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https://issues.apache.org/jira/browse/SPARK-25839?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-25839:
------------------------------------

    Assignee: Apache Spark

> Implement use of KryoPool in KryoSerializer
> -------------------------------------------
>
>                 Key: SPARK-25839
>                 URL: https://issues.apache.org/jira/browse/SPARK-25839
>             Project: Spark
>          Issue Type: Improvement
>          Components: Spark Core
>    Affects Versions: 2.0.2, 2.3.1, 2.3.2
>            Reporter: Patrick Brown
>            Assignee: Apache Spark
>            Priority: Minor
>
> The current implementation of KryoSerializer does not use KryoPool, which is 
> recommended by Kryo due to the creation of a Kryo instance being slow.
>  
> The current implementation references the KryoSerializerInstance private 
> variable cachedKryo as effectively being a pool of size 1. However (in my 
> admittedly somewhat limited research) it seems that frequently (such as in 
> the ClosureCleaner ensureSerializable method) a new instance of 
> KryoSerializerInstance is created, which in turn forces a new instance of 
> Kryo itself to be created, this instance is then dropped from scope, causing 
> the "pool" not to be re-used.
>  
> I have a small set of proposed changes we have been using on an internal 
> production application (running 24x7 for 6+ months, processing 10k+ jobs a 
> day) which implements using a KryoPool inside KryoSerializer which is then 
> used by each KryoSerializerInstance to borrow a Kryo instance.
>  
> I believe this is mainly a performance improvement for applications 
> processing a large number of small jobs, where the cost of instantiating Kryo 
> instances is a larger portion of execution time compared to larger jobs.
>  
> I have discussed this proposed change in the dev mailing list and it was 
> suggested I create this issue and a PR. It was also suggested I accompany 
> that with some performance metrics, which it is my plan to do.



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