ConsumerOffsetChecker returns negative value for log lag

Hi,

I have a Kafka 0.8.1 cluster. I used the ConsumerOffsetChecker tool to
check the lag of consumer groups. I found that for some partition, the tool
returns negative value for the "lag " column. Is this a known issue that
has been seen before? I find that the negative value prevents the consumer
consuming the latest events in these partitions. How can we work around
the problem?

The following is the command:

~/kafka_2.9.2-0.8.1$ bin/kafka-run-class.sh
kafka.tools.ConsumerOffsetChecker --group topic_partition --zkconnect
zk001:2181 --topic the_topic | grep ' -'

The following is part of the output. The topic that I am checking has 128
partitions, and the tool returns negative value for 63 partitions.

topic_partition event 6 202936733
28822327 * -*174114406 topic_partition_m031_29714_20-0

topic_partition event 10 177322216
36578944 * -*140743272 topic_partition_m032_16773_16-0

topic_partition event 11 187891640
28999350 * -*158892290 topic_partition_m032_16773_17-0

Thanks!

-Yu