Round Robin for several consumers in KAFKA

[Liel Shraga (lshraga)]

Hi,

I have 5 separate docker images : 1 for kafka broker, 1 zookeeper , 1 producer 
and 2 consumers.
I publish messages to the topic via the producer.
Basically, I would likw that the messages will be published in a round robin 
algorithm,
so for that purpose I defined the consumers with the same group.id and added 
config of partition.assignment.strategy to be 
org.apache.kafka.clients.consumer.RoundRobinAssignor,
but actually only 1 consumer receive all the messages.
My Producer Code:
public class DiscoveryKafkaProducer{
   Producer<String, String> producer;

   public DiscoveryKafkaProducer(Properties configs) {
       producer = new KafkaProducer<String, String>(configs);
   }
   public void send(String topic, List<String> records) {
         for(String record: records){
               producer.send(new ProducerRecord<String, String>(topic, record));
         }
       producer.flush();
   }

   public void close() throws Exception {
       producer.close();
   }
}

My Consumer Code:
public static void main(String[] args) {
            String server = "lshraga-ubuntu-sp-nac:9092";
            Properties consumerConfigs = new Properties();
            consumerConfigs.put("bootstrap.servers", server);
            consumerConfigs.put("key.deserializer", 
"org.apache.kafka.common.serialization.StringDeserializer");
            consumerConfigs.put("value.deserializer", 
"org.apache.kafka.common.serialization.StringDeserializer");
            consumerConfigs.put("group.id", "discovery");
            consumerConfigs.put("client.id", "discovery");
            consumerConfigs.put("partition.assignment.strategy", 
"org.apache.kafka.clients.consumer.RoundRobinAssignor");
            List<String> list = new ArrayList<String>();
            DiscoveryKafkaConsumer consumer1 = new 
DiscoveryKafkaConsumer(Collections.singletonList(topicName), consumerConfigs);

            try {
                  while (true) {
                        System.out.println("Start to consume");
                      consumer1.poll(1000L);
                  }
            } catch (InterruptedException e) {
                  // TODO Auto-generated catch block
                  e.printStackTrace();
            }

public class DiscoveryKafkaConsumer {
   Consumer<String, String> consumer;
   Integer id;
   public DiscoveryKafkaConsumer(List<String> topics, Properties configs) {
       consumer = new KafkaConsumer<String, String>(configs);
       consumer.subscribe(topics);
   }

   public DiscoveryKafkaConsumer(int i, List<String> topics, Properties 
configs) {
         consumer = new KafkaConsumer<String, String>(configs);
       consumer.subscribe(topics);
       this.id = i;
}

   public void poll(long timeout) throws InterruptedException {
       ConsumerRecords<String,String> records = consumer.poll(timeout);
       System.out.println("Hey!Consumer #" + id + "got records:" + records);
       Map<String, List<String>> results = new HashMap<String, List<String>>();
       records.forEach((cr) -> {
         System.out.println("cr.topic()=" + cr.topic());
           List<String> list = results.get(cr.topic());
           if(list == null) {
               list = new ArrayList<>();
               results.put(cr.topic(), list);
               }
                  list.add(cr.value());
                  System.out.println("list=" + list);
           });
   }
   public void close() throws Exception {
       consumer.close();
   }
What I need to add/condig in order to consume the messages in a Round Robin ?


Thanks,


[banner14]



Liel Shraga
ENGINEER.SOFTWARE ENGINEERING
lshr...@cisco.com<mailto:lshr...@cisco.com>
Tel: +972 2 588 6394

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