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From "L. C. Hsieh (Jira)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-34198) Add RocksDB StateStore as external module
Date Tue, 02 Feb 2021 07:03:00 GMT

    [ https://issues.apache.org/jira/browse/SPARK-34198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17276893#comment-17276893
] 

L. C. Hsieh commented on SPARK-34198:
-------------------------------------

Thanks [~kabhwan] for your point.

Besides the maintenance cost of extra code, I remember one concern of adding it, is the rocksdb
dependency. I think the concern is valid and so it actually does have some differences between
putting in sql core module or as an external module. IIUC, that is why we have external modules.

If raising a discussion in dev mailing list helps, I think I will do it.

The RocksDB StateStore we are working with, is also based on the existing implementation with
our bug fix. So I think the review cost should be as lower as possible even we submit the
changed code. Of course if the original author can contribute the code, it will be great too.
And sure, this depends on what the consensus we get eventually.











> Add RocksDB StateStore as external module
> -----------------------------------------
>
>                 Key: SPARK-34198
>                 URL: https://issues.apache.org/jira/browse/SPARK-34198
>             Project: Spark
>          Issue Type: New Feature
>          Components: Structured Streaming
>    Affects Versions: 3.2.0
>            Reporter: L. C. Hsieh
>            Assignee: L. C. Hsieh
>            Priority: Major
>
> Currently Spark SS only has one built-in StateStore implementation HDFSBackedStateStore.
Actually it uses in-memory map to store state rows. As there are more and more streaming applications,
some of them requires to use large state in stateful operations such as streaming aggregation
and join.
> Several other major streaming frameworks already use RocksDB for state management. So
it is proven to be good choice for large state usage. But Spark SS still lacks of a built-in
state store for the requirement.
> We would like to explore the possibility to add RocksDB-based StateStore into Spark SS.
For the concern about adding RocksDB as a direct dependency, our plan is to add this StateStore
as an external module first.



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