Kafka producer producing values in alternative even partitions like 0,2,4...etc in org.apache.kafka.clients.producer.RoundRobinPartitioner

Question

Kafka producer producing values in alternative even partitions like 0,2,4...etc in org.apache.kafka.clients.producer.RoundRobinPartitioner

I have 6 partitions & their are 6 concurrent consumer to those & following config org.apache.kafka.clients.producer.RoundRobinPartitioner. While producing the messages kafka only puts the messages to 3 partitions on alternative way. which is leaving the other partitions not being utilized & messages in queue for 6 concurrent calls as only 3 are being used.

How can i achieve equal distribution? Is there is any config i'm missing?

props.put(partitioner.class, "org.apache.kafka.clients.producer.RoundRobinPartitioner");

I'm using org.springframework.kafka:spring-kafka jar. And instead of providing key passing null key as in producer record. ie. Not passing any key just passing dto. Below is the producer config :-

 @Bean
    public KafkaTemplate<String, Dto> kafkaTemplate() {
        return new KafkaTemplate<>(producerFactory());
    }
 @Bean
    public ProducerFactory<String, Dto> dtoProducerFactory() {
        Map<String, Object> props = getProducerFactoryConfigMap();
        return new DefaultKafkaProducerFactory<>(props);
    }

 private Map<String, Object> getProducerFactoryConfigMap() {
        Map<String, Object> props = new HashMap<>();
        props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, kafkaConfig.getBootStrapServers());
        props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
        props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, JsonSerializer.class);
        props.put(ProducerConfig.PARTITIONER_CLASS_CONFIG, "org.apache.kafka.clients.producer.RoundRobinPartitioner");;
        kafkaConfig.populateSaslProperties(props);
        props.put(ProducerConfig.ACKS_CONFIG, PRODUCER_ACK_CONFIG);
        return props;
    }