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Kafka, mail # user - Re: a few questions from high level consumer documentation.


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RE: a few questions from high level consumer documentation.
Rob Withers 2013-05-09, 04:37


> -----Original Message-----
> From: Chris Curtin [mailto:[EMAIL PROTECTED]]

> > 1 When you say the iterator may block, do you mean hasNext() may block?
> >
>
> Yes.

Is this due to a potential non-blocking fetch (broker/zookeeper returns an
empty block if offset is current)?  Yet this blocks the network call of the
consumer iterator, do I have that right?  Are there other reasons it could
block?  Like the call fails and a backup call is made?

> > b.      For client crash, what can client do to avoid duplicate messages
> > when restarted? What I can think of is to read last message from log
> > file and ignore the first few received duplicate messages until
> > receiving the last read message. But is it possible for client to read
log file
> directly?
> >
>
> If you can't tolerate the possibility of duplicates you need to look at
the
> Simple Consumer example, There you control the offset storage.

Do you have example code that manages only once, even when a consumer for a
given partition goes away?

What does happen with rebalancing when a consumer goes away?  Is this
behavior of the high-level consumer group?  Is there a way to supply one's
own simple consumer with only once, within a consumer group that rebalances?

What happens if a producer goes away?

thanks much,
rob