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 +1,53 @@
+/*
+ * 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 java.util.List;
+import java.util.Objects;
+
+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;
+
+/**
+ * @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 +1,71 @@
+/*
+ * 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;
+
+import java.util.List;
+
+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 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

@@ -147,14 +147,14 @@ 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,
+	static InstanceInfo getInstanceInfo(String appName, String hostName, String instanceId, int port,
 			LeaseInfo leaseInfo) {
 		InstanceInfo.Builder builder = InstanceInfo.Builder.newBuilder();
 		builder.setAppName(appName);