Add resource labels to Stackdriver metrics configuration properties

Using resource labels is mandatory for most Stackdriver resources other
than 'Global', i.e. k8s_pod. Configuring valid resource type along with
related labels makes it possible to use given metric in a wider set of
GCP solutions, i.e. custom metric based GKE pod horizontal autoscaler.

See gh-26961

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/export/stackdriver/StackdriverProperties.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.actuate.autoconfigure.metrics.export.stackdriver;
 
+import java.util.Map;
+
 import org.springframework.boot.actuate.autoconfigure.metrics.export.properties.StepRegistryProperties;
 import org.springframework.boot.context.properties.ConfigurationProperties;
 
@@ -40,6 +42,11 @@ public class StackdriverProperties extends StepRegistryProperties {
 	 */
 	private String resourceType = "global";
 
+	/**
+	 * Monitored resource's labels.
+	 */
+	private Map<String, String> resourceLabels;
+
 	public String getProjectId() {
 		return this.projectId;
 	}
@@ -56,4 +63,12 @@ public class StackdriverProperties extends StepRegistryProperties {
 		this.resourceType = resourceType;
 	}
 
+	public Map<String, String> getResourceLabels() {
+		return this.resourceLabels;
+	}
+
+	public void setResourceLabels(Map<String, String> resourceLabels) {
+		this.resourceLabels = resourceLabels;
+	}
+
 }

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/export/stackdriver/StackdriverPropertiesConfigAdapter.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.actuate.autoconfigure.metrics.export.stackdriver;
 
+import java.util.Map;
+
 import io.micrometer.stackdriver.StackdriverConfig;
 
 import org.springframework.boot.actuate.autoconfigure.metrics.export.properties.StepRegistryPropertiesConfigAdapter;
@@ -48,4 +50,9 @@ public class StackdriverPropertiesConfigAdapter extends StepRegistryPropertiesCo
 		return get(StackdriverProperties::getResourceType, StackdriverConfig.super::resourceType);
 	}
 
+	@Override
+	public Map<String, String> resourceLabels() {
+		return get(StackdriverProperties::getResourceLabels, StackdriverConfig.super::resourceLabels);
+	}
+
 }

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/metrics/export/stackdriver/StackdriverPropertiesConfigAdapterTests.java

@@ -16,6 +16,9 @@
 
 package org.springframework.boot.actuate.autoconfigure.metrics.export.stackdriver;
 
+import java.util.HashMap;
+import java.util.Map;
+
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -41,4 +44,15 @@ class StackdriverPropertiesConfigAdapterTests {
 		assertThat(new StackdriverPropertiesConfigAdapter(properties).resourceType()).isEqualTo("my-resource-type");
 	}
 
+	@Test
+	void whenPropertiesResourceLabelsAreSetAdapterResourceTypeReturnsThem() {
+		final Map<String, String> labels = new HashMap<>();
+		labels.put("labelOne", "valueOne");
+		labels.put("labelTwo", "valueTwo");
+		StackdriverProperties properties = new StackdriverProperties();
+		properties.setResourceLabels(labels);
+		assertThat(new StackdriverPropertiesConfigAdapter(properties).resourceLabels())
+				.containsExactlyInAnyOrderEntriesOf(labels);
+	}
+
 }