Apache Kafka Component Guide
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Chapter 7. Developing Kafka Producers and Consumers

The examples in this chapter contain code for a basic Kafka producer and consumer, and similar examples for an SSL-enabled cluster. (To configure Kafka for SSL, see Enable SSL for Kafka Clients in the HDP Security Guide.)

For examples of Kafka producers and consumers that run on a Kerberos-enabled cluster, see Producing Events/Messages to Kafka on a Secured Cluster and Consuming Events/Messages from Kafka on a Secured Cluster, in the Security Guide.

Basic Producer Example

package com.hortonworks.example.kafka.producer;

import org.apache.kafka.clients.producer.Callback;
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.clients.producer.RecordMetadata;

import java.util.Properties;
import java.util.Random;

public class BasicProducerExample {

   public static void main(String[] args){

       Properties props = new Properties();
       props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka.example.com:6667");
       props.put(ProducerConfig.ACKS_CONFIG, "all");
       props.put(ProducerConfig.RETRIES_CONFIG, 0);
       props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");
       props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");

       Producer<String, String> producer = new KafkaProducer<String, String>(props);
       TestCallback callback = new TestCallback();
       Random rnd = new Random();
       for (long i = 0; i < 100 ; i++) {
           ProducerRecord<String, String> data = new ProducerRecord<String, String>(
                   "test-topic", "key-" + i, "message-"+i );
           producer.send(data, callback);
       }

       producer.close();
   }


   private static class TestCallback implements Callback {
       @Override
       public void onCompletion(RecordMetadata recordMetadata, Exception e) {
           if (e != null) {
               System.out.println("Error while producing message to topic :" + recordMetadata);
               e.printStackTrace();
           } else {
               String message = String.format("sent message to topic:%s partition:%s  offset:%s", recordMetadata.topic(), recordMetadata.partition(), recordMetadata.offset());
               System.out.println(message);
           }
       }
   }

}

To run the producer example, use the following command:

$ java com.hortonworks.example.kafka.producer.BasicProducerExample

Producer Example for an SSL-Enabled Cluster

The following example adds three important configuration settings for SSL encryption and three for SSL authentication. The two sets of configuration settings are prefaced by comments.

package com.hortonworks.example.kafka.producer;

import org.apache.kafka.clients.CommonClientConfigs;
import org.apache.kafka.clients.producer.Callback;
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.clients.producer.RecordMetadata;
import org.apache.kafka.common.config.SslConfigs;

import java.util.Properties;
import java.util.Random;

public class BasicProducerExample {

   public static void main(String[] args){

       Properties props = new Properties();
       props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka.example.com:6667");

       //configure the following three settings for SSL Encryption
       props.put(CommonClientConfigs.SECURITY_PROTOCOL_CONFIG, "SSL");
       props.put(SslConfigs.SSL_TRUSTSTORE_LOCATION_CONFIG, "/var/private/ssl/kafka.client.truststore.jks");
       props.put(SslConfigs.SSL_TRUSTSTORE_PASSWORD_CONFIG,  "test1234");

       // configure the following three settings for SSL Authentication
       props.put(SslConfigs.SSL_KEYSTORE_LOCATION_CONFIG, "/var/private/ssl/kafka.client.keystore.jks");
       props.put(SslConfigs.SSL_KEYSTORE_PASSWORD_CONFIG, "test1234");
       props.put(SslConfigs.SSL_KEY_PASSWORD_CONFIG, "test1234");
       
       props.put(ProducerConfig.ACKS_CONFIG, "all");
       props.put(ProducerConfig.RETRIES_CONFIG, 0);
       props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");
       props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");

       Producer<String, String> producer = new KafkaProducer<String, String>(props);
       TestCallback callback = new TestCallback();
       Random rnd = new Random();
       for (long i = 0; i < 100 ; i++) {
           ProducerRecord<String, String> data = new ProducerRecord<String, String>(
                   "test-topic", "key-" + i, "message-"+i );
           producer.send(data, callback);
       }

       producer.close();
   }


   private static class TestCallback implements Callback {
       @Override
       public void onCompletion(RecordMetadata recordMetadata, Exception e) {
           if (e != null) {
               System.out.println("Error while producing message to topic :" + recordMetadata);
               e.printStackTrace();
           } else {
               String message = String.format("sent message to topic:%s partition:%s  offset:%s", recordMetadata.topic(), recordMetadata.partition(), recordMetadata.offset());
               System.out.println(message);
           }
       }
   }

}

To run the producer example, use the following command:

$ java com.hortonworks.example.kafka.producer.BasicProducerExample

Basic Consumer Example

package com.hortonworks.example.kafka.consumer;

import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.consumer.ConsumerRebalanceListener;
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.common.TopicPartition;

import java.util.Collection;
import java.util.Collections;
import java.util.Properties;

public class BasicConsumerExample {

   public static void main(String[] args) {

       Properties consumerConfig = new Properties();
       consumerConfig.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka.example.com:6667");
       consumerConfig.put(ConsumerConfig.GROUP_ID_CONFIG, "my-group");
       consumerConfig.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
       consumerConfig.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
       consumerConfig.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
       KafkaConsumer<byte[], byte[]> consumer = new KafkaConsumer<>(consumerConfig);
       TestConsumerRebalanceListener rebalanceListener = new TestConsumerRebalanceListener();
       consumer.subscribe(Collections.singletonList("test-topic"), rebalanceListener);

       while (true) {
           ConsumerRecords<byte[], byte[]> records = consumer.poll(1000);
           for (ConsumerRecord<byte[], byte[]> record : records) {
               System.out.printf("Received Message topic =%s, partition =%s, offset = %d, key = %s, value = %s\n", record.topic(), record.partition(), record.offset(), record.key(), record.value());
           }

           consumer.commitSync();
       }

   }

   private static class  TestConsumerRebalanceListener implements ConsumerRebalanceListener {
       @Override
       public void onPartitionsRevoked(Collection<TopicPartition> partitions) {
           System.out.println("Called onPartitionsRevoked with partitions:" + partitions);
       }

       @Override
       public void onPartitionsAssigned(Collection<TopicPartition> partitions) {
           System.out.println("Called onPartitionsAssigned with partitions:" + partitions);
       }
   }

}

To run the consumer example, use the following command:

# java com.hortonworks.example.kafka.consumer.BasicConsumerExample

Consumer Example for an SSL-Enabled Cluster

The following example adds three important configuration settings for SSL encryption and three for SSL authentication. The two sets of configuration settings are prefaced by comments.

package com.hortonworks.example.kafka.consumer;

import org.apache.kafka.clients.CommonClientConfigs;
import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.consumer.ConsumerRebalanceListener;
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.common.TopicPartition;
import org.apache.kafka.common.config.SslConfigs;

import java.util.Collection;
import java.util.Collections;
import java.util.Properties;

public class BasicConsumerExample {

   public static void main(String[] args) {

       Properties props = new Properties();
       props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka.example.com:6667");
       
       //configure the following three settings for SSL Encryption
       props.put(CommonClientConfigs.SECURITY_PROTOCOL_CONFIG, "SSL");
       props.put(SslConfigs.SSL_TRUSTSTORE_LOCATION_CONFIG, "/var/private/ssl/kafka.client.truststore.jks");
       props.put(SslConfigs.SSL_TRUSTSTORE_PASSWORD_CONFIG,  "test1234");
       
       //configure the following three settings for SSL Authentication
       props.put(SslConfigs.SSL_KEYSTORE_LOCATION_CONFIG, "/var/private/ssl/kafka.client.keystore.jks");
       props.put(SslConfigs.SSL_KEYSTORE_PASSWORD_CONFIG, "test1234");
       props.put(SslConfigs.SSL_KEY_PASSWORD_CONFIG, "test1234");
       
       props.put(ConsumerConfig.GROUP_ID_CONFIG, "my-group");
       props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
       props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
       props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
       KafkaConsumer<byte[], byte[]> consumer = new KafkaConsumer<>(props);
       TestConsumerRebalanceListener rebalanceListener = new TestConsumerRebalanceListener();
       consumer.subscribe(Collections.singletonList("test-topic"), rebalanceListener);

       while (true) {
           ConsumerRecords<byte[], byte[]> records = consumer.poll(1000);
           for (ConsumerRecord<byte[], byte[]> record : records) {
               System.out.printf("Received Message topic =%s, partition =%s, offset = %d, key = %s, value = %s\n", record.topic(), record.partition(), record.offset(), record.key(), record.value());
           }

           consumer.commitSync();
       }

   }

   private static class  TestConsumerRebalanceListener implements ConsumerRebalanceListener {
       @Override
       public void onPartitionsRevoked(Collection<TopicPartition> partitions) {
           System.out.println("Called onPartitionsRevoked with partitions:" + partitions);
       }

       @Override
       public void onPartitionsAssigned(Collection<TopicPartition> partitions) {
           System.out.println("Called onPartitionsAssigned with partitions:" + partitions);
       }
   }

}

To run the consumer example, use the following command:

$ java com.hortonworks.example.kafka.producer.BasicProducerExample