Setting up multiple partitions in Apache Kafka

Question

Im trying to set the no of partitions to 2 from the code,and i have single node setup, (1 zookeeper, 1kafka). when i consume the message i see that kafka is using only one partition to store the data, Do i need to make any modifications to the setup to have multiple partitions ?

 private void setupZookeeper(String[] topicList){

    ZkClient zkClient = null;
    ZkUtils zkUtils = null;
    try {
        String[] zookeeperHosts = {"localhost:2181"}; // If multiple zookeeper then -> String zookeeperHosts = "192.168.20.1:2181,192.168.20.2:2181";
        int sessionTimeOutInMs = 15 * 1000; // 15 secs
        int connectionTimeOutInMs = 10 * 1000; // 10 secs
        //String topicName = "testTopic";
        int noOfPartitions = 2;
        int noOfReplication = 1;

        for(String zookeeper:zookeeperHosts){

            zkClient = new ZkClient(zookeeper, sessionTimeOutInMs, connectionTimeOutInMs, ZKStringSerializer$.MODULE$);
            zkUtils = new ZkUtils(zkClient, new ZkConnection(zookeeper), false);
            for(String topicName: topicList){
                System.out.println("Setting no of partitions ="+noOfPartitions + "for topic" + topicName);
                AdminUtils.createTopic(zkUtils, topicName, noOfPartitions, noOfReplication, 
                         producerConfig(),RackAwareMode.Disabled$.MODULE$);
            }
        }



    } catch (Exception ex) {
        ex.printStackTrace();
    } finally {
        if (zkClient != null) {
            zkClient.close();
        }
    }

My producerConfig, looks like the following:

private Properties producerConfig() {
   Properties props = new Properties();
  props.put("bootstrap.servers", "localhost:9092");

  props.put("acks", "all");
  //props.put("retries", 0);
  props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
  props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

return props;
}

Answer 1

when i consume the message i see that kafka is using only one partition to store the data

The default message partitioning strategy as below, "only one partition used" may be caused by constant message key, same hash value calculated and route to only one partition.

• If a partition is specified in the record, use it;
• If no partition is specified but a key is present choose a partition based on a hash of the key;
• If no partition or key is present choose a partition in a round-robin fashion.

you