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fix: Reduce allocations for classic histogram buckets - #2081

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reduce-allocations
May 6, 2026
Merged

fix: Reduce allocations for classic histogram buckets #2081
zeitlinger merged 9 commits into
mainfrom
reduce-allocations

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@jaydelucajaydeluca commented Apr 30, 2026•
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Related to #2075

This reduces allocation and GC pressure in histogram text formatting by eliminating unnecessary intermediate allocations.

@jaydelucajaydeluca changed the title Reduce allocations for classic histogram buckets feat: Reduce allocations for classic histogram buckets Apr 30, 2026
@jaydelucajaydeluca changed the title feat: Reduce allocations for classic histogram buckets fix: Reduce allocations for classic histogram buckets Apr 30, 2026
@jaydeluca
Create name just one
96a0061
Signed-off-by: Jay DeLuca <jaydeluca4@gmail.com>
@jaydeluca
add benchmark
29f7c73
Signed-off-by: Jay DeLuca <jaydeluca4@gmail.com>
@jaydeluca
more allocations avoided
9444848
Signed-off-by: Jay DeLuca <jaydeluca4@gmail.com>
@jaydeluca
fix lint
5fe88b1
Signed-off-by: Jay DeLuca <jaydeluca4@gmail.com>
@jaydeluca
jaydelucaforce-pushed the reduce-allocations branch from 494d653 to 5fe88b1CompareMay 1, 2026 20:37
@jaydeluca
update benchmarks
b29c0f1
Signed-off-by: Ubuntu <jaydeluca4@gmail.com>
@jaydeluca
format
b1f89ba
Signed-off-by: Jay DeLuca <jaydeluca4@gmail.com>
@jaydeluca
remove shared writer for now
64bc726
Signed-off-by: Jay DeLuca <jaydeluca4@gmail.com>
@jaydeluca
jaydeluca requested a review from CopilotMay 4, 2026 12:27
CopilotAI reviewed May 4, 2026
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Pull request overview

This PR targets allocation reduction in the text exposition layer by removing repeated string building in hot formatting paths and replacing Long.toString(...) calls with direct writer-based long formatting. It also adds benchmark coverage around histogram text rendering so the impact can be measured in the benchmarking module.

Changes:

  • Added a manual writeLong(...) helper in TextFormatUtil and reused it for counts and timestamps.
  • Cached base/suffixed metric names in the Prometheus, OpenMetrics, and OpenMetrics 2 text writers to avoid repeated concatenation in loops.
  • Added a histogram text-format JMH benchmark and updated benchmark tasks to run with the GC profiler.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file
FileDescription
prometheus-metrics-exposition-textformats/src/main/java/io/prometheus/metrics/expositionformats/TextFormatUtil.javaReplaces Long.toString(...) with manual long/timestamp writing helpers.
prometheus-metrics-exposition-textformats/src/main/java/io/prometheus/metrics/expositionformats/PrometheusTextFormatWriter.javaCaches metric names and suffixed variants to reduce per-datapoint allocations in Prometheus text output.
prometheus-metrics-exposition-textformats/src/main/java/io/prometheus/metrics/expositionformats/OpenMetricsTextFormatWriter.javaApplies the same cached-name optimization to OpenMetrics 1 text output.
prometheus-metrics-exposition-textformats/src/main/java/io/prometheus/metrics/expositionformats/OpenMetrics2TextFormatWriter.javaReduces classic histogram bucket-name concatenation in OpenMetrics 2 text output.
mise.tomlUpdates benchmark tasks to pass JMH GC-profiler arguments.
benchmarks/src/main/java/io/prometheus/metrics/benchmarks/HistogramTextFormatBenchmark.javaAdds a dedicated JMH benchmark for classic histogram text rendering.

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Comment thread...sition-textformats/src/main/java/io/prometheus/metrics/expositionformats/TextFormatUtil.java
Comment thread...ormats/src/main/java/io/prometheus/metrics/expositionformats/PrometheusTextFormatWriter.java
Comment threadmise.toml
@jaydeluca
simplify
9168d96
Signed-off-by: Jay DeLuca <jaydeluca4@gmail.com>
@jaydeluca
add command to nightly benchmark job too
314fb28
Signed-off-by: Jay DeLuca <jaydeluca4@gmail.com>
@jaydeluca
jaydeluca marked this pull request as ready for review May 5, 2026 14:31
@zeitlinger
zeitlinger merged commit edd160a into mainMay 6, 2026
14 checks passed
@zeitlinger
zeitlinger deleted the reduce-allocations branch May 6, 2026 09:31
@github-actionsgithub-actionsBot mentioned this pull request May 6, 2026
Merged
zeitlinger added a commit that referenced this pull request Jun 3, 2026
@github-actions@zeitlinger
chore(main): release 1.7.0 (#2092)
574fb73
🤖 I have created a release *beep* *boop*
---
##
[1.7.0](v1.6.1...v1.7.0)
(2026-06-03)
### Features
* Add StableApi marker and API diff check
([#2168](#2168))
([768fd3a](768fd3a))
* add typed metric family descriptors
([#2114](#2114))
([9c3b097](9c3b097))
* track api-diff baseline via Renovate and store diffs in docs/apidiffs
([#2174](#2174))
([3adb890](3adb890))
### Bug Fixes
* **deps:** update dependency com.github.ben-manes.caffeine:caffeine to
v3.2.4 ([#2088](#2088))
([144eb61](144eb61))
* **deps:** update dependency io.dropwizard.metrics:metrics-core to
v4.2.39 ([#2139](#2139))
([5817d13](5817d13))
* **deps:** update dependency io.dropwizard.metrics5:metrics-core to
v5.0.7 ([#2140](#2140))
([261c451](261c451))
* **deps:** update dependency
io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom-alpha
to v2.28.0-alpha
([#2126](#2126))
([b62b5d0](b62b5d0))
* **deps:** update dependency
io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom-alpha
to v2.28.0-alpha
([#2127](#2127))
([e11ce3d](e11ce3d))
* **deps:** update dependency
io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom-alpha
to v2.28.1-alpha
([#2132](#2132))
([b09be38](b09be38))
* **deps:** update dependency
io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom-alpha
to v2.28.1-alpha
([#2133](#2133))
([a241c16](a241c16))
* **deps:** update dependency org.apache.tomcat.embed:tomcat-embed-core
to v11.0.22
([#2099](#2099))
([22125c5](22125c5))
* **deps:** update jetty monorepo to v12.1.10
([#2169](#2169))
([ddd3991](ddd3991))
* **deps:** update jetty monorepo to v12.1.9
([#2102](#2102))
([04bee70](04bee70))
* **deps:** update protobuf
([#2129](#2129))
([320538a](320538a))
* Reduce allocations for classic histogram buckets
([#2081](#2081))
([edd160a](edd160a))
* restore legacy suffix compatibility
([#2100](#2100))
([b2ae70f](b2ae70f))
* restore reserved suffix stripping in
`PrometheusNaming.sanitizeMetricName()`
([#2124](#2124))
([2d0f508](2d0f508))
### Performance Improvements
* Refactored sorting to use optimized sort algorithms
([#2161](#2161))
([25b94fc](25b94fc))
### Documentation
* clarify downstream adapter validation requirements
([#2101](#2101))
([ef8c75c](ef8c75c))
* Document OM2
([#2059](#2059))
([45d753c](45d753c))
* document PushGateway shading workaround
([#2106](#2106))
([8ca0eb8](8ca0eb8))
---
> [!IMPORTANT]
> Close and reopen this PR to trigger CI checks.
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>
jaydeluca pushed a commit that referenced this pull request Jun 4, 2026
@github-actions@zeitlinger@jaydeluca
chore(main): release 1.7.0 (#2092)
d51e654
🤖 I have created a release *beep* *boop*
---
##
[1.7.0](v1.6.1...v1.7.0)
(2026-06-03)
### Features
* Add StableApi marker and API diff check
([#2168](#2168))
([768fd3a](768fd3a))
* add typed metric family descriptors
([#2114](#2114))
([9c3b097](9c3b097))
* track api-diff baseline via Renovate and store diffs in docs/apidiffs
([#2174](#2174))
([3adb890](3adb890))
### Bug Fixes
* **deps:** update dependency com.github.ben-manes.caffeine:caffeine to
v3.2.4 ([#2088](#2088))
([144eb61](144eb61))
* **deps:** update dependency io.dropwizard.metrics:metrics-core to
v4.2.39 ([#2139](#2139))
([5817d13](5817d13))
* **deps:** update dependency io.dropwizard.metrics5:metrics-core to
v5.0.7 ([#2140](#2140))
([261c451](261c451))
* **deps:** update dependency
io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom-alpha
to v2.28.0-alpha
([#2126](#2126))
([b62b5d0](b62b5d0))
* **deps:** update dependency
io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom-alpha
to v2.28.0-alpha
([#2127](#2127))
([e11ce3d](e11ce3d))
* **deps:** update dependency
io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom-alpha
to v2.28.1-alpha
([#2132](#2132))
([b09be38](b09be38))
* **deps:** update dependency
io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom-alpha
to v2.28.1-alpha
([#2133](#2133))
([a241c16](a241c16))
* **deps:** update dependency org.apache.tomcat.embed:tomcat-embed-core
to v11.0.22
([#2099](#2099))
([22125c5](22125c5))
* **deps:** update jetty monorepo to v12.1.10
([#2169](#2169))
([ddd3991](ddd3991))
* **deps:** update jetty monorepo to v12.1.9
([#2102](#2102))
([04bee70](04bee70))
* **deps:** update protobuf
([#2129](#2129))
([320538a](320538a))
* Reduce allocations for classic histogram buckets
([#2081](#2081))
([edd160a](edd160a))
* restore legacy suffix compatibility
([#2100](#2100))
([b2ae70f](b2ae70f))
* restore reserved suffix stripping in
`PrometheusNaming.sanitizeMetricName()`
([#2124](#2124))
([2d0f508](2d0f508))
### Performance Improvements
* Refactored sorting to use optimized sort algorithms
([#2161](#2161))
([25b94fc](25b94fc))
### Documentation
* clarify downstream adapter validation requirements
([#2101](#2101))
([ef8c75c](ef8c75c))
* Document OM2
([#2059](#2059))
([45d753c](45d753c))
* document PushGateway shading workaround
([#2106](#2106))
([8ca0eb8](8ca0eb8))
---
> [!IMPORTANT]
> Close and reopen this PR to trigger CI checks.
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>
Signed-off-by: Jay DeLuca <jaydeluca4@gmail.com>
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