Fixes spring-cloudgh-3685: Collect metrics for application instances

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

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2013-2024 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.cloud.netflix.eureka.server.metrics;
+
+import com.netflix.eureka.registry.PeerAwareInstanceRegistry;
+import io.micrometer.core.instrument.MeterRegistry;
+import org.springframework.boot.actuate.autoconfigure.metrics.CompositeMeterRegistryAutoConfiguration;
+import org.springframework.boot.actuate.autoconfigure.metrics.MetricsAutoConfiguration;
+import org.springframework.boot.autoconfigure.AutoConfigureAfter;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.cloud.netflix.eureka.server.EurekaServerAutoConfiguration;
+import org.springframework.context.annotation.Bean;
+
+/**
+ * @author heowc
+ */
+@ConditionalOnBean(MeterRegistry.class)
+@AutoConfigureAfter({
+		MetricsAutoConfiguration.class,
+		CompositeMeterRegistryAutoConfiguration.class,
+		EurekaServerAutoConfiguration.class})
+class EurekaInstanceMetricsAutoConfiguration {
+
+	@ConditionalOnMissingBean
+	@Bean
+	public EurekaInstanceMetricsBinder eurekaInstanceMetricsBinder(PeerAwareInstanceRegistry instanceRegistry) {
+		return new EurekaInstanceMetricsBinder(instanceRegistry);
+	}
+}

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

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2013-2024 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.cloud.netflix.eureka.server.metrics;
+
+import com.netflix.eureka.registry.PeerAwareInstanceRegistry;
+import io.micrometer.core.instrument.Gauge;
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.Tag;
+import io.micrometer.core.instrument.binder.MeterBinder;
+
+import java.util.List;
+import java.util.Objects;
+
+/**
+ * @author heowc
+ */
+public class EurekaInstanceMetricsBinder implements MeterBinder {
+
+	private final PeerAwareInstanceRegistry instanceRegistry;
+
+	EurekaInstanceMetricsBinder(PeerAwareInstanceRegistry instanceRegistry) {
+		this.instanceRegistry = Objects.requireNonNull(instanceRegistry);
+	}
+
+	@Override
+	public void bindTo(MeterRegistry meterRegistry) {
+		instanceRegistry.getApplications()
+				.getRegisteredApplications()
+				.stream()
+				.flatMap(application -> application.getInstances().stream())
+				.forEach(instanceInfo -> {
+					Gauge.builder("eureka.server.application.instances", () -> 1L)
+							.description("Information about application instances registered on the Eureka server.")
+							.tags(List.of(
+									Tag.of("application", instanceInfo.getAppName()),
+									Tag.of("id", instanceInfo.getId()),
+									Tag.of("host", instanceInfo.getHostName()),
+									Tag.of("port", String.valueOf(instanceInfo.getPort())),
+									Tag.of("status", instanceInfo.getStatus().name())
+							))
+							.register(meterRegistry);
+				});
+	}
+}

spring-cloud-netflix-eureka-server/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports

@@ -1 +1,2 @@
-org.springframework.cloud.netflix.eureka.server.EurekaServerAutoConfiguration
+org.springframework.cloud.netflix.eureka.server.EurekaServerAutoConfiguration
+org.springframework.cloud.netflix.eureka.server.metrics.EurekaInstanceMetricsAutoConfiguration

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

@@ -0,0 +1,57 @@
+package org.springframework.cloud.netflix.eureka.server;
+
+import com.netflix.appinfo.InstanceInfo;
+import com.netflix.eureka.registry.PeerAwareInstanceRegistry;
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.Tag;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.mock.mockito.SpyBean;
+import org.springframework.cloud.netflix.eureka.server.metrics.EurekaInstanceMetricsBinder;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.cloud.netflix.eureka.server.InstanceRegistryTests.getInstanceInfo;
+import static org.springframework.cloud.netflix.eureka.server.InstanceRegistryTests.getLeaseInfo;
+
+@SpringBootTest(classes = InstanceRegistryTests.TestApplication.class,
+		webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT,
+		value = {"spring.application.name=eureka",
+				"logging.level.org.springframework.cloud.netflix.eureka.server.InstanceRegistry=DEBUG"})
+class EurekaInstanceMetricsBinderTests {
+
+	private static final String APP_NAME = "MY-APP-NAME";
+
+	private static final String HOST_NAME = "my-host-name";
+
+	private static final String INSTANCE_ID = "my-host-name:8008";
+
+	private static final int PORT = 8008;
+
+	@SpyBean(PeerAwareInstanceRegistry.class)
+	private InstanceRegistry instanceRegistry;
+
+	@Autowired
+	private MeterRegistry meterRegistry;
+
+	@Autowired
+	private EurekaInstanceMetricsBinder binder;
+
+	@Test
+	void testMetrics() {
+		final InstanceInfo instanceInfo = getInstanceInfo(APP_NAME, HOST_NAME, INSTANCE_ID, PORT, getLeaseInfo());
+		instanceRegistry.register(instanceInfo, false);
+
+		binder.bindTo(meterRegistry);
+
+		assertThat(meterRegistry.get("eureka.server.application.instances").tags(List.of(
+				Tag.of("application", APP_NAME),
+				Tag.of("id", INSTANCE_ID),
+				Tag.of("host", HOST_NAME),
+				Tag.of("port", String.valueOf(PORT)),
+				Tag.of("status", InstanceInfo.InstanceStatus.UP.name())
+		))).isNotNull();
+	}
+}

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

@@ -16,17 +16,12 @@
 
 package org.springframework.cloud.netflix.eureka.server;
 
-import java.util.Arrays;
-import java.util.LinkedList;
-import java.util.List;
-
 import com.netflix.appinfo.InstanceInfo;
 import com.netflix.appinfo.LeaseInfo;
 import com.netflix.discovery.shared.Application;
 import com.netflix.eureka.registry.PeerAwareInstanceRegistry;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.test.context.SpringBootTest;
@@ -40,15 +35,19 @@
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.event.SmartApplicationListener;
 
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.doReturn;
 
 /**
  * @author Bartlomiej Slota
  */
 @SpringBootTest(classes = TestApplication.class, webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT,
-		value = { "spring.application.name=eureka",
-				"logging.level.org.springframework." + "cloud.netflix.eureka.server.InstanceRegistry=DEBUG" })
+		value = {"spring.application.name=eureka",
+				"logging.level.org.springframework." + "cloud.netflix.eureka.server.InstanceRegistry=DEBUG"})
 class InstanceRegistryTests {
 
 	private static final String APP_NAME = "MY-APP-NAME";
@@ -147,15 +146,15 @@ void testRenew() {
 		assertThat(event2.getInstanceInfo()).isEqualTo(instanceInfo2);
 	}
 
-	private LeaseInfo getLeaseInfo() {
+	static LeaseInfo getLeaseInfo() {
 		LeaseInfo.Builder leaseBuilder = LeaseInfo.Builder.newBuilder();
 		leaseBuilder.setRenewalIntervalInSecs(10);
 		leaseBuilder.setDurationInSecs(15);
 		return leaseBuilder.build();
 	}
 
-	private InstanceInfo getInstanceInfo(String appName, String hostName, String instanceId, int port,
-			LeaseInfo leaseInfo) {
+	static InstanceInfo getInstanceInfo(String appName, String hostName, String instanceId, int port,
+										LeaseInfo leaseInfo) {
 		InstanceInfo.Builder builder = InstanceInfo.Builder.newBuilder();
 		builder.setAppName(appName);
 		builder.setHostName(hostName);