Kafka安裝以及基本使用，新手友好

1. kafka安裝

对于后端开发而已，不宜在环境安装方面耗费宝贵的精力。相对于tar包安装等方式，docker安装省时省力。下面主要介绍，如何使用docker安装kafka。

1.1 安装命令

事实上，仅需如下两条命令即可完成kafka安装。

1. zookeeper安装：docker run -d --restart=always --log-driver json-file --log-opt max-size=100m --log-opt max-file=2 --name zookeeper -p 2181:2181 -v /etc/localtime:/etc/localtime wurstmeister/zookeeper
2. kafka安装：docker run -d --restart=always --log-driver json-file --log-opt max-size=100m --log-opt max-file=2 --name kafka -p 9092:9092 -e KAFKA_BROKER_ID=0 -e KAFKA_ZOOKEEPER_CONNECT=192.168.1.10:2181/kafka -e KAFKA_ADVERTISED_LISTENERS=PLAINTEXT://192.168.1.10:9092 -e KAFKA_LISTENERS=PLAINTEXT://0.0.0.0:9092 -v /etc/localtime:/etc/localtime wurstmeister/kafka

1.2 参数说明

-e KAFKA_BROKER_ID=0  在kafka集群中，kafka的唯一ID
-e KAFKA_ZOOKEEPER_CONNECT=172.16.0.13:2181/kafka 配置zookeeper管理kafka的路径
-e KAFKA_ADVERTISED_LISTENERS=PLAINTEXT://192.168.1.10:9092  把kafka的地址端口注册给zookeeper
-e KAFKA_LISTENERS=PLAINTEXT://0.0.0.0:9092 配置kafka的监听端口
-v /etc/localtime:/etc/localtime 容器同步宿主机时间，docker基本都要配置此参数

1.3 注意事项

安装过程可能会遇到一些问题，我这里简单说几点

1. docker命令不熟悉：请移步到另一篇博客简单学习一下：docker常用命令
2. 下载速度缓慢：更新docker镜像为国内源
   • 修改配置文件：vim /etc/docker/daemon.json,修改为：{ "registry-mirrors":["https://n62k26ut.mirror.aliyuncs.com"] }
   • 重启docker服务:service docker restart
3. kafka无法启动，可能原因为swap空间为0：自行百度如何给linux扩展swap空间

2. Kafka基本概念

3. Kafka生产与消费

3.1 简单消费写法

3.1.1 配置消费者

将配置好的消费者工厂类DefaultKafkaConsumerFactory注册到kafka监听工厂KafkaListenerContainerFactory，具体代码如下所示：

@Configuration
@EnableKafka
public class KafkaConfiguration {

	//定义消费者组:当更换此选项，offset会从0开始
    @Value("${person.groupId}")
    private String groupId;

    @Bean
    @ConditionalOnMissingBean(name = "kafkaListenerContainerFactory")
    KafkaListenerContainerFactory<ConcurrentMessageListenerContainer<String, String>> kafkaListenerContainerFactory() {
        ConcurrentKafkaListenerContainerFactory<String, String> factory = new ConcurrentKafkaListenerContainerFactory<>();
        //并发数量
        factory.setConcurrency(2);
        factory.setConsumerFactory(consumerFactory());
        //批量监听:一次消费多条数据
        factory.setBatchListener(true);
        factory.getContainerProperties().setPollTimeout(20000);
        return factory;
    }

    @Bean
    public Map<String, Object> consumerConfigs() {
        Map<String, Object> propsMap = new HashMap<>();
        propsMap.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, false);
        propsMap.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG,"192.168.1.10:21005");
        propsMap.put(ConsumerConfig.AUTO_COMMIT_INTERVAL_MS_CONFIG, "1000");
        propsMap.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, "15000");
        propsMap.put(ConsumerConfig.GROUP_ID_CONFIG, groupId);
        //Key序列化为字符串
        propsMap.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
        //Value序列化为字符串
        propsMap.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
        propsMap.put(ConsumerConfig.MAX_POLL_RECORDS_CONFIG, 500);
        propsMap.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
        return propsMap;
    }

    private ConsumerFactory<String, String> consumerFactory() {
        return new DefaultKafkaConsumerFactory<>(consumerConfigs());
    }

}

3.1.2 具体消费

消费起来也非常简单，直接使用kafkaListener即可对相关topics进行监听

@Component
@Slf4j
public class KafkaReceiver {

    @KafkaListener(topics = {"xxx"}, containerFactory = "kafkaListenerContainerFactory")
    public void process(List<ConsumerRecord<?, ?>> records) {
        try {
            for (ConsumerRecord<?, ?> record : records) {
                Optional<?> kafkaMessage = Optional.ofNullable(record.value());
                if (kafkaMessage.isPresent()) {
                    //实际的消息处理逻辑写在此处
                }
            }
      
        } catch (Exception e) {
            log.error( e.getMessage(), e);
        } 
    }
}

3.2 生产者

3.2.1 生产者配置

生产者配置实际上就是配置kafkaTemplate，比消费者代码更为简单。

package xyz.yq56.kafka.common.config;

import java.util.Map;

import org.apache.commons.collections4.map.HashedMap;
import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.common.serialization.StringDeserializer;
import org.apache.kafka.common.serialization.StringSerializer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.kafka.config.ConcurrentKafkaListenerContainerFactory;
import org.springframework.kafka.config.KafkaListenerContainerFactory;
import org.springframework.kafka.core.DefaultKafkaConsumerFactory;
import org.springframework.kafka.core.DefaultKafkaProducerFactory;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.kafka.core.ProducerFactory;
import org.springframework.kafka.listener.ConcurrentMessageListenerContainer;

import com.google.common.collect.Maps;

@Configuration
public class KafkaConfig {

	// ******************************************* 生产者配置
	// **************************************************//
	@Bean
	public KafkaTemplate<String, String> kafkaTemplate() {
		return new KafkaTemplate<>(producerFactory());
	}

	@Bean
	public ProducerFactory<String, String> producerFactory() {
		return new DefaultKafkaProducerFactory<>(producerConfigs());
	}

	@Bean
	public Map<String, Object> producerConfigs() {
		Map<String, Object> props = Maps.newHashMap();
		props.put(ProducerConfig.ACKS_CONFIG, "0");
		props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "122.51.21.35:9092");
		props.put(ProducerConfig.RETRIES_CONFIG, 3);
		props.put(ProducerConfig.BATCH_SIZE_CONFIG, 150);
		props.put(ProducerConfig.LINGER_MS_CONFIG, 1);
		props.put(ProducerConfig.BUFFER_MEMORY_CONFIG, 33554432);
		props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
		props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
		return props;
	}

	// ******************************************* 消费者配置
	// **************************************************//

	@Bean(value = "kafkaListenerContainerFactory")
	public KafkaListenerContainerFactory<ConcurrentMessageListenerContainer<String, String>> kafkaListenerContainerFactory() {
		ConcurrentKafkaListenerContainerFactory<String, String> factory = new ConcurrentKafkaListenerContainerFactory<>();
		// 并发数量
		factory.setConcurrency(2);
		factory.setConsumerFactory(consumerFactory());
		// 批量监听:一次消费多条数据
		factory.setBatchListener(true);
		factory.getContainerProperties().setPollTimeout(20000);
		return factory;

	}

	public DefaultKafkaConsumerFactory<String, String> consumerFactory() {
		return new DefaultKafkaConsumerFactory<>(ConsumerConfig());
	}

	public Map<String, Object> ConsumerConfig() {
		Map<String, Object> propsMap = new HashedMap<>();
		propsMap.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, false);
		propsMap.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "122.51.21.35:9092");
		propsMap.put(ConsumerConfig.AUTO_COMMIT_INTERVAL_MS_CONFIG, "1000");
		propsMap.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, "15000");
		propsMap.put(ConsumerConfig.GROUP_ID_CONFIG, "123465");
		// Key序列化为字符串
		propsMap.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
		// Value序列化为字符串
		propsMap.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
		propsMap.put(ConsumerConfig.MAX_POLL_RECORDS_CONFIG, 500);
		propsMap.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
		return propsMap;
	}
}

3.2.2 生产者使用

注入kafkaTemplate，然后调用send方法即可

package xyz.yq56.kafka.mq;

import javax.annotation.Resource;

import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.stereotype.Component;

import lombok.extern.slf4j.Slf4j;

@Component
@Slf4j
public class KafkaProducer {

	@Resource
	private KafkaTemplate<String, String> kafkaTemplate;

	public void send(String topic, String message) {
		kafkaTemplate.send(topic, message);
		log.info("发送消息");
	}

}