Why can a group that does not appear in the console consume messages? - ApsaraMQ for Kafka

Symptoms

A group does not appear in the ApsaraMQ for Kafka console. However, consumer threads in this group are consuming messages.

A consumer uses the assign mode to consume messages. In this case, consumer threads may be able to consume messages even if you did not create a group for the consumer in the console.
A consumer uses the subscribe mode to consume messages. After the group to which the consumer belongs is deleted, consumer threads can continue to consume messages when the consumer threads are not stopped or rebalancing is not triggered.
The flexible group creation feature is enabled for your ApsaraMQ for Kafka instance. In this case, consumer threads can consume messages even if you did not create a group for the consumer in the console.

When a consumer uses the assign mode to consume messages, or the flexible group creation feature is enabled for your ApsaraMQ for Kafka instance, create a group in the ApsaraMQ for Kafka console in advance.
We recommend that you use existing groups when possible, because a large number of created groups may affect the stability of the cluster. For information about the group limit, see Limits.
Before you delete a group, make sure that all consumer threads in the group are stopped.
Note If you receive a message accumulation alert for a group that does not appear in the console, troubleshoot the issue by following the instructions provided in Why did I receive a message accumulation alert after I deleted the group?