metric: improve accuracy of timer metric under contention #18219
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excludes contention for recording timing from the timing by locking in the completion time before attempting to record it
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This pull request does not have a backport label. Could you fix it @yaauie? 🙏
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yaauie
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Sep 25, 2025
| public <T, E extends Throwable> T time(ExceptionalSupplier<T, E> exceptionalSupplier) throws E { | ||
| try { | ||
| trackedMillisState.getAndUpdate(TrackedMillisState::withIncrementedConcurrency); | ||
| trackedMillisState.getAndUpdate(existing -> existing.withIncrementedConcurrency(nanoTimeSupplier.getAsLong())); |
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Note: the nanoTimeSupplier.getAsLong() for recording the start time still occurs inside the UnaryConsumer because if this thread loses and is retried, we don't want to record an old start time.
robbavey
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Sep 26, 2025
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Other than the unused imports, LGTM
...tash-core/src/main/java/org/logstash/instrument/metrics/timer/ConcurrentLiveTimerMetric.java
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...tash-core/src/main/java/org/logstash/instrument/metrics/timer/ConcurrentLiveTimerMetric.java
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yaauie
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Sep 26, 2025
...tash-core/src/main/java/org/logstash/instrument/metrics/timer/ConcurrentLiveTimerMetric.java
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...tash-core/src/main/java/org/logstash/instrument/metrics/timer/ConcurrentLiveTimerMetric.java
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* metric: improve accuracy of timer metric excludes contention for recording timing from the timing by locking in the completion time before attempting to record it * remove unused imports
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Release notes
[rn: skip]
What does this PR do?
Improves the accuracy of
ConcurrentLiveTimerMetricin cases where many threads are contending to record their timings.When using
AtomicReference#getAndUpdate(UnaryOperator), the provided operator may be run multiple times in cases where another thread has "won" the update. By moving the capture of the timestamp out of this block, we ensure an accurate recording for the completion time of the measurement and prevent it from including the time contending to write the measurement.Why is it important/What is the impact to the user?
No major user impact, but slightly improves the accuracy of timer-type metrics.
Checklist
[ ] I have made corresponding changes to the documentation[ ] I have made corresponding change to the default configuration files (and/or docker env variables)[ ] I have added tests that prove my fix is effective or that my feature worksAuthor's Checklist
How to test this PR locally
Verification relies on the existing test coverage for
ConcurrentLiveTimerMetric, along with an understanding of what bringing the call toLongSupplier#getAsLongout of block means when the block needs to be re-run.