[Java] Dataflow runner v1 - Propagate drain mode

[stankiewicz]

First part: #36524

Adds:

• drainMode to Work
• bubbles up drainMode up to creation of TimerData
• decodes drainMode to WindowedValue

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[gemini-code-assist]

Summary of Changes

Hello @stankiewicz, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request implements the propagation of a 'drain mode' flag throughout the Apache Beam Dataflow runner's Java worker. This enhancement allows the system to accurately track and react to a job's draining state, which is vital for managing resources and ensuring data integrity during graceful shutdowns. The changes involve updates to the core protocol buffer definitions, modifications to key worker components that handle work items and timers, and extensions to the WindowedValue data structure to carry this new state information.

Highlights

• Protocol Buffer Update: Introduced a new DrainMode enum within beam_fn_api.proto and added an optional drain field to ElementMetadata to explicitly track the draining state of a Dataflow job.
• Drain Mode Propagation: The drainMode boolean flag is now consistently propagated through critical worker components, including Work items, StreamingModeExecutionContext, and WindmillKeyedWorkItem, ensuring its availability across the processing pipeline.
• WindowedValue Enhancements: The WindowedValue interface and its various implementations (e.g., WindowedValues, OutputBuilder) have been updated to include an isDraining() method and an internal draining field, allowing WindowedValue instances to carry the draining status.
• Serialization/Deserialization of Drain Mode: The WindowedValueCoder has been modified to correctly encode and decode the drainMode as part of the ElementMetadata, ensuring that this crucial state is preserved during data transfer.
• Timer Data Integration: The creation of TimerData via WindmillTimerInternals.windmillTimerToTimerData now accepts the drainMode parameter, enabling timers to be aware of the job's draining status.

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[github-actions]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.91%. Comparing base (50f578a) to head (54c52fd).
⚠️ Report is 14 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #36534      +/-   ##
============================================
+ Coverage     55.08%   56.91%   +1.83%     
- Complexity     1667     3395    +1728     
============================================
  Files          1059     1221     +162     
  Lines        165366   186546   +21180     
  Branches       1195     3544    +2349     
============================================
+ Hits          91091   106180   +15089     
- Misses        72104    76997    +4893     
- Partials       2171     3369    +1198     

Flag	Coverage Δ
java	70.33% <ø> (+2.14%)	⬆️

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[stankiewicz]

/gemini review

[gemini-code-assist]

Code Review

This pull request propagates the drainMode flag through various layers of the Dataflow runner, from work item reception down to the creation of TimerData and WindowedValue. The changes are mostly plumbing the new parameter through method calls and constructors.

My review has identified a high-severity issue where the drainMode is not actually applied when creating TimerData, and a couple of areas with duplicated and unnecessarily complex logic for decoding the drain mode. Addressing these points will ensure the feature is correctly implemented and improve code maintainability.

[github-actions]

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R: @kennknowles added as fallback since no labels match configuration

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[stankiewicz]

R: @arunpandianp

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Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control. If you'd like to restart, comment assign set of reviewers

[stankiewicz]

R: @kennknowles can you do first pass?

[kennknowles]

Any new tests for this? I guess it could be somewhat tricky to test or perhaps we have them run internally?

[stankiewicz]

Run Java PreCommit