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Robert Pająk
4ef740f17f
Fixes https://github.com/open-telemetry/opentelemetry-go/issues/7957. - Remove duplicate keys from `attribute.MAP` values by default across SDK resource, log, trace, and metric export paths, including top-level MAP-valued attributes and MAP values nested inside MAP or SLICE values. - Update `log.WithAllowKeyDuplication()` behavior and docs. - Always deduplicate MAP values in resources; `go.opentelemetry.io/otel/sdk/resource` does not provide an opt-out. Resources are typically evaluated once at startup or occasionally updated. The ~12.90% overhead shown in benchmarks will have low impact on an application's runtime latency, and having a strictly normalized Resource map prevents downstream exporter issues. - Preserve top-level `attribute.Set` behavior for resources, scopes, and metric datapoint attributes; this change normalizes MAP-valued attribute values, not the outer attribute collection semantics. - Use last-value-wins semantics and do not increment dropped-attribute counts for MAP duplicate removal. - Keep internal helper code scoped per module: shared source lives in `internal/shared/attrdedup`, then `gotmpl` renders module-local copies under `sdk/internal`, `sdk/log/internal`, and `sdk/metric/internal`. ## Benchmarks Baseline benchmarks were run from a local `main` worktree at `/tmp/opentelemetry-go-main`; branch benchmarks were run from this branch. All comparisons use `-benchmem -count=10`. New helper benchmarks: ```console goos: linux goarch: amd64 pkg: go.opentelemetry.io/otel/sdk/internal/attrdedup cpu: 13th Gen Intel(R) Core(TM) i7-13800H │ this.txt │ │ sec/op │ Value/FastPath-20 186.4n ± 19% Value/DuplicateMap-20 363.4n ± 82% Value/NestedMapInSlice-20 607.4n ± 20% geomean 345.2n │ this.txt │ │ B/op │ Value/FastPath-20 0.000 ± 0% Value/DuplicateMap-20 320.0 ± 0% Value/NestedMapInSlice-20 416.0 ± 0% geomean ¹ ¹ summaries must be >0 to compute geomean │ this.txt │ │ allocs/op │ Value/FastPath-20 0.000 ± 0% Value/DuplicateMap-20 2.000 ± 0% Value/NestedMapInSlice-20 4.000 ± 0% geomean ¹ ¹ summaries must be >0 to compute geomean ``` ```console pkg: go.opentelemetry.io/otel/sdk/resource │ main │ branch │ │ sec/op │ sec/op vs base │ MergeResource_1-20 587.9n ± 28% 677.7n ± 17% +15.28% (p=0.043 n=10) MergeResource_2-20 938.5n ± 11% 1011.8n ± 18% ~ (p=0.393 n=10) MergeResource_3-20 1.301µ ± 8% 1.522µ ± 21% +16.95% (p=0.023 n=10) MergeResource_4-20 1.487µ ± 31% 2.006µ ± 12% +34.90% (p=0.000 n=10) MergeResource_6-20 2.409µ ± 12% 2.962µ ± 15% +22.96% (p=0.001 n=10) MergeResource_8-20 3.336µ ± 10% 3.104µ ± 16% ~ (p=0.247 n=10) MergeResource_16-20 7.750µ ± 6% 8.076µ ± 9% ~ (p=0.190 n=10) geomean 1.821µ 2.056µ +12.90% pkg: go.opentelemetry.io/otel/sdk/trace │ main │ branch │ │ sec/op │ sec/op vs base │ RecordingSpanSetAttributes/WithLimit/false-20 7.907µ ± 6% 11.311µ ± 6% +43.06% (p=0.000 n=10) RecordingSpanSetAttributes/WithLimit/true-20 13.29µ ± 15% 17.13µ ± 6% +28.97% (p=0.002 n=10) TraceStart/with_a_simple_span-20 402.1n ± 2% 406.4n ± 2% ~ (p=0.218 n=10) TraceStart/with_several_links-20 521.8n ± 1% 532.4n ± 2% +2.03% (p=0.000 n=10) TraceStart/with_attributes-20 570.5n ± 2% 594.1n ± 2% +4.12% (p=0.000 n=10) TraceStart/ObservabilityEnabled-20 463.5n ± 1% 469.9n ± 1% +1.38% (p=0.003 n=10) SpanSetAttributesOverCapacity-20 2.539µ ± 8% 2.501µ ± 8% ~ (p=0.684 n=10) SpanWithAttributes_4/AlwaysSample-20 1.650µ ± 23% 1.867µ ± 12% ~ (p=0.063 n=10) SpanWithAttributes_4/NeverSample-20 634.5n ± 11% 683.4n ± 19% ~ (p=0.315 n=10) geomean 1.356µ 1.495µ +10.27% ``` Resource and trace allocation counts were unchanged in the same benchstat run. ```console pkg: go.opentelemetry.io/otel/sdk/log │ main │ branch │ │ sec/op │ sec/op vs base │ LoggerProviderLogger-20 505.1n ± 8% 473.9n ± 15% ~ (p=0.123 n=10) SetAttributes/Unique/NoLimits-20 230.9n ± 9% 238.1n ± 7% ~ (p=0.343 n=10) SetAttributes/NestedDeduplication/Enabled-20 836.0n ± 6% 758.1n ± 8% -9.32% (p=0.011 n=10) SetAttributes/NestedDeduplication/Disabled-20 119.7n ± 1% 127.7n ± 8% ~ (p=0.157 n=10) geomean 328.7n 323.3n -1.65% ``` Log allocation counts were unchanged in the same benchstat run. ```console pkg: go.opentelemetry.io/otel/sdk/metric │ main │ branch │ │ sec/op │ sec/op vs base │ MeasureNewAttributeSet/AlwaysOn/Int64Counter-20 725.7n ± 114% 1504.5n ± 15% +107.32% (p=0.043 n=10) MeasureNewAttributeSet/AlwaysOn/Float64Counter-20 1.106µ ± 14% 1.480µ ± 15% +33.82% (p=0.000 n=10) MeasureNewAttributeSet/AlwaysOn/Int64UpDownCounter-20 1.354µ ± 9% 1.334µ ± 13% ~ (p=0.529 n=10) MeasureNewAttributeSet/AlwaysOn/Float64UpDownCounter-20 1.445µ ± 29% 1.439µ ± 14% ~ (p=0.542 n=10) MeasureNewAttributeSet/AlwaysOn/Int64Histogram-20 1.423µ ± 31% 1.453µ ± 29% ~ (p=0.631 n=10) MeasureNewAttributeSet/AlwaysOn/Float64Histogram-20 1.383µ ± 41% 1.416µ ± 20% ~ (p=0.796 n=10) MeasureNewAttributeSet/AlwaysOn/Int64Gauge-20 1.105µ ± 42% 1.527µ ± 8% +38.21% (p=0.023 n=10) MeasureNewAttributeSet/AlwaysOn/Float64Gauge-20 1.598µ ± 10% 1.355µ ± 37% ~ (p=0.247 n=10) MeasureNewAttributeSet/AlwaysOff/Int64Counter-20 739.1n ± 16% 830.0n ± 17% ~ (p=0.280 n=10) MeasureNewAttributeSet/AlwaysOff/Float64Counter-20 299.2n ± 24% 766.7n ± 29% +156.19% (p=0.000 n=10) MeasureNewAttributeSet/AlwaysOff/Int64UpDownCounter-20 322.2n ± 104% 873.2n ± 7% +171.01% (p=0.000 n=10) MeasureNewAttributeSet/AlwaysOff/Float64UpDownCounter-20 740.5n ± 49% 713.8n ± 21% ~ (p=0.481 n=10) MeasureNewAttributeSet/AlwaysOff/Int64Histogram-20 901.1n ± 33% 988.8n ± 12% ~ (p=0.481 n=10) MeasureNewAttributeSet/AlwaysOff/Float64Histogram-20 1.059µ ± 23% 1.009µ ± 21% ~ (p=0.393 n=10) MeasureNewAttributeSet/AlwaysOff/Int64Gauge-20 408.9n ± 50% 788.0n ± 23% +92.71% (p=0.000 n=10) MeasureNewAttributeSet/AlwaysOff/Float64Gauge-20 544.5n ± 37% 662.1n ± 39% ~ (p=0.725 n=10) AsyncMeasureNewAttributeSet/AlwaysOn-20 6.199µ ± 20% 5.766µ ± 26% ~ (p=0.247 n=10) AsyncMeasureNewAttributeSet/TraceBased-20 1.811µ ± 10% 1.806µ ± 11% ~ (p=0.912 n=10) Instrument/instrumentImpl/aggregate-20 2.577µ ± 10% 2.378µ ± 14% ~ (p=0.247 n=10) Instrument/observable/observe-20 1.863µ ± 17% 1.762µ ± 8% ~ (p=0.255 n=10) InstrumentCreation-20 2.346µ ± 17% 2.215µ ± 8% ~ (p=0.315 n=10) geomean 1.102µ 1.324µ +20.12% ``` Metric B/op geomean was +0.10% and allocs/op geomean was unchanged in the same benchstat run. ## Rejected implementations ### Seen-Pool I tested an alternative `deduplicateMapValue` implementation using a pooled `map[string]struct{}` for duplicate detection, modeled after `sdk/log.Record`'s `seenPool`. The candidate was not kept because it regressed all non-opt-out helper benchmark paths. ```console pkg: go.opentelemetry.io/otel/sdk/internal/attrdedup │ baseline │ seenpool │ │ sec/op │ sec/op vs base │ Value/FastPath-20 143.8n ± 0% 201.6n ± 0% +40.15% (p=0.000 n=20) Value/DuplicateMap-20 669.8n ± 9% 862.9n ± 12% +28.83% (p=0.000 n=20) Value/NestedMapInSlice-20 918.2n ± 9% 1115.0n ± 5% +21.43% (p=0.000 n=20) Value/AllowKeyDuplication-20 1.324n ± 0% 1.324n ± 0% ~ (p=0.389 n=20) geomean 104.0n 126.6n +21.68% ``` The candidate did not change allocation counts, but the `sync.Pool` and map operations added measurable CPU overhead. ### Needs-Style Preflight I tested an alternative implementation modeled after `sdk/log.Record.needsValueLimitsOrDedup`: first scan attribute values to determine whether normalization is needed, then normalize only when the scan says a value would change. The refined candidate preserved the opt-out fast path and avoided an extra slice preflight pass, but was not kept because package-level benchmark results were mixed: resource improved, but trace and metric regressed. ```console pkg: go.opentelemetry.io/otel/sdk/internal/attrdedup │ baseline │ candidate │ │ sec/op │ sec/op vs base │ Value/FastPath-20 144.10n ± 0% 92.52n ± 0% -35.79% (p=0.000 n=10) Value/DuplicateMap-20 682.8n ± 19% 677.1n ± 34% ~ (p=0.796 n=10) Value/NestedMapInSlice-20 900.5n ± 7% 975.5n ± 8% +8.33% (p=0.019 n=10) Value/AllowKeyDuplication-20 1.325n ± 0% 1.325n ± 1% ~ (p=0.860 n=10) geomean 104.1n 94.85n -8.88% ``` ```console pkg: go.opentelemetry.io/otel/sdk/resource MergeResource geomean: 2.209µ -> 1.896µ (-14.17%) pkg: go.opentelemetry.io/otel/sdk/trace Trace benchmark geomean: 1.474µ -> 1.576µ (+6.90%) ``` ```console pkg: go.opentelemetry.io/otel/sdk/log Log benchmark geomean: 330.0n -> 330.6n (+0.18%) ``` ```console pkg: go.opentelemetry.io/otel/sdk/metric Metric benchmark geomean: 1.355µ -> 1.455µ (+7.38%) ``` All candidate allocation geomeans were unchanged. Because the candidate did not improve performance consistently across affected export paths, this PR keeps the original lazy allocation-free no-op implementation.
OpenTelemetry-Go
OpenTelemetry-Go is the Go implementation of OpenTelemetry. It provides a set of APIs to directly measure performance and behavior of your software and send this data to observability platforms.
Project Status
| Signal | Status |
|---|---|
| Traces | Stable |
| Metrics | Stable |
| Logs | Beta1 |
Progress and status specific to this repository is tracked in our project boards and milestones.
Project versioning information and stability guarantees can be found in the versioning documentation.
Compatibility
OpenTelemetry-Go ensures compatibility with the current supported versions of the Go language:
Each major Go release is supported until there are two newer major releases. For example, Go 1.5 was supported until the Go 1.7 release, and Go 1.6 was supported until the Go 1.8 release.
For versions of Go that are no longer supported upstream, opentelemetry-go will stop ensuring compatibility with these versions in the following manner:
- A minor release of opentelemetry-go will be made to add support for the new supported release of Go.
- The following minor release of opentelemetry-go will remove compatibility testing for the oldest (now archived upstream) version of Go. This, and future, releases of opentelemetry-go may include features only supported by the currently supported versions of Go.
Currently, this project supports the following environments.
| OS | Go Version | Architecture |
|---|---|---|
| Ubuntu | 1.26 | amd64 |
| Ubuntu | 1.25 | amd64 |
| Ubuntu | 1.26 | 386 |
| Ubuntu | 1.25 | 386 |
| Ubuntu | 1.26 | arm64 |
| Ubuntu | 1.25 | arm64 |
| macOS | 1.26 | amd64 |
| macOS | 1.25 | amd64 |
| macOS | 1.26 | arm64 |
| macOS | 1.25 | arm64 |
| Windows | 1.26 | amd64 |
| Windows | 1.25 | amd64 |
| Windows | 1.26 | 386 |
| Windows | 1.25 | 386 |
While this project should work for other systems, no compatibility guarantees are made for those systems currently.
Getting Started
You can find a getting started guide on opentelemetry.io.
OpenTelemetry's goal is to provide a single set of APIs to capture distributed traces and metrics from your application and send them to an observability platform. This project allows you to do just that for applications written in Go. There are two steps to this process: instrument your application, and configure an exporter.
Instrumentation
To start capturing distributed traces and metric events from your application it first needs to be instrumented. The easiest way to do this is by using an instrumentation library for your code. Be sure to check out the officially supported instrumentation libraries.
If you need to extend the telemetry an instrumentation library provides or want to build your own instrumentation for your application directly you will need to use the Go otel package. The examples are a good way to see some practical uses of this process.
Export
Now that your application is instrumented to collect telemetry, it needs an export pipeline to send that telemetry to an observability platform.
All officially supported exporters for the OpenTelemetry project are contained in the exporters directory.
| Exporter | Logs | Metrics | Traces |
|---|---|---|---|
| OTLP | ✓ | ✓ | ✓ |
| Prometheus | ✓ | ||
| stdout | ✓ | ✓ | ✓ |
| Zipkin | ✓ |
Contributing
See the contributing documentation.