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From Jacek Laskowski <ja...@japila.pl>
Subject Re: Change parallelism number in Spark Streaming
Date Wed, 26 Jun 2019 22:46:55 GMT
Hi,

No idea. I've just begun exploring the current state of state management in
spark structured streaming. I'd not be surprised if what you're after were
not possible. Stateful stream processing in SSS is fairly young.

Jacek

On Wed, 26 Jun 2019, 21:48 Rong, Jialei, <jialei@amazon.com> wrote:

> Thank you for your quick reply!
>
> Is there any plan to improve this?
>
> I asked this question due to some investigation on comparing those state
> of art streaming systems, among which Flink and DataFlow allow changing
> parallelism number, and by my knowledge of Spark Streaming, it seems it is
> also able to do that: if some “key interval” concept is used, then state
> can somehow decoupled from partition number by consistent hashing.
>
>
>
>
>
> Regards
>
> Jialei
>
>
>
> *From: *Jacek Laskowski <jacek@japila.pl>
> *Date: *Wednesday, June 26, 2019 at 11:00 AM
> *To: *"Rong, Jialei" <jialei@amazon.com.invalid>
> *Cc: *"user @spark" <user@spark.apache.org>
> *Subject: *Re: Change parallelism number in Spark Streaming
>
>
>
> Hi,
>
>
>
> It's not allowed to change the numer of partitions after your streaming
> query is started.
>
>
>
> The reason is exactly the number of state stores which is exactly the
> number of partitions (perhaps multiplied by the number of stateful
> operators).
>
>
>
> I think you'll even get a warning or an exception when you change it after
> restarting the query.
>
>
>
> The number of partitions is stored in a checkpoint location.
>
>
>
> Jacek
>
>
>
> On Wed, 26 Jun 2019, 19:30 Rong, Jialei, <jialei@amazon.com.invalid>
> wrote:
>
> Hi Dear Spark Expert
>
>
>
> I’m curious about a question regarding Spark Streaming/Structured
> Streaming: whether it allows to change parallelism number(the default one
> or the one specified in particular operator) in a stream having stateful
> transform/operator? Whether this will cause my checkpointed state get
> messed up?
>
>
>
>
>
> Regards
>
> Jialei
>
>
>
>

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