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https://issues.apache.org/jira/browse/KAFKA-4402?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15662157#comment-15662157
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ASF GitHub Bot commented on KAFKA-4402:
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GitHub user yaojuncn opened a pull request:

    https://github.com/apache/kafka/pull/2128

    KAFKA-4402: make the KafkaProducer true round robin per topic

    

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/yaojuncn/kafka 
KAFKA-4402-client-producer-round-robin-fix

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/kafka/pull/2128.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #2128
    
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commit d74b0bd4d712223da38b3f2e666e4611bf65b455
Author: yaojuncn <yaoju...@users.noreply.github.com>
Date:   2016-11-13T21:46:44Z

    KAFKA-4402: make the KafkaProducer true round robin per topic

----


> Kafka Producer's DefaultPartitioner is actually not round robin as said in 
> the code comments "If no partition or key is present choose a partition in a 
> round-robin fashion"
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: KAFKA-4402
>                 URL: https://issues.apache.org/jira/browse/KAFKA-4402
>             Project: Kafka
>          Issue Type: Improvement
>            Reporter: Jun Yao
>            Priority: Minor
>
> From this code comments, it is said that Kafka client  Producer's 
> DefaultPartitioner will do round robin if "no partition or key is present", 
> https://github.com/apache/kafka/blob/41e676d29587042994a72baa5000a8861a075c8c/clients/src/main/java/org/apache/kafka/clients/producer/internals/DefaultPartitioner.java#L34
> from the code it looks trying to do round robin as well, as it maintained a 
> counter and try to increase it every time and then will decide which 
> partition to go to; 
> However the issue here is the counter is a global counter that is shared by 
> all the topics, so  it is actually not round robin per topic and sometimes 
> caused unbalanced routing among different partitions. 
> Although we can pass a custom implementation of interface 
> "org.apache.kafka.clients.producer.Partitioner", it might be still good to 
> make the default implementation true round robin as comment. 



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