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fix: restore legacy suffix compatibility#2100

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zeitlinger wants to merge 1 commit intoprometheus:mainfrom
zeitlinger:fix/legacy-gauge-family-name
Open

fix: restore legacy suffix compatibility#2100
zeitlinger wants to merge 1 commit intoprometheus:mainfrom
zeitlinger:fix/legacy-gauge-family-name

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@zeitlinger zeitlinger commented May 5, 2026

Fixes #2095

Summary

Restores OM1/protobuf compatibility for dotted gauge names after
feat: move suffix handling to scrape time (#1955).

The bug was that non-OpenMetrics exposition changed visible output for gauge
names that merely ended in suffix-like dotted strings such as .created and
.total.

Examples:

  • Gauge("test3.created") regressed from test3 to test3_created
  • Gauge("test6.total") regressed from test6 to test6_total

This PR restores the legacy OM1/protobuf behavior while keeping OpenMetrics on
literal-name handling.

This is the extracted prom-side fix from #2093. The Micrometer workflow and
related downstream testing were split into a stacked follow-up PR so this can
merge independently.

What changed

  • Fix OM1 text exposition for dotted gauge names ending in .created and
    .total
  • Fix protobuf exposition for the same compatibility cases
  • Add regression tests that cover the restored OM1/protobuf behavior and the
    preserved OpenMetrics behavior
  • Clean up protobuf family-name resolution so legacy gauge handling lives in
    one path instead of pre-rewriting metadata objects

Follow-up stacked PR

Related

Testing

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

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

Restores legacy OM1 (Prometheus text 0.0.4) and protobuf exposition behavior for gauge names that end with suffix-like dotted strings (e.g. .created, .total), while keeping OpenMetrics output on literal-name handling to avoid reintroducing prior regressions.

Changes:

  • Add regression tests covering OpenMetrics vs OM1/protobuf behavior for Gauge("*.created") and Gauge("*.total").
  • Update PrometheusTextFormatWriter to normalize legacy dotted gauge suffixes when emitting metric names.
  • Update PrometheusProtobufWriterImpl metric-family naming to normalize the same legacy gauge cases, and add a protobuf duplicate-names regression test.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File Description
prometheus-metrics-exposition-textformats/src/test/java/io/prometheus/metrics/expositionformats/ExpositionFormatsTest.java Adds cross-format regression coverage for dotted gauge suffix compatibility.
prometheus-metrics-exposition-textformats/src/main/java/io/prometheus/metrics/expositionformats/PrometheusTextFormatWriter.java Implements legacy dotted gauge suffix normalization for Prometheus text exposition.
prometheus-metrics-exposition-formats/src/test/java/io/prometheus/metrics/expositionformats/DuplicateNamesProtobufTest.java Adds protobuf regression test for .total dotted gauge normalization affecting family naming.
prometheus-metrics-exposition-formats/src/main/java/io/prometheus/metrics/expositionformats/internal/PrometheusProtobufWriterImpl.java Centralizes metric-family name resolution and adds legacy dotted gauge normalization for protobuf.

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if (originalName.endsWith(".total")) {
return PrometheusNaming.escapeName(
originalName.substring(0, originalName.length() - ".total".length()), scheme);
}
if (originalName.endsWith(".total")) {
return PrometheusNaming.escapeName(
originalName.substring(0, originalName.length() - ".total".length()), scheme);
}
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bug: restore OM1/protobuf suffix compatibility after #1955

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