overlap
### Changes
- Repurpose `SegmentsMetadataManager` to manage only segment polling and
caching
- Move all segment metadata read or write APIs to
`IndexerMetadataStorageCoordinator`
- Move implementation of above methods to `SqlSegmentsMetadataQuery`
- Add method `getDatasourcesSnapshot()` to `SegmentMetadataCache`
- After every successful poll in `HeapMemorySegmentMetadataCache`, update
the `DataSourcesSnapshot`
- Add `SqlSegmentsMetadataManagerV2` which is a wrapper over
`SegmentMetadataCache` and
`SqlSegmentsMetadataManager` and can use either one to get the
`DataSourcesSnapshot`
- Use config `druid.manager.segments.useCache` on Coordinator, same as
Overlord
### REST API Changes
- Update `markUsed` and `markUnused` APIs on the Coordinator to never update
the metadata store directly
### Classes to review
- `SqlSegmentsMetadataManagerV2`
- `SqlSegmentsMetadataManager`
- `IndexerSQLMetadataStorageCoordinator`
- `SqlSegmentsMetadataQuery`
### Required follow up work
- Use segment metadata cache even if schema caching is enabled on the
Coordinator
- Add docs for Overlord APIs to mark segments as used or unused
- Update web-console to use Overlord APIs
<hr>
This PR has:
- [ ] been self-reviewed.
- [ ] using the [concurrency
checklist](https://github.com/apache/druid/blob/master/dev/code-review/concurrency.md)
(Remove this item if the PR doesn't have any relation to concurrency.)
- [ ] added documentation for new or modified features or behaviors.
- [ ] a release note entry in the PR description.
- [ ] added Javadocs for most classes and all non-trivial methods. Linked
related entities via Javadoc links.
- [ ] added or updated version, license, or notice information in
[licenses.yaml](https://github.com/apache/druid/blob/master/dev/license.md)
- [ ] added comments explaining the "why" and the intent of the code
wherever would not be obvious for an unfamiliar reader.
- [ ] added unit tests or modified existing tests to cover new code paths,
ensuring the threshold for [code
coverage](https://github.com/apache/druid/blob/master/dev/code-review/code-coverage.md)
is met.
- [ ] added integration tests.
- [ ] been tested in a test Druid cluster.
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