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feat: Add OM2 native histogram text output#2042

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zeitlinger merged 6 commits intoprometheus:mainfrom
zeitlinger:codex/om2-native-histograms
Apr 25, 2026
Merged

feat: Add OM2 native histogram text output#2042
zeitlinger merged 6 commits intoprometheus:mainfrom
zeitlinger:codex/om2-native-histograms

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@zeitlinger zeitlinger commented Apr 23, 2026

Summary

Adds OpenMetrics 2.0 text output for native histograms behind the nativeHistograms flag.

  • serializes native histogram fields (schema, zero_threshold, zero_count, native spans/buckets)
  • supports native gauge histograms with gcount/gsum
  • supports mixed native + classic histograms with classic bucket output last
  • emits all histogram exemplars on composite/native histogram samples
  • adds unit/integration coverage for native histogram content negotiation and edge cases

Validation

  • ./mvnw test -pl prometheus-metrics-exposition-textformats -Dtest=OpenMetrics2TextFormatWriterTest,ExpositionFormatsTest -Dcoverage.skip=true -Dcheckstyle.skip=true
  • mise run build

@zeitlinger
Add OM2 native histogram text output
37e92ca 
Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>
@zeitlinger
Format OM2 native histogram changes
fc803e6 
Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>
@zeitlinger zeitlinger changed the title [codex] Add OM2 native histogram text output feant: Add OM2 native histogram text output Apr 23, 2026
@zeitlinger zeitlinger changed the title feant: Add OM2 native histogram text output feat: Add OM2 native histogram text output Apr 23, 2026
@zeitlinger zeitlinger marked this pull request as ready for review April 23, 2026 09:11
@zeitlinger
fix: align OM2 counters and summaries with current output
ad6766a 
Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>
@zeitlinger
style: apply formatter fixes for OM2 writer
ca35710 
Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>
@zeitlinger
fix OM2 counter start timestamp output
307cbe3 
Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>
@zeitlinger
Merge branch 'main' of https://github.com/prometheus/client_java into…
03f2f43 
… codex/om2-native-histograms

Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>

# Conflicts:
#	prometheus-metrics-exposition-textformats/src/main/java/io/prometheus/metrics/expositionformats/OpenMetrics2TextFormatWriter.java
#	prometheus-metrics-exposition-textformats/src/test/java/io/prometheus/metrics/expositionformats/OpenMetrics2TextFormatWriterTest.java
@zeitlinger zeitlinger merged commit dec8e5b into prometheus:main Apr 25, 2026
14 checks passed
@zeitlinger zeitlinger deleted the codex/om2-native-histograms branch April 25, 2026 20:44
@github-actions github-actions Bot mentioned this pull request Apr 25, 2026
Merged
This was referenced Apr 27, 2026
Closed
Closed
zeitlinger pushed a commit that referenced this pull request Apr 27, 2026
@github-actions
chore(main): release 1.6.0 (#1983)
a1530df 
🤖 I have created a release *beep* *boop*
---


##
[1.6.0](v1.5.1...v1.6.0)
(2026-04-25)


### Features

* Add logic for handling content negotation flag with OM2
([#1986](#1986))
([0fa1ad7](0fa1ad7))
* Add OM2 native histogram text output
([#2042](#2042))
([dec8e5b](dec8e5b))
* add OTel preserve_names for scrape-time suffix handling
([#1956](#1956))
([f794288](f794288))
* compositeValues and exemplarCompliance flags for OM2 writer
([#1991](#1991))
([ff48ae8](ff48ae8))
* move suffix handling to scrape time
([#1955](#1955))
([5a5106c](5a5106c))
* OM2 writer outputs names as provided, no suffix appending
([#1957](#1957))
([5ce2b57](5ce2b57))


### Bug Fixes

* **deps:** update dependency com.google.guava:guava to v33.6.0-jre
([#2021](#2021))
([1382693](1382693))
* **deps:** update dependency commons-io:commons-io to v2.22.0
([#2044](#2044))
([9e05c1d](9e05c1d))
* **deps:** update dependency
io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom-alpha
to v2.27.0-alpha
([#2022](#2022))
([30ac534](30ac534))
* **deps:** update dependency
io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom-alpha
to v2.27.0-alpha
([#2023](#2023))
([2d51a32](2d51a32))
* **deps:** update dependency io.prometheus:prometheus-metrics-bom to
v1.5.1 ([#2004](#2004))
([650ce4b](650ce4b))
* **deps:** update dependency org.apache.tomcat.embed:tomcat-embed-core
to v11.0.21
([#2005](#2005))
([7a36df7](7a36df7))
* **deps:** update dependency
org.springframework.boot:spring-boot-starter-parent to v4.0.5
([#2006](#2006))
([0106c18](0106c18))
* **deps:** update dependency
org.springframework.boot:spring-boot-starter-parent to v4.0.6
([#2046](#2046))
([40a9db8](40a9db8))
* **deps:** update jetty monorepo to v12.1.8
([#2007](#2007))
([acab5b2](acab5b2))
* **deps:** update protobuf
([#2024](#2024))
([8e2214e](8e2214e))
* pass release tag as input to deploy workflow
([#1982](#1982))
([165c921](165c921))
* pin grafana/otel-lgtm to 0.7.2 in OATs acceptance test
([#1992](#1992))
([f17ad9a](f17ad9a))
* Relax metric name validation in Dropwizard5
([#1985](#1985))
([deb782f](deb782f))
* stabilize flaky timer and thread count tests
([#1973](#1973))
([ce5867b](ce5867b))
* Tighten OM2 summary and start timestamp output
([#2041](#2041))
([5699469](5699469))
* trigger Maven deploy from release-please via workflow_dispatch
([#1981](#1981))
([698f956](698f956))

---
> [!IMPORTANT]
> Close and reopen this PR to trigger CI checks.

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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@jaydeluca jaydeluca jaydeluca approved these changes

@fstab fstab Awaiting requested review from fstab fstab is a code owner

@dhoard dhoard Awaiting requested review from dhoard dhoard is a code owner

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@zeitlinger @jaydeluca