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fix(config): keep metric name case in metric-specific properties #2588

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Merged
zeitlinger merged 1 commit into from
Oct 23, 2026
Merged

fix(config): keep metric name case in metric-specific properties #2588

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8 changes: 8 additions & 0 deletions ...metrics-config/src/main/java/io/prometheus/metrics/config/PrometheusPropertiesLoader.java
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Original file line number Diff line number Diff line change
Expand Up @@ -210,10 +210,18 @@ private static Map<Object, Object> loadPropertiesFromEnvironment() {
* <p>For example: exemplarsEnabled → exemplars_enabled exemplars_enabled → exemplars_enabled
* (unchanged)
*
* <p>In metric-specific keys like {@code io.prometheus.metrics.<metric>.<property>} only the
* property name is normalized, because metric names are case-sensitive.
*
* @param key the property key
* @return the normalized property key
*/
static String normalizePropertyKey(String key) {
String metricsPrefix = "io.prometheus.metrics.";
int lastDot = key.lastIndexOf('.');
if (key.startsWith(metricsPrefix) && lastDot >= metricsPrefix.length()) {
return key.substring(0, lastDot + 1) + normalizePropertyKey(key.substring(lastDot + 1));
}
// Insert underscores before uppercase letters to convert camelCase to snake_case
String withUnderscores = key.replaceAll("([a-z])([A-Z])", "$1_$2");
return withUnderscores.toLowerCase(java.util.Locale.ROOT);
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20 changes: 20 additions & 0 deletions ...ics-config/src/test/java/io/prometheus/metrics/config/PrometheusPropertiesLoaderTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,22 @@ void externalPropertiesShouldOverridePropertiesFile() {
.isFalse();
}

@Test
void metricSpecificPropertiesShouldKeepMetricNameCase() {
Properties properties = new Properties();
properties.setProperty(
"io.prometheus.metrics.myLatency.histogram_classic_upper_bounds", ".005, .01, .015");
properties.setProperty("io.prometheus.metrics.HTTP_duration.histogramNativeOnly", "true");

PrometheusProperties prometheusProperties = PrometheusPropertiesLoader.load(properties);
assertThat(
prometheusProperties.getMetricProperties("myLatency").getHistogramClassicUpperBounds())
.containsExactly(0.005, 0.01, 0.015);
assertThat(prometheusProperties.getMetricProperties("HTTP_duration").getHistogramNativeOnly())
.isTrue();
assertThat(prometheusProperties.getMetricProperties("my_latency")).isNull();
}

@Test
void environmentVariablesShouldConfigureMetrics() {
// Simulate environment variables as they would be loaded
Expand Down Expand Up @@ -160,6 +176,10 @@ void normalizePropertyKeyShouldConvertCamelCaseToSnakeCase() {
PrometheusPropertiesLoader.normalizePropertyKey(
"io.prometheus.exporter.openTelemetry.serviceName"))
.isEqualTo("io.prometheus.exporter.open_telemetry.service_name");
assertThat(
PrometheusPropertiesLoader.normalizePropertyKey(
"io.prometheus.metrics.myLatency.histogramNativeOnly"))
.isEqualTo("io.prometheus.metrics.myLatency.histogram_native_only");

// Test that snake_case keys remain unchanged
assertThat(
Expand Down
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