AggregatingReplyingKafkaTemplate releaseStrategy Question - spring

Question

There seem to be an issue when I use AggregatingReplyingKafkaTemplate with template.setReturnPartialOnTimeout(true) in that, it returns timeout exception even if partial results are available from consumers.
In example below, I have 3 consumers to reply to the request topic and i've set the reply timeout at 10 seconds. I've explicitly delayed the response of Consumer 3 to 11 seconds, however, I expect the response back from Consumer 1 and 2, so, I can return partial results. However, I am getting KafkaReplyTimeoutException. Appreciate your inputs. Thanks.
I follow the code based on the Unit Test below.
[ReplyingKafkaTemplateTests][1]
I've provided the actual code below:
#RestController
public class SumController {
#Value("${kafka.bootstrap-servers}")
private String bootstrapServers;
public static final String D_REPLY = "dReply";
public static final String D_REQUEST = "dRequest";
#ResponseBody
#PostMapping(value="/sum")
public String sum(#RequestParam("message") String message) throws InterruptedException, ExecutionException {
AggregatingReplyingKafkaTemplate<Integer, String, String> template = aggregatingTemplate(
new TopicPartitionOffset(D_REPLY, 0), 3, new AtomicInteger());
String resultValue ="";
String currentValue ="";
try {
template.setDefaultReplyTimeout(Duration.ofSeconds(10));
template.setReturnPartialOnTimeout(true);
ProducerRecord<Integer, String> record = new ProducerRecord<>(D_REQUEST, null, null, null, message);
RequestReplyFuture<Integer, String, Collection<ConsumerRecord<Integer, String>>> future =
template.sendAndReceive(record);
future.getSendFuture().get(5, TimeUnit.SECONDS); // send ok
System.out.println("Send Completed Successfully");
ConsumerRecord<Integer, Collection<ConsumerRecord<Integer, String>>> consumerRecord = future.get(10, TimeUnit.SECONDS);
System.out.println("Consumer record size "+consumerRecord.value().size());
Iterator<ConsumerRecord<Integer, String>> iterator = consumerRecord.value().iterator();
while (iterator.hasNext()) {
currentValue = iterator.next().value();
System.out.println("response " + currentValue);
System.out.println("Record header " + consumerRecord.headers().toString());
resultValue = resultValue + currentValue + "\r\n";
}
} catch (Exception e) {
System.out.println("Error Message is "+e.getMessage());
}
return resultValue;
}
public AggregatingReplyingKafkaTemplate<Integer, String, String> aggregatingTemplate(
TopicPartitionOffset topic, int releaseSize, AtomicInteger releaseCount) {
//Create Container Properties
ContainerProperties containerProperties = new ContainerProperties(topic);
containerProperties.setAckMode(ContainerProperties.AckMode.MANUAL_IMMEDIATE);
//Set the consumer Config
//Create Consumer Factory with Consumer Config
DefaultKafkaConsumerFactory<Integer, Collection<ConsumerRecord<Integer, String>>> cf =
new DefaultKafkaConsumerFactory<>(consumerConfigs());
//Create Listener Container with Consumer Factory and Container Property
KafkaMessageListenerContainer<Integer, Collection<ConsumerRecord<Integer, String>>> container =
new KafkaMessageListenerContainer<>(cf, containerProperties);
// container.setBeanName(this.testName);
AggregatingReplyingKafkaTemplate<Integer, String, String> template =
new AggregatingReplyingKafkaTemplate<>(new DefaultKafkaProducerFactory<>(producerConfigs()), container,
(list, timeout) -> {
releaseCount.incrementAndGet();
return list.size() == releaseSize;
});
template.setSharedReplyTopic(true);
template.start();
return template;
}
public Map<String, Object> consumerConfigs() {
Map<String, Object> props = new HashMap<>();
props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG,bootstrapServers);
props.put(ConsumerConfig.GROUP_ID_CONFIG, "test_id");
props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, org.apache.kafka.common.serialization.StringDeserializer.class);
props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, org.apache.kafka.common.serialization.StringDeserializer.class);
return props;
}
public Map<String, Object> producerConfigs() {
Map<String, Object> props = new HashMap<>();
// list of host:port pairs used for establishing the initial connections to the Kakfa cluster
props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG,
bootstrapServers);
props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG,
org.apache.kafka.common.serialization.StringSerializer.class);
props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, org.apache.kafka.common.serialization.StringSerializer.class);
return props;
}
public ProducerFactory<Integer,String> producerFactory() {
return new DefaultKafkaProducerFactory<>(producerConfigs());
}
#KafkaListener(id = "def1", topics = { D_REQUEST}, groupId = "D_REQUEST1")
#SendTo // default REPLY_TOPIC header
public String dListener1(String in) throws InterruptedException {
return "First Consumer : "+ in.toUpperCase();
}
#KafkaListener(id = "def2", topics = { D_REQUEST}, groupId = "D_REQUEST2")
#SendTo // default REPLY_TOPIC header
public String dListener2(String in) throws InterruptedException {
return "Second Consumer : "+ in.toLowerCase();
}
#KafkaListener(id = "def3", topics = { D_REQUEST}, groupId = "D_REQUEST3")
#SendTo // default REPLY_TOPIC header
public String dListener3(String in) throws InterruptedException {
Thread.sleep(11000);
return "Third Consumer : "+ in;
}
}
'''
[1]: https://github.com/spring-projects/spring-kafka/blob/master/spring-kafka/src/test/java/org/springframework/kafka/requestreply/ReplyingKafkaTemplateTests.java

Answer 1

template.setReturnPartialOnTimeout(true) simply means the template will consult the release strategy on timeout (with the timeout argument = true, to tell the strategy it's a timeout rather than a delivery call).
It must return true to release the partial result.
This is to allow you to look at (and possibly modify) the list to decide whether you want to release or discard.
Your strategy ignores the timeout parameter:
(list, timeout) -> {
releaseCount.incrementAndGet();
return list.size() == releaseSize;
});
You need return timeout ? true : { ... }.