kafka分区消费计算

int numPartitionsPerConsumer = numPartitionsForTopic / consumersForTopic.size();
 int consumersWithExtraPartition = numPartitionsForTopic % consumersForTopic.size();

 List partitions = AbstractPartitionAssignor.partitions(topic, numPartitionsForTopic);
 for (int i = 0, n = consumersForTopic.size(); i < n; i++) {
     int start = numPartitionsPerConsumer * i + Math.min(i, consumersWithExtraPartition);
     int length = numPartitionsPerConsumer + (i + 1 > consumersWithExtraPartition ? 0 : 1);
     assignment.get(consumersForTopic.get(i).memberId).addAll(partitions.subList(start, start + length));
 }

利用除数和余数得到结果
比如5个分区，3个消费者
分区：01234
消费：
01
23
4

public class KafkaPartitionTest {

    public static void main(String[] args) {

        int numPartitionsForTopic = 5;
        int consumersForTopicSize = 3;
        int numPartitionsPerConsumer = numPartitionsForTopic / consumersForTopicSize;
        int consumersWithExtraPartition = numPartitionsForTopic % consumersForTopicSize;

        //List partitions = AbstractPartitionAssignor.partitions(topic, numPartitionsForTopic);
        for (int i = 0, n = consumersForTopicSize; i < n; i++) {
            int start = numPartitionsPerConsumer * i + Math.min(i, consumersWithExtraPartition);
            int length = numPartitionsPerConsumer + (i + 1 > consumersWithExtraPartition ? 0 : 1);
            //assignment.get(consumersForTopic.get(i).memberId).addAll(partitions.subList(start, start + length));
            System.out.println("start:" + start);
            System.out.println("start + length:" + (start + length));
        }
    }
}