Fix handling of whole numbers for min/max expected value and slo

Previously, a whole number string would be parsed into a Duration.
Duration values are ignored for distribution summary meters which
results in unexpected values when configuring minimum and maximum
expected values and SLO boundaries.

Strings like 20d are ambiguous as they can be either a duration of
20 days or a double of 20. To preserve existing behavior where 20d
was interpreted as a 20-day duration, strings that contain only
digits are parsed into a double which is ultimately treated as a
number of milliseconds, the same unit as if it had been parsed into
a Duration. Otherwise we fall back to the existing behavior of
trying a Duration and then falling back to parsing a double.

Note that negative values do not need to be considered. As per their
javadoc, DistributionSummary and Timer implementations drop negative
amounts passed to record. As a result, negative values for min and
max expected values and SLO boundaries do not make sense.

Fixes gh-50021

Author: wilkinsona

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

@@ -22,6 +22,7 @@
 import io.micrometer.core.instrument.Meter.Type;
 
 import org.springframework.boot.convert.DurationStyle;
+import org.springframework.util.StringUtils;
 
 /**
  * A meter value that is used when configuring micrometer. Can be a String representation
@@ -86,13 +87,28 @@ private Long getTimerValue() {
 	 * @return a {@link MeterValue} instance
 	 */
 	public static MeterValue valueOf(String value) {
+		if (onlyDigits(value)) {
+			return new MeterValue(Double.parseDouble(value));
+		}
 		Duration duration = safeParseDuration(value);
 		if (duration != null) {
 			return new MeterValue(duration);
 		}
 		return new MeterValue(Double.parseDouble(value));
 	}
 
+	private static boolean onlyDigits(String value) {
+		if (!StringUtils.hasLength(value)) {
+			return false;
+		}
+		for (char c : value.toCharArray()) {
+			if (!Character.isDigit(c)) {
+				return false;
+			}
+		}
+		return true;
+	}
+
 	/**
 	 * Return a new {@link MeterValue} instance for the given double value.
 	 * @param value the source value

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

@@ -35,17 +35,29 @@
 class MeterValueTests {
 
 	@Test
-	void getValueForDistributionSummaryWhenFromNumberShouldReturnDoubleValue() {
+	void getValueForDistributionSummaryWhenFromDecimalNumberShouldReturnDoubleValue() {
 		MeterValue meterValue = MeterValue.valueOf(123.42);
 		assertThat(meterValue.getValue(Type.DISTRIBUTION_SUMMARY)).isEqualTo(123.42);
 	}
 
 	@Test
-	void getValueForDistributionSummaryWhenFromNumberStringShouldReturnDoubleValue() {
+	void getValueForDistributionSummaryWhenFromWholeNumberShouldReturnDoubleValue() {
+		MeterValue meterValue = MeterValue.valueOf(123);
+		assertThat(meterValue.getValue(Type.DISTRIBUTION_SUMMARY)).isEqualTo(123);
+	}
+
+	@Test
+	void getValueForDistributionSummaryWhenFromDecimalNumberStringShouldReturnDoubleValue() {
 		MeterValue meterValue = MeterValue.valueOf("123.42");
 		assertThat(meterValue.getValue(Type.DISTRIBUTION_SUMMARY)).isEqualTo(123.42);
 	}
 
+	@Test
+	void getValueForDistributionSummaryWhenFromWholeNumberStringShouldReturnDoubleValue() {
+		MeterValue meterValue = MeterValue.valueOf("123");
+		assertThat(meterValue.getValue(Type.DISTRIBUTION_SUMMARY)).isEqualTo(123);
+	}
+
 	@Test
 	void getValueForDistributionSummaryWhenFromDurationStringShouldReturnNull() {
 		MeterValue meterValue = MeterValue.valueOf("123ms");

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

@@ -205,13 +205,21 @@ void configureWhenAllPercentilesSetShouldSetPercentilesToValue() {
 	}
 
 	@Test
-	void configureWhenHasSloShouldSetSloToValue() {
+	void configureWhenTimerMeterHasSloShouldSetSloToValue() {
 		PropertiesMeterFilter filter = new PropertiesMeterFilter(
 				createProperties("distribution.slo.spring.boot=1,2,3"));
 		assertThat(filter.configure(createMeterId("spring.boot"), DistributionStatisticConfig.DEFAULT)
 			.getServiceLevelObjectiveBoundaries()).containsExactly(1000000, 2000000, 3000000);
 	}
 
+	@Test
+	void configureWhenDistributionSummaryMeterHasSloShouldSetSloToValue() {
+		PropertiesMeterFilter filter = new PropertiesMeterFilter(createProperties("distribution.slo.example=1,2,3"));
+		assertThat(filter
+			.configure(createMeterId("example", Meter.Type.DISTRIBUTION_SUMMARY), DistributionStatisticConfig.DEFAULT)
+			.getServiceLevelObjectiveBoundaries()).containsExactly(1.0, 2.0, 3.0);
+	}
+
 	@Test
 	void configureWhenHasHigherSloShouldSetPercentilesToValue() {
 		PropertiesMeterFilter filter = new PropertiesMeterFilter(createProperties("distribution.slo.spring=1,2,3"));
@@ -228,13 +236,23 @@ void configureWhenHasHigherSloAndLowerShouldSetSloToLower() {
 	}
 
 	@Test
-	void configureWhenHasMinimumExpectedValueShouldSetMinimumExpectedToValue() {
+	void configureWhenTimerMeterHasMinimumExpectedValueShouldSetMinimumExpectedToValue() {
 		PropertiesMeterFilter filter = new PropertiesMeterFilter(
 				createProperties("distribution.minimum-expected-value.spring.boot=10"));
 		assertThat(filter.configure(createMeterId("spring.boot"), DistributionStatisticConfig.DEFAULT)
 			.getMinimumExpectedValueAsDouble()).isEqualTo(Duration.ofMillis(10).toNanos());
 	}
 
+	@Test
+	void configureWhenDistributionSummaryMeterHasMinimumExpectedValueShouldSetMinimumExpectedToValue() {
+		PropertiesMeterFilter filter = new PropertiesMeterFilter(
+				createProperties("distribution.minimum-expected-value.spring.boot=10"));
+		assertThat(filter
+			.configure(createMeterId("spring.boot", Meter.Type.DISTRIBUTION_SUMMARY),
+					DistributionStatisticConfig.DEFAULT)
+			.getMinimumExpectedValueAsDouble()).isEqualTo(10);
+	}
+
 	@Test
 	void configureWhenHasHigherMinimumExpectedValueShouldSetMinimumExpectedValueToValue() {
 		PropertiesMeterFilter filter = new PropertiesMeterFilter(
@@ -252,13 +270,23 @@ void configureWhenHasHigherMinimumExpectedValueAndLowerShouldSetMinimumExpectedV
 	}
 
 	@Test
-	void configureWhenHasMaximumExpectedValueShouldSetMaximumExpectedToValue() {
+	void configureWhenTimerMeterHasMaximumExpectedValueShouldSetMaximumExpectedToValue() {
 		PropertiesMeterFilter filter = new PropertiesMeterFilter(
 				createProperties("distribution.maximum-expected-value.spring.boot=5000"));
 		assertThat(filter.configure(createMeterId("spring.boot"), DistributionStatisticConfig.DEFAULT)
 			.getMaximumExpectedValueAsDouble()).isEqualTo(Duration.ofMillis(5000).toNanos());
 	}
 
+	@Test
+	void configureWhenDistributionSummaryMeterHasMaximumExpectedValueShouldSetMaximumExpectedToValue() {
+		PropertiesMeterFilter filter = new PropertiesMeterFilter(
+				createProperties("distribution.maximum-expected-value.spring.boot=10"));
+		assertThat(filter
+			.configure(createMeterId("spring.boot", Meter.Type.DISTRIBUTION_SUMMARY),
+					DistributionStatisticConfig.DEFAULT)
+			.getMaximumExpectedValueAsDouble()).isEqualTo(10);
+	}
+
 	@Test
 	void configureWhenHasHigherMaximumExpectedValueShouldSetMaximumExpectedValueToValue() {
 		PropertiesMeterFilter filter = new PropertiesMeterFilter(