KafkaTemplate.send(key,value,topic) with Custom Partitioner?

Question

I saw and implemented the method KafkaTemplate.send(TOPIC,message) with default partitioner class.

But here, I am not passing keys. I have a simple custom partitioner class and I also wanna send to kafka server like KafkaTemplate(TOPIC,key,message) where in producerConfig I set my customPartitioner class for partitioning.

I saw this Will send(Topic, Key, Message) method of KafkaTemplate calls Partition method if I provide custom Partitioner? but I didn't get it fully.

1. my simple customPartitioner class:

public class CustomPartitionar implements Partitioner {
   private PartitionMapper newMapper;
   public CustomPartitionar(){
       newMapper = new PartitionMapper();
   }
   @Override
   public void configure(Map<String, ?> configs) {

   }
   @Override
   public int partition(String topic, Object key, byte[] keyBytes, Object value, byte[] valueBytes,Cluster cluster) {
       int partition = 0;
       String userName = (String) key;
       // Find the id of current user based on the username from another mapper class
       Integer userId = newMapper.findUserId(userName);
       // If the userId not found, default partition is 0
       if (userId != null) {
           partition = userId;
       }
       return partition;
   }
   @Override
   public void close() {
   }
}

2. added this class to producerFactory:

config.put(ProducerConfig.PARTITIONER_CLASS_CONFIG, CustomPartitionar.class);

3. actually my key will be get from "message.getReceiver()" and topic will be get from "message.getTopic()" so my messages will go to desired topic and partition belongs to that user/group..so I just wanna send like:

KafkaTemplate.send(message.getTopic(),message.getReceiver(),message)

can this be possible in a simple way or am I missing something?

Answer 1

The KafkaTemplate has several send methods:

/**
 * Send the data to the default topic with no key or partition.
 * @param data The data.
 * @return a Future for the {@link SendResult}.
 */
ListenableFuture<SendResult<K, V>> sendDefault(V data);

/**
 * Send the data to the default topic with the provided key and no partition.
 * @param key the key.
 * @param data The data.
 * @return a Future for the {@link SendResult}.
 */
ListenableFuture<SendResult<K, V>> sendDefault(K key, V data);

/**
 * Send the data to the default topic with the provided key and partition.
 * @param partition the partition.
 * @param key the key.
 * @param data the data.
 * @return a Future for the {@link SendResult}.
 */
ListenableFuture<SendResult<K, V>> sendDefault(Integer partition, K key, V data);

/**
 * Send the data to the default topic with the provided key and partition.
 * @param partition the partition.
 * @param timestamp the timestamp of the record.
 * @param key the key.
 * @param data the data.
 * @return a Future for the {@link SendResult}.
 * @since 1.3
 */
ListenableFuture<SendResult<K, V>> sendDefault(Integer partition, Long timestamp, K key, V data);

/**
 * Send the data to the provided topic with no key or partition.
 * @param topic the topic.
 * @param data The data.
 * @return a Future for the {@link SendResult}.
 */
ListenableFuture<SendResult<K, V>> send(String topic, V data);

/**
 * Send the data to the provided topic with the provided key and no partition.
 * @param topic the topic.
 * @param key the key.
 * @param data The data.
 * @return a Future for the {@link SendResult}.
 */
ListenableFuture<SendResult<K, V>> send(String topic, K key, V data);

/**
 * Send the data to the provided topic with the provided key and partition.
 * @param topic the topic.
 * @param partition the partition.
 * @param key the key.
 * @param data the data.
 * @return a Future for the {@link SendResult}.
 */
ListenableFuture<SendResult<K, V>> send(String topic, Integer partition, K key, V data);

/**
 * Send the data to the provided topic with the provided key and partition.
 * @param topic the topic.
 * @param partition the partition.
 * @param timestamp the timestamp of the record.
 * @param key the key.
 * @param data the data.
 * @return a Future for the {@link SendResult}.
 * @since 1.3
 */
ListenableFuture<SendResult<K, V>> send(String topic, Integer partition, Long timestamp, K key, V data);

/**
 * Send the provided {@link ProducerRecord}.
 * @param record the record.
 * @return a Future for the {@link SendResult}.
 * @since 1.3
 */
ListenableFuture<SendResult<K, V>> send(ProducerRecord<K, V> record);

/**
 * Send a message with routing information in message headers. The message payload
 * may be converted before sending.
 * @param message the message to send.
 * @return a Future for the {@link SendResult}.
 * @see org.springframework.kafka.support.KafkaHeaders#TOPIC
 * @see org.springframework.kafka.support.KafkaHeaders#PARTITION_ID
 * @see org.springframework.kafka.support.KafkaHeaders#MESSAGE_KEY
 */
ListenableFuture<SendResult<K, V>> send(Message<?> message);