Merge pull request #45203 from shakuzen

* pr/45203:
  Polish 'Support Per-meter configuration for OtlpMetricsProperties'
  Support Per-meter configuration for OtlpMetricsProperties

Closes gh-45203

Author: philwebb

Diff for: spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/export/otlp/OtlpMetricsProperties.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.actuate.autoconfigure.metrics.export.otlp;
 
+import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
 
@@ -53,7 +54,7 @@ public class OtlpMetricsProperties extends StepRegistryProperties {
 	private Map<String, String> headers;
 
 	/**
-	 * Histogram type to be preferred when histogram publishing is enabled.
+	 * Default histogram type when histogram publishing is enabled.
 	 */
 	private HistogramFlavor histogramFlavor = HistogramFlavor.EXPLICIT_BUCKET_HISTOGRAM;
 
@@ -63,8 +64,8 @@ public class OtlpMetricsProperties extends StepRegistryProperties {
 	private int maxScale = 20;
 
 	/**
-	 * Maximum number of buckets to be used for exponential histograms, if configured.
-	 * This has no effect on explicit bucket histograms.
+	 * Default maximum number of buckets to be used for exponential histograms, if
+	 * configured. This has no effect on explicit bucket histograms.
 	 */
 	private int maxBucketCount = 160;
 
@@ -73,6 +74,11 @@ public class OtlpMetricsProperties extends StepRegistryProperties {
 	 */
 	private TimeUnit baseTimeUnit = TimeUnit.MILLISECONDS;
 
+	/**
+	 * Per-meter properties that can be used to override defaults.
+	 */
+	private Map<String, Meter> meter = new LinkedHashMap<>();
+
 	public String getUrl() {
 		return this.url;
 	}
@@ -129,4 +135,42 @@ public void setBaseTimeUnit(TimeUnit baseTimeUnit) {
 		this.baseTimeUnit = baseTimeUnit;
 	}
 
+	public Map<String, Meter> getMeter() {
+		return this.meter;
+	}
+
+	/**
+	 * Per-meter settings.
+	 */
+	public static class Meter {
+
+		/**
+		 * Maximum number of buckets to be used for exponential histograms, if configured.
+		 * This has no effect on explicit bucket histograms.
+		 */
+		private Integer maxBucketCount;
+
+		/**
+		 * Histogram type when histogram publishing is enabled.
+		 */
+		private HistogramFlavor histogramFlavor;
+
+		public Integer getMaxBucketCount() {
+			return this.maxBucketCount;
+		}
+
+		public void setMaxBucketCount(Integer maxBucketCount) {
+			this.maxBucketCount = maxBucketCount;
+		}
+
+		public HistogramFlavor getHistogramFlavor() {
+			return this.histogramFlavor;
+		}
+
+		public void setHistogramFlavor(HistogramFlavor histogramFlavor) {
+			this.histogramFlavor = histogramFlavor;
+		}
+
+	}
+
 }

Diff for: spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/export/otlp/OtlpMetricsPropertiesConfigAdapter.java

@@ -20,15 +20,18 @@
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
 
 import io.micrometer.registry.otlp.AggregationTemporality;
 import io.micrometer.registry.otlp.HistogramFlavor;
 import io.micrometer.registry.otlp.OtlpConfig;
 
+import org.springframework.boot.actuate.autoconfigure.metrics.export.otlp.OtlpMetricsProperties.Meter;
 import org.springframework.boot.actuate.autoconfigure.metrics.export.properties.StepRegistryPropertiesConfigAdapter;
 import org.springframework.boot.actuate.autoconfigure.opentelemetry.OpenTelemetryProperties;
 import org.springframework.boot.actuate.autoconfigure.opentelemetry.OpenTelemetryResourceAttributes;
 import org.springframework.core.env.Environment;
+import org.springframework.util.CollectionUtils;
 
 /**
  * Adapter to convert {@link OtlpMetricsProperties} to an {@link OtlpConfig}.
@@ -88,6 +91,16 @@ public HistogramFlavor histogramFlavor() {
 		return get(OtlpMetricsProperties::getHistogramFlavor, OtlpConfig.super::histogramFlavor);
 	}
 
+	@Override
+	public Map<String, HistogramFlavor> histogramFlavorPerMeter() {
+		return get(perMeter(Meter::getHistogramFlavor), OtlpConfig.super::histogramFlavorPerMeter);
+	}
+
+	@Override
+	public Map<String, Integer> maxBucketsPerMeter() {
+		return get(perMeter(Meter::getMaxBucketCount), OtlpConfig.super::maxBucketsPerMeter);
+	}
+
 	@Override
 	public int maxScale() {
 		return get(OtlpMetricsProperties::getMaxScale, OtlpConfig.super::maxScale);
@@ -103,4 +116,21 @@ public TimeUnit baseTimeUnit() {
 		return get(OtlpMetricsProperties::getBaseTimeUnit, OtlpConfig.super::baseTimeUnit);
 	}
 
+	private <V> Function<OtlpMetricsProperties, Map<String, V>> perMeter(Function<Meter, V> getter) {
+		return (properties) -> {
+			if (CollectionUtils.isEmpty(properties.getMeter())) {
+				return null;
+			}
+			Map<String, V> perMeter = new LinkedHashMap<>();
+			properties.getMeter().forEach((key, meterProperties) -> {
+				V value = getter.apply(meterProperties);
+				if (value != null) {
+					perMeter.put(key, value);
+				}
+			});
+			return (!perMeter.isEmpty()) ? perMeter : null;
+		};
+
+	}
+
 }

Diff for: spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/metrics/export/otlp/OtlpMetricsPropertiesConfigAdapterTests.java

@@ -25,6 +25,7 @@
 import org.junit.jupiter.api.Test;
 
 import org.springframework.boot.actuate.autoconfigure.metrics.export.otlp.OtlpMetricsExportAutoConfiguration.PropertiesOtlpMetricsConnectionDetails;
+import org.springframework.boot.actuate.autoconfigure.metrics.export.otlp.OtlpMetricsProperties.Meter;
 import org.springframework.boot.actuate.autoconfigure.opentelemetry.OpenTelemetryProperties;
 import org.springframework.mock.env.MockEnvironment;
 
@@ -110,6 +111,20 @@ void whenPropertiesHistogramFlavorIsSetAdapterHistogramFlavorReturnsIt() {
 		assertThat(createAdapter().histogramFlavor()).isSameAs(HistogramFlavor.BASE2_EXPONENTIAL_BUCKET_HISTOGRAM);
 	}
 
+	@Test
+	void whenPropertiesHistogramFlavorPerMeterIsNotSetAdapterHistogramFlavorReturnsEmptyMap() {
+		assertThat(createAdapter().histogramFlavorPerMeter()).isEmpty();
+	}
+
+	@Test
+	void whenPropertiesHistogramFlavorPerMeterIsSetAdapterHistogramFlavorPerMeterReturnsIt() {
+		Meter meterProperties = new Meter();
+		meterProperties.setHistogramFlavor(HistogramFlavor.BASE2_EXPONENTIAL_BUCKET_HISTOGRAM);
+		this.properties.getMeter().put("my.histograms", meterProperties);
+		assertThat(createAdapter().histogramFlavorPerMeter()).containsEntry("my.histograms",
+				HistogramFlavor.BASE2_EXPONENTIAL_BUCKET_HISTOGRAM);
+	}
+
 	@Test
 	void whenPropertiesMaxScaleIsNotSetAdapterMaxScaleReturns20() {
 		assertThat(createAdapter().maxScale()).isEqualTo(20);
@@ -132,6 +147,19 @@ void whenPropertiesMaxBucketCountIsSetAdapterMaxBucketCountReturnsIt() {
 		assertThat(createAdapter().maxBucketCount()).isEqualTo(6);
 	}
 
+	@Test
+	void whenPropertiesMaxBucketsPerMeterIsNotSetAdapterMaxBucketsPerMeterReturnsEmptyMap() {
+		assertThat(createAdapter().maxBucketsPerMeter()).isEmpty();
+	}
+
+	@Test
+	void whenPropertiesMaxBucketsPerMeterIsSetAdapterMaxBucketsPerMeterReturnsIt() {
+		Meter meterProperties = new Meter();
+		meterProperties.setMaxBucketCount(111);
+		this.properties.getMeter().put("my.histograms", meterProperties);
+		assertThat(createAdapter().maxBucketsPerMeter()).containsEntry("my.histograms", 111);
+	}
+
 	@Test
 	void whenPropertiesBaseTimeUnitIsNotSetAdapterBaseTimeUnitReturnsMillis() {
 		assertThat(createAdapter().baseTimeUnit()).isSameAs(TimeUnit.MILLISECONDS);

Diff for: spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/metrics/export/otlp/OtlpMetricsPropertiesTests.java

@@ -40,6 +40,7 @@ void defaultValuesAreConsistent() {
 		assertThat(properties.getMaxScale()).isEqualTo(config.maxScale());
 		assertThat(properties.getMaxBucketCount()).isEqualTo(config.maxBucketCount());
 		assertThat(properties.getBaseTimeUnit()).isSameAs(config.baseTimeUnit());
+		assertThat(properties.getMeter()).isEmpty();
 	}
 
 }