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From Till Rohrmann <trohrm...@apache.org>
Subject Re: [DISCUSS] Temporarily remove support for job rescaling via CLI action "modify"
Date Wed, 24 Apr 2019 08:11:45 GMT
+1 for temporarily removing support for the modify command.

Eventually, we have to add it again in order to support auto scaling. The
next time we add it, we should address the known limitations.

Cheers,
Till

On Wed, Apr 24, 2019 at 9:06 AM Paul Lam <paullin3280@gmail.com> wrote:

> Hi Gary,
>
> + 1 to remove it for now. Actually some users are not aware of that it’s
> still experimental, and ask quite a lot about the problem it causes.
>
> Best,
> Paul Lam
>
> 在 2019年4月24日,14:49,Stephan Ewen <sewen@apache.org> 写道:
>
> Sounds reasonable to me. If it is a broken feature, then there is not much
> value in it.
>
> On Tue, Apr 23, 2019 at 7:50 PM Gary Yao <gary@ververica.com> wrote:
>
> Hi all,
>
> As the subject states, I am proposing to temporarily remove support for
> changing the parallelism of a job via the following syntax [1]:
>
>    ./bin/flink modify [job-id] -p [new-parallelism]
>
> This is an experimental feature that we introduced with the first rollout
> of
> FLIP-6 (Flink 1.5). However, this feature comes with a few caveats:
>
>    * Rescaling does not work with HA enabled [2]
>    * New parallelism is not persisted, i.e., after a JobManager restart,
> the job
>      will be recovered with the initial parallelism
>
> Due to the above-mentioned issues, I believe that currently nobody uses
> "modify -p" to rescale their jobs in production. Moreover, the rescaling
> feature stands in the way of our current efforts to rework Flink's
> scheduling
> [3]. I therefore propose to remove the rescaling code for the time being.
> Note
> that it will still be possible to change the parallelism by taking a
> savepoint
> and restoring the job with a different parallelism [4].
>
> Any comments and suggestions will be highly appreciated.
>
> Best,
> Gary
>
> [1]
> https://ci.apache.org/projects/flink/flink-docs-release-1.8/ops/cli.html
> [2] https://issues.apache.org/jira/browse/FLINK-8902
> [3] https://issues.apache.org/jira/browse/FLINK-10429
> [4]
>
>
> https://ci.apache.org/projects/flink/flink-docs-release-1.8/ops/state/savepoints.html#what-happens-when-i-change-the-parallelism-of-my-program-when-restoring
>
>
>

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