The problem of new consumer with 'CONSUME_FROM_LAST_OFFSET' model

[baomingyu]

  When i create consumer using a new consumer group with 'CONSUME_FROM_LAST_OFFSET'
model and subscribe a topic that has been created and has contained messages ,it will
consumer all exit messages rather than begin from last offset.

   I have found this problem is here .RebalancePushImpl.java -- > computePullFromWhere

   case CONSUME_FROM_LAST_OFFSET

  when user new consumer group the result will be 0 rather than last offset or max offset ,
because broker will allways not do return -1 .
  so it will be modified with such way

   if (lastOffset > 0) {
                 result = lastOffset;
             }
             // First start,no offset
             else if (0 == lastOffset) {
             ...

[solomon4github]

one guy found the reason in 2016, https://blog.csdn.net/scutshuxue/article/details/51694334#commentBox

now the latest version is 4.5.1 and we could found the code in org.apache.rocketmq.broker.processor.ConsumerManageProcessor

     if (offset >= 0) {
            responseHeader.setOffset(offset);
            response.setCode(ResponseCode.SUCCESS);
            response.setRemark(null);
        } else {
            long minOffset =
                this.brokerController.getMessageStore().getMinOffsetInQueue(requestHeader.getTopic(),
                    requestHeader.getQueueId());
            if (minOffset <= 0
                && !this.brokerController.getMessageStore().checkInDiskByConsumeOffset(
                requestHeader.getTopic(), requestHeader.getQueueId(), 0)) {
                responseHeader.setOffset(0L);
                response.setCode(ResponseCode.SUCCESS);
                response.setRemark(null);
            } else {
                response.setCode(ResponseCode.QUERY_NOT_FOUND);
                response.setRemark("Not found, V3_0_6_SNAPSHOT maybe this group consumer boot first");
            }
        }

if minOffset <= 0 ,always return 0.

and the client code in org.apache.rocketmq.client.impl.consumer.RebalancePushImpl

case CONSUME_FROM_LAST_OFFSET: {
                long lastOffset = offsetStore.readOffset(mq, ReadOffsetType.READ_FROM_STORE);
                if (lastOffset >= 0) {
                    result = lastOffset;
                }
                // First start,no offset
                else if (-1 == lastOffset) {
                    if (mq.getTopic().startsWith(MixAll.RETRY_GROUP_TOPIC_PREFIX)) {
                        result = 0L;
                    } else {
                        try {
                            result = this.mQClientFactory.getMQAdminImpl().maxOffset(mq);
                        } catch (MQClientException e) {
                            result = -1;
                        }
                    }
                } else {
                    result = -1;
                }
                break;
            }

if (lastOffset >= 0) {
result = lastOffset;
}

it make ‘ConsumeFromWhere’ not work.

It's confusing to me ， and hope someone can solve this.