aho135 opened a new pull request, #19191:
URL: https://github.com/apache/druid/pull/19191

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   This PR is still a WIP. I will be adding additional test coverage for this
   For the initial implementation I've only done Kafka. I plan to implement 
Kinesis and Rabbit in subsequent PR's, followed by documentation for the new 
feature.
   
   This change introduces a new parameter called `backfill` to the 
SupervisorResource reset endpoint. If left unset the current reset behavior 
remains unchanged. When set to true, after the reset is performed, new 
ingestion tasks will be spun up to consume the skipped data. This is a useful 
feature for operating Druid clusters where the most recent data is the most 
important (such as alerting use cases). 
   
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   ### Description
   
   Adds a parameter called `backfill` to the Supervisor reset endpoint to 
automatically ingest skipped data in the case where the offset is reset to 
latest. This requires useEarliestOffset=false, useConcurrentLocks=true because 
there can be conflicting time intervals between the backfill task and the main 
supervisor tasks, useTransaction=false in order to disable metadata updates, 
and the Supervisor needs to be in a running state in order to call 
`updatePartitionLagFromStream()` to get the latest offsets
   
   In addition, this change supports unsupervised SeekableStreamIndexTasks by 
setting `supervised: false` in the SeekableStreamIndexTaskIOConfig. The 
backfill tasks are one-off task submissions so this new flag disables any 
checkpointing (refer to changes in SeekableStreamIndexTaskRunner)
   
   The number of backfill tasks can be controlled through `backfillTaskCount` 
in the Supervisor spec, and defaults to taskCount / 2
   
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   #### Release note
   Adds an optional parameter to the Supervisor reset endpoint to backfill the 
skipped data when the stream is reset to latest
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   <hr>
   
   ##### Key changed/added classes in this PR
    * `SupervisorResource`
    * `SupervisorManager`
    * `SeekableStreamSupervisor`
    * `KafkaSupervisor`
   <hr>
   
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   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.)
   - [ ] added documentation for new or modified features or behaviors. [I plan 
to add documentation for this feature in a follow-up after Rabbit/Kinesis are 
implemented]
   - [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.
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   - [ ] added integration tests.
   - [X] been tested in a test Druid cluster.


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