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https://issues.apache.org/jira/browse/KAFKA-1183?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jason Gustafson updated KAFKA-1183:
-----------------------------------
    Fix Version/s:     (was: 0.10.1.0)
                       (was: 0.8.1)

> DefaultEventHandler causes unbalanced distribution of messages across 
> partitions
> --------------------------------------------------------------------------------
>
>                 Key: KAFKA-1183
>                 URL: https://issues.apache.org/jira/browse/KAFKA-1183
>             Project: Kafka
>          Issue Type: Bug
>          Components: producer 
>    Affects Versions: 0.8.0
>            Reporter: Dragos Dena
>            Assignee: Jun Rao
>         Attachments: KAFKA-1183-trunk.patch
>
>
> KAFKA-959 introduced an optimisation in {{DefaultEventHandler}} that was 
> supposed to have the effect of sending all messages from the same batch to a 
> single partition if no key is specified.
> The problem is that the {{sendPartitionPerTopicCache}} cache, which holds the 
> current selected partition for each topic, isn't actually invalided at the 
> start or end of each batch.
> The observed result is that, after the first request chooses a random 
> partition, all subsequent messages from that producer land in the same 
> partition. If you have a large number of producers, then it should be fine, 
> but if your producer count is comparable to the partition count, then it will 
> get unbalanced.



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