Add property for common key/values on observations

- Deprecates 'management.metrics.tags.*'

Closes gh-33241

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

@@ -79,6 +79,7 @@ public class MetricsProperties {
 		return this.enable;
 	}
 
+	@DeprecatedConfigurationProperty(replacement = "management.observations.key-values")
 	public Map<String, String> getTags() {
 		return this.tags;
 	}

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/observation/ObservationAutoConfiguration.java

@@ -43,6 +43,7 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClas
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.annotation.Order;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for the Micrometer Observation API.
@@ -75,6 +76,12 @@ public class ObservationAutoConfiguration {
 		return ObservationRegistry.create();
 	}
 
+	@Bean
+	@Order(0)
+	PropertiesObservationFilter propertiesObservationFilter(ObservationProperties properties) {
+		return new PropertiesObservationFilter(properties);
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	@ConditionalOnClass(MeterRegistry.class)
 	@ConditionalOnMissingClass("io.micrometer.tracing.Tracer")

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/observation/ObservationProperties.java

@@ -16,6 +16,9 @@
 
 package org.springframework.boot.actuate.autoconfigure.observation;
 
+import java.util.LinkedHashMap;
+import java.util.Map;
+
 import org.springframework.boot.context.properties.ConfigurationProperties;
 
 /**
@@ -30,10 +33,23 @@ public class ObservationProperties {
 
 	private final Http http = new Http();
 
+	/**
+	 * Common key-values that are applied to every observation.
+	 */
+	private Map<String, String> keyValues = new LinkedHashMap<>();
+
 	public Http getHttp() {
 		return this.http;
 	}
 
+	public Map<String, String> getKeyValues() {
+		return this.keyValues;
+	}
+
+	public void setKeyValues(Map<String, String> keyValues) {
+		this.keyValues = keyValues;
+	}
+
 	public static class Http {
 
 		private final Client client = new Client();

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/observation/PropertiesObservationFilter.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2012-2023 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.autoconfigure.observation;
+
+import java.util.Map.Entry;
+
+import io.micrometer.common.KeyValues;
+import io.micrometer.observation.Observation.Context;
+import io.micrometer.observation.ObservationFilter;
+
+/**
+ * {@link ObservationFilter} to apply settings from {@link ObservationProperties}.
+ *
+ * @author Moritz Halbritter
+ */
+class PropertiesObservationFilter implements ObservationFilter {
+
+	private final ObservationFilter delegate;
+
+	PropertiesObservationFilter(ObservationProperties properties) {
+		this.delegate = createDelegate(properties);
+	}
+
+	@Override
+	public Context map(Context context) {
+		return this.delegate.map(context);
+	}
+
+	private static ObservationFilter createDelegate(ObservationProperties properties) {
+		if (properties.getKeyValues().isEmpty()) {
+			return (context) -> context;
+		}
+		KeyValues keyValues = KeyValues.of(properties.getKeyValues().entrySet(), Entry::getKey, Entry::getValue);
+		return (context) -> context.addLowCardinalityKeyValues(keyValues);
+	}
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/observation/ObservationAutoConfigurationTests.java

@@ -189,6 +189,21 @@ class ObservationAutoConfigurationTests {
 		});
 	}
 
+	@Test
+	void shouldSupplyPropertiesObservationFilterBean() {
+		this.contextRunner.run((context) -> assertThat(context).hasSingleBean(PropertiesObservationFilter.class));
+	}
+
+	@Test
+	void shouldApplyCommonKeyValuesToObservations() {
+		this.contextRunner.withPropertyValues("management.observations.key-values.a=alpha").run((context) -> {
+			ObservationRegistry observationRegistry = context.getBean(ObservationRegistry.class);
+			Observation.start("keyvalues", observationRegistry).stop();
+			MeterRegistry meterRegistry = context.getBean(MeterRegistry.class);
+			assertThat(meterRegistry.get("keyvalues").tag("a", "alpha").timer().count()).isOne();
+		});
+	}
+
 	@Test
 	void autoConfiguresGlobalObservationConventions() {
 		this.contextRunner.withUserConfiguration(CustomGlobalObservationConvention.class).run((context) -> {

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/observation/PropertiesObservationFilterTests.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2012-2023 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.autoconfigure.observation;
+
+import io.micrometer.common.KeyValue;
+import io.micrometer.common.KeyValues;
+import io.micrometer.observation.Observation.Context;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link PropertiesObservationFilter}.
+ *
+ * @author Moritz Halbritter
+ */
+class PropertiesObservationFilterTests {
+
+	@Test
+	void shouldDoNothingIfKeyValuesAreEmpty() {
+		PropertiesObservationFilter filter = createFilter();
+		Context mapped = mapContext(filter, "a", "alpha");
+		assertThat(mapped.getLowCardinalityKeyValues()).containsExactly(KeyValue.of("a", "alpha"));
+	}
+
+	@Test
+	void shouldAddKeyValues() {
+		PropertiesObservationFilter filter = createFilter("b", "beta");
+		Context mapped = mapContext(filter, "a", "alpha");
+		assertThat(mapped.getLowCardinalityKeyValues()).containsExactly(KeyValue.of("a", "alpha"),
+				KeyValue.of("b", "beta"));
+	}
+
+	private static Context mapContext(PropertiesObservationFilter filter, String... initialKeyValues) {
+		Context context = new Context();
+		context.addLowCardinalityKeyValues(KeyValues.of(initialKeyValues));
+		return filter.map(context);
+	}
+
+	private static PropertiesObservationFilter createFilter(String... keyValues) {
+		ObservationProperties properties = new ObservationProperties();
+		for (int i = 0; i < keyValues.length; i += 2) {
+			properties.getKeyValues().put(keyValues[i], keyValues[i + 1]);
+		}
+		return new PropertiesObservationFilter(properties);
+	}
+
+}

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

@@ -1100,19 +1100,8 @@ These use the global registry that is not Spring-managed.
 
 [[actuator.metrics.customizing.common-tags]]
 ==== Common Tags
-Common tags are generally used for dimensional drill-down on the operating environment, such as host, instance, region, stack, and others.
-Commons tags are applied to all meters and can be configured, as the following example shows:
 
-[source,yaml,indent=0,subs="verbatim",configprops,configblocks]
-----
-	management:
-	  metrics:
-	    tags:
-	      region: "us-east-1"
-	      stack: "prod"
-----
-
-The preceding example adds `region` and `stack` tags to all meters with a value of `us-east-1` and `prod`, respectively.
+You can configure common tags using the <<actuator#actuator.observability.common-key-values, configprop:management.observations.key-values[] property>>.
 
 NOTE: The order of common tags is important if you use Graphite.
 As the order of common tags cannot be guaranteed by using this approach, Graphite users are advised to define a custom `MeterFilter` instead.

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

@@ -9,9 +9,9 @@ To create your own observations (which will lead to metrics and traces), you can
 
 include::code:MyCustomObservation[]
 
-NOTE: Low cardinality tags will be added to metrics and traces, while high cardinality tags will only be added to traces.
+NOTE: Low cardinality key-values will be added to metrics and traces, while high cardinality key-values will only be added to traces.
 
-Beans of type `ObservationPredicate`, `GlobalObservationConvention` and `ObservationHandler` will be automatically registered on the `ObservationRegistry`.
+Beans of type `ObservationPredicate`, `GlobalObservationConvention`, `ObservationFilter` and `ObservationHandler` will be automatically registered on the `ObservationRegistry`.
 You can additionally register any number of `ObservationRegistryCustomizer` beans to further configure the registry.
 
 For more details please see the https://micrometer.io/docs/observation[Micrometer Observation documentation].
@@ -21,4 +21,20 @@ For JDBC, the https://github.com/jdbc-observations/datasource-micrometer[Datasou
 Read more about it https://jdbc-observations.github.io/datasource-micrometer/docs/current/docs/html/[in the reference documentation].
 For R2DBC, the https://github.com/spring-projects-experimental/r2dbc-micrometer-spring-boot[Spring Boot Auto Configuration for R2DBC Observation] creates observations for R2DBC query invocations.
 
+[[actuator.observability.common-key-values]]
+=== Common Key-Values
+Common key-values are generally used for dimensional drill-down on the operating environment, such as host, instance, region, stack, and others.
+Commons key-values are applied to all observations as low cardinality key-values and can be configured, as the following example shows:
+
+[source,yaml,indent=0,subs="verbatim",configprops,configblocks]
+----
+	management:
+	  observations:
+	    key-values:
+	      region: "us-east-1"
+	      stack: "prod"
+----
+
+The preceding example adds `region` and `stack` key-values to all observations with a value of `us-east-1` and `prod`, respectively.
+
 The next sections will provide more details about logging, metrics and traces.