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From Hyukjin Kwon <gurwls...@gmail.com>
Subject Re: [DISCUSS] Add RocksDB StateStore
Date Tue, 09 Feb 2021 14:10:13 GMT
I'm good with this too.

2021년 2월 9일 (화) 오후 4:16, DB Tsai <dbtsai@dbtsai.com>님이 작성:

> +1 to add it as an external module so people can test it out and give
> feedback easier.
>
> On Mon, Feb 8, 2021 at 10:22 PM Gabor Somogyi <gabor.g.somogyi@gmail.com>
> wrote:
> >
> > +1 adding it any way.
> >
> > On Mon, 8 Feb 2021, 21:54 Holden Karau, <holden@pigscanfly.ca> wrote:
> >>
> >> +1 for an external module.
> >>
> >> On Mon, Feb 8, 2021 at 11:51 AM Cheng Su <chengsu@fb.com.invalid>
> wrote:
> >>>
> >>> +1 for (2) adding to external module.
> >>>
> >>> I think this feature is useful and popular in practice, and option 2
> is not conflict with previous concern for dependency.
> >>>
> >>>
> >>>
> >>> Thanks,
> >>>
> >>> Cheng Su
> >>>
> >>>
> >>>
> >>> From: Dongjoon Hyun <dongjoon.hyun@gmail.com>
> >>> Date: Monday, February 8, 2021 at 10:39 AM
> >>> To: Jacek Laskowski <jacek@japila.pl>
> >>> Cc: Liang-Chi Hsieh <viirya@gmail.com>, dev <dev@spark.apache.org>
> >>> Subject: Re: [DISCUSS] Add RocksDB StateStore
> >>>
> >>>
> >>>
> >>> Thank you, Liang-chi and all.
> >>>
> >>>
> >>>
> >>> +1 for (2) external module design because it can deliver the new
> feature in a safe way.
> >>>
> >>>
> >>>
> >>> Bests,
> >>>
> >>> Dongjoon
> >>>
> >>>
> >>>
> >>> On Mon, Feb 8, 2021 at 9:00 AM Jacek Laskowski <jacek@japila.pl>
> wrote:
> >>>
> >>> Hi,
> >>>
> >>>
> >>>
> >>> I'm "okay to add RocksDB StateStore as external module". See no reason
> not to.
> >>>
> >>>
> >>> Pozdrawiam,
> >>>
> >>> Jacek Laskowski
> >>>
> >>> ----
> >>>
> >>> https://about.me/JacekLaskowski
> >>>
> >>> "The Internals Of" Online Books
> >>>
> >>> Follow me on https://twitter.com/jaceklaskowski
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>> On Tue, Feb 2, 2021 at 9:32 AM Liang-Chi Hsieh <viirya@gmail.com>
> wrote:
> >>>
> >>> Hi devs,
> >>>
> >>> In Spark structured streaming, we need state store for state
> management for
> >>> stateful operators such streaming aggregates, joins, etc. We have one
> and
> >>> only one state store implementation now. It is in-memory hashmap which
> was
> >>> backed up in HDFS complaint file system at the end of every
> micro-batch.
> >>>
> >>> As it basically uses in-memory map to store states, memory consumption
> is a
> >>> serious issue and state store size is limited by the size of the
> executor
> >>> memory. Moreover, state store using more memory means it may impact the
> >>> performance of task execution that requires memory too.
> >>>
> >>> Internally we see more streaming applications that requires large
> state in
> >>> stateful operations. For such requirements, we need a StateStore not
> rely on
> >>> memory to store states.
> >>>
> >>> This seems to be also true externally as several other major streaming
> >>> frameworks already use RocksDB for state management. RocksDB is an
> embedded
> >>> DB and streaming engines can use it to store state instead of memory
> >>> storage.
> >>>
> >>> So seems to me, 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.
> >>>
> >>> Previously there was one attempt SPARK-28120 to add RocksDB StateStore
> into
> >>> Spark SS. IIUC, it was pushed back due to two concerns: extra code
> >>> maintenance cost and it introduces RocksDB dependency.
> >>>
> >>> For the first concern, as more users require to use the feature, it
> should
> >>> be highly used code in SS and more developers will look at it. For
> second
> >>> one, we propose (SPARK-34198) to add it as an external module to
> relieve the
> >>> dependency concern.
> >>>
> >>> Because it was pushed back previously, I'm going to raise this
> discussion to
> >>> know what people think about it now, in advance of submitting any code.
> >>>
> >>> I think there might be some possible opinions:
> >>>
> >>> 1. okay to add RocksDB StateStore into sql core module
> >>> 2. not okay for 1, but okay to add RocksDB StateStore as external
> module
> >>> 3. either 1 or 2 is okay
> >>> 4. not okay to add RocksDB StateStore, no matter into sql core or as
> >>> external module
> >>>
> >>> Please let us know if you have some thoughts.
> >>>
> >>> Thank you.
> >>>
> >>> Liang-Chi Hsieh
> >>>
> >>>
> >>>
> >>>
> >>> --
> >>> Sent from: http://apache-spark-developers-list.1001551.n3.nabble.com/
> >>>
> >>> ---------------------------------------------------------------------
> >>> To unsubscribe e-mail: dev-unsubscribe@spark.apache.org
> >>
> >>
> >>
> >> --
> >> Twitter: https://twitter.com/holdenkarau
> >> Books (Learning Spark, High Performance Spark, etc.):
> https://amzn.to/2MaRAG9
> >> YouTube Live Streams: https://www.youtube.com/user/holdenkarau
>
>
>
> --
> Sincerely,
>
> DB Tsai
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