前言

因工作需要，需在系统利用Kafka监听接口，实现消息队列中，对消息的消费，首选Kafka，因为看中其超高的吞吐量。

基本概念

• 1 Producer: 特指消息的生产者
• 2 Consumer :特指消息的消费者
• 3 Consumer Group :消费者组，可以并行消费Topic中partition的消息
• 4 Broker：缓存代理，Kafa 集群中的一台或多台服务器统称为 broker。
• 5 Topic：特指 Kafka 处理的消息源（feeds of messages）的不同分类。
• 6 Partition：Topic 物理上的分组，一个 topic 可以分为多个 partition，每个 partition 是一个有序的队列。partition 中的每条消息都会被分配一个有序的 id（offset）
• 7 Message：消息，是通信的基本单位，每个 producer 可以向一个 topic（主题）发布一些消息
• 8 稀疏索引：采用稀疏索引的方式，利用二分查找，定位消息。

集成Spring

• 添加Maven依赖 
  由于项目使用Maven进行管理，引入Kafka-Spring相关Jar包，需要添加依赖，此处使用的是Kafka0.10.2

<dependency><groupId>org.springframework.kafka</groupId><artifactId>spring-kafka</artifactId><version>1.2.2.RELEASE</version>
</dependency>

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• 1 版本兼容性 
  配置完Maven依赖以后，还需要确认，因为Kafka与Spring有依赖关系，需要确定Spring的版本是否能和Kafka0.10.2完美兼容，查阅Spring For Apache Kafka 文档可知： 
  　　Compatibility

  • Apache Kafka 0.10.2.0
  • Tested with Spring Framework version dependency is 4.3.7 but it is expected that the framework will work with earlier versions of Spring.
  • Annotation-based listeners require Spring Framework 4.1 or higher, however.
  • Minimum Java version: 7. 
    Kafka 0.10.2 需要SpringFrameWork 4.3.7，但后续会逐渐兼容SpringFrameWork更早期的版本，实践发现，Kafka的生产者里面的api会受SpringFrameWork版本影响，而消费者无影响，因此，可以保持项目中原有springframework不变。

• 2 排除重复包 
  引入Maven依赖以后，Kafka的maven依赖，自动包含了springframework相关jar包，需要排除。

<dependency><groupId>org.springframework</groupId><artifactId>spring-beans</artifactId><version>4.3.9.RELEASE</version><scope>compile</scope></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-context</artifactId><version>4.3.9.RELEASE</version><scope>compile</scope></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-core</artifactId><version>4.3.9.RELEASE</version><scope>compile</scope></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-oxm</artifactId><version>4.3.9.RELEASE</version><scope>compile</scope><optional>true</optional></dependency>

• 3 接口区别 
  Kafka消费者，实现有两种方式：client客户端和listener监听接口，这里因业务需要，采用监听接口的方式实现，Spring提供了四种接口，如下所示：

public interface MessageListener<K, V> {} 1void onMessage(ConsumerRecord<K, V> data);}public interface AcknowledgingMessageListener<K, V> {} 2void onMessage(ConsumerRecord<K, V> data, Acknowledgment acknowledgment);}public interface BatchMessageListener<K, V> {} 3void onMessage(List<ConsumerRecord<K, V>> data);}public interface BatchAcknowledgingMessageListener<K, V> {} 4void onMessage(List<ConsumerRecord<K, V>> data, Acknowledgment acknowledgment);}

对应的解释如下 
1、Use this for processing individual ConsumerRecord s received from the kafka consumer poll() operation when using auto-commit, or one of the container-managed commit methods. 
使用MessageListener接口实现时，当消费者拉取消息之后，消费完成会自动提交offset，即enable.auto.commit为true时，适合使用此接口 
2、Use this for processing individual ConsumerRecord s received from the kafka consumer poll() operation when using one of the manual commit methods. 
使用AcknowledgeMessageListener时，当消费者消费一条消息之后，不会自动提交offset，需要手动ack，即enable.auto.commit为false时，适合使用此接口 
3、Use this for processing all ConsumerRecord s received from the kafka consumer poll() operation when using auto-commit, or one of the container-managed commit methods. AckMode.RECORD is not supported when using this interface since the listener is given the complete batch.

4、Use this for processing all ConsumerRecord s received from the kafka consumer poll() operation when using one of the manual commit methods.

BatchMessageListener和BatchAcknowledgingMessageListener接口作用与上述两个接口大体类似，只是适合批量消费消息决定是否自动提交offset

由于业务较重，且offset自动提交时，出现消费异常或者消费失败的情况，消费者容易丢失消息，所以需要采用手动提交offset的方式，因此，这里实现了AcknowledgeMessageListener接口。

Spring配置文件

配置思路： 
1、确定需要定义的beans：

• 1 consumerProperties 消费者的基本属性，包括指定bootstrap.servers,group.id等
• 2 consumerFactory ：消费者工厂，配置完consumerProperties 后，需要将consumerProperties 作为参数，配置进consumerFactory中
• 3 containProperties： 消费者容器属性对象的bean，这个bean会指定后续自定义的监听接口bean及ackMode（手动提交时，采取什么提交方式）
• 4 messageListenerContainer：消费者容器，启动监听接口的bean，需要将先前定义的consumerFactory 、containProperties配置进这个bean，并定义其init-method = doStart，在启动spring时，便会自动启动监听接口，同时，此bean指定了topic
• 5 kafkaMessageListener：监听接口，这个接口由自己定义，需要将其配置进containProperties中， 
  具体完整消费者的配置文件如下所示：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><!--1、consumer属性配置，hashMap--><bean id="consumerProperties" class="java.util.HashMap"><constructor-arg><map><entry key="bootstrap.servers" value="${kafka.bootstrap.servers}"/><entry key="group.id" value="${kafka.group.id}"/><entry key="enable.auto.commit" value="false"/><entry key="session.timeout.ms" value="15000"/><!--<entry key="auto.offset.reset" value="earliest"/>--><entry key="key.deserializer" value="org.apache.kafka.common.serialization.StringDeserializer"/><entry key="value.deserializer" value="org.apache.kafka.common.serialization.StringDeserializer"/><entry key="value.deserializer.encoding" value="UTF8"/><entry key="value.deserializer.encoding" value="UTF8"/></map></constructor-arg></bean><!--2、Kafka消费者工厂，DefaultKafkaConsumerFactory--><bean id="consumerFactory" class="org.springframework.kafka.core.DefaultKafkaConsumerFactory"><constructor-arg><ref bean="consumerProperties"/></constructor-arg></bean><!--3、监听接口，AcknowledgingMessageListener--><bean id="kafkaMessageListener" class="com.lianjia.bigdata.dataarch.auth.kafka.KafkaMessageListener"><property name="threadPool" ref="kafkaWorkerThreadPool"/></bean><bean id="kafkaWorkerThreadPool" class="org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor"><property name="corePoolSize" value="20"/><property name="maxPoolSize" value="200"/><property name="queueCapacity" value="500"/><property name="keepAliveSeconds" value="1800"/><property name="rejectedExecutionHandler"><bean class="java.util.concurrent.ThreadPoolExecutor$CallerRunsPolicy"/></property></bean><!--4、Kafka消费者容器，属性配置--><bean id="containProperties" class="org.springframework.kafka.listener.config.ContainerProperties"><constructor-arg value="${kafka.topic}"/><property name="ackMode" value="MANUAL_IMMEDIATE"/><property name="messageListener" ref="kafkaMessageListener"/></bean><!--5、Kafka消费者容器--><bean id="messageListenerContainer" class="org.springframework.kafka.listener.KafkaMessageListenerContainer" init-method="doStart" ><constructor-arg ref="consumerFactory"/><constructor-arg ref="containProperties"/></bean>
</bean>

示例代码

写了个简单的测试用例 
生产者： 
实现每秒定时向brokers发送一条消息

import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.common.serialization.IntegerSerializer;
import org.apache.kafka.common.serialization.StringSerializer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import java.util.HashMap;
import java.util.Map;public class SimpleKafkaProducer implements Runnable {protected static final Logger LOGGER = LoggerFactory.getLogger(SimpleKafkaProducer.class);@Overridepublic void run() {Map<String, Object> sendProps = senderProps();Producer producer = new KafkaProducer(sendProps);Integer currentNum = 0;try {LOGGER.info("start produce message");while (true){ProducerRecord<Integer, String> producerRecord = new ProducerRecord<>("testTopic",currentNum, currentNum);producer.send(producerRecord);LOGGER.info("send message:" + currentNum + " And value is " + producerRecord.value());currentNum++;Thread.sleep(1000);}}catch (Exception e){LOGGER.error("send message fail", e);}finally {producer.close();}}public static void main(String[] args) {SimpleKafkaProducer simpleKafkaProducer = new SimpleKafkaProducer();new Thread(simpleKafkaProducer).start();}private Map<String, Object> senderProps() {Map<String, Object> props = new HashMap<>();props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "10.33.106.94:9092");props.put(ProducerConfig.ACKS_CONFIG, "all");props.put(ProducerConfig.RETRIES_CONFIG, 0);props.put(ProducerConfig.BATCH_SIZE_CONFIG, 16384);props.put(ProducerConfig.LINGER_MS_CONFIG, 1);props.put(ProducerConfig.BUFFER_MEMORY_CONFIG, 33554432);props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, IntegerSerializer.class);props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class);return props;}
}

消费者

public class KafkaMessageListener implements AcknowledgingMessageListener<Integer, String> {private static final Logger LOGGER = LoggerFactory.getLogger(KafkaMessageListener.class);@Overridepublic void onMessage(final ConsumerRecord<Integer, String> message, final Acknowledgment acknowledgment) {//TODO 这里具体实现个人业务逻辑// 最后 调用acknowledgment的ack方法，提交offsetacknowledgment.acknowledge();}
}

消费者使用示例：这里参考spring官方文档，简单实现了一个消费者监听接口示例

import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.common.serialization.IntegerDeserializer;
import org.apache.kafka.common.serialization.StringDeserializer;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.kafka.core.DefaultKafkaConsumerFactory;
import org.springframework.kafka.listener.AbstractMessageListenerContainer;
import org.springframework.kafka.listener.AcknowledgingMessageListener;
import org.springframework.kafka.listener.KafkaMessageListenerContainer;
import org.springframework.kafka.listener.config.ContainerProperties;
import org.springframework.kafka.support.Acknowledgment;import javax.annotation.Resource;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CountDownLatch;public class SimpleKafkaConsumer extends SpringUnitTest {protected static final Logger LOGGER = LoggerFactory.getLogger(SimpleKafkaConsumer.class);@Resource(name = "kafkaMessageListener")private  KafkaMessageListener kafkaMessageListener;@Testpublic void TestLinstener(){ContainerProperties containerProps = new ContainerProperties("testTopic");containerProps.setMessageListener(kafkaMessageListener);KafkaMessageListenerContainer<Integer, String> container = createContainer(containerProps);container.setBeanName("messageListenerContainer");container.start();}private static KafkaMessageListenerContainer<Integer, String> createContainer(ContainerProperties containerProps) {Map<String, Object> props = consumerProps();DefaultKafkaConsumerFactory<Integer, String> cf =new DefaultKafkaConsumerFactory<>(props);KafkaMessageListenerContainer<Integer, String> container =new KafkaMessageListenerContainer<>(cf, containerProps);return container;}private static Map<String, Object> consumerProps() {Map<String, Object> props = new HashMap<>();props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "10.33.106.94:9092");props.put(ConsumerConfig.GROUP_ID_CONFIG, "test3");props.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, false);
//        props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG,"earliest");props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, "15000");props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, IntegerDeserializer.class);props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);return props;}}

实现acknowledgeMessageListener接口之前，查阅了网上现有的文档，结果不尽如人意，只能试着自己去参考spring官方文档，慢慢摸索，最终实现手动提交offset的监听接口，当然，Kafka的知识点，远不止这些，后续还将继续学习。