What is the correct way to determine a kafka consumer is ready using assign()?

Clients Java Clients
1

I have read the below discussions

But it is still not clear to me on how to determine a consumer is ready while starting a consumer using assign()

My code looks something like below

List<TopicPartition> topicPartitions = List.of(new TopicPartition("topic", 1));
// auto.offset.reset = latest
consumer.assign(partitions);
// first poll to initiate connection as mentioned in https://stackoverflow.com/a/54336476/785523
consumer.poll(Duration.ofSeconds(1)); 
boolean keepOnReading = true;
while(keepOnReading){
    final var records = consumer.poll(Duration.ofSeconds(1));
    // process records and stop polling by setting keepOnReading to false
}

But I am observing that if I make the first poll to 100ms (consumer.poll(Duration.ofMillis(100)) ) then consumer.poll() on the while loop does not get any records. It works fine if poll duration is 1 second or more. Can someone let me know

  1. What is the reliable way to determine if a consumer is ready using assign().
  2. In case of assign what is the correct way to do a seek after starting a consumer?
  • Kafka Client Version - 3.4.0
  • Kafka Broker Version - confluentinc/cp-kafka:7.3.1