Spring Kafka difference between ContainerProperties(TopicPartitionOffset... topicPartitions) and ContainerProperties(String... topics) - apache-kafka

Question

I am creating a new KafkaMessageListenerContainer using a ContainerProperties.
Using ContainerProperties(String... topics), the Consumer Group looks fine: "state": "STABLE", "isSimpleConsumerGroup": false
Using ContainerProperties(TopicPartitionOffset... topicPartitions), the Consumer Groups is not automatically created. It is finally created when a message is sent but the Consumer Group doesn't look fine: "state": "EMPTY", "isSimpleConsumerGroup": true
What's the difference between them, did I miss something. I am expecting to have the same result using the two different ContainerProperties constructors.
ContainerProperties containerProps = new ContainerProperties(tpo.toArray(new TopicPartitionOffset[tpo.size()]));
containerProps.setGroupId(name);
// ContainerProperties containerProps = new ContainerProperties("poc-topic1",
// "poc-topic2", "poc-topic3");
// containerProps.setGroupId(name);
containerProps.setMessageListener(new TopicMessageListener(name));
DefaultKafkaConsumerFactory<String, Serializable> factory = new DefaultKafkaConsumerFactory<>(
Utils.get().getConsumerProperties());
container = new KafkaMessageListenerContainer<>(factory, containerProps);
// container.setAutoStartup(true);
// container.setBeanName(name);
// container.checkGroupId();
container.start();

Answer 1

That's not correct. The topic subscription causes a consumer group and their partitions distribution between group members.
When you do explicit partition assignment, not consumer group is involved at all.
See more in Apache Kafka docs: https://docs.confluent.io/platform/current/clients/consumer.html#consumer-groups
And respective JavaDocs:
/**
* Manually assign a list of partitions to this consumer. This interface does not allow for incremental assignment
* and will replace the previous assignment (if there is one).
* <p>
* If the given list of topic partitions is empty, it is treated the same as {#link #unsubscribe()}.
* <p>
* Manual topic assignment through this method does not use the consumer's group management
* functionality. As such, there will be no rebalance operation triggered when group membership or cluster and topic
* metadata change. Note that it is not possible to use both manual partition assignment with {#link #assign(Collection)}
* and group assignment with {#link #subscribe(Collection, ConsumerRebalanceListener)}.
* <p>
* If auto-commit is enabled, an async commit (based on the old assignment) will be triggered before the new
* assignment replaces the old one.
*
* #param partitions The list of partitions to assign this consumer
* #throws IllegalArgumentException If partitions is null or contains null or empty topics
* #throws IllegalStateException If {#code subscribe()} is called previously with topics or pattern
* (without a subsequent call to {#link #unsubscribe()})
*/
#Override
public void assign(Collection<TopicPartition> partitions) {
and:
/**
* Subscribe to the given list of topics to get dynamically assigned partitions.
* <b>Topic subscriptions are not incremental. This list will replace the current
* assignment (if there is one).</b> It is not possible to combine topic subscription with group management
* with manual partition assignment through {#link #assign(Collection)}.
*
* If the given list of topics is empty, it is treated the same as {#link #unsubscribe()}.
*
* <p>
* This is a short-hand for {#link #subscribe(Collection, ConsumerRebalanceListener)}, which
* uses a no-op listener. If you need the ability to seek to particular offsets, you should prefer
* {#link #subscribe(Collection, ConsumerRebalanceListener)}, since group rebalances will cause partition offsets
* to be reset. You should also provide your own listener if you are doing your own offset
* management since the listener gives you an opportunity to commit offsets before a rebalance finishes.
*
* #param topics The list of topics to subscribe to
* #throws IllegalArgumentException If topics is null or contains null or empty elements
* #throws IllegalStateException If {#code subscribe()} is called previously with pattern, or assign is called
* previously (without a subsequent call to {#link #unsubscribe()}), or if not
* configured at-least one partition assignment strategy
*/
#Override
public void subscribe(Collection<String> topics) {