org.springframework.kafka.requestreply.KafkaReplyTimeoutException: Reply timed out

Using Kafka to perform the Spring Rest API DELETE operation, but getting the KafkaReplyTimeoutException on return NULL.

If I return some value on the Product POJO, the operation works perfectly, but if I return NULL getting the error.

Listener

    @KafkaListener(id = ProductTopicConstants.DELETE_PRODUCT, topics = ProductTopicConstants.DELETE_PRODUCT,
containerFactory = "getDeleteProductContainerFactory")
@SendTo
public Product DeleteProduct(String id) {
logger.info("Listening to delete product", id);
Product product = productRepository.findByid(id);
if (product == null)
return null;
productRepository.delete(product);
return product;
}

Producer

public record ProductProducer(ReplyingKafkaTemplate<String, Object, Object> _replyTemplate) implements IProductProducer {
@Override
public ProductViewModel Delete(String id) throws InterruptedException, ExecutionException, TimeoutException {
RequestReplyFuture<String, Object, Object> future =
this._replyTemplate.sendAndReceive(new ProducerRecord<>(ProductTopicConstants.DELETE_PRODUCT, 0, null, id));
LOG.info(future.getSendFuture().get(10, TimeUnit.SECONDS).getRecordMetadata().toString());
Product deletedProduct = (Product) future.get(10, TimeUnit.SECONDS).value();
if (deletedProduct == null)
return null;
Product mappedProducts = mapper.convertValue(deletedProduct, new TypeReference<Product>() {
});
return new ProductViewModel(mappedProducts.getId(), mappedProducts.getName(), mappedProducts.getPrice(), mappedProducts.getDescription(), mappedProducts.getVersion());
}}

Factory container

@Bean
public KafkaTemplate<String, Object> kafkaTemplate(ProducerFactory<String, Object> pf) {
return new KafkaTemplate<>(pf);
}
@Bean
public ConsumerFactory<String, String> consumerFactoryGetDeleteProduct() {
return new DefaultKafkaConsumerFactory<>(consumerConfigs(),
new StringDeserializer(),
new JsonDeserializer<>(String.class));
}
@Bean
public KafkaListenerContainerFactory<?> getDeleteProductContainerFactory(ProducerFactory<String, Object> pf) {
ConcurrentKafkaListenerContainerFactory<String, String> factory =
new ConcurrentKafkaListenerContainerFactory<>();
factory.setConsumerFactory(consumerFactoryGetDeleteProduct());
factory.setReplyTemplate(kafkaTemplate(pf));
return factory;
}

Error

org.springframework.kafka.requestreply.KafkaReplyTimeoutException: Reply timed out
at org.springframework.kafka.requestreply.ReplyingKafkaTemplate.lambda$scheduleTimeout$3(ReplyingKafkaTemplate.java:339) ~[spring-kafka-2.5.2.RELEASE.jar:2.5.2.RELEASE]
at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:54) ~[spring-context-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) ~[na:na]
at java.base/java.util.concurrent.FutureTask.run$$$capture(FutureTask.java:264) ~[na:na]
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java) ~[na:na]
at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304) ~[na:na]
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) ~[na:na]
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) ~[na:na]
at java.base/java.lang.Thread.run(Thread.java:832) ~[na:na]

Why would you expect anything different? If you return null there is no reply to send so we get a timeout on the client side.

To return a null value, return KafkaNull.INSTANCE and the ConsumerRecord on the client side will contain null.

@KafkaListener(id = "so63583664", topics = "topic1")
@SendTo
public Object listen(String in) {
	System.out.println(in);
	return in.equals("foo") ? in.toUpperCase() : KafkaNull.INSTANCE;
}

@Bean
public ApplicationRunner runner(ReplyingKafkaTemplate<String, String, String> replyer) {
	return args -> {
		ProducerRecord<String, String> pr = new ProducerRecord<>("topic1", "foo", "foo");
		RequestReplyFuture<String, String, String> future = replyer.sendAndReceive(pr);
		System.out.println(future.get(10, TimeUnit.SECONDS).value());
		pr = new ProducerRecord<>("topic1", "foo", "bar");
		future = replyer.sendAndReceive(pr);
		System.out.println(future.get(10, TimeUnit.SECONDS).value());
	};
}

foo
FOO
bar
null