chore: Sync the translator for otelcol.receiver.prometheus with upstream by ptodev · Pull Request #5308 · grafana/alloy

ptodev · 2026-01-21T11:13:28Z

Brief description of Pull Request

feat(otelcol.receiver.prometheus): It is no longer required to run Alloy with --stability.level=experimental in order to translate Prometheus native histograms into OTLP exponential histograms.

BREAKING CHANGE: otelcol.receiver.prometheus no longer sets start times of OTLP metrics. Grafana Cloud and Mimir do not currently use OTLP metric start times. If you do want your metrics to have them, you can use otelcol.processor.metric_start_time with strategy set to true_reset_point to get the same behaviour.

Pull Request Details

Issue(s) fixed by this Pull Request

Notes to the Reviewer

PR Checklist

Documentation added
Tests updated
Config converters updated

BEGIN_COMMIT_OVERRIDE
feat(otelcol.receiver.prometheus): Remove requirement to run Alloy with --stability.level=experimental in order to translate Prometheus native histograms into OTLP exponential histograms. (#5308)

BREAKING CHANGE: otelcol.receiver.prometheus no longer sets start times of OTLP metrics. Grafana Cloud and Mimir do not currently use OTLP metric start times. If you do want your metrics to have them, you can use otelcol.processor.metric_start_time with strategy set to true_reset_point to get the same behaviour.
END_COMMIT_OVERRIDE

github-actions · 2026-01-23T18:12:44Z

💻 Deploy preview deleted (chore: Sync the translator for otelcol.receiver.prometheus with upstream).

docs/sources/reference/components/otelcol/otelcol.receiver.prometheus.md

### Pull Request Details This component creates "start time" timestamps for OTLP metrics. Those timestamps are similar to the `_created` metrics in the [Prometheus spec](https://prometheus.io/docs/specs/om/open_metrics_spec/). AFAIK they are not widely used. This component is required in order for the translator package in `otelcol.receiver.prometheus` to be updated (#5308). The new translator outsources the responsibility of creating start timestamps to this new processor. The upstream component is called [metricstarttime](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/v0.142.0/processor/metricstarttimeprocessor). I called this one `metric_start_time`, because there is an [open issue](open-telemetry/opentelemetry-collector-contrib#45339) upstream to rename it. ### PR Checklist  - [x] Documentation added - [ ] Tests updated - [x] Config converters updated

docs/sources/reference/components/otelcol/otelcol.receiver.prometheus.md

github-actions · 2026-01-27T18:29:49Z

🔍 Dependency Review

github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatautil v0.142.0 (direct) -> v0.142.0 (indirect) — ✅ Safe

What changed: The module remains at the same version (v0.142.0) but has been moved from a direct to an indirect dependency in go.mod.
Reason: The codebase no longer imports pdatautil directly. The previous usage (e.g., hashing attributes in the Prometheus receiver’s metrics adjuster) was removed along with the entire metrics adjuster implementation.

No code changes are required to adopt this change. The PR already removes the only direct usage.

Evidence:

The metrics_adjuster.go file (which used pdatautil.MapHash) was deleted in this PR. It previously contained:

import (
    ...
    "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatautil"
)
...
func getAttributesSignature(m pcommon.Map) [16]byte {
    ...
    return pdatautil.MapHash(clearedMap)
}

The go.mod change reflects removal from direct require and reappearance as indirect:

- github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatautil v0.142.0
...
+ github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatautil v0.142.0 // indirect

No relevant changelog sections apply (no version change).

Notes

No other dependency versions changed in this PR; only the pdatautil entry moved from direct to indirect, which is consistent with the removal of its direct usage in the code.

docs/sources/reference/components/otelcol/otelcol.receiver.prometheus.md

krajorama

doc part LGTM

docs/sources/reference/components/otelcol/otelcol.processor.metric_start_time.md

docs/sources/reference/components/otelcol/otelcol.receiver.prometheus.md

kgeckhart

Did my best to review what's here mostly for clarity.

internal/component/otelcol/receiver/prometheus/internal/transaction_bench_test.go

internal/component/otelcol/receiver/prometheus/internal/transaction.go

internal/component/otelcol/receiver/prometheus/internal/staleness_end_to_end_test.go

This reconciliation does not include upstream's target allocator.

This reverts commit f929733.

…ld only estimate start time if it didn't exist.

Co-authored-by: Clayton Cornell <131809008+clayton-cornell@users.noreply.github.com>

…tric_start_time.md Co-authored-by: Clayton Cornell <131809008+clayton-cornell@users.noreply.github.com>

Co-authored-by: Kyle Eckhart <kgeckhart@users.noreply.github.com>

… number

… number (2)

docs/sources/reference/components/otelcol/otelcol.processor.metric_start_time.md

docs/sources/reference/components/otelcol/otelcol.receiver.prometheus.md

Co-authored-by: Clayton Cornell <131809008+clayton-cornell@users.noreply.github.com>

ptodev changed the title ~~Sync the translator for otelcol.receiver.prometheus with upstream~~ chore: Sync the translator for otelcol.receiver.prometheus with upstream Jan 21, 2026

ptodev mentioned this pull request Jan 23, 2026

feat: Add an otelcol.processor.metric_start_time component #5342

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ptodev force-pushed the ptodev/nhcb-test-otel-branch branch from 72bf207 to 5efb471 Compare January 23, 2026 18:09

ptodev commented Jan 23, 2026

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ptodev force-pushed the ptodev/nhcb-test-otel-branch branch from 5efb471 to dbde71a Compare January 27, 2026 18:28

ptodev marked this pull request as ready for review January 27, 2026 18:28

ptodev requested review from a team and clayton-cornell as code owners January 27, 2026 18:28

ptodev commented Jan 27, 2026

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ptodev force-pushed the ptodev/nhcb-test-otel-branch branch from deb5bb1 to 2d4ecac Compare January 29, 2026 11:14

krajorama approved these changes Jan 29, 2026

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ptodev force-pushed the ptodev/nhcb-test-otel-branch branch from 5eb68d9 to 37dad5c Compare February 2, 2026 12:10

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clayton-cornell added the type/docs Docs Squad label across all Grafana Labs repos label Feb 4, 2026

ptodev added 10 commits February 4, 2026 16:45

Upgrade OTel Collector dependencies to v0.142.0

35a97d7

Bring back otelcol.receiver.opencensus doc with a removal note

197e743

Copy the latest upstream code from v0.142.0

8c9a60a

This reconciliation does not include upstream's target allocator.

Retain the old semconv feature gate.

19c1c24

Update otelcol.receiver.prometheus wrapper

c9b947e

Revert "Upgrade OTel Collector dependencies to v0.142.0"

508d25c

This reverts commit f929733.

Rollback undesired rebase change

062ebc5

Clarify docs

d6245b9

Clarify what a Prometheus created metric is and that the receiver wou…

e0ed888

…ld only estimate start time if it didn't exist.

Clarify what happens if no processor is added

84c3573

ptodev and others added 5 commits February 4, 2026 16:45

Apply suggestions from code review

4991a86

Co-authored-by: Clayton Cornell <131809008+clayton-cornell@users.noreply.github.com>

Update docs/sources/reference/components/otelcol/otelcol.processor.me…

afab400

…tric_start_time.md Co-authored-by: Clayton Cornell <131809008+clayton-cornell@users.noreply.github.com>

Apply suggestions from code review

c1ec89e

Co-authored-by: Kyle Eckhart <kgeckhart@users.noreply.github.com>

Clarify why tests are commented out

f3f85dd

Use CustomBucketsSchema from the histogram package instead of a magic…

d99725d

… number

ptodev force-pushed the ptodev/nhcb-test-otel-branch branch from 9a64343 to d99725d Compare February 4, 2026 17:14

ptodev requested a review from kgeckhart February 4, 2026 17:14

Use CustomBucketsSchema from the histogram package instead of a magic…

ad0cb01

… number (2)

kgeckhart approved these changes Feb 4, 2026

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clayton-cornell reviewed Feb 5, 2026

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Apply suggestions from code review

c79644b

Co-authored-by: Clayton Cornell <131809008+clayton-cornell@users.noreply.github.com>

ptodev merged commit 237e985 into main Feb 5, 2026
49 of 50 checks passed

ptodev deleted the ptodev/nhcb-test-otel-branch branch February 5, 2026 20:40

grafana-alloybot bot mentioned this pull request Feb 5, 2026

Unreleased Changes #5170

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github-actions bot added the frozen-due-to-age label Feb 20, 2026

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ptodev commented Jan 21, 2026 •

edited by jharvey10

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