danprince1 opened a new pull request #12013:
URL: https://github.com/apache/druid/pull/12013
Fixes #10606.
(This is a rework of previous PR #10699, which was closed without merging)
### Description
Please reference the proposal for detailed information. I will provide a
summary here:
I am proposing an optional new DutiesRunnable in the DruidCoordinator.
Operators can choose whether or not to break primary replicant loading out into
its own DutiesRunnable. If they choose not to enable the dedicated primary
replicant loading, their coordinator will function just as it always has. If
they choose to enable the dedicated primary replicant loading, their
coordinator will add a scheduled DutiesRunnable dedicated to executing matching
LoadRule for segments and only doing the primary replicant load for that
LoadRule when run. The HistoricalManagement DutiesRunnable will continue all
other HistoricalManagement duties including performing non-primary replicant
loading and replicant dropping while executing a matched LoadRule for a segment.
My implementation for the proposal exposes two new Coordinator runtime
configurations for operators:
`druid.coordinator.loadPrimaryReplicantSeparately` and
`druid.coordinator.period.primaryReplicantLoaderPeriod`. If they choose to
enable the first, then a scheduled executor with a configurable backoff period
is configured for loading primary replicants.
Importantly, this PR also **introduces concurrency to the Coordinator**, via
the configuration `druid.coordinator.dutiesRunnableExecutor.threadPoolSize`.
This thread poll was previously hard-coded to contain only 1 thread.
I am marking this with Design Review label because the proposal never got
the traction I wanted to confirm the design. Thus, this will require 2 +1's
from committers before merge.
<hr>
##### Key changed/added classes in this PR
* `DruidCoordinator`
* `LoadRule`
<hr>
This PR has:
- [x] been self-reviewed.
- [x] 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.)
- [x] added documentation for new or modified features or behaviors.
- [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](https://github.com/apache/druid/blob/master/dev/license.md)
- [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](https://github.com/apache/druid/blob/master/dev/code-review/code-coverage.md)
is met.
- [ ] added integration tests.
- [x] been tested in a test Druid cluster.
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