错误如下：
Commit cannot be completed since the group has already rebalanced and assigned the partitions to another member. This means that the time between subsequent calls to poll() was longer than the configured session.timeout.ms, which typically implies that the poll loop is spending too much time message processing. You can address this either by increasing the session timeout or by reducing the maximum size of batches returned in poll() with max.poll.records.
造成的问题：假如consumer.properties配置中max.poll.records=40 (一次最多拉取40条数据) session.timeout.ms=30000 (会话时间)
假设kafka此时一次拉取了40条数据，但在处理第31条的时候抛出了如上的异常，就会导致，本次offset不会提交，完了这40条消息都会在接下来的某刻被再次消费，这其中就包含了其实已经消费了的30条数据
原因：the poll loop is spending too much time message processing， the time between subsequent calls to poll() was longer than the configured session.timeout.ms，好吧其实是一个意思！
意思就是说poll下来数据后，处理这些数据的时间比 session.timeout.ms配置的时间要长，从而导致the group has already rebalanced
解决办法是最后一句话：You can address this either by increasing the session timeout or by reducing the maximum size of batches returned in poll() with max.poll.records.
即要不增大 session.timeout.ms，要不减小max.poll.records ，至于具体配置为多少，得看你处理一条消息花费多长时间 x，需要满足 x乘以max.poll.records < session.timeout.ms