Kafka学习（4）——生产消费实践

1. 基于0.8的生产者和消费者

maven依赖：

    org.apache.kafka
    kafka-clients
    0.9.0.1


    org.apache.kafka
    kafka_2.10
    0.9.0.1

1.1 消息生产

package com.best.kafka.test;

import com.best.xingng.cxf.databinding.json.util.JsonUtil;
import kafka.producer.KeyedMessage;
import kafka.producer.ProducerConfig;

import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import java.util.UUID;


public class LogProcessProducer {

    private static String KAFKA_ZOOKEEPER_CONNECT = "127.0.0.1:2181";
    private static String KAFKA_METADATA_BROKER_LIST = "127.0.0.1:9092";
    private static String KAFKA_ZK_CONNECTION_TIMEOUT_MS = "1000000";
    private static String TOPIC = "test1";

    public void test() {
        //初始化producer
        Properties producerProps = new Properties();
        producerProps.put("zookeeper.connect", KAFKA_ZOOKEEPER_CONNECT);
        producerProps.put("zk.connectiontimeout.ms", KAFKA_ZK_CONNECTION_TIMEOUT_MS);
        producerProps.put("metadata.broker.list", KAFKA_METADATA_BROKER_LIST);
        producerProps.put("key.serializer", "org.apache.kafka.common.serialization.ByteArrayDeserializer");
        producerProps.put("value.serializer", "org.apache.kafka.common.serialization.ByteArrayDeserializer");
        kafka.javaapi.producer.Producer producer = new kafka.javaapi.producer.Producer(new ProducerConfig(producerProps));

        //封装数据
        List> keyedMessages = new ArrayList>();
        for (int i=1; i<=100; i++) {
            String s = "test"; //此处数据类型为String
            KeyedMessage keyedMessage = new KeyedMessage(TOPIC, UUID.randomUUID().toString().getBytes(), SerializerUtil.serializer(s));
            keyedMessages.add(keyedMessage);
        }

        //批量发送
        producer.send(keyedMessages);
    }
}

SerializerUtil一个自定义的序列化帮助类，实现对象的序列化和反序列化。

1.2 消息消费

一方面，kafka认为0.9.*版本的consumer还不够完善，所以推荐使用0.9.*之前的consumer。

另一方面，0.9.*版本不再在zookeeper上维护consumer的offset，而是维护在broker上。

这对旧的kafka-manager来说影响较大，当前最新的kafka-manager-1.3.0.8已经支持broker上维护的offset，我们还未升级。

package com.best.kafka.test;

import kafka.consumer.Consumer;
import kafka.consumer.ConsumerConfig;
import kafka.consumer.ConsumerIterator;
import kafka.consumer.KafkaStream;
import kafka.message.MessageAndMetadata;

import java.util.*;


public class LogProcessConsumer {

    private static String KAFKA_ZOOKEEPER_CONNECT = "127.0.0.1:2181";
    private static String KAFKA_METADATA_BROKER_LIST = "127.0.0.1:9092";
    private static String KAFKA_FETCH_MAX_SIZE = (5*1024*1024) + "";
    private static String TOPIC = "test1";
    private static int PARTITION_NUM = 1;

    public void test() {
        //初始化consumer
        Properties consumerProps = new Properties();
        consumerProps.put("zookeeper.connect", KAFKA_ZOOKEEPER_CONNECT);
        consumerProps.put("metadata.broker.list", KAFKA_METADATA_BROKER_LIST);
        consumerProps.put("key.deserializer", "org.apache.kafka.common.serialization.ByteArrayDeserializer");
        consumerProps.put("value.deserializer", "org.apache.kafka.common.serialization.ByteArrayDeserializer");
        consumerProps.put("auto.commit.enable", "false");
        consumerProps.put("auto.offset.reset", "smallest");
        consumerProps.put("fetch.message.max.bytes", KAFKA_FETCH_MAX_SIZE);
        consumerProps.put("group.id", "test");
        kafka.javaapi.consumer.ConsumerConnector consumerConnector = Consumer.createJavaConsumerConnector(new ConsumerConfig(consumerProps));

        //获取KafkaStream
        int num = 10; // partition数目
        HashMap map = new HashMap();
        map.put(TOPIC, PARTITION_NUM);
        Map>> streamMap = consumerConnector.createMessageStreams(map);
        List> kafkaStreamList = streamMap.get(TOPIC);

        //获取KafkaStream的iterator
        List> consumerIterators = new ArrayList>();
        for (final KafkaStream stream : kafkaStreamList) {
            ConsumerIterator iterator = stream.iterator();
            consumerIterators.add(iterator);
        }

        // 取数据
        for (final ConsumerIterator iterator : consumerIterators) {
            while (iterator.hasNext()) {
                MessageAndMetadata mam = iterator.next();
                if (mam.message() == null) {
                    continue;
                }
                String s = (String) SerializerUtil.deserializer(mam.message());
                System.out.println(s);
                consumerConnector.commitOffsets();
            }
        }
    }
}

• KafkaStream。KafkaStream是kafka的consumer，KafkaStream的数量应和partition的数量保持一致，一个partition对应一个KafkaStream，超过partition数量的KafkaStream其实一直阻塞着，并不会其作用。所以，要增加KafkaStream就必须相应增加partition。
• offset。offset是consumer消费位置的标志，提交offset表明消息被消费。自动提交方式，offset是在iterator.next()之后就会进行。手动提交方式，可以定制消息被后续处理流程处理后再提交，从而确保消息发送的exactly once。如上例，设置auto.commit.enable为false，在print之后手动提交consumerConnector.commitOffsets()，可以确保print每一条消息。
• 消费组。group.id决定了consumer所属的消费组，同一个消费组的consumer共同维护一个offset。
• 初始消费位置。auto.offset.reset决定了一个新的consumer（不同group）消费的位置，默认为largest，表示从最新的消息开始消费；smallest表示从最久的消息开始消费。
• 阻塞消费。默认情况下，未设置consumer.timeout.ms参数，ConsumerIterator.hasNext()是阻塞式的，有数据时，ConsumerIterator.hasNext()返回true，无数据时，程序卡在ConsumerIterator.hasNext()，直到有新的数据进来。如果设置consumer.timeout.ms，则ConsumerIterator.hasNext()是限时消费的，有数据的时候，ConsumerIterator.hasNext()返回true，无数据时，ConsumerIterator.hasNext()等待consumer.timeout.ms时间，如果仍无数据，则抛出ConsumerTimeoutException错误。
• 消息大小。在consumer端关注的是获取的单条消息大小，由fetch.message.max.bytes决定。取出的消息大小超过fetch.message.max.bytes就会报MessageSizeTooLargeException。取出的消息大小是由写入的消息大小决定的，topic的max.message.bytes（默认情况下使用Broker的message.max.bytes）是限制producer对该topic发送的消息大小。所以要求fetch.message.max.bytes大于topic的max.message.bytes。

2. 基于0.9的生产者和消费者

使用0.9客户端对kafka进行消息读写。

0.8.2对Producer进行了较大改变，发送更快。

0.9.0对Consumer进行了较大的改变，去除了0.8上高低版本consumer的区别，使用更加方便。同时offset不再维护到zk上，维护到了broker上，可以降低对zk的依赖。但目前只是beta版本。

maven依赖：

    org.apache.kafka
    kafka-clients
    0.9.0.1

API具体文档见Producer API和Consumer API

参数配置见Producer Config和Consumer Config

2.1 消息生产

客户端加snappy压缩，需要确保snappy-java版本为1.1.1.7

2.2 消息消费

kafka会管理如何分配partition的消费。0.9的KafkaConsumer是一个批量消费。

（1）当某个consumer消费了数据，但是在heartbeat.interval.ms时间内没有commit，它就认为consumer挂了。这个时候就要reblance了。
（2）consumer每次poll时，取出max.partition.fetch.bytes大小的数据。

下面是一个简单的producer-consumser单元测试：

JsonUtil一个自定义的序列化帮助类，实现对象的序列化和反序列化。

package com.best.kafka.test;

import best.kafka.test.serialize.json.JsonUtil;
import junit.framework.Assert;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.clients.producer.ProducerRecord;

import java.util.Iterator;
import java.util.Properties;
import java.util.UUID;
import java.util.concurrent.CopyOnWriteArraySet;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicLong;

/**
 * Kafka090ClientTest
 *
 * @author cnuuid
 * @date 1/9/2016
 * @since
 */
public class Kafka090ClientTest {
    protected final Log logger = LogFactory.getLog(getClass());

    private Kafka090ProducerService kafka090ProducerService = null;
    private Kafka090ConsumeService kafka090ConsumeService = null;

    private volatile boolean flag = true;
    private String topic = "localtest";
    private static int consumerNum = 1;

    final CountDownLatch startGate = new CountDownLatch(1);
    final CountDownLatch endGate = new CountDownLatch(consumerNum);
    AtomicLong counter = new AtomicLong();

    private Properties getProducerProperties() {
        Properties properties = new Properties();
//        properties.put("bootstrap.servers", "127.0.0.1:9092");
        properties.put("bootstrap.servers", "192.168.0.2:9092,192.168.0.3:9092");
        properties.put("key.serializer", "org.apache.kafka.common.serialization.ByteArraySerializer");
        properties.put("value.serializer", "org.apache.kafka.common.serialization.ByteArraySerializer");
        properties.put("buffer.memory", 1024000); //1M
        properties.put("compression.type", "snappy");
        properties.put("retries", 3);
        properties.put("batch.size", 102400); //100k
//        properties.put("client.id", );
//        properties.put("max.block.ms", 60000); //60s
        properties.put("max.request.size", 1024000); //1M
//        properties.put("receive.buffer.bytes", );
//        properties.put("request.timeout.ms", );
        properties.put("block.on.buffer.full", true);
        return properties;
    }

    private Properties getConsumerProperties() {
        Properties properties = new Properties();
//        properties.put("bootstrap.servers", "127.0.0.1:9092");
        properties.put("bootstrap.servers", "192.168.0.2:9092,192.168.0.3:9092");
        properties.put("key.deserializer", "org.apache.kafka.common.serialization.ByteArrayDeserializer");
        properties.put("value.deserializer", "org.apache.kafka.common.serialization.ByteArrayDeserializer");
//        properties.put("fetch.min.bytes", );
        properties.put("group.id", "localtestgroup");
        properties.put("heartbeat.interval.ms", "20000");
//        properties.put("max.partition.fetch.bytes", "3145728");//3M
        properties.put("max.partition.fetch.bytes", "1000");//3M
        properties.put("request.timeout.ms", "60000");
        properties.put("session.timeout.ms", "30000");
        properties.put("group.max.session.timeout.ms", "60000");
        properties.put("auto.offset.reset", "earliest");
        properties.put("enable.auto.commit", "false");
//        properties.put("max.poll.records", "1"); //0.10.0版本可用
//        properties.put("partition.assignment.strategy", );
//        properties.put("receive.buffer.bytes", );
//        properties.put("request.timeout.ms", );
//        properties.put("send.buffer.bytes", );
//        properties.put("client.id", );
//        properties.put("fetch.max.wait.ms", );
        return properties;
    }


    @org.junit.Before
    public void before() throws Exception {
        kafka090ProducerService = new Kafka090ProducerService(getProducerProperties());
        kafka090ConsumeService = new Kafka090ConsumeService(getConsumerProperties(), topic, consumerNum);
    }

    @org.junit.After
    public void after() throws Exception {
        flag = false;
        kafka090ProducerService.close();
        kafka090ConsumeService.close();
    }

    @org.junit.Test
    public void produce() throws InterruptedException {
        int i = 0;
        while(i<1000){
            Message message = new Message();
            message.setContent(i + "");
            ProducerRecord producerRecord = new ProducerRecord(topic, UUID.randomUUID().toString().getBytes(), JsonUtil.toByteJson(message));
            kafka090ProducerService.send(producerRecord);
            System.out.println("put " + i++);
        }
        Thread.sleep(10*1000);
    }

    @org.junit.Test
    public void consume() throws InterruptedException {
        CopyOnWriteArraySet> consumers = kafka090ConsumeService.getConsumers();
        KafkaConsumer consumer = consumers.iterator().next();
        int i = 0;
        while (flag) {
            ConsumerRecords consumerRecords = consumer.poll(100);
            for (ConsumerRecord record : consumerRecords) {
                if (record.value() == null) {
                    continue;
                }
                Message message = JsonUtil.formByteJson(Message.class, record.value());
                System.out.println("consume:" + message.getContent() + "..");
            }
            if (consumerRecords.count()>0) {
                consumer.commitSync();
            }
            System.out.println("loop-" + i);
            Thread.sleep(1000);
        }
    }

    @org.junit.Test
    public void test() throws InterruptedException {
        while (counter.longValue() < 1000) {
            Message message = new Message();
            message.setContent(counter.longValue() + "");
            ProducerRecord producerRecord = new ProducerRecord(topic, UUID.randomUUID().toString().getBytes(), JsonUtil.toByteJson(message));
            kafka090ProducerService.send(producerRecord);
            System.out.println("put " + counter.longValue());
            counter.incrementAndGet();
        }

        Thread.sleep(10 * 1000);

        // consume
        CopyOnWriteArraySet> consumers = kafka090ConsumeService.getConsumers();
        Iterator> iterator = consumers.iterator();
        while (iterator.hasNext()) {
            KafkaConsumer consumer = iterator.next();
            Thread consumeThread = new Thread(new ConsumeTask(consumer));
            consumeThread.start();
        }
        startGate.countDown();
        endGate.await();
        Assert.assertEquals(0l, counter.longValue());
    }

    class ConsumeTask implements Runnable {
        private KafkaConsumer consumer;

        public ConsumeTask(KafkaConsumer consumer) {
            this.consumer = consumer;
        }

        @Override
        public void run() {
            try {
                startGate.await();
                logger.info("Kafka " + Thread.currentThread().getName() + " running...");
                try {
                    int i=0;
                    while (i<50) {
                        ConsumerRecords consumerRecords = consumer.poll(100);
                        for (ConsumerRecord record : consumerRecords) {
                            if (record.value() == null) {
                                continue;
                            }
                            Message message = JsonUtil.formByteJson(Message.class, record.value());
                            counter.decrementAndGet();
                            System.out.println(Thread.currentThread().getName() + " consume:" + message.getContent() + "..");
                        }
                        if (consumerRecords.count() > 0) {
                            consumer.commitSync();
                        }
                        System.out.println("loop-" + i);
                        Thread.sleep(1000);
                        i++;
                    }
                } catch (Exception e) {
                    logger.error("", e);
                }
                Thread.sleep(10 * 1000);
                endGate.countDown();
                logger.info("Kafka " + Thread.currentThread().getName() + " finished.");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

消息体

package com.best.kafka.test;

/**
 * Message
 *
 * @author cnuuid
 * @date 9/1/2016
 * @since
 */
public class Message {
    private String content;

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }
}

生产者producer

package com.best.kafka.test;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerRecord;

import java.util.Properties;

/**
 * Kafka090ProducerService
 *
 * @author cnuuid
 * @date 9/1/2016
 * @since
 */
public class Kafka090ProducerService {
    protected final Log logger = LogFactory.getLog(getClass());

    private Producer producer;

    public Kafka090ProducerService(Properties properties) throws Exception {
        if (properties==null && properties.get("bootstrap.servers")==null
                && properties.get("key.serializer")==null
                && properties.get("value.serializer")==null) {
            throw new Exception("lack of properties");
        } else {
            producer = new KafkaProducer(properties);
        }
    }

    public void close() throws Exception {
        try {
            producer.close();
        } catch (Exception e) {
            logger.error("Close kafka producer or consumer Error!", e);
        }
        logger.info(" kafka has been shut down!");
    }

    public void send(ProducerRecord producerRecord) {
        if (producerRecord!=null) {
            producer.send(producerRecord);
        }
    }
}

消费者consumer

package com.best.kafka.test;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.kafka.clients.consumer.KafkaConsumer;

import java.util.Arrays;
import java.util.Properties;
import java.util.concurrent.CopyOnWriteArraySet;

/**
 * Kafka090ConsumeService
 *
 * @author cnuuid
 * @date 9/1/2016
 * @since
 */
public class Kafka090ConsumeService {
    protected final Log logger = LogFactory.getLog(getClass());

    private CopyOnWriteArraySet> consumers = new CopyOnWriteArraySet>();

    public Kafka090ConsumeService(Properties properties, String topic, int consumerNum) throws Exception {
        if (properties==null && properties.get("bootstrap.servers")==null
                && properties.get("key.serializer")==null
                && properties.get("value.serializer")==null
                && consumerNum<=0
                && StringUtils.isNotBlank(topic)) {
            throw new Exception("lack of properties");
        } else {
            for (int i=0; i< consumerNum; i++) {
                KafkaConsumer consumer = new KafkaConsumer(properties);
                consumer.subscribe(Arrays.asList(topic));
                consumers.add(consumer);
            }
        }
    }

    public void close() throws Exception {
        try {
            if (consumers!=null && consumers.size()>0) {
                for (KafkaConsumer consumer : consumers) {
                    if (consumer!=null) {
                        synchronized (consumer) {
                            if (consumer!=null) {
                                consumer.close();
                                consumer = null;
                            }
                        }
                    }

                }
            }
        } catch (Exception e) {
            logger.error("Close kafka producer or consumer Error!", e);
        }
        logger.info(" kafka has been shut down!");
    }

    public CopyOnWriteArraySet> getConsumers() {
        return consumers;
    }
}