[ISSUE #272]Support subscribe topic from first

[Jargon9]

Hi teams, I have completed support subscribe topic from first. Here is the example :

Could you please review the code?

[ni-ze]

@Jargon9 Before resolve the problem, I will close this pr.

[Jargon9]

@ni-ze Dear Sir Ni, I did not see your code comment. What is the problem you mentioned? I would greatly appreciate it if you could point it out.

[ni-ze]

Maybe you can find it in Files changed. @Jargon9

[Jargon9]

@ni-ze It's a bit strange that I didn't see this comment in the file change or conversation. Thank you very much for pointing it out and I will fix it.

[ni-ze]

@Jargon9 If you can fix this,I will really appreciate.

[Jargon9]

@ni-ze Sorry, there are important things to deal with during the May Day holiday, which has delayed the progress. I will fix it in the next two weeks.

[Jargon9]

@ni-ze I have fix it. Could you please review the code?

[Jargon9]

@ni-ze Dear Mr. Ni, if there are any comments, please let me know in the comments in case I receive no message as before. Thx!

[ni-ze]

@Jargon9 the unionConsumer in PlanetaryEngine is shared by two kind of topics, the source topic and shuffle topic. Source topic is up to user to decide consume from the last or the earliest. But the shuffle topic is consumed from the last always.

[Jargon9]

@ni-ze Got it, I have filtered out shuffle topic ( end with -shuffleTopic) . Is it necessary to filter the state topic (end with -stateTopic)?

[Jargon9]

[Jargon9]

@ni-ze Dear Mr. Ni, If there are any further issues, could you please help point them out？

[ni-ze]

@Jargon9 It does need seek to the beginning of use topic. But we can reset the offset after the rebalance, like the recover the state of shuffle topic. The details can be find in class MessageQueueListenerWrapper, where the state is recovered after rebalance. Reset user topic offset can be invoked here, I think. Sorry for late to reply you.

[Jargon9]

@ni-ze Got it, thanks. I will handle this in this week.

[Jargon9]

@ni-ze Dear sir, I have noticed a problem where if I place resetOffset before originListener. messageQueueChanged, there may be an error （still in rebalance）, while after placing it in originListener. messageQueueChanged, there may be an issue where consumption has already started. Do you have any good suggestions for this issue?

[Jargon9]

[ni-ze]

@Jargon9 Use tool DefaultMQAdminExt to reset offset before start consumer maybe works.

[ni-ze]

Can I have you WeChat？ It finish this as fast as possible, it really have a while from begin. My number:790174623.