Kafka编程实例

编程

Producer是一个应用程序。它创建消息并发送它们到Kafka broker中。这些producer在本质上是不同。比方。前端应用程序。后端服务。代理服务。适配器对于潜在的系统，Hadoop对于的Producer。这些不同的Producer可以使用不同的语言实现。比方java、C和Python。

以下的这部图表解释了消息producer的Kafka API.

以下将具体介绍假设编写一个简单的Producer和Consumer应用程序。

发送简单消息给Kafka broker。Producer端编写类ClusterProducer。

public classClusterProducer extends Thread {
    private static final Log log =LogFactory.getLog(ClusterProducer.class);

    public void sendData() {
        Random rnd = new Random();
        Properties props =PropertiesParser.getProperties(PropertiesSettings.PRODUCER_FILE_NAME);
        if (props == null) {
            log.error("can't loadspecified file " + PropertiesSettings.PRODUCER_FILE_NAME);
           return;
        }
        //set the producer configurationproperties
        ProducerConfig config = newProducerConfig(props);
        Producer<String, String> producer= new Producer<String, String>(config);

        //Send the data
        int count = 1;
        KeyedMessage<String, String>data;
        while (count < 100) {
            String sign = "*";
            String ip = "192.168.2."+ rnd.nextInt(255);
            StringBuffer sb = newStringBuffer();
            for (int i = 0; i < count; i++){
                sb.append(sign);
            }
            log.info("set data:" +sb);
            try {
                Thread.sleep(10);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            data = new KeyedMessage<String,String>(PropertiesSettings.TOPIC_NAME, ip, sb.toString());
            producer.send(data);
            count++;
        }
        producer.close();
    }

    public void run() {
        sendData();
    }

    public static void main(String[] args) {
        new ClusterProducer().sendData();
    }
}

定于Consumer获取端，获取相应topic的数据：

public class Consumerextends Thread {
    private static final Log log =LogFactory.getLog(Consumer.class);
    private final ConsumerConnector consumer;
    private final String topic;

    public Consumer(String topic) {
        consumer =kafka.consumer.Consumer.createJavaConsumerConnector(
                createConsumerConfig());
        this.topic = topic;
    }

    private static ConsumerConfigcreateConsumerConfig() {
        Properties props = new Properties();
       props.put("zookeeper.connect", KafkaProperties.zkConnect);
        props.put("group.id",KafkaProperties.groupId);
       props.put("zookeeper.session.timeout.ms", "400");
       props.put("zookeeper.sync.time.ms", "200");
       props.put("auto.commit.interval.ms", "1000");

        return new ConsumerConfig(props);

    }

    public void run() {
        Map<String, Integer>topicCountMap = new HashMap<String, Integer>();
        topicCountMap.put(topic, newInteger(1));
        Map<String,List<KafkaStream<byte[], byte[]>>> consumerMap =consumer.createMessageStreams(topicCountMap);
        KafkaStream<byte[], byte[]>stream = consumerMap.get(topic).get(0);
        ConsumerIterator<byte[], byte[]>it = stream.iterator();
        while (it.hasNext()) {
            log.info("+message: " +new String(it.next().message()));
        }
    }

    public static void main(String[] args) {
        Consumer client = new Consumer("cluster_statistics_topic");
        client.

辅助类：

public interface PropertiesSettings {

    final static String CONSUMER_FILE_NAME = "consumer.properties";
    final static String PRODUCER_FILE_NAME = "producer.properties";
    final static String TOPIC_NAME = "cluster_statistics_topic";
    final static String TOPIC_A = "cluster_statistics_topic_A";
}

package com.kafka.utils;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

/**
 * @author JohnLiu
 * @version 0.1.0
 * @date 2014/8/27
 */
public class PropertiesParser {

    private static final Log log = LogFactory.getLog(PropertiesParser.class);
    /* properties file type */
    Properties props = null;

    /* constructor method*/
    public PropertiesParser(Properties props) {
        this.props = props;
    }

    /**
     * Get the trimmed String value of the property with the given
     * <code>name</code>.  If the value the empty String (after
     * trimming), then it returns null.
     */
    public String getStringProperty(String name) {
        return getStringProperty(name, null);
    }

    /**
     * Get the trimmed String value of the property with the given
     * <code>name</code> or the given default value if the value is
     * null or empty after trimming.
     */
    public String getStringProperty(String name, String def) {
        String val = props.getProperty(name, def);
        if (val == null) {
            return def;
        }

        val = val.trim();

        return (val.length() == 0) ? def : val;
    }

    private Properties loadPropertiesFile() {
        Properties props = new Properties();
        InputStream in;
        ClassLoader cl = getClass().getClassLoader();
        if (cl == null)
            cl = findClassloader();
        if (cl == null)
            try {
                throw new ProcessingException("Unable to find a class loader on the current thread or class.");
            } catch (ProcessingException e) {
                e.printStackTrace();
            }
        in = cl.getResourceAsStream(PropertiesSettings.CONSUMER_FILE_NAME);
        try {
            props.load(in);
        } catch (IOException ioe) {
            log.error("can't load " + PropertiesSettings.CONSUMER_FILE_NAME, ioe);
        }
        return props;
    }

    private ClassLoader findClassloader() {
        // work-around set context loader for windows-service started jvms (QUARTZ-748)
        if (Thread.currentThread().getContextClassLoader() == null && getClass().getClassLoader() != null) {
            Thread.currentThread().setContextClassLoader(getClass().getClassLoader());
        }
        return Thread.currentThread().getContextClassLoader();
    }

    public static Properties getProperties(final String fileName) {
        Properties props = new Properties();
        InputStream in = Thread.currentThread().getContextClassLoader()
                .getResourceAsStream(fileName);
        try {
            props.load(in);
        } catch (IOException ioe) {
            log.error("can't load " + fileName, ioe);
        }
        return props;
    }
}

配置參数文件consumer.properties：

zookeeper.connect=bigdata09:2181,bigdata08:2181,bigdata07:2181
group.id=cluster_group
zookeeper.session.timeout.ms=400
zookeeper.sync.time.ms=200
auto.commit.interval.ms=1000

配置參数文件producer.properties：

metadata.broker.list=bigdata09:9092,bigdata08:9092,bigdata07:9092
serializer.class=kafka.serializer.StringEncoder
#partitioner.class=com.kafka.producer.SimplePartitioner
request.required.acks=1

分别运行上面的代码，能够发送或者得到相应topic信息。

Enjoy yourself!(*^__^*) ……