prometheus: validate exponential histogram scale range (#6779) by highlyavailable · Pull Request #6822 · open-telemetry/opentelemetry-go

highlyavailable · 2025-05-24T17:39:00Z

Fixes #6779

Changes

Added scale validation for Prometheus exponential histograms in addExponentialHistogramMetric
Rejects scales below -4 (logs error and skips data point)
Clamps scales above 8 down to 8 (logs warning)
Prometheus native histograms support scales in range [-4, 8]

Testing

All existing tests pass
Added TestExponentialHistogramScaleValidation to verify error handling doesn't break normal operation

MrAlias · 2025-05-26T14:38:56Z

cc @dashpole

codecov · 2025-05-30T03:24:20Z

Codecov Report

Attention: Patch coverage is 90.32258% with 6 lines in your changes missing coverage. Please review.

Project coverage is 82.3%. Comparing base (f2058fa) to head (76a9ca2).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
exporters/prometheus/exporter.go	90.3%	5 Missing and 1 partial ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #6822   +/-   ##
=====================================
  Coverage   82.3%   82.3%           
=====================================
  Files        263     263           
  Lines      24420   24476   +56     
=====================================
+ Hits       20101   20151   +50     
- Misses      3937    3942    +5     
- Partials     382     383    +1

Files with missing lines	Coverage Δ
exporters/prometheus/exporter.go	`82.3% <90.3%> (+1.5%)`	⬆️

... and 3 files with indirect coverage changes

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Fixes open-telemetry#6779 Add scale validation for Prometheus exponential histograms to ensure compatibility with Prometheus native histogram format. Changes: - Validate scale is within Prometheus supported range [-4, 8] - Reject scales below -4 (log error and skip data point) - Downscale histograms with scale > 8 by re-aggregating buckets - Add comprehensive test coverage for scale validation and downscaling - Implement downscaling logic based on OpenTelemetry Collector Contrib The downscaling implementation merges buckets using bit-shifting to maintain accuracy while conforming to Prometheus limitations.

highlyavailable · 2025-05-30T13:23:48Z

Hey @MrAlias, I updated my PR based on your feedback. Now there is only 1 new commit, and its passing test cases. Let me know if there are any issues with the change, and thanks for the initial feedback

Removed unnecessary logic for trimming leading and trailing zeros in the downscaleExponentialBucket function.

…alidation-clean

highlyavailable · 2025-06-13T18:51:22Z

It looks like one of the ci compatibility checks is now failing,

ci / compatibility-test (1.23.0, macos-13, amd64) (pull_request) Failing after 1m

Would it be possible to rerun and see if the test fails? Additionally, it looks like the markdown lint check is failing on the CHANGELOG.md format, is this fine?

CHANGELOG.md:46 MD024/no-duplicate-heading/no-duplicate-header Multiple headings with the same content [Context: "### Fixed"]

dashpole · 2025-06-13T18:55:18Z

Fixed your changelog

dashpole · 2025-06-13T19:00:12Z

@open-telemetry/go-approvers This is needs one more review, and then is ready to go

…alidation-clean

### Added - The `go.opentelemetry.io/otel/semconv/v1.33.0` package. The package contains semantic conventions from the `v1.33.0` version of the OpenTelemetry Semantic Conventions. See the [migration documentation](./semconv/v1.33.0/MIGRATION.md) for information on how to upgrade from `go.opentelemetry.io/otel/semconv/v1.32.0.`(#6799) - The `go.opentelemetry.io/otel/semconv/v1.34.0` package. The package contains semantic conventions from the `v1.34.0` version of the OpenTelemetry Semantic Conventions. (#6812) - Add metric's schema URL as `otel_scope_schema_url` label in `go.opentelemetry.io/otel/exporters/prometheus`. (#5947) - Add metric's scope attributes as `otel_scope_[attribute]` labels in `go.opentelemetry.io/otel/exporters/prometheus`. (#5947) - Add `EventName` to `EnabledParameters` in `go.opentelemetry.io/otel/log`. (#6825) - Add `EventName` to `EnabledParameters` in `go.opentelemetry.io/otel/sdk/log`. (#6825) - Changed handling of `go.opentelemetry.io/otel/exporters/prometheus` metric renaming to add unit suffixes when it doesn't match one of the pre-defined values in the unit suffix map. (#6839) ### Changed - The semantic conventions have been upgraded from `v1.26.0` to `v1.34.0` in `go.opentelemetry.io/otel/bridge/opentracing`. (#6827) - The semantic conventions have been upgraded from `v1.26.0` to `v1.34.0` in `go.opentelemetry.io/otel/exporters/zipkin`. (#6829) - The semantic conventions have been upgraded from `v1.26.0` to `v1.34.0` in `go.opentelemetry.io/otel/metric`. (#6832) - The semantic conventions have been upgraded from `v1.26.0` to `v1.34.0` in `go.opentelemetry.io/otel/sdk/resource`. (#6834) - The semantic conventions have been upgraded from `v1.26.0` to `v1.34.0` in `go.opentelemetry.io/otel/sdk/trace`. (#6835) - The semantic conventions have been upgraded from `v1.26.0` to `v1.34.0` in `go.opentelemetry.io/otel/trace`. (#6836) - `Record.Resource` now returns `*resource.Resource` instead of `resource.Resource` in `go.opentelemetry.io/otel/sdk/log`. (#6864) - Retry now shows error cause for context timeout in `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc`, `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc`, `go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc`, `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`, `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`, `go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`. (#6898) ### Fixed - Stop stripping trailing slashes from configured endpoint URL in `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc`. (#6710) - Stop stripping trailing slashes from configured endpoint URL in `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`. (#6710) - Stop stripping trailing slashes from configured endpoint URL in `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc`. (#6710) - Stop stripping trailing slashes from configured endpoint URL in `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`. (#6710) - Validate exponential histogram scale range for Prometheus compatibility in `go.opentelemetry.io/otel/exporters/prometheus`. (#6822) - Context cancellation during metric pipeline produce does not corrupt data in `go.opentelemetry.io/otel/sdk/metric`. (#6914) ### Removed - `go.opentelemetry.io/otel/exporters/prometheus` no longer exports `otel_scope_info` metric. (#6770)

highlyavailable requested review from MrAlias, XSAM, dashpole, dmathieu and pellared as code owners May 24, 2025 17:39

highlyavailable force-pushed the fix/prometheus-exponential-histogram-scale-validation-clean branch from 6f10f59 to 4c1e41b Compare May 24, 2025 23:48

MrAlias added the pkg:exporter:prometheus Related to the Prometheus exporter package label May 26, 2025

MrAlias added this to the v1.37.0 milestone May 26, 2025

MrAlias reviewed May 26, 2025

View reviewed changes

Comment thread CHANGELOG.md Outdated

Comment thread exporters/prometheus/exporter.go

highlyavailable force-pushed the fix/prometheus-exponential-histogram-scale-validation-clean branch from 4c1e41b to 95c4664 Compare May 30, 2025 03:22

highlyavailable force-pushed the fix/prometheus-exponential-histogram-scale-validation-clean branch from 332fca7 to e058c03 Compare May 30, 2025 11:16

highlyavailable force-pushed the fix/prometheus-exponential-histogram-scale-validation-clean branch from e058c03 to 764b9f2 Compare May 30, 2025 11:47

dashpole reviewed May 30, 2025

View reviewed changes

Comment thread exporters/prometheus/exporter.go Outdated

Based on @dashpole 's feedback

f6be0b5

Removed unnecessary logic for trimming leading and trailing zeros in the downscaleExponentialBucket function.

pellared requested review from MrAlias and dashpole June 9, 2025 08:57

dashpole reviewed Jun 9, 2025

View reviewed changes

Comment thread exporters/prometheus/exporter_test.go Outdated

dashpole approved these changes Jun 9, 2025

View reviewed changes

pellared modified the milestones: v1.37.0, Subsequent v1.37.0 Jun 12, 2025

highlyavailable and others added 2 commits June 13, 2025 13:25

Remove unused gauge metric tests (mistakingly added from a different PR)

55e6ccc

Merge branch 'main' into fix/prometheus-exponential-histogram-scale-v…

136254d

…alidation-clean

dashpole approved these changes Jun 13, 2025

View reviewed changes

dashpole reviewed Jun 13, 2025

View reviewed changes

Comment thread CHANGELOG.md

Update CHANGELOG.md

41518cb

dmathieu approved these changes Jun 16, 2025

View reviewed changes

Merge branch 'main' into fix/prometheus-exponential-histogram-scale-v…

76a9ca2

…alidation-clean

dmathieu merged commit cba6502 into open-telemetry:main Jun 16, 2025
32 checks passed

pellared mentioned this pull request Jun 24, 2025

Release 1.37.0/0.59.0/0.13.0 #6925

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prometheus: validate exponential histogram scale range (#6779)#6822

prometheus: validate exponential histogram scale range (#6779)#6822
dmathieu merged 6 commits intoopen-telemetry:mainfrom
highlyavailable:fix/prometheus-exponential-histogram-scale-validation-clean

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