apply review

docs/modules/ROOT/pages/spring-cloud-netflix.adoc

@@ -606,15 +606,14 @@ Spring Cloud Netflix Eureka Server does not support Spring AOT transformations o
 
 === Metrics
 
-Starting with version 4.1.1, `MultuGuage` listens events related to Eureka instances and creates and updates Eureka instance information in the metrics registry. By default, this setting is disabled, if you want to enable it, you need to change `eureka.server.metrics.enabled` to `true`.
+`EurekaInstanceMonitor` listens to events related to Eureka instance registration and creates/updates `Gauge`s for Eureka instance information Micrometer's `MeterRegistry`. By default, this behavior is disabled. Ff you want to enable it, you need to set `eureka.server.metrics.enabled` to `true`.
 
-The multi-gauge is named `eureka.server.instance.status` and has the following tags (value are merged based on tags)
+By default, the `Gauge`s are named `eureka.server.instances` and have the following tags:
 
 - `application`: application name
+- `status`: instance status (`UP`, `DOWN`, `STARTING`, `OUT_OF_SERVICE`, `UNKNOWN`, see: `com.netflix.appinfo.InstanceInfo.InstanceStatus`)
 
-- `status`: instance status
-
-You can add additional tags by implementing `EurekaInstanceTagsProvider` separately. However, status is added separately because it is always needed.
+You can add additional tags by injecting your own implementation of `EurekaInstanceTagsProvider`.
 
 == Configuration properties
 

spring-cloud-netflix-eureka-server/src/main/java/org/springframework/cloud/netflix/eureka/server/metrics/DefaultEurekaInstanceTagsProvider.java

@@ -24,7 +24,7 @@
  * Default implementation for {@link EurekaInstanceTagsProvider}.
  *
  * @author Wonchul Heo
- * @since 4.1.1
+ * @since 4.1.2
  */
 class DefaultEurekaInstanceTagsProvider implements EurekaInstanceTagsProvider {
 

spring-cloud-netflix-eureka-server/src/main/java/org/springframework/cloud/netflix/eureka/server/metrics/EurekaInstanceMetricsAutoConfiguration.java

@@ -32,8 +32,8 @@
 /**
  * Auto-configuration for Eureka Instance metrics.
  *
- * @author wonchul heo
- * @since 4.1.1
+ * @author Wonchul Heo
+ * @since 4.1.2
  */
 @ConditionalOnClass(MeterRegistry.class)
 @ConditionalOnBean(MeterRegistry.class)

spring-cloud-netflix-eureka-server/src/main/java/org/springframework/cloud/netflix/eureka/server/metrics/EurekaInstanceMonitor.java

@@ -36,7 +36,7 @@
  * {@link PeerAwareInstanceRegistry}.
  *
  * @author Wonchul Heo
- * @since 4.1.1
+ * @since 4.1.2
  */
 public class EurekaInstanceMonitor implements SmartApplicationListener {
 
@@ -52,12 +52,13 @@ public class EurekaInstanceMonitor implements SmartApplicationListener {
 		this.instanceRegistry = Objects.requireNonNull(instanceRegistry);
 		this.tagProvider = Objects.requireNonNull(tagProvider);
 		this.eurekaInstances = MultiGauge.builder("eureka.server.instances")
-				.description("Count of application instances registered with the Eureka server.")
+				.description("Number of application instances registered with the Eureka server.")
 				.register(meterRegistry);
 	}
 
 	@Override
 	public boolean supportsEventType(Class<? extends ApplicationEvent> eventType) {
+		// If events that change state are added, an event class must be added.
 		return EurekaInstanceCanceledEvent.class.isAssignableFrom(eventType)
 				|| EurekaInstanceRegisteredEvent.class.isAssignableFrom(eventType)
 				|| EurekaInstanceRenewedEvent.class.isAssignableFrom(eventType);
@@ -69,6 +70,7 @@ public void onApplicationEvent(ApplicationEvent event) {
 				.flatMap(application -> application.getInstances().stream())
 				.collect(Collectors.groupingBy(tagProvider::eurekaInstanceTags, Collectors.counting()));
 		eurekaInstances.register(aggregatedCounts.entrySet().stream()
-				.map(it -> MultiGauge.Row.of(it.getKey(), it.getValue())).collect(Collectors.toList()), true);
+				.map(entry -> MultiGauge.Row.of(entry.getKey(), entry.getValue())).collect(Collectors.toList()), true);
 	}
+
 }

spring-cloud-netflix-eureka-server/src/main/java/org/springframework/cloud/netflix/eureka/server/metrics/EurekaInstanceTagsProvider.java

@@ -17,14 +17,13 @@
 package org.springframework.cloud.netflix.eureka.server.metrics;
 
 import com.netflix.appinfo.InstanceInfo;
-import io.micrometer.core.instrument.Tag;
 import io.micrometer.core.instrument.Tags;
 
 /**
- * Provides {@link Tag Tags} for Eureka instance metrics.
+ * Provides {@link Tags} for Eureka instance metrics.
  *
  * @author Wonchul Heo
- * @since 4.1.1
+ * @since 4.1.2
  */
 public interface EurekaInstanceTagsProvider {
 

spring-cloud-netflix-eureka-server/src/test/java/org/springframework/cloud/netflix/eureka/server/EurekaInstancesFixture.java → spring-cloud-netflix-eureka-server/src/test/java/org/springframework/cloud/netflix/eureka/server/EurekaInstanceFixture.java

@@ -19,9 +19,9 @@
 import com.netflix.appinfo.InstanceInfo;
 import com.netflix.appinfo.LeaseInfo;
 
-public final class EurekaInstancesFixture {
+public final class EurekaInstanceFixture {
 
-	private EurekaInstancesFixture() {
+	private EurekaInstanceFixture() {
 	}
 
 	public static LeaseInfo getLeaseInfo() {

spring-cloud-netflix-eureka-server/src/test/java/org/springframework/cloud/netflix/eureka/server/EurekaInstanceMonitorTests.java

@@ -22,7 +22,6 @@
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.Tag;
 import io.micrometer.core.instrument.Tags;
-import io.micrometer.core.instrument.search.MeterNotFoundException;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
@@ -32,9 +31,8 @@
 import org.springframework.context.annotation.Configuration;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatThrownBy;
-import static org.springframework.cloud.netflix.eureka.server.EurekaInstancesFixture.getInstanceInfo;
-import static org.springframework.cloud.netflix.eureka.server.EurekaInstancesFixture.getLeaseInfo;
+import static org.springframework.cloud.netflix.eureka.server.EurekaInstanceFixture.getInstanceInfo;
+import static org.springframework.cloud.netflix.eureka.server.EurekaInstanceFixture.getLeaseInfo;
 
 /**
  * @author Wonchul Heo
@@ -45,6 +43,7 @@
 class EurekaInstanceMonitorTests {
 
 	private static final String FOO_APP_NAME = "FOO-APP-NAME";
+
 	private static final String BAR_APP_NAME = "BAR-APP-NAME";
 
 	@Autowired
@@ -54,8 +53,11 @@ class EurekaInstanceMonitorTests {
 	private MeterRegistry meterRegistry;
 
 	private InstanceInfo fooInstanceInfo;
+
 	private InstanceInfo fooInstanceInfo2;
+
 	private InstanceInfo barInstanceInfo;
+
 	private InstanceInfo barInstanceInfo2;
 
 	@BeforeEach
@@ -70,9 +72,7 @@ void setup() {
 
 	@Test
 	void testNoRegistration() {
-		assertThatThrownBy(() -> {
-			meterRegistry.get("eureka.server.instances").meter();
-		}).isInstanceOf(MeterNotFoundException.class);
+		assertThat(meterRegistry.find("eureka.server.instances").gauge()).isNull();
 	}
 
 	@Test
@@ -151,10 +151,9 @@ private static Tags tags(InstanceInfo instanceInfo) {
 	}
 
 	private void assertEurekaInstance(Map<Tags, Long> meterRegistryCounts) {
-		meterRegistryCounts.forEach((tags, count) -> {
-			assertThat((long) meterRegistry.get("eureka.server.instances").tags(tags).gauge().value())
-					.isEqualTo(count);
-		});
+		meterRegistryCounts.forEach((tags,
+				count) -> assertThat((long) meterRegistry.get("eureka.server.instances").tags(tags).gauge().value())
+						.isEqualTo(count));
 	}
 
 	@Configuration(proxyBeanMethods = false)
@@ -163,4 +162,5 @@ private void assertEurekaInstance(Map<Tags, Long> meterRegistryCounts) {
 	protected static class Application {
 
 	}
+
 }

spring-cloud-netflix-eureka-server/src/test/java/org/springframework/cloud/netflix/eureka/server/InstanceRegistryTests.java

@@ -37,8 +37,8 @@
 import org.springframework.context.event.SmartApplicationListener;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.springframework.cloud.netflix.eureka.server.EurekaInstancesFixture.getInstanceInfo;
-import static org.springframework.cloud.netflix.eureka.server.EurekaInstancesFixture.getLeaseInfo;
+import static org.springframework.cloud.netflix.eureka.server.EurekaInstanceFixture.getInstanceInfo;
+import static org.springframework.cloud.netflix.eureka.server.EurekaInstanceFixture.getLeaseInfo;
 
 /**
  * @author Bartlomiej Slota