[receiver/prometheus] Generate Scope Attributes from otel_scope_<attribute-name> labels by ArthurSens · Pull Request #46612 · open-telemetry/opentelemetry-collector-contrib

ArthurSens · 2026-03-03T21:08:33Z

Description

Add support for extracting scope attributes from otel_scope_ labels on metrics in the Prometheus receiver, per the spec change.
This is gated behind receiver.prometheusreceiver.UseScopeAttributeLabels (alpha, disabled by default). The gate acts as a switch:

Disabled (default): existing behavior — scope attributes come from otel_scope_info, and otel_scope_ labels are treated as regular data point attributes.
Enabled: scope attributes are read from otel_scope_ labels on every metric, otel_scope_info is ignored.

Link to tracking issue

Fixes #41502

Testing

Added integration tests (TestScopeAttributeLabelsFeatureGate) covering both gate states: enabled extracts scope attributes and splits scopes; disabled preserves otel_scope_* as regular labels.
Existing TestScopeInfoScopeAttributes and all internal tests pass unchanged.

krajorama · 2026-03-16T07:48:44Z

+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  Scope attributes are always extracted from `otel_scope_<attribute-name>` labels on metrics.


Isn't it also true now that we drop any extra scope attributes from the resulting attributes? Which is a breaking change if somebody relied on them?

I'm not sure what you mean here. Could you elaborate?

Add something like "labels starting with otel_scope_" are no longer included as metric attributes, and are put in scope attributes instead"

krajorama · 2026-03-16T07:50:38Z

 	name      string
 	version   string
 	schemaURL string
+	attrsHash uint64


I'm not sure about the cardinality of scopes , but you can run into conflicts with hashes.
Since we sort attributes (I think), maybe it would be better to just make a concatenated copy of the scope attributes here using some non utf-8 delimeter ?

Yeah, I tried that, but it has a big performance penalty. Building the string adds 10-15% to allocs and seconds/op for the whole Append method.

I don't understand hash collision well enough to say this penalty is worth it for better reliability, though 😅

I think we use hashes all over the place in the receiver. From my testing with the otel-go SDK, collisions aren't remotely likely until you get into the ~10 billion cardinality range for the cache.

If we want to revisit this, lets do it outside of this PR.

krajorama · 2026-03-16T07:53:45Z

+	base := getSortedNotUsefulLabels(mType)
+	exclusions := make([]string, 0, len(base)+ls.Len())
+	exclusions = append(exclusions, base...)
+	seen := make(map[string]struct{}, len(base))


How frequently do we call this function? Isn't this an extra allocation for every sample? Could we add a benchmark ?

Yes, good catch. I'm adding a commit so we only allocate exclusions if we find a label prefixed with otel_scope_, otherwise we just return base.

Regarding the benchmark, we already have a testbed. I can run it if you feel like this really needs to be properly benchmarked :)

ArthurSens · 2026-03-16T20:48:58Z

I went through your feedback @krajorama, but couldn't find the time to address everything. I'll let you know once all comments have been addressed!

ArthurSens · 2026-03-17T20:39:35Z

This should be ready for another round of reviews @krajorama @dashpole :)

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

…etry#5004) Fixes open-telemetry#4752 ## Changes Stabilizes the conversion of labels prefixed with `otel_scope_` to OTLP Instrumentation scope. Implementation has been done in open-telemetry/opentelemetry-collector-contrib#46612 For non-trivial changes, follow the [change proposal process](https://github.com/open-telemetry/opentelemetry-specification/blob/main/CONTRIBUTING.md#proposing-a-change). * [X] Related issues open-telemetry#4752 * [ ] Related [OTEP(s)](https://github.com/open-telemetry/oteps) # * [ ] Links to the prototypes (when adding or changing features) * [X] [`CHANGELOG.md`](https://github.com/open-telemetry/opentelemetry-specification/blob/main/CHANGELOG.md) file updated for non-trivial changes * For trivial changes, include `[chore]` in the PR title to skip the changelog check * [ ] [Spec compliance matrix](https://github.com/open-telemetry/opentelemetry-specification/blob/main/spec-compliance-matrix/template.yaml) updated if necessary --------- Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com> Co-authored-by: David Ashpole <dashpole@google.com>

ArthurSens requested review from a team and dashpole as code owners March 3, 2026 21:08

github-actions Bot assigned codeboten Mar 3, 2026

github-actions Bot added receiver/prometheus Prometheus receiver pkg/translator/prometheus labels Mar 3, 2026

github-actions Bot requested review from Aneurysm9, bertysentry and krajorama March 3, 2026 21:08

ArthurSens force-pushed the scope-attribute-labels branch from 3c55be3 to f7f7e9c Compare March 3, 2026 21:14

jmacd approved these changes Mar 4, 2026

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dashpole reviewed Mar 5, 2026

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Comment thread pkg/translator/prometheus/constants.go Outdated

dashpole reviewed Mar 5, 2026

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Comment thread receiver/prometheusreceiver/internal/transaction.go Outdated

ArthurSens force-pushed the scope-attribute-labels branch 2 times, most recently from 67df249 to aa64109 Compare March 12, 2026 20:03

ArthurSens mentioned this pull request Mar 13, 2026

[prometheus] Stabilize Prometheus -> OTLP: Instrumentation Scope open-telemetry/opentelemetry-specification#4752

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krajorama suggested changes Mar 16, 2026

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dashpole approved these changes Mar 16, 2026

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ArthurSens force-pushed the scope-attribute-labels branch from aa64109 to 7b6c049 Compare March 16, 2026 20:48

ArthurSens force-pushed the scope-attribute-labels branch from a9da81f to c3b016e Compare March 17, 2026 20:29

dashpole reviewed Mar 18, 2026

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Comment thread receiver/prometheusreceiver/internal/transaction.go Outdated

dashpole reviewed Mar 18, 2026

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Comment thread receiver/prometheusreceiver/internal/transaction.go Outdated

ArthurSens force-pushed the scope-attribute-labels branch from 2b0dc35 to cafa4ff Compare March 27, 2026 21:47

ArthurSens added 6 commits March 30, 2026 14:30

Start using otel_scope_* prefix to identify Scope Attributes

5284062

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

add changelog

2d2a2f7

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

Fix linting

9bd4556

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

Update reference to the spec

7c334e6

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

Keep both behaviors, use feature gate to deprecate otel_scope_info

319daaa

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

Remove obselete labels from 'notUsefulLabels'

ca66e44

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

ArthurSens added 7 commits March 30, 2026 14:30

Replace nested if with switch case

e3bcae2

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

feature gates are ordered

ae7a244

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

Only allocate if found label with otel_scope_ prefix

3d236bd

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

make gotidy

7425cf6

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

otel_scope_info becomes a regular metric when feature gate is enabled

952e086

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

Use pcommon.MapHash for hash building

12a426e

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

make gotidy

2b45ea6

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

ArthurSens force-pushed the scope-attribute-labels branch from cafa4ff to 2b45ea6 Compare March 30, 2026 17:34

dashpole approved these changes Mar 30, 2026

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ArthurSens added the ready to merge Code review completed; ready to merge by maintainers label Mar 30, 2026

atoulme merged commit 12a1810 into open-telemetry:main Mar 30, 2026
208 checks passed

This was referenced Apr 1, 2026

Stabilize Prometheus labels -> OTLP Instrumentation Scope open-telemetry/opentelemetry-specification#5004

Merged

[receiver/prometheus] Stabilize and remove feature gate IgnoreScopeInfoMetric #47312

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ArthurSens commented Mar 3, 2026

Description

Link to tracking issue

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ArthurSens commented Mar 16, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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ArthurSens commented Mar 17, 2026

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ArthurSens commented Mar 16, 2026 •

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