kafka consumer

分配策略

1. range

8个partition，3个consumer：
consumer 1: partition 1、partition 2、partition 3
consumer 2: partition 4、partition 5、partition 6
consumer 3: partition 7、partition 8

1. round robin

consumer 1: partition 1、partition 4、partition 7
consumer 2: partition 2、partition 5、partition 8
consumer 3: partition 3、partition 6

1. sticky