Kafka + Spring Batch Listener Flush Batch - apache-kafka

Question

Using Kafka Broker: 1.0.1
spring-kafka: 2.1.6.RELEASE
I'm using a batched consumer with the following settings:
// Other settings are not shown..
props.put(ConsumerConfig.MAX_POLL_RECORDS_CONFIG, "100");
I use spring listener in the following way:
#KafkaListener(topics = "${topics}", groupId = "${consumer.group.id}")
public void receive(final List<String> data,
#Header(KafkaHeaders.RECEIVED_PARTITION_ID) final List<Integer> partitions,
#Header(KafkaHeaders.RECEIVED_TOPIC) Set<String> topics,
#Header(KafkaHeaders.OFFSET) final List<Long> offsets) { // ......code... }
I always find the a few messages remain in the batch and not received in my listener. It appears to be that if the remaining messages are less than a batch size, it isn't consumed (may be in memory and published to my listener). Is there any way to have a setting to auto-flush the batch after a time interval so as to avoid the messages not being flushed?
What's the best way to deal with such kind of situation with a batch consumer?

Answer 1

I just ran a test without any problems...
#SpringBootApplication
public class So50370851Application {
public static void main(String[] args) {
SpringApplication.run(So50370851Application.class, args);
}
#Bean
public ApplicationRunner runner(KafkaTemplate<String, String> template) {
return args -> {
for (int i = 0; i < 230; i++) {
template.send("so50370851", "foo" + i);
}
};
}
#KafkaListener(id = "foo", topics = "so50370851")
public void listen(List<String> in) {
System.out.println(in.size());
}
#Bean
public NewTopic topic() {
return new NewTopic("so50370851", 1, (short) 1);
}
}
and
spring.kafka.consumer.auto-offset-reset=earliest
spring.kafka.consumer.enable-auto-commit=false
spring.kafka.consumer.max-poll-records=100
spring.kafka.listener.type=batch
and
100
100
30
Also, the debug logs shows after a while that it is polling and fetching 0 records (and this gets repeated over and over).
That implies the problem is on the sending side.