kfaraz opened a new pull request, #18098:
URL: https://github.com/apache/druid/pull/18098
### Description
Follow up to #17390
Once we start maintaining a `TaskLockbox` for each datasource, the
single-threaded design of the `SegmentAllocationQueue` would become the
bottleneck.
This patch makes `SegmentAllocationQueue` multithreaded so that allocation
for multiple datasources
can happen in parallel.
### Changes
- Add config `druid.indexer.tasklock.batchAllocationNumThreads` with default
value 5
- Compute the number of worker threads in `SegmentAllocationQueue` that
perform segment allocation
- Add a manager thread which polls the allocation queue and submits jobs to
workers
- Emit metric `task/action/batch/submitted` for the count of submitted jobs
### Future improvements
A future improvement could be to skip a job if another job for the same
datasource is already running on a worker.
### Release note
Add config `druid.indexer.tasklock.batchAllocationNumThreads` with default
value 5 to control the number of
segment allocation threads. This allows for concurrent segment allocations
if there are segment allocations
happening for several different datasources.
Note that setting this config to a very large value will put undue strain on
the metadata store and only hamper performance.
<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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