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https://issues.apache.org/jira/browse/KAFKA-2092?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14610622#comment-14610622
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Jason Gustafson commented on KAFKA-2092:
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[~azaroth], since the partitioner is exposed to the user on the client side, I
don't think it's necessarily a problem that keys are written to two partitions
(clients can partition however they want). However, wouldn't this make the
consumer's partition assignment strategy a bit trickier? Right now the
assignment of partition to consumer is static; each consumer in a consumer
group consumes from a disjoint subset of the overall partitions. But it doesn't
seem like that can work here since the keys might be paired across any 2
partitions. If the consumer knows what key they want, then they can find the
partitions to consume from, but generally to consume all keys from a given
partition, wouldn't a consumer have to consume all other partitions as well? If
we include this patch in kafka core, we might need to solve this problem.
> New partitioning for better load balancing
> ------------------------------------------
>
> Key: KAFKA-2092
> URL: https://issues.apache.org/jira/browse/KAFKA-2092
> Project: Kafka
> Issue Type: Improvement
> Components: producer
> Reporter: Gianmarco De Francisci Morales
> Assignee: Jun Rao
> Attachments: KAFKA-2092-v1.patch
>
>
> We have recently studied the problem of load balancing in distributed stream
> processing systems such as Samza [1].
> In particular, we focused on what happens when the key distribution of the
> stream is skewed when using key grouping.
> We developed a new stream partitioning scheme (which we call Partial Key
> Grouping). It achieves better load balancing than hashing while being more
> scalable than round robin in terms of memory.
> In the paper we show a number of mining algorithms that are easy to implement
> with partial key grouping, and whose performance can benefit from it. We
> think that it might also be useful for a larger class of algorithms.
> PKG has already been integrated in Storm [2], and I would like to be able to
> use it in Samza as well. As far as I understand, Kafka producers are the ones
> that decide how to partition the stream (or Kafka topic).
> I do not have experience with Kafka, however partial key grouping is very
> easy to implement: it requires just a few lines of code in Java when
> implemented as a custom grouping in Storm [3].
> I believe it should be very easy to integrate.
> For all these reasons, I believe it will be a nice addition to Kafka/Samza.
> If the community thinks it's a good idea, I will be happy to offer support in
> the porting.
> References:
> [1]
> https://melmeric.files.wordpress.com/2014/11/the-power-of-both-choices-practical-load-balancing-for-distributed-stream-processing-engines.pdf
> [2] https://issues.apache.org/jira/browse/STORM-632
> [3] https://github.com/gdfm/partial-key-grouping
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