Merge pull request #27584 from polarbear567

* pr/27584:
  Polish "Add expiry and bufferLength configuration properties"
  Add expiry and bufferLength configuration properties

Closes gh-27584

Author: snicoll

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/MetricsProperties.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.actuate.autoconfigure.metrics;
 
+import java.time.Duration;
 import java.util.LinkedHashMap;
 import java.util.Map;
 
@@ -296,6 +297,21 @@ public static class Distribution {
 		 */
 		private final Map<String, String> maximumExpectedValue = new LinkedHashMap<>();
 
+		/**
+		 * Maximum amount of time that samples for meter IDs starting with the specified
+		 * name are accumulated to decaying distribution statistics before they are reset
+		 * and rotated. The longest match wins, the key `all` can also be used to
+		 * configure all meters.
+		 */
+		private final Map<String, Duration> expiry = new LinkedHashMap<>();
+
+		/**
+		 * Number of histograms for meter IDs starting with the specified name to keep in
+		 * the ring buffer. The longest match wins, the key `all` can also be used to
+		 * configure all meters.
+		 */
+		private final Map<String, Integer> bufferLength = new LinkedHashMap<>();
+
 		public Map<String, Boolean> getPercentilesHistogram() {
 			return this.percentilesHistogram;
 		}
@@ -316,6 +332,14 @@ public Map<String, String> getMaximumExpectedValue() {
 			return this.maximumExpectedValue;
 		}
 
+		public Map<String, Duration> getExpiry() {
+			return this.expiry;
+		}
+
+		public Map<String, Integer> getBufferLength() {
+			return this.bufferLength;
+		}
+
 	}
 
 }

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/PropertiesMeterFilter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -89,7 +89,8 @@ public DistributionStatisticConfig configure(Meter.Id id, DistributionStatisticC
 						convertMeterValue(id.getType(), lookup(distribution.getMinimumExpectedValue(), id, null)))
 				.maximumExpectedValue(
 						convertMeterValue(id.getType(), lookup(distribution.getMaximumExpectedValue(), id, null)))
-				.build().merge(config);
+				.expiry(lookupWithFallbackToAll(distribution.getExpiry(), id, null))
+				.bufferLength(lookupWithFallbackToAll(distribution.getBufferLength(), id, null)).build().merge(config);
 	}
 
 	private double[] convertServiceLevelObjectives(Meter.Type meterType, ServiceLevelObjectiveBoundary[] slo) {

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/metrics/PropertiesMeterFilterTests.java

@@ -41,6 +41,7 @@
  * @author Phillip Webb
  * @author Jon Schneider
  * @author Artsiom Yudovin
+ * @author Leo Li
  */
 class PropertiesMeterFilterTests {
 
@@ -275,6 +276,71 @@ void configureWhenHasHigherMaximumExpectedValueAndLowerShouldSetMaximumExpectedV
 				.getMaximumExpectedValueAsDouble()).isEqualTo(Duration.ofMillis(10000).toNanos());
 	}
 
+	@Test
+	void configureWhenHasExpiryShouldSetExpiryToValue() {
+		PropertiesMeterFilter filter = new PropertiesMeterFilter(
+				createProperties("distribution.expiry[spring.boot]=5ms"));
+		assertThat(filter.configure(createMeterId("spring.boot"), DistributionStatisticConfig.DEFAULT).getExpiry())
+				.isEqualTo(Duration.ofMillis(5));
+	}
+
+	@Test
+	void configureWhenHasHigherExpiryShouldSetExpiryToValue() {
+		PropertiesMeterFilter filter = new PropertiesMeterFilter(createProperties("distribution.expiry.spring=5ms"));
+		assertThat(filter.configure(createMeterId("spring.boot"), DistributionStatisticConfig.DEFAULT).getExpiry())
+				.isEqualTo(Duration.ofMillis(5));
+	}
+
+	@Test
+	void configureWhenHasHigherExpiryAndLowerShouldSetExpiryToHigher() {
+		PropertiesMeterFilter filter = new PropertiesMeterFilter(
+				createProperties("distribution.expiry.spring=5ms", "distribution.expiry[spring.boot]=10ms"));
+		assertThat(filter.configure(createMeterId("spring.boot"), DistributionStatisticConfig.DEFAULT).getExpiry())
+				.isEqualTo(Duration.ofMillis(10));
+	}
+
+	@Test
+	void configureWhenAllExpirySetShouldSetExpiryToValue() {
+		PropertiesMeterFilter filter = new PropertiesMeterFilter(createProperties("distribution.expiry.all=5ms"));
+		assertThat(filter.configure(createMeterId("spring.boot"), DistributionStatisticConfig.DEFAULT).getExpiry())
+				.isEqualTo(Duration.ofMillis(5));
+	}
+
+	@Test
+	void configureWhenHasBufferLengthShouldSetBufferLengthToValue() {
+		PropertiesMeterFilter filter = new PropertiesMeterFilter(
+				createProperties("distribution.buffer-length.spring.boot=3"));
+		assertThat(
+				filter.configure(createMeterId("spring.boot"), DistributionStatisticConfig.DEFAULT).getBufferLength())
+						.isEqualTo(3);
+	}
+
+	@Test
+	void configureWhenHasHigherBufferLengthShouldSetBufferLengthToValue() {
+		PropertiesMeterFilter filter = new PropertiesMeterFilter(
+				createProperties("distribution.buffer-length.spring=3"));
+		assertThat(
+				filter.configure(createMeterId("spring.boot"), DistributionStatisticConfig.DEFAULT).getBufferLength())
+						.isEqualTo(3);
+	}
+
+	@Test
+	void configureWhenHasHigherBufferLengthAndLowerShouldSetBufferLengthToHigher() {
+		PropertiesMeterFilter filter = new PropertiesMeterFilter(
+				createProperties("distribution.buffer-length.spring=2", "distribution.buffer-length.spring.boot=3"));
+		assertThat(
+				filter.configure(createMeterId("spring.boot"), DistributionStatisticConfig.DEFAULT).getBufferLength())
+						.isEqualTo(3);
+	}
+
+	@Test
+	void configureWhenAllBufferLengthSetShouldSetBufferLengthToValue() {
+		PropertiesMeterFilter filter = new PropertiesMeterFilter(createProperties("distribution.buffer-length.all=3"));
+		assertThat(
+				filter.configure(createMeterId("spring.boot"), DistributionStatisticConfig.DEFAULT).getBufferLength())
+						.isEqualTo(3);
+	}
+
 	private Id createMeterId(String name) {
 		Meter.Type meterType = Type.TIMER;
 		return createMeterId(name, meterType);

spring-boot-project/spring-boot-docs/src/docs/asciidoc/actuator/metrics.adoc

@@ -1153,6 +1153,10 @@ The following properties allow per-meter customization:
 | configprop:management.metrics.distribution.percentiles[]
 | Publish percentile values computed in your application
 
+| configprop:management.metrics.distribution.expiry[], configprop:management.metrics.distribution.buffer-length[]
+| Give greater weight to recent samples by accumulating them in ring buffers which rotate after a configurable expiry, with a
+configurable buffer length.
+
 | configprop:management.metrics.distribution.slo[]
 | Publish a cumulative histogram with buckets defined by your service-level objectives.
 |===