(You started a new Kafka Connect worker.

As documented in the official Apache Kafka Connect framework documentation, Kafka Connect workers form a logical cluster by using a Kafka consumer group. The configuration property that identifies this cluster is group.id.

All Kafka Connect workers configured with the same group.id automatically join the same Connect cluster. Kafka’s group coordination protocol is then used to distribute connector and task configurations among the workers, providing fault tolerance, scalability, and automatic rebalancing.

Option A (cluster.id) is a Kafka internal identifier used by brokers and is not configurable for Kafka Connect workers. Option B (worker.id) does not exist as a valid Kafka Connect configuration. Option D (connector.id) identifies individual connectors within a Connect cluster, not the worker cluster itself.

Therefore, the group.id property is the correct and officially documented configuration that determines which Kafka Connect cluster a worker belongs to.