Apache Kafka-Spring Kafka生产消费@KafkaListener源码解析

小小工匠

发布于 2021-08-17 17:00:26

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概述

【依赖】

	<dependency>
			<groupId>org.springframework.kafka</groupId>
			<artifactId>spring-kafka</artifactId>
	</dependency>

【配置】

#kafka
spring.kafka.bootstrap-servers=10.11.114.247:9092
spring.kafka.producer.acks=1
spring.kafka.producer.retries=3
spring.kafka.producer.batch-size=16384
spring.kafka.producer.buffer-memory=33554432
spring.kafka.producer.key-serializer=org.apache.kafka.common.serialization.StringSerializer
spring.kafka.producer.value-serializer=org.springframework.kafka.support.serializer.JsonSerializer


spring.kafka.consumer.group-id=zfprocessor_group
spring.kafka.consumer.enable-auto-commit=false
spring.kafka.consumer.auto-offset-reset=earliest
spring.kafka.consumer.key-deserializer=org.apache.kafka.common.serialization.StringDeserializer
spring.kafka.consumer.value-deserializer=org.springframework.kafka.support.serializer.JsonDeserializer
spring.kafka.consumer.properties.spring.json.trusted.packages=com.artisan.common.entity.messages
spring.kafka.consumer.max-poll-records=500
spring.kafka.consumer.fetch-min-size=10
spring.kafka.consumer.fetch-max-wait=10000ms

spring.kafka.listener.missing-topics-fatal=false
spring.kafka.listener.type=batch
spring.kafka.listener.ack-mode=manual


logging.level.org.springframework.kafka=ERROR
logging.level.org.apache.kafka=ERROR

Spring-kafka生产者源码流程

ListenableFuture<SendResult<Object, Object>> result = kafkaTemplate.send(TOPICA.TOPIC, messageMock);

主要的源码流程如下

Spring-kafka消费者源码流程（`@EnableKafka`和`@KafkaListener` ）

消费的话，比较复杂

 @KafkaListener(topics = TOPICA.TOPIC ,groupId = CONSUMER_GROUP_PREFIX + TOPICA.TOPIC)
    public void onMessage(MessageMock messageMock){
        logger.info("【接受到消息][线程:{} 消息内容：{}]", Thread.currentThread().getName(), messageMock);
    }

划重点，主要关注

Flow

作为引子，我们继续来梳理下源码

继续

继续

KafkaBootstrapConfiguration的主要功能是创建两个bean

KafkaListenerAnnotationBeanPostProcessor

实现了如下接口

implements BeanPostProcessor, Ordered, BeanFactoryAware, SmartInitializingSingleton

主要功能就是监听@KafkaListener注解。 bean的后置处理器需要重写 postProcessAfterInitialization

@Override
	public Object postProcessAfterInitialization(final Object bean, final String beanName) throws BeansException {
		if (!this.nonAnnotatedClasses.contains(bean.getClass())) {
		   // 获取对应的class
			Class<?> targetClass = AopUtils.getTargetClass(bean);
			// 查找类是否有@KafkaListener注解
			Collection<KafkaListener> classLevelListeners = findListenerAnnotations(targetClass);
			final boolean hasClassLevelListeners = classLevelListeners.size() > 0;
			final List<Method> multiMethods = new ArrayList<>();
			// 查找类中方法上是否有对应的@KafkaListener注解，
			Map<Method, Set<KafkaListener>> annotatedMethods = MethodIntrospector.selectMethods(targetClass,
					(MethodIntrospector.MetadataLookup<Set<KafkaListener>>) method -> {
						Set<KafkaListener> listenerMethods = findListenerAnnotations(method);
						return (!listenerMethods.isEmpty() ? listenerMethods : null);
					});
			if (hasClassLevelListeners) {
				Set<Method> methodsWithHandler = MethodIntrospector.selectMethods(targetClass,
						(ReflectionUtils.MethodFilter) method ->
								AnnotationUtils.findAnnotation(method, KafkaHandler.class) != null);
				multiMethods.addAll(methodsWithHandler);
			}
			if (annotatedMethods.isEmpty()) {
				this.nonAnnotatedClasses.add(bean.getClass());
				this.logger.trace(() -> "No @KafkaListener annotations found on bean type: " + bean.getClass());
			}
			else {
				// Non-empty set of methods
				for (Map.Entry<Method, Set<KafkaListener>> entry : annotatedMethods.entrySet()) {
					Method method = entry.getKey();
					for (KafkaListener listener : entry.getValue()) {
						// 处理@KafkaListener注解   重点看 
						processKafkaListener(listener, method, bean, beanName);
					}
				}
				this.logger.debug(() -> annotatedMethods.size() + " @KafkaListener methods processed on bean '"
							+ beanName + "': " + annotatedMethods);
			}
			if (hasClassLevelListeners) {
				processMultiMethodListeners(classLevelListeners, multiMethods, bean, beanName);
			}
		}
		return bean;
	}

重点方法

	protected void processKafkaListener(KafkaListener kafkaListener, Method method, Object bean, String beanName) {
		Method methodToUse = checkProxy(method, bean);
		MethodKafkaListenerEndpoint<K, V> endpoint = new MethodKafkaListenerEndpoint<>();
		endpoint.setMethod(methodToUse);
		processListener(endpoint, kafkaListener, bean, methodToUse, beanName);
	}

继续 processListener

protected void processListener(MethodKafkaListenerEndpoint<?, ?> endpoint, KafkaListener kafkaListener,
			Object bean, Object adminTarget, String beanName) {

		String beanRef = kafkaListener.beanRef();
		if (StringUtils.hasText(beanRef)) {
			this.listenerScope.addListener(beanRef, bean);
		}
		// 构建 endpoint
		endpoint.setBean(bean);
		endpoint.setMessageHandlerMethodFactory(this.messageHandlerMethodFactory);
		endpoint.setId(getEndpointId(kafkaListener));
		endpoint.setGroupId(getEndpointGroupId(kafkaListener, endpoint.getId()));
		endpoint.setTopicPartitions(resolveTopicPartitions(kafkaListener));
		endpoint.setTopics(resolveTopics(kafkaListener));
		endpoint.setTopicPattern(resolvePattern(kafkaListener));
		endpoint.setClientIdPrefix(resolveExpressionAsString(kafkaListener.clientIdPrefix(), "clientIdPrefix"));
		String group = kafkaListener.containerGroup();
		if (StringUtils.hasText(group)) {
			Object resolvedGroup = resolveExpression(group);
			if (resolvedGroup instanceof String) {
				endpoint.setGroup((String) resolvedGroup);
			}
		}
		String concurrency = kafkaListener.concurrency();
		if (StringUtils.hasText(concurrency)) {
			endpoint.setConcurrency(resolveExpressionAsInteger(concurrency, "concurrency"));
		}
		String autoStartup = kafkaListener.autoStartup();
		if (StringUtils.hasText(autoStartup)) {
			endpoint.setAutoStartup(resolveExpressionAsBoolean(autoStartup, "autoStartup"));
		}
		resolveKafkaProperties(endpoint, kafkaListener.properties());
		endpoint.setSplitIterables(kafkaListener.splitIterables());

		KafkaListenerContainerFactory<?> factory = null;
		String containerFactoryBeanName = resolve(kafkaListener.containerFactory());
		if (StringUtils.hasText(containerFactoryBeanName)) {
			Assert.state(this.beanFactory != null, "BeanFactory must be set to obtain container factory by bean name");
			try {
				factory = this.beanFactory.getBean(containerFactoryBeanName, KafkaListenerContainerFactory.class);
			}
			catch (NoSuchBeanDefinitionException ex) {
				throw new BeanInitializationException("Could not register Kafka listener endpoint on [" + adminTarget
						+ "] for bean " + beanName + ", no " + KafkaListenerContainerFactory.class.getSimpleName()
						+ " with id '" + containerFactoryBeanName + "' was found in the application context", ex);
			}
		}

		endpoint.setBeanFactory(this.beanFactory);
		String errorHandlerBeanName = resolveExpressionAsString(kafkaListener.errorHandler(), "errorHandler");
		if (StringUtils.hasText(errorHandlerBeanName)) {
			endpoint.setErrorHandler(this.beanFactory.getBean(errorHandlerBeanName, KafkaListenerErrorHandler.class));
		}
		// 将endpoint注册到registrar
		this.registrar.registerEndpoint(endpoint, factory);
		if (StringUtils.hasText(beanRef)) {
			this.listenerScope.removeListener(beanRef);
		}
	}

继续看 registerEndpoint

	public void registerEndpoint(KafkaListenerEndpoint endpoint, KafkaListenerContainerFactory<?> factory) {
		Assert.notNull(endpoint, "Endpoint must be set");
		Assert.hasText(endpoint.getId(), "Endpoint id must be set");
		// Factory may be null, we defer the resolution right before actually creating the container
		// 把endpoint封装为KafkaListenerEndpointDescriptor
		KafkaListenerEndpointDescriptor descriptor = new KafkaListenerEndpointDescriptor(endpoint, factory);
		synchronized (this.endpointDescriptors) {
			if (this.startImmediately) { // Register and start immediately
				this.endpointRegistry.registerListenerContainer(descriptor.endpoint,
						resolveContainerFactory(descriptor), true);
			}
			else {
			   // 将descriptor添加到endpointDescriptors
				this.endpointDescriptors.add(descriptor);
			}
		}
	}

总的来看：得到一个含有KafkaListener基本信息的Endpoint，将Endpoint被封装到KafkaListenerEndpointDescriptor，KafkaListenerEndpointDescriptor被添加到KafkaListenerEndpointRegistrar.endpointDescriptors中，至此这部分的流程结束了，感觉没有下文呀。

KafkaListenerEndpointRegistrar.endpointDescriptors 这个List中的数据怎么用呢？

public class KafkaListenerEndpointRegistrar implements BeanFactoryAware, InitializingBean {}

KafkaListenerEndpointRegistrar 实现了 InitializingBean 接口，重写 afterPropertiesSet，该方法会在bean实例化完成后执行

	@Override
	public void afterPropertiesSet() {
		registerAllEndpoints();
	}

继续 registerAllEndpoints();

	protected void registerAllEndpoints() {
		synchronized (this.endpointDescriptors) {
		// 遍历KafkaListenerEndpointDescriptor 
			for (KafkaListenerEndpointDescriptor descriptor : this.endpointDescriptors) {
			   	// 注册 
				this.endpointRegistry.registerListenerContainer(
						descriptor.endpoint, resolveContainerFactory(descriptor));
			}
			this.startImmediately = true;  // trigger immediate startup
		}
	}

继续

	public void registerListenerContainer(KafkaListenerEndpoint endpoint, KafkaListenerContainerFactory<?> factory) {
		registerListenerContainer(endpoint, factory, false);
	}

public void registerListenerContainer(KafkaListenerEndpoint endpoint, KafkaListenerContainerFactory<?> factory,
			boolean startImmediately) {

		Assert.notNull(endpoint, "Endpoint must not be null");
		Assert.notNull(factory, "Factory must not be null");

		String id = endpoint.getId();
		Assert.hasText(id, "Endpoint id must not be empty");
		synchronized (this.listenerContainers) {
			Assert.state(!this.listenerContainers.containsKey(id),
					"Another endpoint is already registered with id '" + id + "'");   
	      // 创建Endpoint对应的MessageListenerContainer，将创建好的MessageListenerContainer放入listenerContainers
			MessageListenerContainer container = createListenerContainer(endpoint, factory);
			this.listenerContainers.put(id, container);
			// 如果KafkaListener注解中有对应的group信息，则将container添加到对应的group中
			if (StringUtils.hasText(endpoint.getGroup()) && this.applicationContext != null) {
				List<MessageListenerContainer> containerGroup;
				if (this.applicationContext.containsBean(endpoint.getGroup())) {
					containerGroup = this.applicationContext.getBean(endpoint.getGroup(), List.class);
				}
				else {
					containerGroup = new ArrayList<MessageListenerContainer>();
					this.applicationContext.getBeanFactory().registerSingleton(endpoint.getGroup(), containerGroup);
				}
				containerGroup.add(container);
			}
			if (startImmediately) {
				startIfNecessary(container);
			}
		}
	}

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