Empty consumer group with no id

Clients
1

In a kafka cluster running on confluent cloud I have a number of consumers. When I make a GET request to {confluentUrl}/kafka/v3/clusters/{cluster_id}/consumer-groups, one of the consumer groups has the following properties:

"consumer_group_id": "",
"is_simple": true,
"partition_assignor": "",
"state": "EMPTY",

Everything in the cluster appears to be functioning fine, but I am concerned about this consumer group. It is subscribed to a topic, and is ~100000 messages behind.

How does something like this happen? Is it possible to delete this consumer group?

2

This seems to be a consumer group created once but whose threads never finished joining. You can easily delete this consumer group using the kafka-consumer-groups.sh utility. But first, check if there are no client threads for it:

kafka-consumer-groups.sh \
--bootstrap-server <KAFKA_ENDPOINT> \
--command-config consumer.properties \
--group <GROUP_NAME> \
--describe \
--members

If there are none (likely) then you can delete the consumer group:

kafka-consumer-groups.sh \
--bootstrap-server <KAFKA_ENDPOINT> \
--command-config consumer.properties \
--group <GROUP_NAME> \
--delete \

— @riferrei