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https://issues.apache.org/jira/browse/KAFKA-4600?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16806244#comment-16806244
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Guozhang Wang commented on KAFKA-4600:
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NPE inside KafkaStreams is just another observation of the root cause. Maybe
reading the attached PR (https://github.com/apache/kafka/pull/3181) would
better illustrate the scenario. Note that for this ticket, the more severe
observation is that `happily consuming messages from the new partition. When
the state is relied upon for correct processing, this can be very bad, e.g.
data loss can occur.`, and we'd want to `very least the assignment should fail
so the consumer doesn't see any messages from the new partitions, and the
rebalance can be reattempted.` The PR of KAFKA-5154 did this purpose.
> Consumer proceeds on when ConsumerRebalanceListener fails
> ---------------------------------------------------------
>
> Key: KAFKA-4600
> URL: https://issues.apache.org/jira/browse/KAFKA-4600
> Project: Kafka
> Issue Type: Bug
> Components: consumer
> Affects Versions: 0.10.1.1
> Reporter: Braedon Vickers
> Priority: Major
> Fix For: 0.11.0.0
>
>
> One of the use cases for a ConsumerRebalanceListener is to load state
> necessary for processing a partition when it is assigned. However, when
> ConsumerRebalanceListener.onPartitionsAssigned() fails for some reason (i.e.
> the state isn't loaded), the error is logged and the consumer proceeds on as
> if nothing happened, happily consuming messages from the new partition. When
> the state is relied upon for correct processing, this can be very bad, e.g.
> data loss can occur.
> It would be better if the error was propagated up so it could be dealt with
> normally. At the very least the assignment should fail so the consumer
> doesn't see any messages from the new partitions, and the rebalance can be
> reattempted.
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