fix: prevent lost iterations in CircularKey concurrent worker race#49
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Pull request overview
This PR addresses a concurrency race when multiple workers share a single DocumentGenerator using CircularKey, ensuring only one worker performs the end-of-pass iteration check and counter reset.
Changes:
- Added double-checked locking (
synchronized (this.keys)) around end-of-pass handling inhas_next_read(),has_next_update(), andhas_next_expiry(). - Ensured these methods return
trueimmediately after a successful iteration rollover + reset, preserving progress across passes.
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| if (this.ws.dr.expiryItr.get() < this.ws.dr.expiry_e) | ||
| return true; | ||
| try { | ||
| if ((boolean)this.iterationsMethod.invoke(this.keys, null)) { |
| return true; | ||
| try { | ||
| if ((boolean)this.iterationsMethod.invoke(this.keys)) { | ||
| this.resetRead(); |
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| if ((boolean)this.iterationsMethod.invoke(this.keys)) { | ||
| this.resetUpdate(); | ||
| this.ws.mutated += 1; | ||
| return true; |
Two workers sharing a DocumentGenerator could both detect end-of-pass (updateItr >= update_e) before either called resetUpdate(), causing double-decrements of the plain-int iterations counter in CircularKey. Each race event silently dropped one full pass, producing fewer total mutations than expected (observed: 54204 vs 60000 ep_dcp_items_sent in CDC history retention tests). Add double-checked locking (synchronized on this.keys) in has_next_read(), has_next_update(), and has_next_expiry() so only one worker triggers checkIterations() + reset per pass-end event. The fast unsynchronized path is preserved for normal in-pass execution, keeping full worker concurrency for deduplication-sensitive tests.
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| synchronized (this.keys) { | ||
| if (this.ws.dr.updateItr.get() < this.ws.dr.update_e) | ||
| return true; | ||
| if (this.keyInstance.getSimpleName().equals(CircularKey.class.getSimpleName())) { | ||
| try { | ||
| if ((boolean)this.iterationsMethod.invoke(this.keys)) { | ||
| this.resetUpdate(); | ||
| this.ws.mutated += 1; | ||
| return true; | ||
| } | ||
| } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e1) { | ||
| e1.printStackTrace(); | ||
| } | ||
| } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e1) { | ||
| e1.printStackTrace(); | ||
| } | ||
| } | ||
| if (TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis())-startTime<ws.mutation_timeout) { | ||
| this.resetUpdate(); | ||
| this.ws.mutated += 1; | ||
| return true; | ||
| if (TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis())-startTime<ws.mutation_timeout) { | ||
| this.resetUpdate(); | ||
| this.ws.mutated += 1; | ||
| return true; | ||
| } | ||
| } |
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Two workers sharing a DocumentGenerator could both detect end-of-pass (updateItr >= update_e) before either called resetUpdate(), causing double-decrements of the plain-int iterations counter in CircularKey.
Each race event silently dropped one full pass, producing fewer total mutations than expected (observed: 54204 vs 60000 ep_dcp_items_sent in CDC history retention tests).
Add double-checked locking (synchronized on this.keys) in has_next_read(), has_next_update(), and has_next_expiry() so only one worker triggers checkIterations() + reset per pass-end event.
The fast unsynchronized path is preserved for normal in-pass execution, keeping full worker concurrency for deduplication-sensitive tests.