Snippet from ConsumerPartitionAssignor

ConsumerPartitionAssignor.java

public interface ConsumerPartitionAssignor {


    /**
     * Return serialized data that will be included in the {@link Subscription} sent to the leader
     * and can be leveraged in {@link #assign(Cluster, GroupSubscription)} ((e.g. local host/rack information)
     */
    default ByteBuffer subscriptionUserData(Set<String> topics) {
        return null;
    }


    /**
     * Perform the group assignment given the member subscriptions and current cluster metadata.
     */
    GroupAssignment assign(Cluster metadata, GroupSubscription groupSubscription);


    /**
     * Callback which is invoked when a group member receives its assignment from the leader.
     */
    default void onAssignment(Assignment assignment, ConsumerGroupMetadata metadata) {
    }
    
    ...
}