Auto-configure Micrometer's Kafka consumer metrics

Closes gh-14525

spring-boot-project/spring-boot-actuator-autoconfigure/pom.xml

@@ -198,6 +198,11 @@
 			<artifactId>commons-dbcp2</artifactId>
 			<optional>true</optional>
 		</dependency>
+		<dependency>
+			<groupId>org.apache.kafka</groupId>
+			<artifactId>kafka-clients</artifactId>
+			<optional>true</optional>
+		</dependency>
 		<dependency>
 			<groupId>org.apache.logging.log4j</groupId>
 			<artifactId>log4j-core</artifactId>

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

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2012-2018 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
+ *
+ *      http://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.metrics;
+
+import java.util.Collections;
+
+import javax.management.MBeanServer;
+
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.binder.kafka.KafkaConsumerMetrics;
+import org.apache.kafka.clients.consumer.KafkaConsumer;
+
+import org.springframework.boot.autoconfigure.AutoConfigureAfter;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+/**
+ * Auto-configuration for Kafka metrics.
+ *
+ * @author Andy Wilkinson
+ * @since 2.1.0
+ */
+@Configuration
+@AutoConfigureAfter({ MetricsAutoConfiguration.class, JmxAutoConfiguration.class })
+@ConditionalOnClass({ KafkaConsumerMetrics.class, KafkaConsumer.class })
+@ConditionalOnBean(MeterRegistry.class)
+public class KafkaMetricsAutoConfiguration {
+
+	@Bean
+	@ConditionalOnMissingBean
+	@ConditionalOnBean(MBeanServer.class)
+	public KafkaConsumerMetrics kafkaConsumerMetrics(MBeanServer mbeanServer) {
+		return new KafkaConsumerMetrics(mbeanServer, Collections.emptyList());
+	}
+
+}

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/resources/META-INF/spring.factories

@@ -35,6 +35,7 @@ org.springframework.boot.actuate.autoconfigure.management.HeapDumpWebEndpointAut
 org.springframework.boot.actuate.autoconfigure.management.ThreadDumpEndpointAutoConfiguration,\
 org.springframework.boot.actuate.autoconfigure.metrics.CompositeMeterRegistryAutoConfiguration,\
 org.springframework.boot.actuate.autoconfigure.metrics.JvmMetricsAutoConfiguration,\
+org.springframework.boot.actuate.autoconfigure.metrics.KafkaMetricsAutoConfiguration,\
 org.springframework.boot.actuate.autoconfigure.metrics.Log4J2MetricsAutoConfiguration,\
 org.springframework.boot.actuate.autoconfigure.metrics.LogbackMetricsAutoConfiguration,\
 org.springframework.boot.actuate.autoconfigure.metrics.MetricsAutoConfiguration,\

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/metrics/KafkaMetricsAutoConfigurationTests.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2012-2018 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
+ *
+ *      http://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.metrics;
+
+import io.micrometer.core.instrument.binder.kafka.KafkaConsumerMetrics;
+import org.junit.Test;
+
+import org.springframework.boot.actuate.autoconfigure.metrics.test.MetricsRun;
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link KafkaMetricsAutoConfiguration}.
+ *
+ * @author Andy Wilkinson
+ */
+public class KafkaMetricsAutoConfigurationTests {
+
+	private final ApplicationContextRunner contextRunner = new ApplicationContextRunner()
+			.with(MetricsRun.simple()).withConfiguration(
+					AutoConfigurations.of(KafkaMetricsAutoConfiguration.class));
+
+	@Test
+	public void whenThereIsNoMBeanServerAutoConfigurationBacksOff() {
+		this.contextRunner.run((context) -> assertThat(context)
+				.doesNotHaveBean(KafkaConsumerMetrics.class));
+	}
+
+	@Test
+	public void whenThereIsAnMBeanServerKafkaConsumerMetricsIsConfigured() {
+		this.contextRunner
+				.withConfiguration(AutoConfigurations.of(JmxAutoConfiguration.class))
+				.run((context) -> assertThat(context)
+						.hasSingleBean(KafkaConsumerMetrics.class));
+	}
+
+	@Test
+	public void allowsCustomKafkaConsumerMetricsToBeUsed() {
+		this.contextRunner
+				.withConfiguration(AutoConfigurations.of(JmxAutoConfiguration.class))
+				.withUserConfiguration(CustomKafkaConsumerMetricsConfiguration.class)
+				.run((context) -> assertThat(context)
+						.hasSingleBean(KafkaConsumerMetrics.class)
+						.hasBean("customKafkaConsumerMetrics"));
+	}
+
+	@Configuration
+	static class CustomKafkaConsumerMetricsConfiguration {
+
+		@Bean
+		public KafkaConsumerMetrics customKafkaConsumerMetrics() {
+			return new KafkaConsumerMetrics();
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-docs/src/main/asciidoc/production-ready-features.adoc

@@ -1707,6 +1707,7 @@ Spring Boot registers the following core metrics when applicable:
 ** Number of classes loaded/unloaded
 * CPU metrics
 * File descriptor metrics
+* Kafka consumer metrics
 * Log4j2 metrics: record the number of events logged to Log4j2 at each level
 * Logback metrics: record the number of events logged to Logback at each level
 * Uptime metrics: report a gauge for uptime and a fixed gauge representing the