Make sure that RabbitMQ metrics are configured early

The ConnectionFactory can be used early in user configuration to
configure an `Exchange`. Such connection may not hold the proper
MetricCollector and can be cached, leading to missed metrics
information.

This commit moves the configuration of RabbitMQ metrics to a
BeanPostProcessor so that the proper MetricCollector is configured
before any connection is created.

Closes gh-12855

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

+/*
+ * 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.amqp;
+
+import com.rabbitmq.client.ConnectionFactory;
+import com.rabbitmq.client.MetricsCollector;
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.Tags;
+
+import org.springframework.amqp.rabbit.connection.AbstractConnectionFactory;
+import org.springframework.beans.factory.config.BeanPostProcessor;
+import org.springframework.boot.actuate.metrics.amqp.RabbitMetrics;
+import org.springframework.context.ApplicationContext;
+import org.springframework.core.Ordered;
+import org.springframework.util.StringUtils;
+
+/**
+ * {@link BeanPostProcessor} that configures RabbitMQ metrics. Such arrangement is
+ * necessary because a connection can be eagerly created and cached without a reference
+ * to a proper {@link MetricsCollector}.
+ *
+ * @author Stephane Nicoll
+ */
+public class RabbitConnectionFactoryMetricsPostProcessor
+		implements BeanPostProcessor, Ordered {
+
+	private static final String CONNECTION_FACTORY_SUFFIX = "connectionFactory";
+
+	private final ApplicationContext context;
+
+	private volatile MeterRegistry meterRegistry;
+
+	RabbitConnectionFactoryMetricsPostProcessor(ApplicationContext context) {
+		this.context = context;
+	}
+
+	@Override
+	public Object postProcessAfterInitialization(Object bean, String beanName) {
+		if (bean instanceof AbstractConnectionFactory) {
+			bindConnectionFactoryToRegistry(getMeterRegistry(), beanName,
+					(AbstractConnectionFactory) bean);
+		}
+		return bean;
+	}
+
+	private void bindConnectionFactoryToRegistry(MeterRegistry registry, String beanName,
+			AbstractConnectionFactory connectionFactory) {
+		ConnectionFactory rabbitConnectionFactory = connectionFactory
+				.getRabbitConnectionFactory();
+		String connectionFactoryName = getConnectionFactoryName(beanName);
+		new RabbitMetrics(rabbitConnectionFactory, Tags.of("name", connectionFactoryName))
+				.bindTo(registry);
+	}
+
+	/**
+	 * Get the name of a ConnectionFactory based on its {@code beanName}.
+	 * @param beanName the name of the connection factory bean
+	 * @return a name for the given connection factory
+	 */
+	private String getConnectionFactoryName(String beanName) {
+		if (beanName.length() > CONNECTION_FACTORY_SUFFIX.length()
+				&& StringUtils.endsWithIgnoreCase(beanName, CONNECTION_FACTORY_SUFFIX)) {
+			return beanName.substring(0,
+					beanName.length() - CONNECTION_FACTORY_SUFFIX.length());
+		}
+		return beanName;
+	}
+
+	private MeterRegistry getMeterRegistry() {
+		if (this.meterRegistry == null) {
+			this.meterRegistry = this.context.getBean(MeterRegistry.class);
+		}
+		return this.meterRegistry;
+	}
+
+	@Override
+	public int getOrder() {
+		return Ordered.HIGHEST_PRECEDENCE;
+	}
+
+}

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

@@ -16,24 +16,20 @@
 
 package org.springframework.boot.actuate.autoconfigure.metrics.amqp;
 
-import java.util.Map;
-
 import com.rabbitmq.client.ConnectionFactory;
 import io.micrometer.core.instrument.MeterRegistry;
-import io.micrometer.core.instrument.Tags;
 
 import org.springframework.amqp.rabbit.connection.AbstractConnectionFactory;
-import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.actuate.autoconfigure.metrics.MetricsAutoConfiguration;
 import org.springframework.boot.actuate.autoconfigure.metrics.export.simple.SimpleMetricsExportAutoConfiguration;
-import org.springframework.boot.actuate.metrics.amqp.RabbitMetrics;
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.util.StringUtils;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for metrics on all available
@@ -49,41 +45,10 @@ import org.springframework.util.StringUtils;
 @ConditionalOnBean({ AbstractConnectionFactory.class, MeterRegistry.class })
 public class RabbitMetricsAutoConfiguration {
 
-	private static final String CONNECTION_FACTORY_SUFFIX = "connectionFactory";
-
-	private final MeterRegistry registry;
-
-	public RabbitMetricsAutoConfiguration(MeterRegistry registry) {
-		this.registry = registry;
-	}
-
-	@Autowired
-	public void bindConnectionFactoriesToRegistry(
-			Map<String, AbstractConnectionFactory> connectionFactories) {
-		connectionFactories.forEach(this::bindConnectionFactoryToRegistry);
-	}
-
-	private void bindConnectionFactoryToRegistry(String beanName,
-			AbstractConnectionFactory connectionFactory) {
-		ConnectionFactory rabbitConnectionFactory = connectionFactory
-				.getRabbitConnectionFactory();
-		String connectionFactoryName = getConnectionFactoryName(beanName);
-		new RabbitMetrics(rabbitConnectionFactory, Tags.of("name", connectionFactoryName))
-				.bindTo(this.registry);
-	}
-
-	/**
-	 * Get the name of a ConnectionFactory based on its {@code beanName}.
-	 * @param beanName the name of the connection factory bean
-	 * @return a name for the given connection factory
-	 */
-	private String getConnectionFactoryName(String beanName) {
-		if (beanName.length() > CONNECTION_FACTORY_SUFFIX.length()
-				&& StringUtils.endsWithIgnoreCase(beanName, CONNECTION_FACTORY_SUFFIX)) {
-			return beanName.substring(0,
-					beanName.length() - CONNECTION_FACTORY_SUFFIX.length());
-		}
-		return beanName;
+	@Bean
+	public static RabbitConnectionFactoryMetricsPostProcessor rabbitConnectionFactoryMetricsPostProcessor(
+			ApplicationContext applicationContext) {
+		return new RabbitConnectionFactoryMetricsPostProcessor(applicationContext);
 	}
 
 }