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zeitlinger · 2026-01-28T17:09:42Z

Summary

No Breaking Changes. This is fully backward compatible:

✅ Existing camelCase properties in files still work
✅ Existing system properties still work
✅ Property precedence maintains existing behavior (external > system > file)
✅ New environment variable layer added between external and system properties

Migration Guide

No migration required. However, to adopt the new features:

To use environment variables: Convert property names to uppercase with underscores
- io.prometheus.exporter.httpServer.port → IO_PROMETHEUS_EXPORTER_HTTP_SERVER_PORT
To use snake_case (recommended): Update properties files
- io.prometheus.metrics.exemplarsEnabled → io.prometheus.metrics.exemplars_enabled
- Old camelCase names continue to work

Notes

adjust new property added in Add GC duration histogram #1738

Copilot

Pull request overview

Adds an environment-variable configuration layer and standardizes property naming to snake_case while preserving backward compatibility via key normalization.

Changes:

Introduces PropertySource to unify external, environment, and “regular” (system/file/classpath) properties with defined precedence.
Adds environment-variable loading (IO_PROMETHEUS_*) and camelCase→snake_case normalization for file/system/external keys.
Updates config docs, test resources, and tests to use the new snake_case property names and new loader APIs.

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/PropertySource.java	New abstraction for multi-source property lookup with precedence and key transformations.
prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/PrometheusPropertiesLoader.java	Loads properties from file/classpath/system, adds env var layer, normalizes keys, validates leftovers.
prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/Util.java	Refactors property lookup helpers to read from `PropertySource` and improve key formatting in errors.
prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/MetricsProperties.java	Migrates internal property-name constants to snake_case and updates loading/validation paths.
prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/ExporterProperties.java	Switches exporter property keys to snake_case and loads via `PropertySource`.
prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/ExporterHttpServerProperties.java	Updates prefix/key naming to snake_case and loads via `PropertySource`.
prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/ExporterFilterProperties.java	Renames filter keys to snake_case and updates loader wiring.
prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/ExporterOpenTelemetryProperties.java	Renames OTel keys to snake_case and updates loader wiring.
prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/ExporterPushgatewayProperties.java	Renames pushgateway keys to snake_case and updates loader wiring.
prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/ExemplarsProperties.java	Renames exemplars keys to snake_case and loads via `PropertySource`.
prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/UtilTest.java	Updates tests to use `PropertySource`-based APIs.
prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/PrometheusPropertiesTest.java	Updates loading tests to use `PropertySource` and asserts properties are consumed.
prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/PrometheusPropertiesLoaderTest.java	Updates loader tests to snake_case keys.
prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/MetricsPropertiesTest.java	Updates expected exception messages and property keys to snake_case.
prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/ExporterPropertiesTest.java	Updates keys and loader helper to use `PropertySource`.
prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/ExporterHttpServerPropertiesTest.java	Updates keys and loader helper to use `PropertySource`.
prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/ExporterFilterPropertiesTest.java	Updates keys and loader helper to use `PropertySource`.
prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/ExporterOpenTelemetryPropertiesTest.java	Updates keys and loader helper to use `PropertySource`.
prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/ExporterPushgatewayPropertiesTest.java	Updates loader helper to use `PropertySource`.
prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/ExemplarsPropertiesTest.java	Updates keys and loader helper to use `PropertySource`.
prometheus-metrics-config/src/test/resources/prometheus.properties	Updates test properties file to snake_case keys.
prometheus-metrics-config/src/test/resources/emptyUpperBounds.properties	Updates test properties key to snake_case.
docs/content/config/config.md	Documents env var support, precedence, and snake_case naming; updates examples/tables.

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Copilot

Pull request overview

Copilot reviewed 24 out of 24 changed files in this pull request and generated 7 comments.

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jaydeluca · 2026-02-06T10:45:29Z

+  private static void validateAllPropertiesProcessed(PropertySource propertySource) {
+    for (String key : propertySource.getRemainingKeys()) {
+      if (key.startsWith("io.prometheus") || key.startsWith("io_prometheus")) {
        throw new PrometheusPropertiesException(key + ": Unknown property");


i know this isn't new behavior, but I found this to be surprising that we would throw for this condition as opposed to just logging a warning. For example, if we deprecate a property and someone forgets to remove it from their config, their service will crash?

Fail early is an idiom in this library (@fstab probably has more background info). That means that we have to be very careful with removing - probably only in a major release.

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

zeitlinger requested review from Copilot and jaydeluca January 28, 2026 17:09

Copilot started reviewing on behalf of zeitlinger January 28, 2026 17:10 View session

Copilot AI reviewed Jan 28, 2026

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zeitlinger force-pushed the feature/env-var-properties branch from 1d05224 to 8ee2b21 Compare January 29, 2026 11:51

zeitlinger mentioned this pull request Jan 29, 2026

Target release with recent improvements #1834

Closed

jaydeluca requested a review from Copilot February 2, 2026 16:28

Copilot started reviewing on behalf of jaydeluca February 2, 2026 16:28 View session

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jaydeluca approved these changes Feb 6, 2026

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jaydeluca mentioned this pull request Feb 6, 2026

add branch coverage, better javadoc lints #1851

Merged

zeitlinger added 13 commits February 6, 2026 12:32

env var properties

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

env var properties

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

env var properties

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

env var properties

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

env var properties

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

fix env var properties

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

fix env var properties

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

fix env var properties

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

format

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

use correct underscore escaping

df7cd67

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

fix

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

fix

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

fix

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

zeitlinger force-pushed the feature/env-var-properties branch from ffd74a0 to 16923c7 Compare February 6, 2026 11:33

zeitlinger enabled auto-merge (squash) February 6, 2026 11:35

zeitlinger merged commit 801277d into main Feb 6, 2026
14 checks passed

zeitlinger deleted the feature/env-var-properties branch February 6, 2026 11:42

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support environment variables in properties#1828

support environment variables in properties#1828
zeitlinger merged 13 commits into
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zeitlinger commented Jan 28, 2026 •

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Summary

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zeitlinger commented Jan 28, 2026 •

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