[CELEBORN-2277] Replace synchronized in Flusher.getWorkerIndex with AtomicInteger#3621
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cxzl25 wants to merge 2 commits intoapache:mainfrom
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[CELEBORN-2277] Replace synchronized in Flusher.getWorkerIndex with AtomicInteger#3621cxzl25 wants to merge 2 commits intoapache:mainfrom
cxzl25 wants to merge 2 commits intoapache:mainfrom
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yew1eb
approved these changes
Mar 9, 2026
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@cxzl25, please update the description of pull request. |
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Pull request overview
This PR updates the worker-side storage Flusher to reduce lock contention by replacing a synchronized round-robin worker index increment with an AtomicInteger.updateAndGet CAS-based increment.
Changes:
- Replaced
nextWorkerIndexfrom a mutableIntguarded bysynchronizedto anAtomicInteger. - Updated
getWorkerIndexto compute the next index viaAtomicInteger.updateAndGet(...).
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worker/src/main/scala/org/apache/celeborn/service/deploy/worker/storage/Flusher.scala
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What changes were proposed in this pull request?
Replace the synchronized block in getWorkerIndex with an AtomicInteger.updateAndGet call using a CAS-based atomic operation.
Why are the changes needed?
The synchronized keyword locks the entire object and causes thread contention under high concurrency. Using AtomicInteger reduces lock scope to a single variable and avoids blocking overhead for this lightweight index increment operation.
Does this PR resolve a correctness bug?
No
Does this PR introduce any user-facing change?
No
How was this patch tested?
GHA