Async Post Load Test Fixes

[dustin12]

Fixes two problems found in async during load testing:

1. We should not do any blocking operations under a lock in commit_finished_items. Add items outside the lock.
2. Timers should be skewed so they don't all fire at once.

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[gemini-code-assist]

Summary of Changes

Hello @dustin12, 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 addresses critical performance and stability issues identified during load testing of asynchronous processing within the system. The primary focus is on optimizing resource utilization and preventing contention by ensuring that blocking operations do not occur under locks and by distributing the load of timer-triggered events. These changes collectively aim to enhance the robustness and efficiency of the asynchronous DoFn, particularly under high-load scenarios.

Highlights

• Non-blocking operations under lock: Refactored the commit_finished_items method to ensure that potentially blocking schedule_item calls are performed outside of critical sections protected by locks, improving concurrency and preventing deadlocks or performance bottlenecks.
• Timer Skewing: Implemented a mechanism to introduce randomness into timer firing times, preventing all timers from triggering simultaneously. This 'skewing' helps distribute load and avoid 'thundering herd' issues during peak activity.
• Improved State Coder: Updated the TO_PROCESS state specification to use FastPrimitivesCoder instead of StrUtf8Coder, allowing for more flexible and efficient serialization of primitive types.
• Reduced Scheduling Sleep Time: Decreased the sleep duration in the schedule_item method from 1 second to 0.01 seconds, making the item scheduling process more responsive and reducing perceived latency.
• Configurable Timer Frequency: Made the _timer_frequency parameter configurable during the initialization of AsyncWrapper, allowing for more dynamic control over timer behavior.

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[github-actions]

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[codecov]

Codecov Report

❌ Patch coverage is 14.28571% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 40.21%. Comparing base (db92a3a) to head (4192812).
⚠️ Report is 13 commits behind head on master.

Files with missing lines	Patch %	Lines
sdks/python/apache_beam/transforms/async_dofn.py	14.28%	12 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             master   #36596       +/-   ##
=============================================
- Coverage     56.93%   40.21%   -16.72%     
  Complexity     3394     3394               
=============================================
  Files          1222     1222               
  Lines        186787   186915      +128     
  Branches       3545     3545               
=============================================
- Hits         106348    75174    -31174     
- Misses        77067   108369    +31302     
  Partials       3372     3372               

Flag	Coverage Δ
python	40.51% <14.28%> (-40.50%)	⬇️

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[github-actions]

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R: @jrmccluskey for label python.

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[dustin12]

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