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https://issues.apache.org/jira/browse/SPARK-21097?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16551572#comment-16551572
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James commented on SPARK-21097:
-------------------------------

Hi [~bradkaiser]

 

I find that you consider the memory space when preserving the cache. Have you 
consider the load balance?

e.g. if you want to preserve data from C to A and B, but A has higher cpu load 
than B. should we choose B as candidate if there is future computation on the 
cache data from C?

 

Thanks

> Dynamic allocation will preserve cached data
> --------------------------------------------
>
>                 Key: SPARK-21097
>                 URL: https://issues.apache.org/jira/browse/SPARK-21097
>             Project: Spark
>          Issue Type: Improvement
>          Components: Block Manager, Scheduler, Spark Core
>    Affects Versions: 2.2.0, 2.3.0
>            Reporter: Brad
>            Priority: Major
>         Attachments: Preserving Cached Data with Dynamic Allocation.pdf
>
>
> We want to use dynamic allocation to distribute resources among many notebook 
> users on our spark clusters. One difficulty is that if a user has cached data 
> then we are either prevented from de-allocating any of their executors, or we 
> are forced to drop their cached data, which can lead to a bad user experience.
> We propose adding a feature to preserve cached data by copying it to other 
> executors before de-allocation. This behavior would be enabled by a simple 
> spark config. Now when an executor reaches its configured idle timeout, 
> instead of just killing it on the spot, we will stop sending it new tasks, 
> replicate all of its rdd blocks onto other executors, and then kill it. If 
> there is an issue while we replicate the data, like an error, it takes too 
> long, or there isn't enough space, then we will fall back to the original 
> behavior and drop the data and kill the executor.
> This feature should allow anyone with notebook users to use their cluster 
> resources more efficiently. Also since it will be completely opt-in it will 
> unlikely to cause problems for other use cases.



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