Use sync.Map and atomics for lastvalue aggregations by dashpole · Pull Request #7478 · open-telemetry/opentelemetry-go

dashpole · 2025-10-08T19:23:18Z

Depends on #7474

This applies similar optimizations as #7427 to the last value aggregation.

Changes for last value are contained in 27e1482.

Parallel benchmarks:

                                                                   │   main.txt   │               lv.txt               │
                                                                   │    sec/op    │   sec/op     vs base               │
SyncMeasure/NoView/ExemplarsDisabled/Int64Gauge/Attributes/10-24     264.60n ± 3%   66.46n ± 1%  -74.88% (p=0.002 n=6)
SyncMeasure/NoView/ExemplarsDisabled/Float64Gauge/Attributes/10-24   270.25n ± 4%   69.69n ± 1%  -74.21% (p=0.002 n=6)
geomean                                                               267.4n        68.05n       -74.55%

codecov · 2025-10-08T19:25:36Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.2%. Comparing base (19a5a68) to head (a97f113).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #7478   +/-   ##
=====================================
  Coverage   86.2%   86.2%           
=====================================
  Files        302     302           
  Lines      21971   21985   +14     
=====================================
+ Hits       18950   18963   +13     
- Misses      2640    2641    +1     
  Partials     381     381

Files with missing lines	Coverage Δ
sdk/metric/internal/aggregate/aggregate.go	`100.0% <100.0%> (ø)`
sdk/metric/internal/aggregate/lastvalue.go	`100.0% <100.0%> (ø)`

... and 2 files with indirect coverage changes

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dashpole · 2025-12-11T18:56:14Z

@MrAlias @dmathieu this is ready for review. It follows the same pattern as the previous sum and histogram PRs, but should be much simpler.

dashpole · 2025-12-16T14:22:02Z

@dmathieu I think this needed another approval prior to merging.

@MrAlias should I revert this to give you time to review?

dmathieu · 2025-12-16T14:46:14Z

Urgh sorry, I missed the lack of second approval.

MrAlias · 2025-12-16T15:29:20Z

I was about halfway though this. I can take another look and see.

MrAlias

Overall this looks good. Minor feedback on comments and the return value.

MrAlias · 2025-12-16T15:54:57Z

+) int {
 	// Ignore if dest is not a metricdata.Gauge. The chance for memory reuse of
-	// the DataPoints is missed (better luck next time).
+	// the lastValuePoints is missed (better luck next time).


Suggested change

// the lastValuePoints is missed (better luck next time).

// the DataPoints is missed (better luck next time).

This is still referring to the dest field.

MrAlias · 2025-12-16T15:58:08Z

+	s.hotColdValMap[readIdx].values.Clear()
 	*dest = gData
-
 	return n


Suggested change

return n

return i

If range for some reason does not iterate over n values, this will be incorrect.

MrAlias · 2025-12-16T16:01:00Z


-func newLastValue[N int64 | float64](limit int, r func(attribute.Set) FilteredExemplarReservoir[N]) *lastValue[N] {
-	return &lastValue[N]{
+// lastValue summarizes a set of measurements as the last one made.


Suggested change

// lastValue summarizes a set of measurements as the last one made.

// lastValueMap summarizes a set of measurements as the last one made.

dashpole · 2025-12-16T16:04:20Z

@MrAlias are you OK with a follow-up PR?

MrAlias · 2025-12-16T16:10:49Z

@MrAlias are you OK with a follow-up PR?

Yeah 👍

dashpole · 2025-12-16T16:48:37Z

#7718

Addresses #7478 (review), which was left after the PR merged.

Addresses open-telemetry#7478 (review), which was left after the PR merged.

### Added - Add `Enabled` method to all synchronous instrument interfaces (`Float64Counter`, `Float64UpDownCounter`, `Float64Histogram`, `Float64Gauge`, `Int64Counter`, `Int64UpDownCounter`, `Int64Histogram`, `Int64Gauge`,) in `go.opentelemetry.io/otel/metric`. This stabilizes the synchronous instrument enabled feature, allowing users to check if an instrument will process measurements before performing computationally expensive operations. (#7763) - Add `AlwaysRecord` sampler in `go.opentelemetry.io/otel/sdk/trace`. (#7724) - Add `go.opentelemetry.io/otel/semconv/v1.39.0` package. The package contains semantic conventions from the `v1.39.0` version of the OpenTelemetry Semantic Conventions. See the [migration documentation](https://github.com/open-telemetry/opentelemetry-go/blob/298cbedf256b7a9ab3c21e41fc5e3e6d6e4e94aa/semconv/v1.39.0/MIGRATION.md) for information on how to upgrade from `go.opentelemetry.io/otel/semconv/v1.38.0.` (#7783, #7789) ### Changed - `Exporter` in `go.opentelemetry.io/otel/exporter/prometheus` ignores metrics with the scope `go.opentelemetry.io/contrib/bridges/prometheus`. This prevents scrape failures when the Prometheus exporter is misconfigured to get data from the Prometheus bridge. (#7688) - Improve performance of concurrent histogram measurements in `go.opentelemetry.io/otel/sdk/metric`. (#7474) - Add experimental observability metrics in `go.opentelemetry.io/otel/exporters/stdout/stdoutmetric`. (#7492) - Improve the concurrent performance of `HistogramReservoir` in `go.opentelemetry.io/otel/sdk/metric/exemplar` by 4x. (#7443) - Improve performance of concurrent synchronous gauge measurements in `go.opentelemetry.io/otel/sdk/metric`. (#7478) - Improve performance of concurrent exponential histogram measurements in `go.opentelemetry.io/otel/sdk/metric`. (#7702) - Improve the concurrent performance of `FixedSizeReservoir` in `go.opentelemetry.io/otel/sdk/metric/exemplar`. (#7447) - The `rpc.grpc.status_code` attribute in the experimental metrics emitted from `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc` is replaced with the `rpc.response.status_code` attribute to align with the semantic conventions. (#7854) - The `rpc.grpc.status_code` attribute in the experimental metrics emitted from `go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc` is replaced with the `rpc.response.status_code` attribute to align with the semantic conventions. (#7854) ### Fixed - Fix bad log message when key-value pairs are dropped because of key duplication in `go.opentelemetry.io/otel/sdk/log`. (#7662) - Fix `DroppedAttributes` on `Record` in `go.opentelemetry.io/otel/sdk/log` to not count the non-attribute key-value pairs dropped because of key duplication. (#7662) - Fix `SetAttributes` on `Record` in `go.opentelemetry.io/otel/sdk/log` to not log that attributes are dropped when they are actually not dropped. (#7662) - `WithHostID` detector in `go.opentelemetry.io/otel/sdk/resource` to use full path for `ioreg` command on Darwin (macOS). (#7818) - Fix missing `request.GetBody` in `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp` to correctly handle HTTP2 GOAWAY frame. (#7794) ### Deprecated - Deprecate `go.opentelemetry.io/otel/exporters/zipkin`. For more information, see the [OTel blog post deprecating the Zipkin exporter](https://opentelemetry.io/blog/2025/deprecating-zipkin-exporters/). (#7670) --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

dashpole force-pushed the optimize_lastvalue branch from f6c58df to 27e1482 Compare October 8, 2025 19:23

MrAlias added this to the v1.39.0 milestone Oct 16, 2025

dashpole mentioned this pull request Oct 24, 2025

Improve concurrent performance of exponential histogram measurements #7535

Closed

dashpole mentioned this pull request Dec 1, 2025

Reconsider usage of generics in sdk/metric/internal/aggregate #7589

Open

MrAlias modified the milestones: v1.39.0, v1.40.0 Dec 4, 2025

dashpole force-pushed the optimize_lastvalue branch 4 times, most recently from 21ba34b to 1d5d6d3 Compare December 11, 2025 18:41

use sync Map and atomics for last value aggregation

081a206

dashpole force-pushed the optimize_lastvalue branch from 1d5d6d3 to 081a206 Compare December 11, 2025 18:48

dashpole marked this pull request as ready for review December 11, 2025 18:55

dashpole requested review from MrAlias, XSAM, dmathieu, flc1125 and pellared as code owners December 11, 2025 18:55

dmathieu approved these changes Dec 15, 2025

View reviewed changes

dmathieu and others added 2 commits December 15, 2025 12:06

Merge branch 'main' into optimize_lastvalue

a5b0006

Merge branch 'main' into optimize_lastvalue

a97f113

dmathieu merged commit 68d2f72 into open-telemetry:main Dec 16, 2025
33 checks passed

MrAlias reviewed Dec 16, 2025

View reviewed changes

dashpole added a commit to dashpole/opentelemetry-go that referenced this pull request Dec 16, 2025

address feedback from open-telemetry#7478

29b5678

dashpole mentioned this pull request Dec 16, 2025

address feedback from #7478 #7718

Merged

dashpole deleted the optimize_lastvalue branch December 16, 2025 16:48

dashpole added a commit that referenced this pull request Dec 16, 2025

address feedback from #7478 (#7718)

fa89e4c

Addresses #7478 (review), which was left after the PR merged.

dashpole added a commit to dashpole/opentelemetry-go that referenced this pull request Dec 17, 2025

address feedback from open-telemetry#7478 (open-telemetry#7718)

5a174fe

Addresses open-telemetry#7478 (review), which was left after the PR merged.

MrAlias mentioned this pull request Jan 16, 2026

Optimize the metric SDK #7796

Open

39 tasks

MrAlias mentioned this pull request Feb 2, 2026

Release v1.40.0 #7859

Merged

This was referenced Mar 3, 2026

Bump go.opentelemetry.io/otel/sdk from 1.37.0 to 1.40.0 in /flytectl flyteorg/flyte#6959

Open

Bump go.opentelemetry.io/otel/sdk from 1.35.0 to 1.40.0 in /flytecopilot flyteorg/flyte#6960

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Use sync.Map and atomics for lastvalue aggregations#7478

Use sync.Map and atomics for lastvalue aggregations#7478
dmathieu merged 3 commits intoopen-telemetry:mainfrom
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	// the lastValuePoints is missed (better luck next time).
	// the DataPoints is missed (better luck next time).

	// lastValue summarizes a set of measurements as the last one made.
	// lastValueMap summarizes a set of measurements as the last one made.

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