Kafka 客户端开发

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发布于 2019-06-26 15:51:24

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发布于 2019-06-26 15:51:24

前两篇文章讲述了 Kafka 的工作机制和服务器集群部署。至此，Kafka 服务器已就绪，本文分别以官方API、Spring、SpringBoot三种构建方式，讲述了 Kafka 消费生产者和消费者的开发。

1 开发概述

Kafka 中，客户端与服务端是通过 TCP 协议进行的； Kafka 公布了所有功能协议(与特定语言无关)，并把 Java 客户端作为 kafka 项目的一部分进行维护。其他非 Java 语言的客户端则作为独立的开源项目提供，非 Java 客户端的名单可在这里。

Kafka 提供了五类 API：

Producer API: 向主题(一个或多个)发布消息；
Consumer API: 订阅主题(一个或多个)，拉取这些主题上发布的消息；
Stream API: 作为流处理器，从主题消费消息，向主题发布消息，把输出流转换为输入流；可参考例子；
Connect API: 作为下游或上游，把主题连接到应用程序或数据系统(比如关系数据库)，通常不需要直接使用这些API，而是使用现成的连接器；
AdminClient API: 管理(或巡查) topic, brokers, 或其他 kafka 对象；

2 基于官方 API 开发

2.1 Maven 依赖

<dependency>
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-classic</artifactId>
    <version>1.2.3</version>
</dependency>
<dependency>
    <groupId>org.apache.kafka</groupId>
    <artifactId>kafka-clients</artifactId>
    <version>1.0.0</version>
</dependency>

2.2 logback.xml(日志配置，可选)

<?xml version="1.0" encoding="UTF-8"?>
<configuration scan="false">
    <contextName>logback</contextName>
    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
            <pattern>%d{HH:mm:ss.SSS}  %p  [%F:%L] - %m%n</pattern>
        </encoder>
    </appender>
    <root level="INFO">
        <appender-ref ref="CONSOLE" />
    </root>
</configuration>

2.3 演示类 KafkaClientDemo.java

生产者：相应函数为 KafkaClientDemo.producerDemo()，其中 props 完整参数配置项见 Producer Configs 消费者：相应函数为 KafkaClientDemo.consumerDemo()，其中 props 完整参数配置项见 New Consumer Configs 和 Old Consumer Configs

public class KafkaClientDemo {
    private static final Logger logger = LoggerFactory.getLogger(KafkaClientDemo.class);
    private static final String BROKER_SERVERS = "centos:9091,centos:9092,centos:9093";
    private static final String TOPIC_NAME = "topicName";
    public static void producerDemo() {
        // 配置选项
        Properties props = new Properties();
        props.put("bootstrap.servers", BROKER_SERVERS); // [必填] Kafka Broker 地址列表
        props.put("key.serializer", "org.apache.kafka.common.serialization.IntegerSerializer"); // [必填] KEY 的序列化类
        props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer"); // [必填] VALUE 的序列化类
        // props.put("partitioner.class", "org.apache.kafka.clients.producer.internals.DefaultPartitioner"); // [默认值] 结合主题的分区个数和KEY，使得消息平均地分配给分区
        Producer<Integer, String> producer = new KafkaProducer<Integer, String>(props); // 建立连接
        for (int id = 1; id <= 8; ++id) {
            final int key = id;
            final String value = String.format("msg#%d", key);
            ProducerRecord<Integer, String> record = new ProducerRecord<Integer, String>(TOPIC_NAME, key, value);
            producer.send(record, new Callback() {
                public void onCompletion(RecordMetadata meta, Exception e) {
                    logger.info("KafkaProducer.push(\"{}\", {}, {}, {}, \"{}\") OK.",
                            meta.topic(), meta.partition(), meta.offset(), key, value);
                }
            }); // 推送消息
        }
        producer.flush(); // 提交
        producer.close(); // 关闭连接
    }
    public static void consumerDemo() {
        // 配置选项
        Properties props = new Properties();
        props.put("bootstrap.servers", BROKER_SERVERS); // [必填] Kafka Broker 地址列表
        props.put("key.deserializer", "org.apache.kafka.common.serialization.IntegerDeserializer"); // [必填] KEY 的反序列化类
        props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer"); // [必填] VALUE 的反序列化类
        props.put("group.id", "groupName"); // [必填] 本消费者所属分组
        // 开始消费
        KafkaConsumer<Integer, String> consumer = new KafkaConsumer<Integer, String>(props); // 建立连接
        consumer.subscribe(Arrays.asList(TOPIC_NAME)); // 订阅主题
        while (true) {
            ConsumerRecords<Integer, String> records = consumer.poll(1000); // 拉取消息
            if (records.isEmpty()) {
                break;
            }
            logger.info("KafkaConsumer.poll({}) OK.", records.count());
            for (ConsumerRecord<Integer, String> record : records) {
                logger.info("KafkaConsumer.poll(\"{}\", {}, {}, {}, \"{}\") OK.",
                        record.topic(), record.partition(), record.offset(),
                        record.key(), record.value());
            }
        }
        consumer.close(); // 关闭连接
    }
    public static void main(String[] args) {
        KafkaClientDemo.producerDemo();
        KafkaClientDemo.consumerDemo();
    }
}

2.4 运行结果

## 生产者
11:36:56.345  INFO  [KafkaClientDemo.java:36] - KafkaProducer.push("topicName", 0, 3, 1, "msg#1") OK.
11:36:56.346  INFO  [KafkaClientDemo.java:36] - KafkaProducer.push("topicName", 0, 4, 7, "msg#7") OK.
11:36:56.348  INFO  [KafkaClientDemo.java:36] - KafkaProducer.push("topicName", 0, 5, 8, "msg#8") OK.
11:36:56.349  INFO  [KafkaClientDemo.java:36] - KafkaProducer.push("topicName", 1, 2, 3, "msg#3") OK.
11:36:56.349  INFO  [KafkaClientDemo.java:36] - KafkaProducer.push("topicName", 1, 3, 4, "msg#4") OK.
11:36:56.370  INFO  [KafkaClientDemo.java:36] - KafkaProducer.push("topicName", 2, 3, 2, "msg#2") OK.
11:36:56.371  INFO  [KafkaClientDemo.java:36] - KafkaProducer.push("topicName", 2, 4, 5, "msg#5") OK.
11:36:56.371  INFO  [KafkaClientDemo.java:36] - KafkaProducer.push("topicName", 2, 5, 6, "msg#6") OK.
## 消费者
11:36:56.764  INFO  [KafkaClientDemo.java:62] - KafkaConsumer.poll(3) OK.
11:36:56.766  INFO  [KafkaClientDemo.java:64] - KafkaConsumer.poll("topicName", 0, 3, 1, "msg#1") OK.
11:36:56.766  INFO  [KafkaClientDemo.java:64] - KafkaConsumer.poll("topicName", 0, 4, 7, "msg#7") OK.
11:36:56.766  INFO  [KafkaClientDemo.java:64] - KafkaConsumer.poll("topicName", 0, 5, 8, "msg#8") OK.
11:36:56.771  INFO  [KafkaClientDemo.java:62] - KafkaConsumer.poll(5) OK.
11:36:56.771  INFO  [KafkaClientDemo.java:64] - KafkaConsumer.poll("topicName", 1, 2, 3, "msg#3") OK.
11:36:56.771  INFO  [KafkaClientDemo.java:64] - KafkaConsumer.poll("topicName", 1, 3, 4, "msg#4") OK.
11:36:56.773  INFO  [KafkaClientDemo.java:64] - KafkaConsumer.poll("topicName", 2, 3, 2, "msg#2") OK.
11:36:56.773  INFO  [KafkaClientDemo.java:64] - KafkaConsumer.poll("topicName", 2, 4, 5, "msg#5") OK.
11:36:56.773  INFO  [KafkaClientDemo.java:64] - KafkaConsumer.poll("topicName", 2, 5, 6, "msg#6") OK.

3 基于 Spring 开发

官网: http://projects.spring.io/spring-kafka/ 介绍: https://docs.spring.io/spring-kafka/docs/2.1.2.RELEASE/reference/html/ API: http://docs.spring.io/spring-kafka/docs/2.1.2.RELEASE/api/

3.1 Maven 依赖

环境要求: Apache Kafka 1.0.0， Java 8+

<dependency><!-- logback 日志 -->
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-classic</artifactId>
    <version>1.2.3</version>
</dependency>
<dependency><!-- spring-kafka -->
    <groupId>org.springframework.kafka</groupId>
    <artifactId>spring-kafka</artifactId>
    <version>2.1.2.RELEASE</version>
</dependency>

3.2 spring.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context.xsd">
    <!-- Bean 类的扫描路径(package name) -->
    <context:component-scan base-package="wang.kefeng"/>
    <!-- 生产者工厂(KafkaProducerFactory): 用于创建 KafkaProducer 对象(KafkaTemplate) -->
    <bean id="producerFactory"
          class="org.springframework.kafka.core.DefaultKafkaProducerFactory">
        <constructor-arg>
            <map>
                <entry key="bootstrap.servers" value="centos:9091,centos:9092,centos:9093"/>
                <entry key="key.serializer" value="org.apache.kafka.common.serialization.IntegerSerializer"/>
                <entry key="value.serializer" value="org.apache.kafka.common.serialization.StringSerializer"/>
            </map>
        </constructor-arg>
    </bean>
    <!-- 生产者模板(KafkaTemplate): 用于发布消息 -->
    <bean id="kafkaTemplate" class="org.springframework.kafka.core.KafkaTemplate">
        <constructor-arg ref="producerFactory"/>
        <constructor-arg name="autoFlush" value="true"/>
        <property name="defaultTopic" value="topicName"/>
        <property name="producerListener"><!-- 消息发送成功的回调 -->
            <bean class="wang.kefeng.KafkaProducerListener"/>
        </property>
    </bean>
    <!-- 消费者工厂(KafkaConsumerFactory): 用于创建 KafkaConsumer 对象 -->
    <bean id="consumerFactory"
          class="org.springframework.kafka.core.DefaultKafkaConsumerFactory">
        <constructor-arg>
            <map>
                <entry key="bootstrap.servers" value="centos:9091,centos:9092,centos:9093"/>
                <entry key="key.deserializer" value="org.apache.kafka.common.serialization.IntegerDeserializer"/>
                <entry key="value.deserializer" value="org.apache.kafka.common.serialization.StringDeserializer"/>
                <entry key="group.id" value="groupName"/>
            </map>
        </constructor-arg>
    </bean>
    <!-- 消费者容器 -->
    <bean class="org.springframework.kafka.listener.KafkaMessageListenerContainer" init-method="doStart">
        <constructor-arg ref="consumerFactory"/>
        <constructor-arg><!-- 配置信息 -->
            <bean class="org.springframework.kafka.listener.config.ContainerProperties">
                <constructor-arg value="topicName"/>
                <property name="messageListener"><!-- 消息接收成功的回调 -->
                    <bean class="wang.kefeng.KafkaConsumerListener"/>
                </property>
            </bean>
        </constructor-arg>
    </bean>
</beans>

3.3 KafkaProducerListener.java

public class KafkaProducerListener extends ProducerListenerAdapter<Integer, String> {
    private static final Logger logger = LoggerFactory.getLogger(KafkaProducerListener.class);
    @Override
    public void onSuccess(String topic, Integer partition, Integer key, String value, RecordMetadata recordMetadata) {
        logger.info("KafkaProducerListener.onSuccess(\"{}\", {}, \"{}\") OK.", topic, key, value);
    }
    @Override
    public void onError(String topic, Integer partition, Integer key, String value, Exception exception) {
        logger.warn("KafkaProducerListener.onError(\"{}\", {}, \"{}\") OK.", topic, key, value);
    }
    @Override
    public boolean isInterestedInSuccess() {
        return true;
    }
}

3.4 KafkaProducerListener.java

public class KafkaConsumerListener implements MessageListener<Integer, String> {
    private static final Logger logger = LoggerFactory.getLogger(KafkaConsumerListener.class);
    public void onMessage(ConsumerRecord<Integer, String> record) {
        logger.info("KafkaConsumerListener.onMessage(\"{}\", {}, \"{}\") OK.",
                record.topic(), record.key(), record.value());
    }
}

3.5 KafkaClientDemo.java

@Component
public class KafkaClientDemo {
    @Resource
    private KafkaTemplate<Integer, String> kafkaTemplate;
    public void producerDemo() {
        for (int key = 1; key <= 8; ++key) {
            String value = String.format("msg#%d", key);
            kafkaTemplate.sendDefault(key, value);
        }
    }
    public static void main(String[] args) {
        try (ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:spring.xml")) {
            context.start(); // 启动消费者线程，收到消息后自动回调 KafkaConsumerListener.onMessage()
            context.getBean(KafkaClientDemo.class).producerDemo(); // 生产消费
            try {
                Thread.sleep(600000); // 等待消费者线程(10min)
            } catch (InterruptedException e) {
            }
        }
    }
}

3.6 运行结果

## 生产者
13:05:13.734  INFO  [KafkaProducerListener.java:16] - KafkaProducerListener.onSuccess("topicName", 1, "msg#1") OK.
13:05:13.740  INFO  [KafkaProducerListener.java:16] - KafkaProducerListener.onSuccess("topicName", 2, "msg#2") OK.
13:05:13.759  INFO  [KafkaProducerListener.java:16] - KafkaProducerListener.onSuccess("topicName", 3, "msg#3") OK.
13:05:13.765  INFO  [KafkaProducerListener.java:16] - KafkaProducerListener.onSuccess("topicName", 4, "msg#4") OK.
13:05:13.770  INFO  [KafkaProducerListener.java:16] - KafkaProducerListener.onSuccess("topicName", 5, "msg#5") OK.
13:05:13.778  INFO  [KafkaProducerListener.java:16] - KafkaProducerListener.onSuccess("topicName", 6, "msg#6") OK.
13:05:13.783  INFO  [KafkaProducerListener.java:16] - KafkaProducerListener.onSuccess("topicName", 7, "msg#7") OK.
13:05:13.788  INFO  [KafkaProducerListener.java:16] - KafkaProducerListener.onSuccess("topicName", 8, "msg#8") OK.
## 消费者
13:05:16.920  INFO  [KafkaConsumerListener.java:15] - KafkaConsumerListener.onMessage("topicName", 3, "msg#3") OK.
13:05:16.920  INFO  [KafkaConsumerListener.java:15] - KafkaConsumerListener.onMessage("topicName", 4, "msg#4") OK.
13:05:16.922  INFO  [KafkaConsumerListener.java:15] - KafkaConsumerListener.onMessage("topicName", 1, "msg#1") OK.
13:05:16.922  INFO  [KafkaConsumerListener.java:15] - KafkaConsumerListener.onMessage("topicName", 7, "msg#7") OK.
13:05:16.922  INFO  [KafkaConsumerListener.java:15] - KafkaConsumerListener.onMessage("topicName", 8, "msg#8") OK.
13:05:16.922  INFO  [KafkaConsumerListener.java:15] - KafkaConsumerListener.onMessage("topicName", 2, "msg#2") OK.
13:05:16.922  INFO  [KafkaConsumerListener.java:15] - KafkaConsumerListener.onMessage("topicName", 5, "msg#5") OK.
13:05:16.922  INFO  [KafkaConsumerListener.java:15] - KafkaConsumerListener.onMessage("topicName", 6, "msg#6") OK.

4 基于 SpringBoot 开发

创建 SpringBoot 工程。

4.1 Maven 依赖

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

4.2 application.properties

# Brokers 地址列表
spring.kafka.bootstrap-servers=centos:9091,centos:9092,centos:9093
# 默认消费者组
spring.kafka.consumer.group-id=groupName
# 序列化/反序列化
spring.kafka.producer.key-serializer=org.apache.kafka.common.serialization.StringSerializer
spring.kafka.producer.value-serializer=org.apache.kafka.common.serialization.StringSerializer
spring.kafka.consumer.key-deserializer=org.apache.kafka.common.serialization.StringDeserializer
spring.kafka.consumer.value-deserializer=org.apache.kafka.common.serialization.StringDeserializer

4.3 KafkaClientDemo.java

@Component
@EnableScheduling
public class KafkaClientDemo {
    private static final String TOPIC_NAME = "topicName";
    private static final Logger logger = LoggerFactory.getLogger(KafkaClientDemo.class);
    private int key = 0;
    @Autowired
    private KafkaTemplate kafkaTemplate;
    // 生产者: 每秒推送一个消息
    @Scheduled(fixedRate = 1000)
    public void producerDemo() {
        String message = String.format("msg#%d", ++key);
        logger.info("KafkaClientDemo.producerDemo(\"{}\") ...", message);
        kafkaTemplate.send(TOPIC_NAME, message);
    }
    // 消费者1: 订阅主题(topicName)并接收消息
    @KafkaListener(topics = {TOPIC_NAME})
    public void consumerDemo1(String message) {
        logger.info("KafkaClientDemo.consumerDemo1(\"{}\") OK.", message);
    }
    // 消费者2: 订阅主题(topicName)并接收消息
    @KafkaListener(topics = {TOPIC_NAME})
    public void consumerDemo2(String message) {
        logger.info("KafkaClientDemo.consumerDemo2(\"{}\") OK.", message);
    }
}

4.4 运行结果

运行 SpringBoot 的 Application 类(无需任何调整)，结果如下：

## 可见：一个生产者定时投递消息；两个消费者(属于同一消费者组 groupName)交替收取消息。
14:36:52.586  INFO  [KafkaClientDemo.java:30] - KafkaClientDemo.producerDemo("msg#1") ...
14:36:52.889  INFO  [KafkaClientDemo.java:37] - KafkaClientDemo.consumerDemo1("msg#1") OK.
14:36:53.583  INFO  [KafkaClientDemo.java:30] - KafkaClientDemo.producerDemo("msg#2") ...
14:36:53.603  INFO  [KafkaClientDemo.java:43] - KafkaClientDemo.consumerDemo2("msg#2") OK.
14:36:54.583  INFO  [KafkaClientDemo.java:30] - KafkaClientDemo.producerDemo("msg#3") ...
14:36:54.613  INFO  [KafkaClientDemo.java:37] - KafkaClientDemo.consumerDemo1("msg#3") OK.
14:36:55.583  INFO  [KafkaClientDemo.java:30] - KafkaClientDemo.producerDemo("msg#4") ...
14:36:55.600  INFO  [KafkaClientDemo.java:37] - KafkaClientDemo.consumerDemo1("msg#4") OK.
14:36:56.583  INFO  [KafkaClientDemo.java:30] - KafkaClientDemo.producerDemo("msg#5") ...
14:36:56.598  INFO  [KafkaClientDemo.java:43] - KafkaClientDemo.consumerDemo2("msg#5") OK.

作者：王克锋

出处：https://kefeng.wang/2017/11/18/kafka-development/

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